Effect of Increasing freezing point Sea Ice Albedo, on controlling Arctic Climate variables in ICON

Climate models have difficulties accurately representing Arctic mid-latitude linkages. This might partly be caused by surface parametrizations that are not able to accurately represent the Arctic surface conditions. As a result, large uncertainties arise in the modelling of energy exchange between the surface and the atmosphere, since sea ice surface albedo (SIA) controls the energy input in the Arctic region. The present study aims to gain insights in how the SIA parameterization scheme in the Icosahedral Nonhydrostatic (ICON) model can influence Arctic climate.

In order to identify the sources of error in the current SIA parameterization scheme, it is evaluated against Arctic observational data. The data includes both on-ice measurements to capture the SIA temporal evolution (MOSAiC), as well as airborne measurements from several flight campaigns performed within the (AC)³ project to capture a larger spatial variability. The offline evaluation, in which the SIA parametrization is isolated from the ICON model and observations are used as input for the parametrization, shows that the biggest disagreement between the scheme and the observations occurs at freezing point temperatures.  

Inspired by this outcome and to better understand how SIA parametrization can control the Arctic climate, a simulation with increased SIA at freezing point temperatures is performed. With this long term, limited area, pan-arctic simulation, changes in energy exchange between surface and atmosphere are analyzed. 

This work was supported by the DFG funded Transregio-project TRR 172 “Arctic Amplification (AC)³“.