Seasonal sensitivity of the jet stream to Arctic temperatures on subseasonal timescales
The unprecedented loss of sea ice and associated amplified warming of the Arctic in recent years has spurred research on how these changes may impact the jet streams, and thus weather, at lower latitudes. Even with the disagreement in the literature on the magnitude of the effect of Arctic warming on midlatitude weather, most studies seem to agree that any circulation response will be a strong function of season. However, what has been largely neglected until now is how the seasonality of the midlatitude circulation itself may impact the seasonality of its response.
In this work, we quantify the seasonal sensitivity of the jet-stream to Arctic warming on short (subseasonal) timescales. We decouple the seasonality of the circulation from that of the warming by quantifying the response of the jet stream to a 1 Kelvin warming of the Arctic lower troposphere. Since modeling evidence suggests that any jet response will be small compared to internal variability, we make use of 4800 years of climate simulations to extract the forced signal from the noise. Unlike most previous studies that employ instantaneous or lagged correlations, we take an approach from causality theory, namely, Granger causality, to ensure that we are capturing the jet response to Arctic warming and not the other way around. We demonstrate a clear seasonality in the jet-stream sensitivity to Arctic warming and discuss the implications for mean-state climate model biases.
Dr. Barnes obtained B.S. in Mathematics and B.S. in Physics from University of Minnesota in 2007, and Ph.D. in Atmospheric Science from University of Washington in 2012. Her research focuses on large-scale atmospheric dynamics including its response to climate change, atmospheric transport, and stratosphere-troposphere exchange, on the role of moisture in the general circulation, and on the global and regional air quality.