A 40-year global data set of visible-channel remote-sensing reflectances and coccolithophore bloom occurrence derived from the Advanced Very High Resolution Radiometer catalogue

Loveday, Benjamin R.; Smyth, Tim

doi:10.5194/essd-10-2043-2018

Cited by 12 publications

(17 citation statements)

References 37 publications

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“…However, if one follows the proposed scenario for 2001-2017, the TA increase in summer in 2008-2017 during the cooling phase in the NASPG could be linked to a weakening of calcification. In this region, this seems supported by the absence of coccolithophore blooms in recent years (2010-2017) as identified from remote-sensing reflectance records (Loveday and Smyth, 2018).…”

Section: Summer Trends For Different Periodsmentioning

confidence: 64%

Ocean carbonate system variability in the North Atlantic Subpolar surface water (1993–2017)

Leseurre¹,

Monaco²,

Reverdin³

et al. 2020

Biogeosciences

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Abstract. The North Atlantic is one of the major ocean sinks for natural and anthropogenic atmospheric CO2. Given the variability of the circulation, convective processes or warming–cooling recognized in the high latitudes in this region, a better understanding of the CO2 sink temporal variability and associated acidification needs a close inspection of seasonal, interannual to multidecadal observations. In this study, we investigate the evolution of CO2 uptake and ocean acidification in the North Atlantic Subpolar Gyre (50–64∘ N) using repeated observations collected over the last 3 decades in the framework of the long-term monitoring program SURATLANT (SURveillance de l'ATLANTique). Over the full period (1993–2017) pH decreases (−0.0017 yr−1) and fugacity of CO2 (fCO2) increases (+1.70 µatm yr−1). The trend of fCO2 in surface water is slightly less than the atmospheric rate (+1.96 µatm yr−1). This is mainly due to dissolved inorganic carbon (DIC) increase associated with the anthropogenic signal. However, over shorter periods (4–10 years) and depending on the season, we detect significant variability investigated in more detail in this study. Data obtained between 1993 and 1997 suggest a rapid increase in fCO2 in summer (up to +14 µatm yr−1) that was driven by a significant warming and an increase in DIC for a short period. Similar fCO2 trends are observed between 2001 and 2007 during both summer and winter, but, without significant warming detected, these trends are mainly explained by an increase in DIC and a decrease in alkalinity. This also leads to a pH decrease but with contrasting trends depending on the region and season (between −0.006 and −0.013 yr−1). Conversely, data obtained during the last decade (2008–2017) in summer show a cooling of surface waters and an increase in alkalinity, leading to a strong decrease in surface fCO2 (between −4.4 and −2.3 µatm yr−1; i.e., the ocean CO2 sink increases). Surprisingly, during summer, pH increases up to +0.0052 yr−1 in the southern subpolar gyre. Overall, our results show that, in addition to the accumulation of anthropogenic CO2, the temporal changes in the uptake of CO2 and ocean acidification in the North Atlantic Subpolar Gyre present significant multiannual variability, not clearly directly associated with the North Atlantic Oscillation (NAO). With such variability it is uncertain to predict the near-future evolution of air–sea CO2 fluxes and pH in this region. Thus, it is highly recommended to maintain long-term observations to monitor these properties in the next decade.

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Section: Summer Trends For Different Periodsmentioning

confidence: 64%

Ocean carbonate system variability in the North Atlantic Subpolar surface water (1993–2017)

Leseurre¹,

Monaco²,

Reverdin³

et al. 2020

Biogeosciences

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“…Determination of the coccolith content (CC) was performed through establishing mixed-layer depth (MLD) within the bloom area. The climatology of Montegut et al (2004) was applied. The identified areas of Emiliania huxleyi blooms with retrieved concentrations of coccoliths were overlapped by the respective climatological MLD fields, and for each pixel, the value of MLD was further used to calculate CC.…”

Section: Coccolith Content Particulate Inorganic Carbon Andmentioning

confidence: 99%

“…Data on MLD were derived from the Montegut climatology (Montegut et al, 2004). Data on bathymetry inherent in the target seas were taken from the website http:// www.ngdc.noaa.gov/mgg/bathymetry/arctic/arctic.html (last access: 10 January 2019; Jakobsson et al, 2012).…”

Section: Data Sourcesmentioning

confidence: 99%

A synthetic satellite dataset of the spatio-temporal distributions of <i>Emiliania huxleyi</i> blooms and their impacts on Arctic and sub-Arctic marine environments (1998–2016)

Kondrik

Kazakov

Pozdnyakov

2019

Earth Syst. Sci. Data

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Abstract. A 19-year (1998–2016) continuous dataset is presented of coccolithophore Emiliania huxleyi distributions and activity, i.e. the release of CaCO3 in water and the decrease of uptake of dissolved CO2 by Emiliania huxleyi cells (e.g. Kondrik et al., 2018a), in Arctic and sub-Arctic seas. The dataset is based on optical remote-sensing data (mostly OC CCI data) with assimilation of different relevant in situ observations, preprocessed with authorial algorithms. Alongside bloom locations, we provide both detailed information on E. huxleyi impacts on carbon balance and the sub-datasets of quantified coccolith concentrations, particulate inorganic carbon content and CO2 partial pressure in water driven by coccolithophores. All data are presented on a regular 4×4 km grid at a temporal resolution of 8 days. The paper describes the theoretical and methodological basis for all processing and modelling steps. The data are available on Zenodo: https://doi.org/10.5281/zenodo.1402033.

