期刊名称：Journal of Advances in Modeling Earth Systems
电子版ISSN：1942-2466
出版年度：2021
卷号：13
期号：3
页码：e2020MS002366
DOI：10.1029/2020MS002366
出版社：John Wiley & Sons, Ltd.
摘要：The IPSL‐CM6‐LR atmosphere‐ocean coupled model exhibits a pronounced multicentennial variability of the Atlantic meridional overturning circulation (AMOC), driven by delayed freshwater accumulation and release in the Arctic. The AMOC fluctuations are preceded by salinity‐driven density anomalies in the main deep convection sites in the Labrador and Greenland seas. During a strong AMOC, a combination of reduced sea ice volume and anomalous currents reduces the freshwater export from the Arctic and leads instead to a slow accumulation of freshwater in the central Arctic. Simultaneously, the saltier Atlantic inflow through the Barents Sea results in a positive salinity anomaly in the Eastern Arctic subsurface. When the surface Central Arctic freshwater pool finally reaches the Lincoln Sea, the oceanic currents around Greenland reorganize, leading to the export of the anomalous Arctic freshwater to the North Atlantic, enhancing the stratification in deep convection sites. The AMOC then decreases, positive salinity anomalies appear in the Central Arctic, and the variability switches to the opposite phase. These AMOC and sea ice fluctuations have broader climate impacts, with a strong AMOC leading to a mean warming of about 0.4°C north of 20°N, reaching up to 1°C in the Arctic lower troposphere during winter. In all seasons, a northward displacement of the intertropical convergence zone is also simulated. Plain Language Abstract The North Atlantic Ocean is known to have large climate fluctuations emerging from the different components of the climate system and their interactions. These fluctuations play a crucial role in the North American and European climate or the Arctic sea ice. A proper understanding of such internal variations is key to attribute the observed climate changes to anthropogenic activities or to assess the skill of decadal forecast systems. However, investigations of the long‐term basin‐scale variations are restrained by the limited instrumental observations. Therefore, an atmosphere‐ocean general circulation model is used here to explore the low‐frequency variability. This model simulates a large variability in the North Atlantic with a period between 1 century and 1 millennium. We found that this variability owes its existence to the freshwater exchanges between the North Atlantic and Arctic. Such North Atlantic variability has important impacts, as typical positive anomalies of the Atlantic oceanic northward heat transport reduce the sea ice, warm up the whole Northern Hemisphere by 0.4°C, and shift northward the intertropical convergence zone.
