Evolution and Consequences of Short-term Fluctuations Ofarctic Sea-ice Motion and Deformation From The 1950's To 2000.
Abstract
The Arctic sea ice and its temporal evolution under inclusion of high-frequency dy- namical processes are studied using a dynamic-thermodynamic sea-ice model. In a previous intercomparison and validation study [Heil and Hibler, submitted], using data from drifting buoy arrays and RGPS, we concluded that the viscous-plastic coulom- bic rheology out-performs others in successfully simulating ice deformation. Here we study the evolution of Arctic sea-ice thickness, extent, and volume from multidecadal simulations with and without explicit treatment of high-frequency processes. Atmo- spheric forcing is based on six hourly NCEP data from 1948 to 2000, and a monthly climatology is used to prescribe cloud fraction. Oceanic forcing for surface currents and oceanic heat content has been taken from the output of an oceanic GCM [Polyakov et al, 1998]. By comparing the sea-ice output fields between the two simulations we determine the effect of high-frequency sea-ice dynamics on the overall evolution of the pack. Buoy and RGPS data are used to verify our results. The differences in sea-ice pa- rameters between the two model simulations are used to explain how high-frequency processes interact with interannual and decadal changes in sea-ice motion and defor- mation. The long-term changes are due to modified atmospheric forcing associated with the Arctic Oscillation (AO) and decadal variability. For example, observations from drifting buoys suggest that the sea-ice drift reacts near-instantaneously to large- scale changes in the atmospheric forcing [Rigor et al, in press], and also suggest increased short-term sea-ice divergence during high AO years [Heil, 2001]. During winter repeated cycles of opening and closing of the ice pack would give rise to an increase in the thermodynamic ice-growth rate. The output of our model will be used to estimate to which degree the latter counterbalances the advective loss of sea ice and consequent thinning of the Arctic sea ice, which has been reported for recent years (e.g., Rothrock et al. [1999], Wadhams and Davis [2000], or Tucker et al. [2001]). In consequence, the relationship between the ice divergence and atmospheric forcing as well as between the Arctic Ocean sea-ice mass budget and atmospheric forcing are reevaluated.
- Publication:
-
EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27..254H