Numerical Modeling of Sensitivity of Arctic Atmospheric Condition to Sea Ice Changes

Over the past 20 years dramatic climate change has occurred in the Arctic, including a shift in Arctic Ocean circulation, regional increases in surface air temperatures, thawing of the permafrost, and a trend toward decreased surface atmospheric pressure. Probably the most significant change is the rapid decline of ice coverage and thickness over the past two decades. Multi-year sea ice concentrations have decreased drastically. The coverage of the multi-year ice now comprises just 10 percent of winter ice cover, down from 40 percent 20 years ago. These changes are certain to have serious impacts on the Arctic weather and regional climate.

In this study we examine the impact of the evolving sea ice states on the Arctic atmospheric conditions using the Navy's regional numerical weather prediction model (Coupled Ocean/Atmosphere Mesoscale Prediction System - COAMPS®) driven by the sea ice surface conditions predicted by the Arctic Cap Nowcast/Forecast System (ACNFS). ACNFS is a coupled sea ice and ocean model that generates real-time forecasts of ice concentration, ice edge location, ice thickness, ice draft and ice drift for all sea ice covered areas in the northern hemisphere (poleward of 40N). These fields are used by COAMPS as the surface boundary condition, which directly modulates distribution of turbulent and radiative surface fluxes. The improved physical parameterizations in COAMPS are compared with the benchmark simulations and evaluated for the Arctic conditions. Systematic verification of the boundary layer structure over the evolving sea ice with high heterogeneity is performed against the Arctic surface observations and data from previous field experiments.