Name

Evelien Dekker
PhD student at MISU

Title

Nudging the Arctic ocean to quantify sea ice feedbacks

Abstract

With Arctic summer sea ice potentially disappearing halfway through this century, the surface albedo and insulating effects of Arctic sea ice will decrease considerably. The ongoing Arctic sea ice retreat also affects the strength of the Planck, lapse-rate, cloud and surface albedo feedbacks, but their combined effect on climate sensitivity has not been quantified. This study presents an estimate of the combined Arctic sea ice related climate feedbacks , which includes the nonlinear interactions between the various feedbacks. To do so, we apply a new nudging method to keep Arctic sea ice at its present-day (PD) distribution under a changing climate in a 50 year CO2 doubling simulation using a fully coupled global climate model (EC-Earth v2.3).
We nudge the Arctic Ocean to the (monthly-dependent) year 2000 mean temperature and minimum salinity fields on a mask representing mean PD sea ice cover. Using this method, we are able to preserve about 95% of the PD mean March and 77 % of the September PD Arctic sea ice extent. Using simulations with and without sea ice nudging, we can estimate the climate response associated with Arctic sea ice changes. The Arctic sea ice feedback yields a range of 0.28 - 0.68 W/m² K. The total sea ice feedback thus amplifies the climate response for a doubling of CO2, in line with earlier findings. Our estimate of the Arctic sea ice feedback agrees reasonably well with earlier CMIP5 global climate feedback estimates and shows that the Arctic sea ice retreat amplifies to a considerable extent the global climate response.

 

Time and Place

Thursday April 12th, 14.15
Rossbysalen C609, Arrhenius Laboratory, 6th floor

 

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