Mapping of the air–sea CO2 flux in the Arctic Ocean and its adjacent seas: Basin-wide distribution and seasonal to interannual variability

Yasunaka, Sayaka; Murata, Akihiko; Watanabe, Eiji; Chierici, Melissa; Fransson, Agneta; Heuven, Steven van; Hoppema, Mario; Ishii, Masayoshi; Johannessen, Truls; Kosugi, Naohiro; Lauvset, Siv K.; Mathis, Jeremy T.; Nishino, Shigeto; Omar, Abdirahman M; Olsen, Are; Sasano, Daisuke; Takahashi, Taro; Wanninkhof, Rik

doi:10.1016/j.polar.2016.03.006

Cited by 79 publications

(120 citation statements)

References 50 publications

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“…The observed pCO 2 data (Fig. 4 in Yasunaka et al, 2016), especially since 2005, have clearly shown an annual cycle compatible with the SOCAT seasonal flux variability.…”

Section: Discussionsupporting

confidence: 62%

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Effect of gas-transfer velocity parameterization choice on air–sea CO2 fluxes in the North Atlantic Ocean and the European Arctic

Wróbel

Piskozub

2016

Ocean Sci.

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Abstract. The oceanic sink of carbon dioxide (CO 2 ) is an important part of the global carbon budget. Understanding uncertainties in the calculation of this net flux into the ocean is crucial for climate research. One of the sources of the uncertainty within this calculation is the parameterization chosen for the CO 2 gas-transfer velocity. We used a recently developed software toolbox, called the FluxEngine , to estimate the monthly air-sea CO 2 fluxes for the extratropical North Atlantic Ocean, including the European Arctic, and for the global ocean using several published quadratic and cubic wind speed parameterizations of the gastransfer velocity. The aim of the study is to constrain the uncertainty caused by the choice of parameterization in the North Atlantic Ocean. This region is a large oceanic sink of CO 2 , and it is also a region characterized by strong winds, especially in winter but with good in situ data coverage. We show that the uncertainty in the parameterization is smaller in the North Atlantic Ocean and the Arctic than in the global ocean. It is as little as 5 % in the North Atlantic and 4 % in the European Arctic, in comparison to 9 % for the global ocean when restricted to parameterizations with quadratic wind dependence. This uncertainty becomes 46, 44, and 65 %, respectively, when all parameterizations are considered. We suggest that this smaller uncertainty (5 and 4 %) is caused by a combination of higher than global average wind speeds in the North Atlantic (> 7 ms −1 ) and lack of any seasonal changes in the direction of the flux direction within most of the region. We also compare the impact of using two different in situ pCO 2 data sets (Takahashi et al. (2009) and Surface Ocean CO 2 Atlas (SOCAT) v1.5 and v2.0, for the flux calculation. The annual fluxes using the two data sets differ by 8 % in the North Atlantic and 19 % in the European Arctic. The seasonal fluxes in the Arctic computed from the two data sets disagree with each other possibly due to insufficient spatial and temporal data coverage, especially in winter.

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“…The observed pCO 2 data (Fig. 4 in Yasunaka et al, 2016), especially since 2005, have clearly shown an annual cycle compatible with the SOCAT seasonal flux variability.…”

Section: Discussionsupporting

confidence: 62%

“…It is impossible to decide in this study which data set is more accurate as only new data can settle this. However, new data, not included in the SOCAT versions we used, have been available due to the recent analysis by Yasunaka et al (2016). The observed pCO 2 data (Fig.…”

Section: Discussionmentioning

confidence: 99%

Effect of gas-transfer velocity parameterization choice on air–sea CO2 fluxes in the North Atlantic Ocean and the European Arctic

Wróbel

Piskozub

2016

Ocean Sci.

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“…Extrapolated flux estimates reported by Yasunaka et al . [] for the Barents Sea, the Chukchi Sea, and an average for the whole Arctic Ocean found the strongest sea‐air CO 2 flux (i.e., ocean CO 2 influx) of approximately −12 mmol m −2 d −1 occurred in winter in the ice‐free regions of the Barents Sea (due to storm events). The summer CO 2 influxes were highest in the Chukchi Sea in summer of −10 mmol m −2 d −1 .…”

Section: Discussionmentioning

confidence: 99%

Effects of sea‐ice and biogeochemical processes and storms on under‐ice water fCO₂ during the winter‐spring transition in the high Arctic Ocean: Implications for sea‐air CO₂ fluxes

et al. 2017

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We performed measurements of carbon dioxide fugacity (fCO2) in the surface water under Arctic sea ice from January to June 2015 during the Norwegian young sea ICE (N‐ICE2015) expedition. Over this period, the ship drifted with four different ice floes and covered the deep Nansen Basin, the slopes north of Svalbard, and the Yermak Plateau. This unique winter‐to‐spring data set includes the first winter‐time under‐ice water fCO2 observations in this region. The observed under‐ice fCO2 ranged between 315 µatm in winter and 153 µatm in spring, hence was undersaturated relative to the atmospheric fCO2. Although the sea ice partly prevented direct CO2 exchange between ocean and atmosphere, frequently occurring leads and breakup of the ice sheet promoted sea‐air CO2 fluxes. The CO2 sink varied between 0.3 and 86 mmol C m−2 d−1, depending strongly on the open‐water fractions (OW) and storm events. The maximum sea‐air CO2 fluxes occurred during storm events in February and June. In winter, the main drivers of the change in under‐ice water fCO2 were dissolution of CaCO3 (ikaite) and vertical mixing. In June, in addition to these processes, primary production and sea‐air CO2 fluxes were important. The cumulative loss due to CaCO3 dissolution of 0.7 mol C m−2 in the upper 10 m played a major role in sustaining the undersaturation of fCO2 during the entire study. The relative effects of the total fCO2 change due to CaCO3 dissolution was 38%, primary production 26%, vertical mixing 16%, sea‐air CO2 fluxes 16%, and temperature and salinity insignificant.

