Abstract:
To fully understand the potential impacts of the shrinking Arctic sea ice, we need to better understand the various roles of Arctic sea ice plays in our climate. In this talk, I will focus on how Arctic sea ice-air two-way interactions amplify multidecadal variability in the North Atlantic but dampen El Niño-Southern Oscillation (ENSO) variability in the Pacific. Using CESM1 model simulations with and without the sea ice-air interactions and collaborated with observational data, we show that variations in cold-season sea ice concentrations (SIC) around Arctic marginal ice zones can significantly amplify multidecadal variations in surface latent and sensible fluxes from the Labrador Sea to the Nordic Seas, leading to larger variations in upper ocean density and deep water formation in these seas, thereby amplifying the amplitudes of Atlantic Multidecadal Oscillation (AMO) and the Atlantic meridional overturning circulation. In the Pacific sector, SIC variations from the Bering Sea to Okhotsk Sea (BOS) lead to increased absorption of solar radiation due to asymmetric albedo effects of SIC anomalies. This results in warming in the northern North Pacific Ocean, which excites an anomalous tropospheric Rossby wave propagating equatorward into the tropical Pacific to strengthen cross-equator winds and deepen the thermocline there. These mean changes dampen ENSO amplitude via weakened thermocline and zonal advective feedbacks. Thus, Arctic sea ice–air interactions affect both the mean state and variability in the tropical Pacific and imply increased ENSO amplitude but weakened AMO as Arctic sea ice and its interactions with the atmosphere diminish under global warming.
Key References:
Deng, J. and A. Dai, 2022: Sea ice-air interactions amplify multidecadal variability in the North Atlantic and Arctic region. Nature Communications, 13, 2100. https://www.nature.com/articles/s41467-022-29810-7.
Deng, J., and A. Dai, 2024: Arctic sea ice-air interactions weaken El Niño/Southern Oscillation. Science Advances, 10, eadk3990, https://doi.org/10.1126/sciadv.adk3990.
Bio:
Dr. Dai is a Distinguished Professor of the Department of Atmospheric & Environmental Sciences at the University at Albany, State University of New York, USA. He obtained his PhD in Atmospheric Science from Columbia University in 1996 and worked at NCAR from1997-2012. He is an internationally renowned climate scientist with a focus on climate variability and change, Arctic climate, the global water cycle, hydroclimate, drought, the diurnal cycle, and climate data analysis. With more than 200 peer-reviewed publications, he has received 64,000-plus citations with an H-index of 91. He is one of the world’s top 1% Highly Cited Researchers and is ranked #2 in Meteorology/Atmospheric Science based on 2019 citations according to a Stanford study. He served as the Chair of the Climate Variability and Change Committee and Editor of Journal of Climate of the American Meteorological Society (AMS), and he is an AMS Fellow. Dr. Dai is currently working on causes and impacts of Arctic rapid warming and sea-ice loss; changes in atmospheric thermodynamic conditions under global warming; the role of internal variability and external forcing in historical climate changes; and historical and future changes in precipitation, drought and other hydroclimate fields.
