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Cited by 13Geology and Paleoclimatology ResearchClimate variability and modelsMarine and environmental studies

Coupled Oceanic and Atmospheric Controls of Deglacial Southeastern South America Precipitation and Western South Atlantic Productivity

Open access
Meier, Karl J. F., Jaeschke, Andrea, Rethemeyer, Janet, Chiessi, Cristiano M., Albuquerque, Ana Luiza S., Wall, Vincent, Friedrich, Oliver, Bahr, André·2022·Frontiers in Marine Science
DOI 10.3389/fmars.2022.878116
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Abstract

Various mechanisms were proposed as substantial drivers of (sub)tropical South American hydroclimate changes during the last deglaciation. However, the interpretation of past precipitation records from the regions affected by the South American Summer Monsoon, the dominant hydroclimatic system in (sub)tropical South America, still insufficiently consider feedbacks between oceanic and atmospheric processes evident in modern observational data. Here, we evaluate ocean-atmosphere feedbacks active in the region from 19 to 4 ka based on a multi-proxy record comprising lipid biomarker, bulk sediment elemental composition and foraminiferal geochemistry from a sediment core retrieved from the tropical western South Atlantic offshore eastern Brazil at 22°S. Our proxy data together with existing paleoclimate records show that the consideration of large scale synoptic climatic features across South America is crucial for understanding the past spatio-temporal rainfall variability, especially during the last deglaciation. While the paleohydrological data from our study site show relatively stable precipitation across the deglaciation in the core region of the South Atlantic Convergence Zone, distinct hydroclimatic gradients developed across the continent during Heinrich Stadial 1, which climaxed at 16 ka. By then, the prevalent atmospheric and oceanic configuration caused more frequent extreme climatic events associated with positive rainfall in the northern portion of eastern South America and in the southeastern portion of the continent. These climatic extremes resulted from substantial warming of the sub(tropical) western South Atlantic sea surface that fostered oceanic moisture transport towards the continent and the reconfiguration of quasi-stationary atmospheric patterns. We further find that enhanced continental precipitation in combination with low glacial sea level strongly impacted marine ecosystems via enhanced terrigenous organic matter input in line with augmented nutrient release to the ocean. Extreme rainfall events similar to those that occurred during Heinrich Stadial 1 are likely to recur in South America as a consequence of global warming, because the projected reduction of the intra-hemispheric temperature gradient may lead to the development of atmospheric patterns similar to those in force during Heinrich Stadial 1.

AI snapshot

Written from the paper’s full text.

TL;DR

A multiproxy marine sediment record from Core M125-35-3 off SE Brazil (~22°S) shows that deglacial southeastern South America precipitation and western South Atlantic productivity were controlled by coupled ocean-atmosphere processes, not SACZ intensity alone. During Heinrich Stadial 1, especially ~16 ka, warming of the (sub)tropical South Atlantic and reorganized atmospheric circulation produced a SACZ/SALLJ precipitation dipole and enhanced terrigenous nutrient input that boosted marine productivity.

Key findings

  • Core M125-35-3 (21°53.606’S, 040°00.279’W, 428.6 m water depth) covers 4–19 ka at an average ~57 yr resolution; ln(K/Al) and ln(Al/Si) indicate relatively stable or slightly wetter conditions in the Paraíba do Sul/SACZ core region during HS1 compared with the LGM, drier conditions during the Bølling-Allerød, a slight increase during the Younger Dryas, and successively wetter conditions during the Holocene.
  • At ~16 ka, a negative SACZ/SALLJ dipole developed, with drying in SESA/core SACZ and wet conditions in SSESA/La Plata, coeval with warming at Core M125-35-3 and cooling at mid-latitude Core GeoB6211-2 (32.5°S); this is attributed to more stationary Rossby waves and a Chaco Jet Event-like SALLJ under a reduced hemispheric thermal gradient.
  • Alkenone and crenarchaeol mass accumulation rates were higher during HS1, reached minimum values in the early Holocene, and increased after ~7 ka; n-alkane MARs peaked at ~3200 ng cm⁻² ka⁻¹ at ~15.0 ka, and all biomarker proxies decreased rapidly at the Bølling-Allerød onset ~14.6 ka, coincident with meltwater pulse 1a (~20 m sea-level rise within ~500 years).
  • Terrigenous proxies (Σ Fe, Al, Ti, K)/Ca, brGDGT MARs, and the BIT index anti-correlate with deglacial sea-level rise; enhanced HS1 terrigenous input plus low sea level increased nutrient supply and marine productivity, while δ13Cplank remained relatively constant during HS1 and increased by ~0.5‰ during the Holocene.

Methods

  • Gravity core M125-35-3 was retrieved from the upper continental slope off the Paraíba do Sul River mouth, SE Brazil; 4.25 m of sediment was recovered, and 89 samples were analyzed for lipid biomarkers and bulk sediment elemental composition between 25 and 170 cm (4–19 ka), with average ~1.5 cm spacing; foraminiferal geochemistry was sampled at 1 cm spacing over the same interval.
  • Lipid biomarkers (n-alkanes, alkenones, brGDGTs, crenarchaeol) were analyzed by GC-FID and UHPLC-QQQ APCI MS; bulk sediment elemental composition was measured by XRF; stable carbon isotopes were measured on 50–60 handpicked tests of Globigerinoides ruber (pink) from the 355–400 µm fraction using a Thermo Fisher MAT 253plus with Kiel IV carbonate preparation.
  • The age model used AMS 14C dates recalibrated with MARINE20 and a ΔR correction, constrained with the CRAN R package Bacon; it covers ~19.3 to ~4.0 ka, with sedimentation rates increasing from ~10 cm/kyr during the latest LGM to maximum values of ~18.0 cm/kyr during the early deglaciation along HS1, decreasing after ~14.2 ka to ~4.0 cm/kyr, and reaching ~8 cm/kyr at 4.0 ka.

Limitations

  • The paper states that Fe/K records need to be interpreted with caution because decreased bottom current activity can favor deposition of fine-grained Al-rich illite and chlorite from the circumantarctic area, potentially increasing Fe/K values, and because early diagenetic effects may influence Fe/K; it also notes that a sufficient mechanism explaining the substantial reconfiguration of lower atmospheric circulation and moisture transport across South America is still lacking.
  • The paper states that δ13Cplank may give only supporting evidence for paleo-productivity because isotopic fractionation from enhanced marine productivity during HS1 may have been compensated by enhanced input of 13C-depleted terrestrial organic matter, resulting in no notable fractionation.
  • Evident from the text: the study relies on a single marine core and proxy assumptions (e.g., ln(K/Al), ln(Al/Si), BIT, n-alkanes, δ13Cplank), and interpretations of the SACZ/SALLJ dipole depend on comparison with distant speleothem and marine records, carrying chronological and spatial correlation uncertainty; n-alkanes could have secondary sources, although the average CPI of 3.2 is used to argue for well-preserved terrestrial n-alkanes.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3389/fmars.2022.878116

Cites

133 of 133 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

  • Findingnone given
    § Introduction

    Past precipitation variability and associated river run-off had a great influence on nutrient availability and marine productivity in the western tropical South Atlantic.

