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Cited by 134Oceanographic and Atmospheric ProcessesClimate variability and modelsMarine and coastal ecosystems

Canary current upwelling: More or less?

Open access
Barton, E.D., Field, D.B., Roy, C.·2013·Progress in Oceanography
DOI 10.1016/j.pocean.2013.07.007
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Abstract

It has been hypothesized that coastal upwelling in the four major eastern boundary current systems might be intensified as global warming could result in a greater land-sea temperature gradient and hence strengthen alongshore winds. Recent research has suggested a substantial increase of upwelling intensity off Northwest Africa. Evidence there is based on the derivation of a proxy for upper ocean temperatures from the alkenone unsaturation index (U37K') derived from two sediment cores recovered off Cape Ghir, Morocco. An accelerating decrease of over 1. °C during the last century was concluded for near surface temperature near the Cape. Support for this conclusion was found in an increase in Bakun's upwelling index for the same area. The evidence for a general intensification of upwelling within the whole Canary current upwelling system is examined here. Using available estimates of wind from PFEL, NCAR/NCEP, ECMWF, ICOADS and WASWind plus measured wind data from coastal meteorological stations, no evidence of a coherent intensification in winds at the regional scale off Northwest Africa is found. Moreover, sea surface temperature records from ships-of-opportunity (ICOADS data set) and also from the Pathfinder satellite AVHRR data set show a significant and correlated increase at all latitudes in the region, including in the area around Cape Ghir. It is concluded that there is no evidence for a general increase in upwelling intensity off Northwest Africa or Iberia. The apparent lowering of SST off Cape Ghir indicated by the alkenone unsaturation index can be explained by coccolithophorids (phytoplankton from which the U37K' signal is derived) living deeper in the water column. The distribution of most phytoplankton (including coccolithophorids) will deepen and have less overlap with mixed layer temperatures as the ocean warms, resulting in a near surface temperature estimate that is increasingly biased by subsurface temperatures and lower than the actual SST. © 2013 Elsevier Ltd.

AI snapshot

Written from the paper’s full text.

TL;DR

The paper tests the hypothesis that coastal upwelling in the Canary Current system has intensified, and finds no evidence of a coherent regional increase in upwelling-favourable winds off Northwest Africa or Iberia. It argues that the apparent alkenone-derived SST cooling off Cape Ghir is an artefact of coccolithophorids living deeper in the water column as the ocean warms.

Key findings

  • Using wind estimates from PFEL, NCAR/NCEP, ECMWF, ICOADS and WASWind plus measured wind data from coastal meteorological stations, "no evidence of a coherent intensification in winds at the regional scale off Northwest Africa is found."
  • Sea surface temperature records from ships-of-opportunity (ICOADS) and the Pathfinder satellite AVHRR data set "show a significant and correlated increase at all latitudes in the region, including in the area around Cape Ghir."
  • The authors conclude "there is no evidence for a general increase in upwelling intensity off Northwest Africa or Iberia," in direct contrast to earlier studies (e.g. McGregor et al. 2007, who reported a 1.2 °C SST reduction off Cape Ghir over the last century, and Narayan et al. 2010).
  • The apparent lowering of SST off Cape Ghir from the alkenone unsaturation index (U^K′_37) is explained by coccolithophorids living deeper in the water column; as the ocean warms, their distribution deepens and overlaps less with mixed-layer temperatures, biasing the near-surface temperature estimate low relative to actual SST.

Methods

  • Design: re-examination of the evidence for general intensification of upwelling across the whole Canary Current upwelling system, using publicly available wind and SST data sets for the North Atlantic upwelling region between Dakar, Senegal (15°N) and Galicia, Spain (43°N).
  • Data: wind from PFEL, NCAR/NCEP, ECMWF, ICOADS and WASWind, plus measured wind from coastal meteorological stations; SST from ICOADS ships-of-opportunity and Pathfinder AVHRR satellite data; sediment-core alkenone (U^K′_37) proxy records from two cores off Cape Ghir, Morocco (from McGregor et al.).
  • Analysis: documentation of temporal trends in atmospheric forcing and oceanic response, consideration of factors affecting reliability of the different wind and SST time series, and exploration of the SST–alkenone proxy temperature relationship.

Limitations

  • The paper states that "the evidence that wind velocity is increasing and SST decreasing in the NW African upwelling region as a whole has many uncertainties," and notes that different analyses give conflicting results (e.g. Pardo et al. found weakening, Narayan et al. found increasing upwelling intensity).
  • Evident from the supplied text: only the abstract, introduction and the start of the Data section (pages 1–3 of 42) are available, so the paper's detailed results, statistical tests and its own stated limitations section are not present in the provided fragment.

