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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.
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Changes in the Arctic Ocean Carbon Cycle With Diminishing Ice Cover
Abstract Less than three decades ago only a small fraction of the Arctic Ocean (AO) was ice free and then only for short periods. The ice cover kept sea surfacepCO2at levels lower relative to other ocean basins that have been exposed year round to ever increasing atmospheric levels. In this study, we evaluate sea surfacepCO2measurements collected over a 6‐year period along a fixed cruise track in the Canada Basin. The measurements show that meanpCO2levels are significantly higher during low ice years. ThepCO2increase is likely driven by ocean surface heating and uptake of atmospheric CO2with large interannual variability in the contributions of these processes. These findings suggest that increased ice‐free periods will further increase sea surfacepCO2, reducing the Canada Basin's current role as a net sink of atmospheric CO2.
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- Award ID(s):
- 1751363
- PAR ID:
- 10375344
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 47
- Issue:
- 12
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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