    “We highlight that past precipitation variability and associated river run-off had a great influence on nutrient availability and marine productivity in the western tropical South Atlantic.”
    Quote in the paperNot a substantial claim
  • Findingreasoning
    § Abstract

    Distinct hydroclimatic gradients developed across the continent during Heinrich Stadial 1, climaxing at ~16 ka.

    “distinct hydroclimatic gradients developed across the continent during Heinrich Stadial 1, which climaxed at ~16 ka.”
    Quote in the paperSubstantial claim
  • Findingnone given
    § Introduction

    The quantity of terrestrial influx to the study site is largely determined by shelf extension and only subordinately controlled by precipitation intensity.

    “Yet, the quantity of terrestrial influx to our study site is largely determined by the shelf extension and only subordinately controlled by precipitation intensity.”
    Quote in the paperNot a substantial claim
  • Findingreasoning
    § Abstract

    Enhanced continental precipitation in combination with low glacial sea level strongly impacted marine ecosystems via enhanced terrigenous organic matter input and augmented nutrient release to the ocean.

    “We further find that enhanced continental precipitation in combination with low glacial sea level strongly impacted marine ecosystems via enhanced terrigenous organic matter input in line with augmented nutrient release to the ocean.”
    Quote in the paperSubstantial claim
  • Findingown data
    § Abstract

    Paleohydrological data from the study site show relatively stable precipitation across the deglaciation in the core region of the South Atlantic Convergence Zone.

    “While the paleohydrological data from our study site show relatively stable precipitation across the deglaciation in the core region of the South Atlantic Convergence Zone”
    Quote in the paperSubstantial claim
  • May combine two claims. 60
  • Classified as probably not a substantial claim. 40

  • May combine two claims.

    Findingown data
    § Materials and Methods

    The calculated carbon preference index (CPI) from Core M125-35-3 is on average 3.2, relatively high and comparable to modern soils, pointing to a predominance of well preserved terrestrial n-alkanes.

    “However, the calculated carbon preference index (CPI) from Core M125-35-3 is at average 3.2 (not shown), thus relatively high and comparable to modern soils, pointing to a predominance of well preserved terrestrial n-alkanes ().”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results

    Alkenone and crenarchaeol MARs reveal distinctly higher oceanic productivity during HS1, approach minimum values during the early Holocene, and show a subsequent continuous increase that accelerates after ~7 ka.

    “In contrast, alkenone and crenarchaeol MARs reveal distinctly higher oceanic productivity during HS1, approach minimum values during the early Holocene, and show a subsequent continuous increase that accelerates after ~7 ka.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning
    § Discussion

    The BIT index remains low during the Holocene, although a slight increase of terrestrial-derived brGDGTs is observed.

    “Further, the BIT index remains low during the Holocene, although a slight increase of terrestrial-derived brGDGTs is observed (Figures 3H, I).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Discussion

    Elemental ratios typically associated with continental runoff (Σ Fe, Al, Ti, K)/Ca, MARs of brGDGTs and the BIT index are clearly anti-correlated with the deglacial rising sea level and reveal a steady decreasing trend from the LGM towards the B/A.

    “Namely, elemental ratios typically associated with continental runoff (Σ Fe, Al, Ti, K)/Ca, MARs of brGDGTs and the BIT index are clearly anti-correlated with the deglacial rising sea level (Figures 3H–K) and reveal a steady decreasing trend from the LGM towards the B/A.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results

    Mass accumulation rates of n-alkanes show increasing values and higher variability during HS1.

    “In contrast, mass accumulation rates of n-alkanes show increasing values and higher variability during HS1 (Figure 3G).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Results

    MARs of brGDGTs, crenarchaeol and alkenones mimic the pattern of other proxies but show an increase after ~7.0 ka during the mid-Holocene, with much higher amplitude in crenarchaeol and alkenone MARs.

    “MARs of brGDGTs, crenarchaeol and alkenones of Core M125-35-3 mimic this pattern, but show an increase after ~7.0 ka during the mid-Holocene, which is of much higher amplitude in crenarchaeol and alkenone MARs (Figures 3D, E, H).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data
    § Materials and Methods

    From the onset of the Holocene at ~11.7 ka, sedimentation rates slightly increased to 8 cm/kyr at the youngest part of the record at 4.0 ka.

    “From the onset of the Holocene at ~11.7 ka, sedimentation rates slightly increase to 8 cm/kyr at the youngest part of the record at 4.0 ka (Figure S1 in Supplementary Material).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Results

    Drier conditions prevailed during the B/A, followed by a slight increase in moisture availability across the Paraíba do Sul catchment during the YD stadial.

    “Drier conditions prevail during the B/A followed by a slight increase in moisture availability across the Paraíba do Sul catchment during the YD stadial.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The terrigenous proxies in Core M125-35-3 reflect conditions in the Paraíba do Sul catchment.

  • May combine two claims.

    Findingown data
    § Discussion

    Simultaneously, the SST record from Core M125-35-3 shows an increase in temperatures towards ~30°C, which is somewhat lower than the SST peak at 16 ka.

    “Simultaneously, the SST record from Core M125-35-3 shows an increase in temperatures towards ~30°C, which is somewhat lower as the SST peak at 16 ka (Figure 4H).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Findingown data
    § Materials and Methods

    The improved age model covers the interval from ~19.3 ka to the late Holocene around ~4.0 ka, comprising the last deglaciation.

    “The improved age model covers the interval from ~19.3 ka to the late Holocene around ~4.0 ka comprising the last deglaciation, which we define as the period between the Last Glacial Maximum (LGM) and the beginning of the Holocene (H) including HS1, the B/A, and the YD.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Discussion

    Neither HS1 nor YD intervals stick out as a climatic extreme in Core M125-35-3.

    “Indeed, neither of these intervals stick out as a climatic extreme in Core M125-35-3.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Results

    δ13Cplank remains relatively constant during HS1 and increases steadily by ~0.5 ‰ during the Holocene.

    “δ13Cplank remains relatively constant during HS1 and increases steadily by ~0.5 ‰ during the Holocene (Figure 3C).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation
    § Materials and Methods

    Long-chain n-alkanes are components of leaf-waxes from vascular plants and can be used as tracer for terrestrial input of organic matter to marine sediments.

