Arctic amplification as a rapid response to increased CO2
- 1Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA
- 2Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA
- 3Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA
- 4Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology, Zürich, Zürich, Switzerland
- 5Department of Physical and Environmental Sciences, University of Toronto, Scarborough, Toronto, Ontario, Canada
Arctic amplification (AA), or enhanced surface warming of the Arctic, is ubiquitous in observations, and in model simulations subjected to increased greenhouse gas (GHG) forcing. Despite its importance, the mechanisms driving AA are not entirely understood. Here, we show that in CMIP5 (Coupled Model Intercomparison Project 5) general circulation models (GCMs), AA develops within a few months following an instantaneous quadrupling of atmospheric CO2. We find that this rapid AA response can be attributed to the lapse rate feedback, which acts to disproportionately warm the Arctic, even before any significant changes in Arctic sea ice occur. Only on longer timescales (beyond the first few months) does the decrease in sea ice become an important contributor to AA via the albedo feedback and increased ocean-to-atmosphere heat flux. An important limitation of our CMIP5 analysis is that internal climate variability is large on the short time scales considered. To overcome this limitation – and thus better isolate the GHG-forced response – we produced a large ensemble (100 members) of instantaneous CO2-quadrupling simulations using a single GCM, the NCAR Community Earth System Model (CESM1). In our new CESM1 ensemble we find the same rapid AA response seen in the CMIP5 models, confirming that AA ultimately owes its existence to fast atmospheric processes.
How to cite: Janoski, T., Previdi, M., Chiodo, G., Smith, K., and Polvani, L.: Arctic amplification as a rapid response to increased CO2, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8500, https://doi.org/10.5194/egusphere-egu21-8500, 2021.
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