Program uses Singapore Time and is 8 hours ahead of GMT

OS Kamide Lecture/Live Q&A Thu-04 Aug 12:00 – 12:45

Atlantic Multidecadal Sea Surface Temperature Variability in the Current and Changing Climate

Owing to their large thermal inertia, oceanic modes of variability constitute an instrumental component of the Earth’s climate system, modulating the low-frequency climate variabilities. Among such low-frequency modes of oceanic variability is the Atlantic Multidecadal Oscillation/Variability (AMO/AMV). AMO is a multidecadal fluctuation in the sea surface temperature over the North Atlantic, and is known to have wide-ranging global impacts, including its influence on Sahel droughts, summertime Asian monsoon, Atlantic hurricanes, and large-scale atmospheric flow such as the North Atlantic storm track and jet stream.

In spite of its significance, the mechanism behind the AMO formation is still under debate. The development of warm sea surface temperature anomalies associated with AMO has conventionally been attributed to the heat convergence associated with the modulation of the Atlantic Meridional Overturning Circulation (AMOC), one of the major ocean circulation systems of the Earth, contributing to up to 25% of the northward global atmosphere-ocean heat transport in the Northern Hemisphere. Recent studies, however, pointed towards the importance of atmospheric stochastic and aerosol forcings in shaping the sea surface temperature anomalies. The exact partitioning of each of their roles is still under debate, hampered by the tightly coupled nature of the atmosphere and ocean.

Meanwhile, AMOC is projected to weaken under the warming climate. Some studies suggest that this weakening of AMOC is associated with a characteristic sea surface temperature pattern over the subpolar North Atlantic basin, the exact location where one of the maximum loadings of the AMO-associated sea surface temperature anomalies emerge. The fate of AMO modulation under the global warming is yet to be known, masked by the overwhelming warming signal.

In this talk, I will provide a brief review of our current understanding of this multidecadal SST signal over the North Atlantic basin, and introduce some new findings from our recent studies. In particular, focus will be placed on a new AMO formation mechanism we have proposed and the future modulation of AMO under global warming.

Professor Ayako Yamamoto was born in Nagano, Japan. She has received her BSc from York University, Canada, and MSc and PhD from McGill University, Canada, in Atmospheric and Oceanic Sciences. After completion of her degrees, she came back to Japan to undertake research at the Japan Agency for Marine-Earth Science and Technology as a postdoctoral fellow. She is currently an assistant professor at Tokyo University of Marine Science and Technology. She has diverse research interest, with her previous works including troposphere-stratosphere interactions, large-scale air-sea interactions, as well as the role of mesoscale eddies in ocean biogeochemistry. Her primary research interest lies in the dynamical understanding of the role of the ocean in shaping the current and future large-scale climate, and how the oceanic variability is determined by the atmosphere in turn on interannual to longer time scales.