    “Long-chain n-alkanes are components of leaf-waxes from vascular plants and can be used as tracer for terrestrial input of organic matter to marine sediments (; ).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Materials and Methods

    Alkenones in marine sediments originate from haptophyte algae and high flux rates may reflect higher surface oceanic productivity.

    “Alkenones in marine sediments originate from haptophyte algae (i.e., coccolithophorides, dominated by Emiliania huxleyi) and high flux rates may therefore reflect higher surface oceanic productivity (; ; ; ; ).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § Abstract

    Extreme rainfall events similar to those during Heinrich Stadial 1 are likely to recur in South America as a consequence of global warming, because the projected reduction of the intra-hemispheric temperature gradient may lead to atmospheric patterns similar to those during Heinrich Stadial 1.

    “Extreme rainfall events similar to those that occurred during Heinrich Stadial 1 are likely to recur in South America as a consequence of global warming, because the projected reduction of the intra-hemispheric temperature gradient may lead to the development of atmospheric patterns similar to those in force during Heinrich Stadial 1.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Study design and conductnone given
    § Materials and Methods

    Analyzing a single species within a narrow size range ensures that foraminiferal respiration and symbiont activity uniformly affect the δ13C record.

    “However, as we analyze a single species within a narrow size range, our record should be uniformly affected by these influences.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation
    § Materials and Methods

    The calcification depth of G. ruber (p) at this study site is the mixed layer between 30 and 40 m water depth, comparable to the estimated calcification depth of G. ruber in the Pacific Ocean.

    “The calcification depth of G. ruber (p) at this study site was determined by () as the mixed layer between 30 and 40 m water depth, which is comparable to the estimated calcification depth of G. ruber in the Pacific Ocean ().”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Introduction

    During the SAMS season, the La Plata basin (including the Paraná catchment) receives large amounts of tropical moisture when a northerly low-level flow is channeled east of the Andes and feeds convective storms over the subtropical plains.

    “During the SAMS season, the La Plata basin (including the Paraná catchment) receives large amounts of tropical moisture, when a northerly low-level flow is channeled east of the Andes and feeds convective storms over the subtropical plains (; ; ; ).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § Materials and Methods

    Since G. ruber (p) occurs throughout the entire record of Core M125-35-3 and is associated with oligotrophic waters carried by the Brazil Current, one would not expect a substitution of different water-masses.

    “Since G. ruber (p) occurs throughout the entire record of Core M125-35-3 and this species is associated to the oligotrophic waters carried by the Brazil Current one would not expect a substitution of different water-masses.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Introduction

    High (low) austral summer insolation leads to increased (decreased) moisture convection across the Amazon basin, which increases (decreases) moisture export towards the southeast, seasonally feeding the SACZ and resulting in increased (decreased) SAMS rainfall over most parts of South America.

    “High (low) insolation lead to increased (decreased) moisture convection across the Amazon basin, which in turn increases (decreases) moisture export towards the southeast, seasonally feeding the SACZ and resulting in increased (decreased) SAMS rainfall over most parts of South America”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § Materials and Methods

    Low (high) ln(K/Al) reflect wetter (drier) conditions within the catchment area.

    “As related to past hydroclimate, low (high) ln(K/Al) reflect wetter (drier) conditions within the catchment area.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Introduction

    The SACZ/SALLJ dipole evolves as a feedback to changes in the spatial configuration of sea-surface temperatures (SST) in the western South Atlantic: a negative (positive) SACZ/SALLJ dipole is associated with warming (cooling) north (south) of 30°S.

    “The SACZ/SALLJ dipole appears to evolve as a feedback to changes in the spatial configuration of sea-surface temperatures (SST) in the western South Atlantic: a negative (positive) SACZ/SALLJ dipole is associated with warming (cooling) north (south) of 30°S (; ; ; ; ; ).”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given
    § Materials and Methods

    Concentrations of alkenones, n-alkanes, brGDGTs and crenarchaeol were converted to mass accumulation rates to ensure their independency of other sedimentary components.

    “Concentrations of alkenones, n-alkanes, brGDGTs and crenarchaeol were converted to Mass Accumulation Rates (MAR) to ensure their independency of other sedimentary components.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Introduction

    On orbital timescales, precipitation associated with the South American Monsoon System and South Atlantic Convergence Zone was mainly controlled by austral summer insolation.

    “Past precipitation records from (sub)tropical South America highlighted that on orbital timescales, precipitation associated to the South American Monsoon System (SAMS) and South Atlantic Convergence Zone (SACZ), which is a particular feature of the SAMS, was mainly controlled by austral summer insolation.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisecitation
    § Introduction

    The southward shift of the ITCZ results from increased northward atmospheric heat transport into the colder hemisphere during phases of weak AMOC, necessary to compensate the interhemispheric heat imbalance, and is in line with an intensification and cross-equatorial extension of the Northern Hemisphere Hadley Cell.

    “The southward shift of the ITCZ results from increased northward atmospheric heat transport into the colder hemisphere during phases of weak AMOC that is necessary to compensate the interhemispheric heat imbalance, and is in line with an intensification and a cross-equatorial extension of the Northern Hemisphere Hadley-Cell”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing), S4 (based). May combine two claims.

    Premisecitation
    § Introduction

    Deglacial high-latitude forced climatic perturbations and concomitant southward ITCZ shifts boosted SACZ strength, favoring moisture transport towards tropical and subtropical South America.

    “The latter studies implied that the deglacial high-latitude forced climatic perturbations and concomitant southward ITCZ shifts further boosted SACZ strength, thereby favoring moisture transport towards tropical and subtropical South America.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premiseown data
    § Materials and Methods

    The sediment trap study revealed no significant seasonal changes in the occurrence of G. ruber (p), thus likely reflecting annual mean conditions.

    “The sediment trap study revealed no significant seasonal changes in the occurrence of G. ruber (p), thus likely reflecting annual mean conditions.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Materials and Methods

    Accumulation rates of brGDGTs were attributed to terrestrial soil bacteria and indicate changes in surface erosion and discharge towards the core location.

    “Further, we focus on accumulation rates of brGDGTs, which were attributed to terrestrial soil bacteria (; ) and indicate changes in surface erosion and discharge towards our core location.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given
    § Introduction

    During austral winter, rainfall over SESA is related to mid-latitude cyclonic activity over the South Atlantic, affecting the Paraíba do Sul catchment less intensively than the southern part of SESA.

    “During austral winter, rainfall is related to mid-latitude cyclonic activity over the South Atlantic (), affecting the Paraíba do Sul catchment less intensively than the southern part of SESA.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisecitation
    § Introduction

    During austral summer, the coastal realms of SSESA receive increased rainfall when the SACZ is connected with the area of convection over the Amazon basin.

