The exceptional atmospheric conditions that have accelerated Greenland Ice Sheet mass loss in recent decades have been repeatedly recognized as a possible dynamical response to Arctic amplification. AER Principal Scientist Judah Cohen collaborated with scientists at the University of Georgia and Columbia University on a study that reveals two potentially synergistic mechanisms linking high latitude warming to the observed increase in Greenland blocking associated with melting of the ice sheet. Consistent with a prominent hypothesis associating Arctic amplification and persistent weather extremes, we find that the summer atmospheric circulation over the North Atlantic has become wavier and link this wavier flow to more prevalent Greenland blocking. A concomitant decline in terrestrial snow cover has likely contributed to this mechanism by further amplifying warming at high latitudes; however, we also identify a direct stationary Rossby wave response to low spring North American snow cover that enforces an anomalous anticyclone over Greenland, thus helping to anchor the ridge over Greenland in this wavier atmospheric state.
Figure 1. Spring snow cover extent (SCE) has a strong relationship with summer atmospheric circulation over Greenland that promotes surface melt. Panels present lagged correlation plots relating June (left column), July (middle column), and August (right column) atmospheric circulation over Greenland to antecedent monthly SCE area over the Northern Hemisphere (top row), Eurasia (middle row), and North America (bottom row). The color-coded bars in each panel document the correlation coefficient relating GBI (black), and sinuosity or waviness of the atmospheric circulation (Sag) (orange) measured during the summer month labeled at the top of each column to lagged monthly SCE area as noted along the x-axis. Likewise, triangles note the correlation between the principal-component-based NAO and lagged monthly SCE area. Filled bars and bold triangles indicate statistical significance at α = 0.05. Hypothesis tests were calculated individually for each time lag, with no multiple testing adjustment.
Citation: Summer Atmospheric Circulation Over Greenland in Response to Arctic Amplification and Diminished Spring Snow Cover
J. R. Preece, T. L. Mote, J. Cohen, L. J. Wachowicz, J. A. Knox, M. Tedesco, G. J. Kooperman
Nature Communications, 14, 3759 (2023).