Abstract
Arctic summer sea ice has decreased dramatically over the last few
decades, with a substantial part of this decline attributed to internal
variability. However, models show large differences in their simulated
internal variability, increasing projection uncertainty and
complications with model-observation comparisons. Here we will present
results that aim to quantify the contribution of internal variability in
different models which provide large ensemble simulations, and compare
them with estimates from observations. In particular, we are comparing
five models from the CLIVAR multi-model large ensemble (CanESM2, CESM1,
CSIRO MK36, GFDL ESM2M, and MPI ESM1) with observations. So far, we have
found a large range in simulated pan-Arctic sea ice area standard
deviation from 0.35 million km2 (CSIRO MK36) to 0.74 million km2 (CESM1)
for mean September areas between 4.00-4.25 million km2. Spatially, the
detrended standard deviation in the central Arctic is consistently
over-represented in models compared to observations. Conversely, the
marginal seas are simulated to have slightly below to several times
below observed detrended standard deviation. Further analysis on a more
regional scale will be done over the coming months to further
characterize the realism of simulated internal variability in Arctic sea
ice.