    “During austral summer, the coastal realms of SSESA receive increased rainfall when the SACZ is connected with the area of convection over the Amazon basin ().”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given
    § Materials and Methods

    Reproducibility of GDGT concentrations was <9%.

    “Reproducibility of GDGT concentrations was < 9 %.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Study design and conductcitation
    § Materials and Methods

    Sampling foraminiferal tests from the 355-400 μm size fraction avoids size-related ontogenetic effects.

    “To avoid size-related ontogenetic effects (), foraminiferal tests were sampled from the 355-400 µm size fraction () of the dried sediment.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Introduction

    Eastward propagating atmospheric Rossby waves were the main driver of SACZ variability.

    “, for instance, found that eastward propagating atmospheric Rossby waves were the main driver of SACZ variability.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisereasoning
    § Introduction

    This configuration could cause extreme weather events with marked droughts in the SACZ domain and floods in SSESA, such as during the year 2014, as the SALLJ provides significant Amazon moisture export towards SSESA.

    “This configuration could cause extreme weather events with marked droughts in the SACZ domain and floods in SSESA such as during the year 2014 as the SALLJ provides significant Amazon moisture export towards SSESA () (Figure 2).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation
    § Introduction

    The negative dipole pattern is linked to teleconnections associated with cooling of the North Atlantic, which leads to a southward shift of the ITCZ and enhanced cross-equatorial moisture flux over northwestern South America, finally feeding the northerly SALLJ in its CJE configuration during a negative SACZ/SALLJ dipole mode.

    “Further, the negative dipole pattern has been linked to teleconnections associated with cooling of the North Atlantic, which leads to a southward shift of the ITCZ and enhanced cross-equatorial moisture flux over northwestern South America, finally feeding the northerly SALLJ in its CJE configuration during a negative SACZ/SALLJ dipole mode (; ) (Figure 2).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Introduction

    Southward shifts of the ITCZ and associated adjustment of moisture flux pathways across tropical South America were invoked to indirectly affect precipitation in the realm of the SACZ.

    “Southward shifts of the ITCZ and the associated adjustment of moisture flux pathways across tropical South America were further invoked to indirectly affect precipitation in the realm of the SACZ”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisereasoning
    § Introduction

    With the onset of SAMS activity during austral summer, increased summer insolation enhances convection over tropical South America, which induces increased moisture flux towards the continent in line with prevailing NE trade winds.

    “With the onset of SAMS activity during austral summer, increased summer insolation enhances convection over tropical South America which induces increased moisture flux towards the continent in line with prevailing NE trade winds.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data
    § Materials and Methods

    Analytic precision based on repeated measurements of the in-house standard is < 0.03 ‰ for δ13C.

    “Analytic precision based on repeated measurements of the in-house standard is < 0.03 ‰ for δ13C.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data
    § Materials and Methods

    Analytical precision for alkenone and n-alkane measurements was <5% based on replicate standard analyses.

    “Analytical precision for alkenone and n-alkane measurements was < 5% based on replicate standard analyses.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation
    § Introduction

    Existing high-resolution SACZ reconstructions covering the last deglaciation are primarily based on terrestrial climate archives such as speleothems, while climate reconstructions from the core region of the SACZ based on marine sediment archives are still sparse.

    “Further, existing high-resolution SACZ reconstructions covering the last deglaciation are primarily based on terrestrial climate archives such as speleothems (; ; ; ), while climate reconstructions from the core region of the SACZ based on marine sediment archives are still sparse ().”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Introduction

    The hinterland region of eastern Brazil is characterized by a marked dry season during austral winter.

    “the hinterland region is characterized by a marked dry season during austral winter (; )”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisereasoning
    § Introduction

    The moist air is transported southward resulting in strong precipitation in the SACZ.

    “The moist air is transported southward resulting in strong precipitation in the SACZ ().”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § Introduction

    A dipole pattern is determined by moisture flux carried during CJE (NCJE), leading to enhanced (decreased) precipitation over SSESA and dryer (wetter) conditions in the core region of the SACZ in SESA.

    “Accordingly, a dipole pattern is determined by moisture flux carried during CJE (NCJE), leading to enhanced (decreased) precipitation over SSESA and dryer (wetter) conditions in the core region of the SACZ in SESA.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Introduction

    The dry season becomes more extreme towards semi-arid northeastern Brazil because intensification of the Hadley Cell and descending convective motion of the Walker circulation results in increased aridity.

    “The dry season becomes more extreme towards the semi-arid northeastern Brazil where an intensification of the Hadley Cell and descending convective motion of the Walker circulation results in increased aridity (; ; ; ).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given
    § Introduction

    The SALLJ appears in two configurations: the Chaco Jet Event (CJE) and the No Chaco Jet Event (NCJE).

    “It is noteworthy that the SALLJ appears in two different configurations (Figures 1, 2) (): (i) the Chaco Jet Event (CJE); and (ii) the No Chaco Jet Event (NCJE).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § Abstract

    These climatic extremes resulted from substantial warming of the sub(tropical) western South Atlantic sea surface that fostered oceanic moisture transport towards the continent and the reconfiguration of quasi-stationary atmospheric patterns.

    “These climatic extremes resulted from substantial warming of the sub(tropical) western South Atlantic sea surface that fostered oceanic moisture transport towards the continent and the reconfiguration of quasi-stationary atmospheric patterns.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Premisenone given
    § Introduction

    Synoptic climatic features were not considered in past paleo-precipitation studies from South America, so the variability of SACZ-related precipitation and its controlling mechanisms during rapid climatic perturbations such as HS1 are not well constrained.

    “Since such synoptic climatic features were not considered in past paleo-precipitation studies from South America, the variability of SACZ-related precipitation and its controlling mechanisms during phases of rapid climatic perturbations during the last deglaciation such as during HS1 are not well constrained yet.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § Introduction

    Atmospheric blocking by the persistent anticyclone diminishes easterly moisture flux during NCJE and reinforces northerly moisture flux towards SSESA via the CJE.

    “Atmospheric blocking by the persistent anticyclone diminishes easterly moisture flux during NCJE and reinforces northerly moisture flux towards SSESA via the CJE (Figures 1, 2).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given
    § Materials and Methods

    In the surface ocean (habitat of G. ruber (p)), photosynthesis dominates over respiration.

    “In the surface ocean (i.e. habitat of G. ruber (p)), however, photosynthesis dominates over respiration ().”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation
    § Materials and Methods

    ln(K/Al) and ln(Al/Si) ratios have been used to infer changes in continental moisture availability favoring chemical weathering in monsoonal dominated realms.

