Seminar: Dr. Frédéric Laliberté 2

Please join us as we welcome Dr. Frédéric Laliberté, a Visiting fellow at Environment Canada in the Climate Processes group of the Climate Research Division, for his seminar titled "Does the large scale circulation drive the Summer Arctic tropospheric variability and warming?" Coffee will be served.

Abstract

Under anthropogenic forcing, the Arctic surface warms much faster than most regions of the globe, both in models and observations. This rapid warming, known as the Arctic amplification of warming, is stronger during winter but is noticeable in all seasons. It extends over the whole tropospheric column so that on a fixed isobar, warming is more pronounced closer to the North Pole. Because it has been suggested that such an amplification might influence climate and weather patterns in midlatitudes, understanding the mechanisms that might contribute to its appearance under anthropogenic forcing has become an important goal of climate science.

In this presentation, I will present analyses that propose how the summer Arctic variability could be driven by midlatitude near-surface variability through the large scale atmospheric circulation, both in models and observations. I will further present evidence showing that the relationship between the summer Arctic variability and midlatitude near-surface variability might be sufficient to explain the inter-model spread in Arctic tropospheric warming. I will conclude by explaining how, in models but not in reanalyzed observations, the large scale circulation might be sufficient to propagate most of this tropospheric warming down to the surface, ultimately constraining how the summer Arctic tropospheric lapse rate might change under in simulated anthropogenic scenarios.