Arctic Ocean CO<sub>2</sub> uptake: an improved multiyear estimate of the air–sea CO<sub>2</sub> flux incorporating chlorophyll <i>a</i> concentrations

Abstract

Abstract. We estimated monthly air–sea CO2 fluxes in the Arctic Ocean and its adjacent seas north of 60∘ N from 1997 to 2014. This was done by mapping partial pressure of CO2 in the surface water (pCO2w) using a self-organizing map (SOM) technique incorporating chlorophyll a concentration (Chl a), sea surface temperature, sea surface salinity, sea ice concentration, atmospheric CO2 mixing ratio, and geographical position. We applied new algorithms for extracting Chl a from satellite remote sensing reflectance with close examination of uncertainty of the obtained Chl a values. The overall relationship between pCO2w and Chl a was negative, whereas the relationship varied among seasons and regions. The addition of Chl a as a parameter in the SOM process enabled us to improve the estimate of pCO2w, particularly via better representation of its decline in spring, which resulted from biologically mediated pCO2w reduction. As a result of the inclusion of Chl a, the uncertainty in the CO2 flux estimate was reduced, with a net annual Arctic Ocean CO2 uptake of 180 ± 130 Tg C yr−1. Seasonal to interannual variation in the CO2 influx was also calculated.

Air‐Sea CO2 Flux Estimates in Stratified Arctic Coastal Waters: How Wrong Can We Be?

“…In contrast, samples from the shallowest rosette bottles (at 1–3 m) indicated a drawdown nearly half as large (Table S3, 2014 data). Extrapolating over a 90‐day ice melt period and beyond the area of an individual cruise, as when data are incorporated into regional or Earth system models, would compound this error; for example, an error such as what we observed, extrapolated over the entire Arctic basin, would constitute 15% of the total annual drawdown estimated for the high Arctic Ocean (Yasunaka et al, ). Further, strong gradients in TIC and A T between samples collected by the surface rosette and from small boats (Figure ) indicate that even the shallowest rosette samples often do not accurately represent undisturbed surface waters.…”

“…As a whole, the Arctic Ocean currently appears to serve as a net atmospheric CO 2 sink (e.g., Evans et al, ; Land et al, ; Yasunaka et al, ). However, that net sink is likely sensitive to the seasonal progression of ice coverage (e.g., Else, Galley, et al, ; Evans et al, ) and presumably river runoff, which appears to be increasing (e.g., Dai et al, ; Déry et al, ).…”

Impacts of Temperature, CO2, and Salinity on Phytoplankton Community Composition in the Western Arctic Ocean

“…For example, the predictions of temperature rise at the end of this century ranged about 3 • C in surface mixed layer (∼100 m) or 6-13 • C in the surface air under the RCP8.5 scenario (Overland et al, 2014). Environmental conditions at the surface of the Chukchi Sea are highly dynamic in space and time ranging between 0 and 8 • C for temperature, between <250 and ∼350 µatm pCO 2 and between 24 and 32 for salinity Yamamoto-Kawai et al, 2016;Yasunaka et al, 2018). Extremely high CO 2 levels ranging from 700 to >1000 µatm have been observed just below the surface mixed layer from September to October (Yamamoto-Kawai et al, 2016).…”

Review on ocean acidification and carbon cycling in the Arctic Ocean

“…Cai等人 [42] 基于全球边缘海的 分析数据, 认为整个北冰洋的大气CO 2 吸收速率为41 Tg C a −1 . 然而Bates等人 [43] [44] . 总 体而言, 北冰洋对大气中 CO 2 吸收速率仍然存在很大不确定性.…”

“…最近实测资料和模式研究的结果表明, CO 2 吸 收、海冰融化和次表层水的上涌造成表层海水的酸 化 [16,17,44,62] , 太平洋冬季水输运造成的次表层海水的 酸化 [17] 以及北大西洋水携带人为CO 2 下沉输运导致 的中层水酸化 [61] . 然而, 国外的西北冰洋酸化研究 面截面积增长了6倍, 平均每年增长1.5%.…”