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Abstract The southeastern Atlantic Ocean is a crucial yet understudied region for the ocean absorption of anthropogenic carbon (C_anth). Data from the A12 (2020) and A13.5 (2010) cruises offer an opportunity to examine changes in dissolved inorganic carbon (DIC), its stable isotope (δ¹³C), and C_anthover the past decade within a limited region (1∼3°E, 32∼42°S). For the decade of 2010–2020, C_anthinvasion was observed from the sea surface down to 1,200 m based on both DIC and δ¹³C data. The mean C_anthincrease rate (1.08 ± 0.26 mol m⁻² yr⁻¹) during this period accelerated from 0.87 ± 0.05 mol m⁻² yr⁻¹during the previous period (1983/84–2010). The δ¹³C‐based C_anthincrease closely matches the DIC‐based estimation below 500 m but is 26% higher in the upper ocean. This discrepancy is likely due to δ¹³C's longer air‐sea exchange timescale, seasonal variability in the upper ocean, and the chosen ratio of anthropogenically induced changes in δ¹³C and DIC. Finally, column inventory changes based on the two methods also exhibit very similar mean C_anthuptake rates. The paired DIC concentration and stable isotope dataset may enhance our ability to constrain C_anthaccumulation and its controlling mechanisms in the ocean. 

Rapid climate warming and sea-ice loss have induced major changes in the sea surface partial pressure of CO2 ( pCO2I). However, the long-term trends in the western Arctic Ocean are unknown. Here we show that in 1994–2017, summer pCO2I in the Canada Basin increased at twice the rate of atmospheric increase. Warming and ice loss in the basin have strengthened the pCO2I seasonal amplitude, resulting in the rapid decadal increase. Consequently, the summer air–sea CO2 gradient has reduced rapidly, and may become near zero within two decades. In contrast, there was no significant pCO2I increase on the Chukchi Shelf, where strong and increasing biological uptake has held pCO2I low, and thus the CO2 sink has increased and may increase further due to the atmospheric CO2 increase. Our findings elucidate the contrasting physical and biological drivers controlling sea surface pCO2I variations and trends in response to climate change in the Arctic Ocean. 

Abstract The South Atlantic Ocean is an important region for anthropogenic CO₂(C_anth) uptake and storage in the world ocean, yet is less studied. Here, after an extensive sensitivity test and method comparison, we applied an extended multiple linear regression method with six characteristic water masses to estimate C_anthchange or increase (ΔC_anth) between 1980s and 2010s in the South Atlantic Ocean using two meridional transects (A16S and A13.5) and one zonal transect (A10). Over a period of about 25 years, the basin‐wide ΔC_anthwas 3.86 ± 0.14 Pg C decade⁻¹. The two basins flanking the Mid‐Atlantic Ridge had different meridional patterns of ΔC_anth, yielding an average depth‐integrated ΔC_anthin the top 2000 m of 0.91 ± 0.25 mol m⁻² yr⁻¹along A16S on the west and 0.57 ± 0.22 mol m⁻² yr⁻¹along A13.5 on the east. The west‐east basin ΔC_anthcontrasts were most prominent in the tropical region (0–20°S) in the Surface Water (SW), approximately from equator to 35°S in the Subantarctic Mode Water (Subantarctic Mode Water (SAMW)), and all latitudes in the Antarctic Intermediate Water (AAIW). Less ΔC_anthin the eastern basin than the western basin was caused by weaker ventilation driven by SAMW and AAIW formation and subduction and stronger Antarctic Bottom Water (AABW) formation in the former than the latter. In addition to the spatial heterogeneity, C_anthincrease rates accelerated from the 1990s to the 2000s, consistent with the overall increase in air‐sea CO₂exchange in the South Atlantic Ocean. 

Abstract The Arctic Ocean has turned from a perennial ice‐covered ocean into a seasonally ice‐free ocean in recent decades. Such a shift in the air‐ice‐sea interface has resulted in substantial changes in the Arctic carbon cycle and related biogeochemical processes. To quantitatively evaluate how the oceanic CO₂sink responds to rapid sea ice loss and to provide a mechanistic explanation, here we examined the air‐sea CO₂flux and the regional CO₂sink in the western Arctic Ocean from 1994 to 2019 by two complementary approaches: observation‐based estimation and a data‐driven box model evaluation. ThepCO₂observations and model results showed that summer CO₂uptake significantly increased by about 1.4 ± 0.6 Tg C decade⁻¹in the Chukchi Sea, primarily due to a longer ice‐free period, a larger open area, and an increased primary production. However, no statistically significant increase in CO₂sink was found in the Canada Basin and the Beaufort Sea based on both observations and modeled results. The reduced sea ice coverage in summer in the Canada Basin and the enhanced wind speed in the Beaufort Sea potentially promoted CO₂uptake, which was, however, counteracted by a rapidly decreased air‐seapCO₂gradient therein. Therefore, the current and future Arctic Ocean CO₂uptake trends cannot be sufficiently reflected by the air‐seapCO₂gradient alone because of the sea ice variations and other environmental factors.