Why does the Arctic temperature rise faster in the cold season?

The Arctic warming response to increasing greenhouse gas is substantially greater than the rest of the globe. It has been suggested that this phenomenon, commonly referred to as Arctic amplification, and its peak in boreal fall and winter result primarily from the so-called lapse-rate feedback, which is associated with the vertical structure of tropospheric warming, rather than from the sea-ice albedo feedback, which operates mainly in boreal summer. However, future climate model projections show consistently that an overall reduction of sea-ice in the Arctic region leads to a gradual weakening of Arctic amplification, thereby implying a key role for sea-ice albedo feedback. To resolve this apparent contradiction, a new study accepted in Earth’s Future conducted a comprehensive analysis using atmosphere-ocean reanalysis datasets and a variety of climate model simulations. This study showed that the Arctic Ocean acts as a heat capacitor, storing anomalous heat resulting from the sea-ice loss during summer, which is then released back into the atmosphere during fall and winter. The ocean heat-driven strong air-sea heat fluxes in fall and winter in sea-ice retreat regions in conjunction with a stably stratified lower troposphere lead to a surface-intensified warming and moistening, augmenting longwave feedback processes to further enhance the pronounced Arctic warming in the cold season. These results strongly suggest that the warm-season ocean heat recharge and cold-season heat discharge link and integrate the warm and cold season feedbacks, and thereby effectively explain the predominance of the Arctic amplification in fall and winter.

Figure 8 from Chung et al. (2020): A schematic diagram illustrating the contribution of anomalous seasonal ocean heat uptake and release to fall and winter Arctic amplification. The upper ocean stores heat resulting from GHG-induced sea-ice loss during summer, and the accumulated heat is then released back into the atmosphere during fall and winter. Due to a stable condition in the lowermost part of the atmosphere during the cold season, a large fraction of the heat and moisture released from sea-ice retreat regions is trapped in that layer. The surface-intensified warming and moistening in turn acts to further promote LW feedback processes, including the lapse-rate feedback, to enhance the warming.

Chung, E.S., Ha, K.J., Timmermann, A., Stuecker, M.F., Bodai, T., & Lee, S.-K. (2020). Cold‐Season Arctic Amplification Driven by Arctic Ocean‐Mediated Seasonal Energy Transfer. Earths Future, 8, e2020EF001898 https://doi.org/10.1029/2020EF001898.

2 thoughts on “Why does the Arctic temperature rise faster in the cold season?

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  1. Thanks Sang-Ki!! I’m keenly interested in the literature on Arctic Amplification & it impacts on extreme weather over the mid-latitudes. I’m familiar with the early work of Jennifer Francis (Francis&Vavrus_2012, attached) that I thought made perfect (intuitive) sense. The latitudinal temperature & pressure gradients weaken, causing the jet stream to slow and meander more. What you would expect if this is the case, is that blocking patterns (both ridges and troughs) become more frequent resulting in heat waves, drought and lengthened heating season on the one hand and more extreme winter events such as we we’re experiencing now. But, there’s a problem! In the winter the Arctic is iced over again so where is the source of heating? Now, however there’s been an explosion of newer literature that calls that simplicity into question, such as Cohen_etal_2018 (also attached). Apparently that intuitive mechanism is only demonstrable under certain conditions such as where in the Arctic significant atmospheric heating occurs. And now you have described this interesting paper by Chung_etal_2020 that throws another monkey wrench into the pot. But it’s a monkey wrench that helps me to understand how summer ice retreat can affect extreme weather into the winter months!

    The reason for my interest in the subject relates to my being interested in advocacy for climate action. We see examples of extreme weather almost daily on news programs, the wildfires in summer, midwest flooding in the spring and now extreme blizzard conditions in the dead of winter. If I can give layman talks in public venues to explain this then any time my audience sees these things on TV they will make the connection to climate change and the urgent need for action, regardless of whether any particular extreme event is actually attributable to AA — the idea is for lay people to make the connection. Of course, my Powerpoint can’t go into these kinds of scientific exotica, I have to keep it simple. So I compare the Francis mechanism to meandering rivers in low gravitational gradient environments like the Amazon. I wish I had a way of simplifying the Chung_etal mechanism!

    Anyway, it’s been difficult for me to adequately follow the literature on AA and its impacts because I can’t chase down the papers any more. Which leads me to ask, can you send me the pdf of Chung_etal?

    As always, thank you. – Dave

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  2. Hi David,

    Thank you for the comment and sharing your thoughts. I just shared the preprint with you through google drive. You should have an email notification by now.

    Here are two papers you mentioned.
    Francis, J. A., and Vavrus, S. J. (2012), Evidence linking Arctic amplification to extreme weather in mid‐latitudes, Geophys. Res. Lett., 39, L06801, https://doi.org/10.1029/2012GL051000. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2012GL051000

    Cohen, J., Pfeiffer, K. & Francis, J.A. Warm Arctic episodes linked with increased frequency of extreme winter weather in the United States. Nat Commun 9, 869 (2018). https://doi.org/10.1038/s41467-018-02992-9
    https://www.nature.com/articles/s41467-018-02992-9

    If you look at Figures 1b,c and d in Chung et al., the Arctic amplification has occurred and will occur predominantly in winter, which is counter-intuitive given that sea-ice albedo feedback, which is widely known as the main drive of Arctic amplification, cannot occur in winter (i.e., there is no sunlight). The major finding in Chung et al. is that the Arctic Ocean can store extra heat coming through the declining sea-ice area in summer, and then release the heat back to the atmosphere in winter to warm the lower atmosphere. Lapse rate and LW feedback also play an important role amplifying the warming signal in winter. Figure 8 from Chung et al. is a nice schematic summary.

    Best,

    Sang-Ki

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