    “In addition, we utilize ln(K/Al) and ln(Al/Si) ratios, which have been used to infer changes in continental moisture availability favoring chemical weathering in monsoonal dominated realms (; ; ; ; ).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisereasoning
    § Introduction

    During austral summer, modern precipitation over SESA is dominated by the seasonal expansion and intensification of the SAMS/SACZ, with greatest influence in the northern part of SESA in the core region of the SACZ including the Paraíba do Sul catchment.

    “During austral summer, modern precipitation over SESA is dominated by the seasonal expansion and intensification of the SAMS/SACZ, which influence is greatest in the northern part of SESA in the core region of the SACZ including the Paraíba do Sul catchment”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation
    § Materials and Methods

    ln(K/Al) represents a measure of the intensification of chemical weathering because K is indicative for minerals (illite, potassium feldspar) predominant in dry regions with increased rates of mechanical over chemical weathering.

    “Here, ln(K/Al) represents a measure of the intensification of chemical weathering as K is indicative for minerals (i.e. illite, potassium feldspar) which are predominant in dry regions with increased rates of mechanical over chemical weathering (; ; ).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisecitation
    § Materials and Methods

    ln(Al/Si) has previously been used as proxy for chemical weathering intensity in South America.

    “We further compare the ln(K/Al) record with the ln(Al/Si) ratio, which has previously been used as proxy for chemical weathering intensity in South America ().”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § Materials and Methods

    δ13Cplank of Core M125-35-3 likely reflects the rate of photosynthesis and amount of exported 12C enriched particulate organic matter from the reservoir.

    “Thus, δ13Cplank of Core M125-35-3 likely reflects the rate of photosynthesis and amount of exported 12C enriched particulate organic matter from the reservoir.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The δ13C of planktonic foraminifera shells reflects the carbon isotopic composition of dissolved inorganic carbon (DIC) in seawater during calcification.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data
    § Materials and Methods

    For each element presented in this study, the standard calibration curves reveal a strong correlation (r2 > 0.8).

    “For each element presented in this study, the standard calibration curves reveal a strong correlation (r2 > 0.8).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § Introduction

    During austral winter, the main source of precipitation in SSESA is frontal rainfall caused by incursions of sub-Antarctic cold fronts meeting tropical air masses.

    “During austral winter, the main source of precipitation is frontal rainfall caused by incursions of sub-Antarctic cold fronts meeting tropical air masses (; ).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductreasoning
    § Materials and Methods

    Sample spacing for lipid biomarker and elemental analyses was adjusted to changing sedimentation rates in Core M125-35-3 to generate a temporally evenly resolved record.

    “Sample spacing for lipid biomarker and elemental analyses was not equidistant (in average ~1.5 cm) and adjusted to changing sedimentation rates in Core M125-35-3 to generate a temporally evenly resolved record.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Materials and Methods

    Decreased ln(Al/Si) are due to increased fluvial input of fine-grained quartz-rich material caused by higher rates of physical erosion in line with less humid conditions, while higher Al indicates stronger chemical weathering during wetter conditions.

    “Decreased ln(Al/Si) are due to increased fluvial input of fine-grained quartz-rich material caused by higher rates of physical erosion in line with less humid conditions, while higher Al indicates stronger chemical weathering during wetter conditions (; ).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Materials and Methods

    Al is associated with products of intensive chemical weathering, being especially enriched in kaolinite, which is characteristic for tropical humid conditions.

    “Al is associated in products of intensive chemical weathering, being especially enriched in kaolinite, which is characteristic for tropical humid conditions (; ).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisereasoning
    § Introduction

    The global redistribution of heat had a determining influence on the latitudinal position and strength of atmospheric convection belts over the tropical Atlantic and affected the latitudinal position of the Intertropical Convergence Zone.

    “This global redistribution of heat had a determining influence on the latitudinal position and strength of atmospheric convection belts over the tropical Atlantic and affected the latitudinal position of the Intertropical Convergence Zone (ITZC).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given
    § Materials and Methods

    δ13CDIC of seawater reflects local changes in the balance between photosynthesis (increasing δ13C) and respiration (decreasing δ13C).

    “With respect to biotic effects, δ13CDIC of seawater reflects local changes in the balance between photosynthesis (increasing in δ13C) and respiration (decreasing δ13C).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation
    § Introduction

    The NCJE protrudes eastward around 25°S, fostering moisture transport towards the SACZ at similar latitudes.

    “Instead, the NCJE protrudes eastward around 25°S, fostering moisture transport towards the SACZ at similar latitudes (; ; ) (Figure 2).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S1 (asserted).

    Premisecitation
    § Discussion

    Precipitation availability in ESA and to a lesser degree in SESA depended on atmospheric and oceanographic changes that resulted from the diminished interhemispheric heat transfer caused by a weakened AMOC.

    “proposed that precipitation availability in ESA and to a lesser degree in SESA depended on atmospheric and oceanographic changes that resulted from the diminished interhemispheric heat transfer caused by a weakened AMOC.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation
    § Discussion

    Meltwater pulse 1a was a phase of rapid sea level rise in which sea level rose by ~20 m within ~500 years.

    “a phase of rapid sea level rise in which sea level rose by ~20 m within ~500 years”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § Discussion

    Terrestrial siliciclastic sediment and organic-matter flux to the upper slope off the Paraíba do Sul was maximal during HS1 and subsequently declined during the late deglacial and Holocene, largely owing to rising eustatic sea level and ensuing coastline retreat.

    “To summarize, we infer that terrestrial siliciclastic sediment and organic-matter flux to the upper slope off the Paraíba do Sul was maximal during HS1 and subsequently declined during the late deglacial and Holocene, largely owing to the rising eustatic sea level and ensuing coastline retreat.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Terrestrial input into oligotrophic waters carried by the Brazil Current alongshore southeastern Brazil provides an important nutrient source for oceanic biota.
    • The authors state this as an assumption: A slightly invigorated continental hydrological cycle and particularly a marked low sea level enhanced nutrient and organic matter flux into the western tropical South Atlantic during HS1, boosting oceanic productivity.

  • May combine two claims.

    Premisereasoning
    § Discussion

    Increased (decreased) moisture sourced from the warmer (colder) tropical South (North) Atlantic was transported with the SE (NE) trade winds during austral summer (winter).

    “Based on model and proxy data, inferred that increased (decreased) moisture sourced from the warmer (colder) tropical South (North) Atlantic was transported with the SE (NE) trade winds during austral summer (winter).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § Discussion

    After flooding the shelf, the influx of terrestrial (organic) matter to the continental slope was substantially reduced and became rather insensitive to continental climatic variability compared to the period before the B/A.

