IPCC models underestimate future sea ice loss - New scientific paper
- 06 Oct 2011, 15:00
- Verity Payne
© Lars Witting/ARC-PIC.COM
IPCC climate models do not capture Arctic sea ice
drift acceleration: Consequences in terms of projected sea ice
thinning and decline
A new paper in the Journal of Geophysical Research offers fresh
insights into Arctic sea ice. Researchers compared observations of
Arctic sea ice with projections from IPCC models. Arctic sea ice
thins and drifts faster in the summer months, accelerating sea ice
decline. The paper finds that IPCC climate models underestimate
observed Arctic sea ice loss, particularly thinning trends. This
means that the IPCC projections for ice-free Arctic summer seas by
2100 are likely to be too conservative.
Background:
Arctic sea ice varies seasonally (growing in winter and
retreating in summer) but satellite records over the last three
decades show an overall
decline in sea ice extent. The Arctic is thought to be warming
at around
twice the global rate. This is thought
primarily to be because ice reflects incoming solar energy -
loss of ice reduces this reflection, leading to greater regional
warming. Sea ice loss has been
accelerating over the last few years, faster than
projected by IPCC AR4 models.
Abstract:
"IPCC climate models underestimate the
decrease of the Arctic sea ice extent. The recent Arctic sea ice
decline is also characterized by a rapid thinning and by an
increase of sea ice kinematics (velocities and deformation rates),
with both processes being coupled through positive feedbacks. In
this study we show that IPCC climate models underestimate the
observed thinning trend by a factor of almost 4 on average and fail
to capture the associated accelerated motion. The coupling between
the ice state (thickness and concentration) and ice velocity is
unexpectedly weak in most models. In particular, sea ice drifts
faster during the months when it is thick and packed than when it
is thin, contrary to what is observed; also models with larger
long-term thinning trends do not show higher drift acceleration.
This weak coupling behavior (1) suggests that the positive
feedbacks mentioned above are underestimated and (2) can partly
explain the models' underestimation of the recent sea ice area,
thickness, and velocity trends. Due partly to this weak coupling,
ice export does not play an important role in the simulated
negative balance of Arctic sea ice mass between 1950 and 2050. If
we assume a positive trend on ice speeds at straits equivalent to
the one observed since 1979 within the Arctic basin, first-order
estimations give shrinking and thinning trends that become
significantly closer to the observations."
Citation and link:
Rampal, P., J. Weiss, C. Dubois, and J.-M. Campin (2011), IPCC
climate models do not capture Arctic sea ice drift acceleration:
Consequences in terms of projected sea ice thinning and
decline, J. Geophys. Res., 116, C00D07,
doi:10.1029/2011JC007110.