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

Integrity signals

Registry

Crossref · 10.1016/j.pocean.2013.07.007

Cites

62 of 62 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

2 of 11 cited sources checked · 2 supported · 0 flagged

  • Findingown data
    § Abstract

    Sea surface temperature records from ships-of-opportunity (ICOADS data set) and from the Pathfinder satellite AVHRR data set show a significant and correlated increase at all latitudes in the region, including in the area around Cape Ghir.

    “Moreover, sea surface temperature records from ships-of-opportunity (ICOADS data set) and also from the Pathfinder satellite AVHRR data set show a significant and correlated increase at all latitudes in the region, including in the area around Cape Ghir.”
    Quote in the paperSubstantial claim
  • Findingown data
    § Abstract

    No evidence of a coherent intensification in winds at the regional scale off Northwest Africa is found using available wind estimates from PFEL, NCAR/NCEP, ECMWF, ICOADS and WASWind plus measured wind data from coastal meteorological stations.

    “Using available estimates of wind from PFEL, NCAR/NCEP, ECMWF, ICOADS and WASWind plus measured wind data from coastal meteorological stations, no evidence of a coherent intensification in winds at the regional scale off Northwest Africa is found.”
    Quote in the paperSubstantial claim
  • Premisecitation
    § 1. Introduction

    McGregor et al. (2007) found strong support for the hypothesis through evidence of a dramatic lowering of inferred SSTs in the northwest African upwelling region over the last century.

    “More recently, McGregor et al. (2007) found strong support for the hypothesis through evidence of a dramatic lowering of inferred SSTs in the northwest African upwelling region over the last century.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites McGregor et al., 2007 source
  • Interpretationown data
    § Abstract

    There is no evidence for a general increase in upwelling intensity off Northwest Africa or Iberia.

    “It is concluded that there is no evidence for a general increase in upwelling intensity off Northwest Africa or Iberia.”
    • Also stated in: § 1. Introduction · boosted
      “Our results clearly indicate that there is no evidence for increasing intensity of upwelling along this seaboard, in direct contrast to earlier studies.”
    Quote in the paperSubstantial claim
  • Premisecitation
    § 1. Introduction

    The reported northward encroachment of more sub-tropical and tropical species of fish is incongruent with decreasing temperatures in this coastal zone.

    “For example, the reported northward encroachment of more sub-tropical and tropical species of fish (Quéro et al., 1998; Brander et al., 2003; Graham & Harrod, 2009) is incongruent with decreasing temperatures in this coastal zone.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Quéro et al., 1998

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites Brander et al., 2003 source
    • cites Graham & Harrod, 2009 source
  • Classified as probably not a substantial claim. 4
  • May combine two claims. 2

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

    Premisecitation
    § 1. Introduction

    Pardo et al. found weakening of the upwelling intensity in the Iberian/Canary and NW African regions.

    “Pardo et al. found “weakening of the upwelling intensity in the Iberian/Canary and NW African regions”.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites Pardo et al., 2011 source

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

    Premisecitation
    § 1. Introduction

    More detailed studies such as Narayan et al. (2010) and Pardo et al. (2011) have examined long-term variation in the Canaries and other upwelling zones with varied results.

    “Other more detailed studies like Narayan et al. (2010) and Pardo et al. (2011) have examined long term variation in the Canaries and other upwelling zones with varied results.”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites Narayan et al., 2010 source
    • cites Pardo et al., 2011 source

  • May combine two claims.

    Premisecitation
    § 1. Introduction

    McGregor et al.'s alkenone unsaturation index indicates a reduction of sea surface temperature in the Cape Ghir upwelling of 1.2°C over the last century, coincident with the observed increase in atmospheric CO2 levels.

    “Their alkenone unsaturation index indicates a reduction of sea surface temperature (SST) in the Cape Ghir upwelling of 1.2oC over the last century, coincident with the observed increase in atmospheric CO2 levels.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites McGregor et al., 2007 source

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

    Premisecitation
    § 1. Introduction

    Bakun (1990) presented evidence of a tendency for stronger upwelling in the Californian, Iberian, Moroccan and Peruvian areas during the period from 1945 to 1985.

    “Bakun (1990) presented evidence of a tendency for stronger upwelling in the Californian, Iberian, Moroccan and Peruvian areas during the period from 1945 to 1985.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Bakun, 1990 source

  • May combine two claims.

    Interpretationreasoning
    § Abstract

    The distribution of most phytoplankton, including coccolithophorids, will deepen and have less overlap with mixed layer temperatures as the ocean warms, resulting in a near surface temperature estimate that is increasingly biased by subsurface temperatures and lower than the actual SST.

    “The distribution of most phytoplankton (including coccolithophorids) will deepen and have less overlap with mixed layer temperatures as the ocean warms, resulting in a near surface temperature estimate that is increasingly biased by subsurface temperatures and lower than the actual SST.”
    Quote in the paperSubstantial claim

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

    Premisecitation
    § 1. Introduction

    Global studies of trends in Large Marine Ecosystems, including the Canary Current LME, concluded that the most striking result is consistent warming by amounts exceeding 0.6°C over 25 years in mid to low latitudes.