    “After flooding the shelf, the influx of terrestrial (organic) matter to the continental slope was substantially reduced and became rather insensitive to continental climatic variability compared to the period before the B/A that is characterized by high sediment input to the slope.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The broad shelf off SE Brazil functions as a sediment trap during interglacial high sea level stands.

  • May combine two claims.

    Premisecitation
    § Discussion

    Late Pleistocene pollen-based reconstructions from Southern and SE Brazil suggest an expansion of Atlantic rainforests and gallery forests after 17.0 ka and somewhat later starting at 15 ka in SESA.

    “This is in line with late Pleistocene pollen-based reconstructions from Southern and SE Brazil suggesting an expansion of Atlantic rainforests and gallery forests after 17.0 ka (; ; ) and somewhat later starting at 15 ka in SESA (; ).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given
    § Discussion

    The positive precipitation anomalies in Lapa Sem Fim and Paixão Caves were related to so-called "Mega-SACZ-Events" that were presumed to be a consequence of enhanced convection of tropical-sourced moisture towards ESA and SESA.

    “The positive precipitation anomalies in Lapa Sem Fim and Paixão Caves were related to so-called “Mega-SACZ-Events” that were presumed to be a consequence of enhanced convection of tropical-sourced moisture towards ESA and SESA ().”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given
    § Discussion

    Today, Botuverá Cave receives precipitation all year round with no pronounced dry season, with austral summer moisture from SACZ/SAMS and austral winter moisture from extra tropical cyclones.

    “Today, Botuverá Cave receives precipitation all year round with no pronounced dry season (during austral summer moisture derives from the SACZ/SAMS, during austral winter moisture is related to extra tropical cyclones (; ).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation
    § Discussion

    Changes in the hydroclimate during the B/A onset were rather small, as existing pollen-based vegetation records of the Atlantic rainforest do not reveal a marked decrease or retreat.

    “However, as existing pollen-based vegetation records of the Atlantic rainforest do not reveal a marked decrease or retreat (; ), we infer that changes in the hydroclimate were rather small.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § Discussion

    During HS1, a greater seasonal contrast in rainfall probably characterized the region, with a dry season during austral winter and wet austral summer season induced by the SAMS/SACZ.

    “During HS1, however, a greater seasonal contrast in rainfall probably characterized the region, with a dry season during austral winter and wet austral summer season induced by the SAMS/SACZ.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § Discussion

    The drier conditions above the Paraíba do Sul catchment during the B/A can be assigned to stabilization of temperatures in South America coinciding with the Antarctic Cold Reversal, indicating overall cooler and likely drier conditions at the southern margins of the SAMS.

    “Drier conditions above the Paraíba do Sul catchment (Figures 4A, B) during the B/A can be assigned to the stabilization of temperatures in South America in coincidence with the Antarctic Cold Reversal indicating overall cooler and likely dryer conditions at the southern margins of the SAMS (; ; ).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisecitation
    § Discussion

    Intensification of SAMS/SACZ activity over ESA during HS1 was previously suggested based on speleothem precipitation records from Lapa Sem Fim and Paixão Caves.

    “Intensification of SAMS/SACZ activity over ESA during HS1 was previously suggested by based on speleothem precipitation records from Lapa Sem Fim and Paixão Caves (Figures 1, 4I, J).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data
    § Discussion

    Precipitation intensity in the core domain of the SACZ (at least over the Paraíba do Sul catchment) did not vary markedly over the deglaciation, with slightly more precipitation during HS1 and the YD compared to the drier B/A.

    “Based on the ln(K/Al) and ln(Al/Si) data from Core M125-35-3 (Figures 4A, B), we suggest that precipitation intensity in the core domain of the SACZ (at least over the Paraíba do Sul catchment) did not vary markedly over the deglaciation, with slightly more precipitation during HS1 and the YD compared to the drier B/A.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The Paraíba do Sul catchment is within the core region of the SACZ.

  • May combine two claims.

    Interpretationreasoning
    § Discussion

    Around ~16 ka, a minimum in δ18O indicates the wettest phase in the Paixão record, and this minimum occurs synchronously with slightly dryer conditions across the Paraíba do Sul catchment area, suggesting a northward displacement of the SACZ.

    “An exception occurred around ~16 ka, when a minimum in δ18O indicate the wettest phase in the Paixão record. Minimum δ18O occurs synchronously with slightly dryer conditions across the Paraíba do Sul catchment area suggesting a northward displacement of the SACZ.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The Paraíba do Sul catchment is within the core region of the SACZ.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationown data
    § Discussion

    The rapid decrease in n-alkanes and brGDGTs might be intensified by a shift to slightly dryer conditions during the B/A onset, as reflected by ln(K/Al) and ln(Al/Si) records leading to decreased terrestrial run-off.

    “We note, that the rapid decrease in n-alkanes and brGDGTs might be intensified by a shift to slightly dryer conditions during the B/A onset as reflected by our ln(K/Al) and ln(Al/Si) records leading to decreased terrestrial run-off”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: A slightly invigorated continental hydrological cycle and particularly a marked low sea level enhanced nutrient and organic matter flux into the western tropical South Atlantic during HS1, boosting oceanic productivity.

  • May combine two claims.

    Interpretationreasoning
    § Discussion

    The YD precipitation increase was likely related to warming of the Southern Hemisphere and enhanced moisture influx into South America due to Northern Hemisphere cooling leading to a southward shift of the ITCZ.

    “This precipitation increase was likely related to warming of the Southern Hemisphere and enhanced moisture influx into South America due to Northern Hemisphere cooling leading to a southward shift of the ITCZ (; ).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § Discussion

    Based on available data from Botuverá Cave, a reduction in winter-time precipitation can be inferred, while the SACZ-related precipitation appeared to have been relatively stable.

    “Hence, based on available data from Botuverá Cave, a reduction in winter-time precipitation can be inferred, while the SACZ-related precipitation appeared to have been relatively stable.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given
    § Materials and Methods

    Adding one additional AMS 14C age improved the accuracy of the late deglacial shift from the Bølling-Allerød (B/A) interstadial to the Younger Dryas (YD) stadial in the age model.

    “For this study, we modified the initial model as we added one additional AMS 14C age to improve the accuracy of the late deglacial shift from the Bølling-Allerød (B/A) interstadial to the Younger Dryas (YD) stadial (Table 1).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data
    § Discussion

    Soil run-off decreased as observed from brGDGTs mass accumulation rates during HS1, which may indicate suppressed top-soil erosion induced by forest expansion.

    “Simultaneously, soil run-off decreased as observed from brGDGTs mass accumulation rates during HS1, which may indicate suppressed top-soil erosion induced by forest expansion (Figure 3H).”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The terrigenous proxies in Core M125-35-3 reflect conditions in the Paraíba do Sul catchment.

