Early Wintertime CO₂ Uptake in the Western Arctic Ocean

Abstract

The ocean is estimated to be absorbing about 2.5 ± 0.6 GtC yr −1 of anthropogenic carbon dioxide (CO 2 ) and to have absorbed since 1959 about 24% of the anthropogenic CO 2 that has been released into the atmosphere by human activities such as fossil fuel burning, deforestation, and cement production (Friedlingstein et al., 2020). The ocean has thus played a major role in alleviating global warming by its uptake of anthropogenic CO 2 . However, the capacity of the ocean to absorb anthropogenic CO 2 is unlikely to remain unchanged in the future. Ongoing global warming and the associated changes of climate are expected to change ocean physical and biogeochemical conditions that control air-sea CO 2 exchanges. Periodic assessment of spatiotemporal changes of oceanic CO 2 is therefore crucial.Estimation of air-sea fluxes of CO 2 based on observations of partial pressures of atmospheric and surface seawater CO 2 (pCO 2 ) is a straightforward approach to the evaluation of the CO 2 sink of the ocean. In fact, Takahashi et al. (2002) have used this approach to estimate the CO 2 sink of the global ocean; they compiled about 960,000 surface seawater pCO 2 data and estimated the annual uptake of CO 2 by the global ocean to be 2.2 PgC yr −1 . In 2007, following this pioneering study, the international marine carbon community decided to produce a database of surface seawater pCO 2 measurements (IOCCP, 2007

Quantitative Assessment of Factors Contributing to Variations in Sea Surface pCO2 in the Pacific Sector of the Arctic Ocean

“…The winter pCO 2 averaged 383 μatm and ranged from 373 to 390 μatm, depending on the DIC and TA. According to Murata et al (2022), the high values of pCO 2 during early winter in this area are 370-400 μatm. The implication is that our estimates are reasonable and, considering that the water is covered with ice in the winter, can be assumed to be spatially uniform.…”

“…DIC in surface seawater was also continuously measured by the coulometric titration method (Johnson, 1992;Johnson et al, 1985) using a DICmeasuring system (Nihon ANS, Inc., Japan) installed on the R/V Mirai. The measuring method was the same as in Murata et al (2022). In addition, at surface water sampling stations (Figure 1b), seawater samples pumped via the same intake used for pCO 2 measurements were collected (a) in 10-mL polyethylene screw-cap vials (Eiken Chemical Co., Ltd, Japan) for nutrient measurements (NO 3 , NO 2 , NH 4 + , PO 4 3 , Si(OH) 4 ), (b) in 15-mL glass screw-cap vials (Nichiden-Rika Glass Co. Ltd, Kobe, Japan) for δ 18 O measurement, and (c) in 110-mL glass vials (Laboran Screw Tube Bottle, AS ONE, Tokyo, Japan) that had been acid-washed and combusted (450°C, 4 hr) for CDOM measurements.…”

Floating microplastic inventories in the southern Beaufort Sea, Arctic Ocean

“…An off-axis, integrated-cavity, output spectroscopy gas analyzer (Off-Axis ICOS; 911-0011, Los Gatos Research, Mountain View, CA, USA) was used for pCO 2 measurement; a coulometer was used as the detector for TCO 2 ; temperature and salinity were measured using a thermosalinograph (SBE-45; Sea-Bird Electronics, Inc., Bellevue, WA, USA). Details of these measurements are described by Murata et al (2022).…”

“…Seawater was collected by using a pump placed 4.5 m below the sea surface. Total alkalinity was then calculated from pCO 2 , TCO 2 , temperature, and salinity (Murata et al, 2022). The fractions of seaice meltwater and other freshwaters (consisting of precipitation, riverine water, and freshwater carried by Pacific-origin water) in surface seawater at a depth of 4.5 m during the sampling period were calculated from salinity and total alkalinity as described by Yamamoto-Kawai et al (2005).…”