    “In global studies of trends in Large Marine Ecosystems, including the Canary Current LME (Belkin, 2009; Sherman et al., 2009), it was concluded that the “most striking result is the consistent warming” by amounts exceeding 0.6oC over 25 years in mid to low latitudes.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Belkin, 2009 source
    • cites Sherman et al., 2009 source
6 of 6

  • The paper relies on this without support.

    The UK’37 alkenone unsaturation index signal is derived from coccolithophorids.

    “coccolithophorids (phytoplankton from which the View the MathML sourceU37K′ signal is derived)”
1 of 1

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Barton et al. conclude no intensification in winds off Northwest Africa.

    “They therefore conclude no intensification in winds off Northwest Africa.”

    From Recent Trends in SST, Chl‐<i>a</i>, Productivity and Wind Stress in Upwelling and Open Ocean Areas in the Upper Eastern North Atlantic Subtropical Gyre (2021) · cites this paper as Barton et al. (2013)

    The Introduction (p. 3) says evidence that wind velocity is increasing across the Northwest African upwelling region has many uncertainties, and concludes there is no evidence for increasing upwelling intensity. That supports the general direction of the claim, but the stated conclusion concerns upwelling, not specifically an absence of wind intensification. (LLM, conf=0.79)

    Experimental — accuracy not yet measured

  • The Bakun Hypothesis was originally supported by emerging interregional patterns of observed sea-surface wind stress and has been periodically tested against time series of observed data in all four regional eastern boundary upwelling systems.

    “This idea was originally supported by emerging interregional patterns of observed sea-surface wind stress, and has been periodically tested against time series of observed data in all four regional EBUS [12,13].”

    From Anticipated Effects of Climate Change on Coastal Upwelling Ecosystems (2015) · cites this paper as [12]

    Split into 2 atoms — 0 confirmed, 2 partially supported, 0 disputed, 0 misattributed, 0 unverifiable. Expand the claim to see per-atom verdicts.

    Experimental — accuracy not yet measured

  • Barton et al. (2013) underline variations in different data sets and locations, even positive and negative trends for the same location.

    “Barton et al. (2013) support this discussion by underlining the variations in different data sets and locations (even positive and negative trends for the same location).”

    From Recent Trends in SST, Chl‐<i>a</i>, Productivity and Wind Stress in Upwelling and Open Ocean Areas in the Upper Eastern North Atlantic Subtropical Gyre (2021) · cites this paper as Barton et al. (2013)

Cites

Flagged first, then by citations

2 of the 64 references couldn’t be matched to a known paper.

Research works printed but not linked: 3

  1. Isemer, H.-J., 1995. Trends in marine surface winds speed: ocean weather stations versus voluntary observing ships. In: Proceedings of the International COADS Workshop, Kiel, Germany, NOAA Environmental Research Laboratories and Institut fur Meereskunde, pp. 68–84.
  2. Prahl, 2007, Biogeochemical assessment of alkenone export depth in the summertime euphotic zone of the Gulf of California, Extended Abstracts Presented at the ACS National Meeting, 47, 483
  3. Smith, 1968, Upwelling, Oceanography and Marine Biology, Annual Review, 6, 11

Cited by

Sorted by citations

Related

Authors
Barton, E. D., Field, D. B., & Roy, C.
Affiliations
  • Instituto de Investigacións Mariñas (ES)
  • Hawaii Pacific University (US)
  • Centre National de la Recherche Scientifique (FR)
Corresponding author
Barton, E.D.
Venue
Progress in Oceanography
Publisher
Elsevier BV
Published
2013-09
Volume
116
Pages
167-178
ISSN
0079-6611 (ISSN-L)
DOI
10.1016/j.pocean.2013.07.007
OpenAlex
W2004932320
Cited by
134
References
64
Citations by year
2026: 7 · 2025: 5 · 2024: 13 · 2023: 10 · 2022: 19 · 2021: 11 · 2020: 14 · 2019: 10 · 2018: 11 · 2017: 8 · 2016: 8 · 2015: 11 · 2014: 4 · 2013: 3
FWCI
6.10
Type
journal article
Language
en
Open access
Licence
Locations
  • Progress In Oceanography (publishedVersion)
  • HAL (Le Centre pour la Communication Scientifique Directe) (submittedVersion)
  • DIGITAL.CSIC (Spanish National Research Council (CSIC)) (submittedVersion, other-oa)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Oceanography › Oceanographic and Atmospheric Processes
  • Physical Sciences › Environmental Science › Global and Planetary Change › Climate variability and models
  • Physical Sciences › Earth and Planetary Sciences › Oceanography › Marine and coastal ecosystems
Keywords
global warming, alkenone unsaturation index, sea surface temperature, coccolithophores, mixed layer temperature, alongshore winds, Maghreb, Iberia, eastern boundary currents

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