  • May combine two claims.

    Study design and conductcitation
    § Materials and Methods

    All AMS 14C ages were recalibrated with the MARINE20 calibration curve and a ΔR = -84 ± 125.

    “All AMS 14C ages (Table 1) were recalibrated with the most recent MARINE20 calibration curve () and as recent findings on the marine radiocarbon reservoir effect off the Brazilian coast were published by , we considered a ΔR = -84 ± 125.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § Discussion

    The isotopic fractionation displayed by δ13Cplank may point to limited influx of 13C-depleted terrestrial organic matter and diminished deposition in terrestrial derived sediments.

    “In addition, the isotopic fractionation displayed by δ13Cplank may point to limited influx of 13C-depleted terrestrial organic matter and diminished deposition in terrestrial derived sediments.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Terrestrial input into oligotrophic waters carried by the Brazil Current alongshore southeastern Brazil provides an important nutrient source for oceanic biota.

  • May combine two claims.

    Interpretationreasoning
    § Discussion

    High (low) SSTs in the sub(tropical) western South Atlantic probably contributed to warm and moist (cool and dry) air towards the continent.

    “High (low) SSTs in the sub(tropical) western South Atlantic probably contributed to warm and moist (cool and dry) air towards the continent.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation
    § Discussion

    Precipitation variability in ESA and SESA was driven by a mechanism independent of SAMS/SACZ activity.

    “showed that precipitation variability in ESA and SESA was driven by a mechanism independent of SAMS/SACZ activity.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning
    § Discussion

    A gradual trend towards increasing precipitation in the northern portions of ESA may imply a relative increase in convective rainfall associated with a marked southward shift of the ITCZ during HS1.

    “A gradual trend towards increasing precipitation in the northern portions of ESA may imply a relative increase in convective rainfall associated with a marked southward shift of the ITCZ during HS1.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation
    § Discussion

    Low δ18O values in Botuverá Cave speleothems point at the Amazon basin as the dominant moisture source during HS1, which today fuels the SACZ.

    “A greater seasonal contrast is also supported by low δ18O values in Botuverá Cave speleothems that point at the Amazon basin as the dominant moisture source during HS1 (), which today fuels the SACZ.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § Discussion

    The δ13C in the western subtropical South Atlantic must be considered an open system, where the reservoir and fixation of light 12C by oceanic productivity is constantly compensated by run-off of terrestrial organic matter, resulting in no notable fractionation in the δ13Cplank record during HS1.

    “The δ13C in the western subtropical South Atlantic must be considered an open system, where the reservoir and fixation of light 12C by oceanic productivity is constantly compensated by run-off of terrestrial organic matter resulting in no notable fractionation in our δ13Cplank record during HS1.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Terrestrial input into oligotrophic waters carried by the Brazil Current alongshore southeastern Brazil provides an important nutrient source for oceanic biota.

  • May combine two claims.

    Interpretationown data
    § Discussion

    The southerly located Botuverá Cave in SESA seems to be unaffected by this oceanic sub(tropical) moisture source as its precipitation record reveals continuously dryer conditions, especially during austral winter.

    “In contrast, the southerly located Botuverá Cave in SESA seems to be unaffected by this oceanic sub(tropical) moisture source as its precipitation record reveals continuously dryer conditions, especially during austral winter.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductown data
    § Discussion

    A secondary source of n-alkanes that may bias the n-alkane MARs can be excluded, as the calculated carbon preference index (CPI) from Core M125-35-3 is at average 3.2, relatively high and comparable to modern soils, pointing to a predominance of well preserved terrestrial n-alkanes.

    “A secondary source of n-alkanes, which may bias the n-alkane MARs can be excluded, as the calculated carbon preference index (CPI) from Core M125-35-3 is at average 3.2 (not shown), thus relatively high and comparable to modern soils, pointing to a predominance of well preserved terrestrial n-alkanes (; ; ).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisecitation
    § Discussion

    Previous studies have emphasized the role of an intensification and/or expansion of the SACZ for providing enhanced moisture for ESA and SESA during HS1.

    “Previous studies have emphasized the role of an intensification and/or expansion of the SACZ for providing enhanced moisture for ESA and SESA during HS1 (; ; ; ).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation
    § Discussion

    Palynological studies from southern and southeastern Brazil indicate the dominance of Poaceae reflecting rather cold and dry conditions, while modern-like Araucaria forests, which are intolerant to long dry seasons, were absent.

    “This is supported by palynological studies from southern and southeastern Brazil indicating the dominance of Poaceae reflecting rather cold and dry conditions, while modern-like Araucaria forests, which are intolerant to long dry seasons, were absent (; ; ).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § Discussion

    Meltwater pulse 1a marks a threshold, facilitated by the broad shelf off SE Brazil, when transgression suddenly flooded a wide area, which functions as a sediment trap during interglacial high sea level stands.

    “Thus, we argue that meltwater pulse 1a marks a threshold, facilitated by the broad shelf off SE Brazil, when transgression suddenly flooded a wide area (Figure 1), which functions as a sediment trap during interglacial high sea level stands.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The broad shelf off SE Brazil functions as a sediment trap during interglacial high sea level stands.

  • May combine two claims.

    Interpretationreasoning
    § Discussion

    During HS1, SE trade winds delivering oceanic-sourced moisture were primarily responsible for enhanced precipitation in tropical ESA (e.g., at Paixão and Lapa Sem Fim Caves) and to a lesser degree in the south where they contributed to the slightly wetter conditions across the Paraíba do Sul catchment.

    “It thus appears that during HS1 SE trade winds delivering oceanic-sourced moisture were primarily responsible for enhanced precipitation in tropical ESA (e.g., at Paixão and Lapa Sem Fim Caves) and to a lesser degree in the south where they contributed to the slightly wetter conditions across the Paraíba do Sul catchment.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The Paraíba do Sul catchment is within the core region of the SACZ.

  • Classified as probably not a substantial claim.

    Study design and conductcitation
    § Materials and Methods

    The CRAN R package Bacon (version 2.5.7) was used to constrain the chronostratigraphy of Core M125-35-3.

    “As done in () we used the CRAN R package Bacon (version 2.5.7) () to constrain the chronostratigraphy of Core M125-35-3.”
    Quote in the paperSubstantial claim
95 of 95

  • The authors state this as an assumption.

    Crenarchaeol is specific to nitrifying marine mesophilic Thaumarchaeota.

    “which is assumed to be specific to nitrifying marine mesophilic Thaumarchaeota”

  • The authors state this as an assumption.

    The response of the internal C46 standard is congruent with that of measured GDGTs.

