I am interested in understanding how the various components of the climate system respond on human timescales to imposed external forcings (e.g. human emissions of greenhouse gases, aerosol pollution, volcanic eruptions, geoengineering via stratospheric aerosol injections) on global and regional scales, and in the context of internal variability. Key to the ability to narrow uncertainty in future climate change is understanding how sensitive the climate is to forcing by understanding climate feedbacks, distinguishing the forced response from internal variability, and understanding interactions between the two influences. To that end, I use a hierarchy of numerical climate models in sometimes clever ways to understand the forced response of distinct components of the climate system and how they feed back to the system.
Below I describe some of my current and recent research projects.
Below I describe some of my current and recent research projects.
The influence of Arctic sea ice loss on climate Arctic sea ice is experiencing a dramatic loss in area and thickness, in large part because of human-induced climate change. This loss of ice has a profound impact on Arctic climate. More open Arctic Ocean allows the ocean to absorb more summer heat than before, which is later released back to the cold winter atmosphere. The dark ocean surface also changes the reflectivity (albedo) of the Arctic, reflecting less solar radiation back to space. These two factors result in a much warmer Arctic atmosphere when sea ice melts, and are important reasons for "Arctic amplification" whereby the Arctic atmosphere is warming twice as fast as the globe as a whole. Changes in stability, clouds, and poleward heat transport also play a role.
The loss of Arctic sea ice may also have an important influence on climate outside of the polar region, by changing large-scale circulation. This is currently a very active area of research. As part of the Canadian Sea Ice and Snow Evolution (CanSISE) project, I am working to understand the effect that changes in sea ice have on the atmosphere, in particular on atmospheric circulation. I have undertaken a couple different projects under this theme. Arctic sea ice loss and its influence on Eurasian climate For a quick summary of some of my recent work about whether Arctic sea ice loss had anything to do with an observed winter cooling trend over Eurasia, check out my member profile on the CanSISE website. That research resulted in this article published in Nature Geoscience. Is the influence of Arctic sea ice loss separable from the greenhouse gas forcing that caused it? A lot of effort has gone into isolating the effect that sea ice loss has on the atmosphere (via specialized climate model simulations). Whether we can think of the changing climate in a warming world as the response to greenhouse gas forcing that is modulated in some way by Arctic sea ice loss depends on whether the two effects can be separated (via climate models). Here I explicitly isolate both Arctic sea ice loss and greenhouse gas forcing (by a doubling of CO2 concentration) and test whether their separate responses add up to the response of their combined forcings. This work is currently in revision for Geophysical Research Letters. More soon. |
Minimum Arctic sea ice extent in 2012, the lowest on record since the satellite era began in 1979. (image source: earthobservatory.nasa.gov)
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