Member Research Profile - Kelly McCusker, PDF

Could you briefly describe your position within the CanSISE Network?

I am a Post-doctoral Fellow (which falls under "Highly Qualified Personnel"), conducting research at the Canadian Centre for Climate modelling and analysis (CCCma) located at the University of Victoria. 


What is your primary research goal?

My primary research goal is to understand the impact that changes in Arctic sea ice have on atmospheric temperature and circulation, both locally in the Arctic and remotely in the midlatitudes. This is an exciting topic of research right now because Arctic  sea ice area has been declining rapidly  in the last decade or so, and while we know that this causes an

Arctic sea ice extent on August 26, 2012 compared to median (click to enlarge). Image by Jesse Allen from the NASA Earth Observatory: http://tinyurl.com/ovoh4l8
Arctic sea ice extent on August 26, 2012 compared to median (click to enlarge). Image by Jesse Allen from the NASA Earth Observatory: http://tinyurl.com/ovoh4l8

increase in warming locally in the Arctic, there are open questions as to whether or not the sea ice loss can have an influence on weather patterns outside the Arctic. I am currently investigating whether sea ice loss in the Barents-Kara Seas region of the Arctic could cause colder winters in Eurasia by fundamentally changing atmospheric circulation in the region. Understanding this potential link is important for understanding how winter weather could change in the future, as sea ice declines further. 

 

Can you tell us a bit more about the potential links between sea ice loss and temperature?

Sea ice acts as a cap over the Arctic Ocean, reflecting the Sun's energy and keeping it from being absorbed by the underlying seawater. When more sea ice melts during summer and autumn, more area of open water is available to absorb the Sun's energy. This heat is then later released during winter when the overlying air is colder than the newly opened areas of water beneath it. The result is that the near-surface  atmospheric  air temperature  warms over the  Arctic,  contributing to what is known as "Arctic amplification" where the Arctic warms more than the rest of the globe under increasing 

Areas of open water are sources for heat to the atmosphere in winter. Credit: Ted Scambos, NSIDC
Areas of open water are sources for heat to the atmosphere in winter. Credit: Ted Scambos, NSIDC

greenhouse gases. Thus on a planetary scale, sea-ice loss modifies the equator-to-pole temperature gradient, and this can have implications for the strength of the midlatitude westerly winds and other circulation features. At a regional level, sea ice loss in the Barents-Kara Seas can cause warming above it through the above mentioned mechanism, which thickens the atmosphere and can produce a weak high pressure aloft, especially in winter. This feature is hypothesized to drive polar air to the south over Eurasia, generating colder Eurasian winters. Of course temperature itself can change through other factors and influence the evolution of sea ice, so this is a very complex question. See next.

 

Please explain how you investigate these potential links?

In the real world, there are many components to the climate system that interact in tightly coupled, complex ways. In order to isolate the influence of sea ice alone, I use global climate computer models developed by Environment Canada to test how changes in sea ice area in isolation can affect the atmosphere. I also use observational data collected by satellites and others as a point for comparison.

 

Tell us about something unexpected that you have recently uncovered.

Perhaps the most surprising recent finding is that, in our idealized modelling results, we do not find that Arctic sea ice loss affects Eurasian winter temperature in a systematic way, which is counter to some previous findings. When simulated Arctic sea ice decreases, the response of Eurasian winter temperature is equally likely to cool or warm on decadal and even century-timescales. However, we do find that Eurasian winter can exhibit periods of cooling that are statistically significant on decadal/multi-decadal timescales, but are not robust to a larger sample size of model response years. In other words, it appears that internal climate variability (naturally chaotic variations in weather patterns) can produce Eurasian cooling that could be mistakenly attributed to sea ice loss.

 

What implications does this have for future studies?

One immediate implication of these results is that we have shown that many more ensemble members (or model run years) than are usually analyzed are necessary to determine the true response to sea ice loss, because internal climate variability is so large, especially over Eurasia in winter. Additionally, Barents-Kara sea ice loss does not appear to be a good predictor of Eurasian winter temperature, indicating that other sources for predictability should be the focus of future work.

 

How does your research fit into the broader scope of the CanSISE Network?

This work fits into Theme C of the CanSISE network, which is 'Snow and sea ice processes and climate interactions', with sub-focus on 'connecting snow and sea ice to the large-scale general circulation'. My research is on the modelling side of the network, as opposed to observational, and is an opportunity to provide feedback on the performance of the Canadian atmospheric and earth system climate models in the Arctic. I also am able to utilize in-network expert knowledge about observational datasets that I use as benchmarks and as boundary conditions to my model simulations.

 

What are your next steps?

Our next steps include investigating the role that ocean coupling plays in how Arctic sea ice loss influences the atmosphere -- Does the ocean communicate changes in sea ice to the atmosphere outside the Arctic? We will also turn that question on its head and investigate how ocean coupling both inside and outside of the Arctic can help us predict Arctic sea ice changes.

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