    “presuming a congruent response between the standard and measured GDGTs”

  • The paper relies on this without support.

    The δ13C of planktonic foraminifera shells reflects the carbon isotopic composition of dissolved inorganic carbon (DIC) in seawater during calcification.

    “The δ13C of planktonic foraminifera shells are used to reconstruct the carbon isotopic composition of dissolved inorganic carbon (DIC) in seawater during calcification.”

  • The paper relies on this without support.

    The terrigenous proxies in Core M125-35-3 reflect conditions in the Paraíba do Sul catchment.

    “Both, ln(Al/Si) and ln(K/Al) ratios indicate slightly wetter conditions across the catchment of the Paraíba do Sul during HS1 compared to the LGM (Figures 3A, B).”

  • The paper relies on this without support.

    Terrestrial input into oligotrophic waters carried by the Brazil Current alongshore southeastern Brazil provides an important nutrient source for oceanic biota.

    “Terrestrial input into oligotrophic waters carried by the Brazil Current alongshore southeastern Brazil would provide an important nutrient source for oceanic biota.”

  • The authors state this as an assumption.

    Enhanced marine productivity during higher terrestrial run-off increases deposition of carbonate and the relative content of Ca in the sediment.

    “which agrees with the presumption that enhanced marine productivity during higher terrestrial run-off increases deposition of carbonate and the relative content of Ca in the sediment ()”

  • The authors state this as an assumption.

    A slightly invigorated continental hydrological cycle and particularly a marked low sea level enhanced nutrient and organic matter flux into the western tropical South Atlantic during HS1, boosting oceanic productivity.

    “Thus, it is consistent to assume that a slightly invigorated continental hydrological cycle and particularly a marked low sea level enhanced nutrient and organic matter flux into the western tropical South Atlantic during HS1, boosting oceanic productivity.”

  • The paper relies on this without support.

    The Paraíba do Sul catchment is within the core region of the SACZ.

    “As the Paraíba do Sul catchment is within the core region of the SACZ”

  • The paper relies on this without support.

    The broad shelf off SE Brazil functions as a sediment trap during interglacial high sea level stands.

    “which functions as a sediment trap during interglacial high sea level stands”

  • The authors state this as an assumption.

    The late deglacial precipitation pattern associated with SACZ/SAMS variability was stabilized by the configuration of perpetually propagating non-stationary Rossby waves inhibiting sustained phases of extreme rainfall in SSESA such as during ~16 ka.

    “Thus, we assume, that late deglacial precipitation pattern associated with SACZ/SAMS variability was stabilized by the configuration of perpetually propagating non-stationary Rossby waves inhibiting sustained phases of extreme rainfall in SSESA such as during ~16 ka.”

  • The authors state this as an assumption.

    The quantity of oceanic-sourced moisture feeding SESA was greatly reduced during the YD because warming of the western tropical South Atlantic was much weaker compared to HS1.

    “we assume that the quantity of oceanic-sourced moisture feeding SESA was greatly reduced because warming of the western tropical South Atlantic was much weaker compared to HS1.”
11 of 11

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Different reservoir corrections stated for the same age calibration

    Minor

    The age-model methods specify a reservoir correction of −84 ± 125, whereas the note beneath Table 1 specifies −81 ± 124 for the calibrated ages.

1 of 1

Cites

Flagged first, then by citations

2 of the 135 references couldn’t be matched to a known paper.

Research works printed but not linked: 6

  1. Fleitmann, 2008, White Paper on “Speleothem-Based Climate Proxy Records”
  2. Gan, 2004, The South America Monsoon Circulation and Its Relationship to Rainfall Over West-Central Brazil, J. Climate, 17, 47, 10.1175/1520-0442(2004)017<0047:TSAMCA>2.0.CO;2 · DOI
  3. Liebmann, 2004, Subseasonal Variations of Rainfall in South America in the Vicinity of the Low-Level Jet East of the Andes and Comparison to Those in the South Atlantic Convergence Zone, J. Climate, 17, 3829, 10.1175/1520-0442(2004)017<3829:SVORIS>2.0.CO;2 · DOI
  4. Marengo, 2004, Climatology of the Low-Level Jet East of the Andes as Derived From the NCEP–NCAR Reanalyses: Characteristics and Temporal Variability, J. Climate, 17, 2261, 10.1175/1520-0442(2004)017<2261:COTLJE>2.0.CO;2 · DOI
  5. Masson-Delmotte, 2021, Ipc
  6. Tintelnot, 1995, Transport and Deposition of Fine-Grained Sediments on the Brazilian Continental Shelf as Revealed by Clay Mineral Distribution

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Authors
Meier, K. J. F., Jaeschke, A., Rethemeyer, J., Chiessi, C. M., Albuquerque, A. L. S., Wall, V., Friedrich, O., & Bahr, A.
Affiliations
  • Heidelberg University (DE)
  • University of Cologne (DE)
  • Universidade de São Paulo (BR)
Corresponding author
Meier, Karl J. F.
Venue
Frontiers in Marine Science
Publisher
Frontiers Media SA
Published
2022-06-30
Volume
9
ISSN
2296-7745 (ISSN-L)
DOI
10.3389/fmars.2022.878116
OpenAlex
W4283717864
Semantic Scholar
d93ea6226a85a5bbc439dcbfe7d3d3d83b8c663b
Cited by
10
References
135
Citations by year
2026: 2 · 2025: 4 · 2024: 4
FWCI
0.76
Type
journal article
Language
en
Open access
Licence
Locations
  • Frontiers in Marine Science (publishedVersion, cc-by)
  • Kölner Universitäts PublikationsServer (Universität zu Köln) (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
Funders
  • Deutsche Forschungsgemeinschaft (HO 5927/1-1 , BA 3809/14-1, 268236062, SFB1211)
  • Fundação de Amparo à Pesquisa do Estado de São Paulo (2018/15123-4, 2019/24349-9)
  • Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (88881.313535/201901)
  • Conselho Nacional de Desenvolvimento Científico e Tecnológico (s312458/2020-7)
  • Alexander von Humboldt-Stiftung
Topics
  • Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Geology and Paleoclimatology Research
  • Physical Sciences › Environmental Science › Global and Planetary Change › Climate variability and models
  • Physical Sciences › Earth and Planetary Sciences › Oceanography › Marine and environmental studies
Keywords
last deglaciation, South American Summer Monsoon, ocean-atmosphere feedback, Heinrich Stadial 1, South Atlantic Convergence Zone, lipid biomarkers, foraminiferal geochemistry, sediment elemental composition, heavy rainfall, sea surface temperature warming, nutrient release, paleohydrology, eastern Brazil, paleoclimate

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-16.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-16.

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