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“…In addition, one cannot exclude the impact of blooms of coccolithophorids observed in the NASPG, as variability of such blooms may also impact on TA concentrations and thus deviate from the TA/S regional relation. Recently, Loveday and Smyth (2018) show significant differences of such blooms over decades in the North Atlantic. An interesting topic would be to re-explore TA distribution and TA/S relations for different periods.…”

Section: C16mentioning

confidence: 99%

Responses to review 2 (Are Olsen)

Leseurre¹

2019

Preprint

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Review 2 (Are Olsen): "This contribution presents the trends in a very impressive set of data from the western subpolar North Atlantic, collected within the framework of the SURATLANT program. While the paper presents the data and trends more or less adequately, it fails in properly attributing them to (climatic + oceanographic + biological) drivers. These aspects are C1 BGD Interactive comment Printer-friendly version Discussion paper unclear, speculative, and somewhat confused. As such, major revisions are required. My major comments are:" We thank Are Olsen for his fast review, comments and questions that will be taken into account when revising the manuscript. Below we list our responses before preparing a revised manuscript. 1. Samples are collected two to four times a year. My sense is that with such rare sampling one might be very prone to getting false trends because of differences in the timing of the data collection, also in combination with timing of the spring bloom. For example, the strong increase in region C+D+E summer DIC in 2001-2008 might be generated by earlier sampling/later spring bloom. "While some effort seems to have been taken to deal with this; reconstructed data; it is not quite clear how this is done, and how well it works. Some improvement is needed in this description (page 5 lines 1-19). Is it possible to test this scheme by using data from a year with sampling in all of the months used (e.g. Jan-March)? At least for SST and SSS this can be done as there should be continuous TSG data vailable, and for fCO2 there are data available from the VOSs Nuka Arctica and Atlantic Companion, which crosses the study area. These can be retrieved from SOCAT and used to test the method". Response: We fully agree with the reviewer. For the analysis of trends, one should take care of the timing of sampling especially in summer (as well as different tracks for some transects). This is why previous studies focused on winter data (e.g. Metzl et al., 2010; Fröb et al., 2019). Here, in addition to winter 2008-2017 not previously analyzed, we also tried for the first time to evaluate the trends in summer (June-July-August), i.e. after the spring bloom that generally occurs in April-May-June (with a date variable between regions and dates). Do we detect (or not) different view on the trends when comparing winter and summer? On average for 1993-2017, we observed that DIC and fCO2 increase (and pH decrease) in both winter and summer (but with different rates). C2 BGD Interactive comment Printer-friendly version Discussion paper Results are much more different when trends are limited to short periods. Concerning the "strong increase in region C+D+E summer DIC in 2001-2008". This is apparently driven by low DIC observed in summer 2001 and high DIC in summer 2007 (medium concentrations observed in 2004-2005, but no data in 2006). Note that for this particular summer 2007 transect samples were taken in early August 2007 and thus correction to standardize to mid-July should not introduce suspicious bias. As sugge...

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A 40-year global data set of visible-channel remote-sensing reflectances and coccolithophore bloom occurrence derived from the Advanced Very High Resolution Radiometer catalogue

Cited by 12 publications

References 37 publications

Ocean carbonate system variability in the North Atlantic Subpolar surface water (1993–2017)

Ocean carbonate system variability in the North Atlantic Subpolar surface water (1993–2017)

A synthetic satellite dataset of the spatio-temporal distributions of <i>Emiliania huxleyi</i> blooms and their impacts on Arctic and sub-Arctic marine environments (1998–2016)

Responses to review 2 (Are Olsen)

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A 40-year global data set of visible-channel remote-sensing reflectances and coccolithophore bloom occurrence derived from the Advanced Very High Resolution Radiometer catalogue

Cited by 12 publications

References 37 publications

Ocean carbonate system variability in the North Atlantic Subpolar surface water (1993–2017)

Ocean carbonate system variability in the North Atlantic Subpolar surface water (1993–2017)

A synthetic satellite dataset of the spatio-temporal distributions of &lt;i&gt;Emiliania huxleyi&lt;/i&gt; blooms and their impacts on Arctic and sub-Arctic marine environments (1998–2016)

Responses to review 2 (Are Olsen)

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A synthetic satellite dataset of the spatio-temporal distributions of <i>Emiliania huxleyi</i> blooms and their impacts on Arctic and sub-Arctic marine environments (1998–2016)