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“…Laruelle et al (2014) used more than 3 × 10 6 pCO 2 measurements from the SOCATv2 database Bakker et al, 2016 to demonstrate very strong disparities in air-seawater CO 2 exchange at the regional scale and pro-G. G. Laruelle et al: Global coastal pCO 2 maps nounced seasonal variations, especially at temperate latitudes. Furthermore, it was suggested that, despite the presence of a seasonally varying sea-ice cover, Arctic continental shelves are a regional hotspot of CO 2 uptake (Bates et al, 2006;Laruelle et al, 2014;Yasunaka et al, 2016). However, even with this much larger dataset compared to previous studies, large regions of the global coastal ocean remained either void of data or very poorly monitored in space and time, including the seasonal cycle.…”

Section: Introductionmentioning

confidence: 91%

Global high-resolution monthly pCO2 climatology for the coastal ocean derived from neural network interpolation

Laruelle

Landschützer

Gruber³

et al. 2017

Biogeosciences

146

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Abstract. In spite of the recent strong increase in the number of measurements of the partial pressure of CO 2 in the surface ocean (pCO 2 ), the air-sea CO 2 balance of the continental shelf seas remains poorly quantified. This is a consequence of these regions remaining strongly under-sampled in both time and space and of surface pCO 2 exhibiting much higher temporal and spatial variability in these regions compared to the open ocean. Here, we use a modified version of a two-step artificial neural network method (SOM-FFN; to interpolate the pCO 2 data along the continental margins with a spatial resolution of 0.25 • and with monthly resolution from 1998 to 2015. The most important modifications compared to the original SOM-FFN method are (i) the much higher spatial resolution and (ii) the inclusion of sea ice and wind speed as predictors of pCO 2 . The SOM-FFN is first trained with pCO 2 measurements extracted from the SOCATv4 database. Then, the validity of our interpolation, in both space and time, is assessed by comparing the generated pCO 2 field with independent data extracted from the LD-VEO2015 database. The new coastal pCO 2 product confirms a previously suggested general meridional trend of the annual mean pCO 2 in all the continental shelves with high values in the tropics and dropping to values beneath those of the atmosphere at higher latitudes. The monthly resolution of our data product permits us to reveal significant differences in the seasonality of pCO 2 across the ocean basins. The shelves of the western and northern Pacific, as well as the shelves in the temperate northern Atlantic, display particularly pronounced seasonal variations in pCO 2, while the shelves in the southeastern Atlantic and in the southern Pacific reveal a much smaller seasonality. The calculation of temperature normalized pCO 2 for several latitudes in different oceanic basins confirms that the seasonality in shelf pCO 2 cannot solely be explained by temperature-induced changes in solubility but are also the result of seasonal changes in circulation, mixing and biological productivity. Our results also reveal that the amplitudes of both thermal and nonthermal seasonal variations in pCO 2 are significantly larger at high latitudes. Finally, because this product's spatial extent includes parts of the open ocean as well, it can be readily merged with existing global open-ocean products to produce a true global perspective of the spatial and temporal variability of surface ocean pCO 2 .

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Mapping of the air–sea CO2 flux in the Arctic Ocean and its adjacent seas: Basin-wide distribution and seasonal to interannual variability

Cited by 79 publications

References 50 publications

Effect of gas-transfer velocity parameterization choice on air–sea CO<sub>2</sub> fluxes in the North Atlantic Ocean and the European Arctic

Effect of gas-transfer velocity parameterization choice on air–sea CO<sub>2</sub> fluxes in the North Atlantic Ocean and the European Arctic

Effects of sea‐ice and biogeochemical processes and storms on under‐ice water fCO₂ during the winter‐spring transition in the high Arctic Ocean: Implications for sea‐air CO₂ fluxes

Global high-resolution monthly <i>p</i>CO<sub>2</sub> climatology for the coastal ocean derived from neural network interpolation

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Mapping of the air–sea CO2 flux in the Arctic Ocean and its adjacent seas: Basin-wide distribution and seasonal to interannual variability

Cited by 79 publications

References 50 publications

Effect of gas-transfer velocity parameterization choice on air–sea CO&lt;sub&gt;2&lt;/sub&gt; fluxes in the North Atlantic Ocean and the European Arctic

Effect of gas-transfer velocity parameterization choice on air–sea CO&lt;sub&gt;2&lt;/sub&gt; fluxes in the North Atlantic Ocean and the European Arctic

Effects of sea‐ice and biogeochemical processes and storms on under‐ice water fCO2 during the winter‐spring transition in the high Arctic Ocean: Implications for sea‐air CO2 fluxes

Global high-resolution monthly &lt;i&gt;p&lt;/i&gt;CO&lt;sub&gt;2&lt;/sub&gt; climatology for the coastal ocean derived from neural network interpolation

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Effect of gas-transfer velocity parameterization choice on air–sea CO<sub>2</sub> fluxes in the North Atlantic Ocean and the European Arctic

Effect of gas-transfer velocity parameterization choice on air–sea CO<sub>2</sub> fluxes in the North Atlantic Ocean and the European Arctic

Effects of sea‐ice and biogeochemical processes and storms on under‐ice water fCO₂ during the winter‐spring transition in the high Arctic Ocean: Implications for sea‐air CO₂ fluxes

Global high-resolution monthly <i>p</i>CO<sub>2</sub> climatology for the coastal ocean derived from neural network interpolation