Investigating the Relative Roles of Dynamics and Thermodynamics in Sea-Ice Volume Changes in the Canada Basin

Abstract

The Canada Basin (CB) has seen significant sea-ice loss in recent decades. We use output from the Pan-Arctic Ice-Ocean Modeling and Assimilation System to examine the 1979–2023 evolution of seasonal sea-ice volume (SIV) changes in the CB partitioned into advective and thermodynamic changes. In winter, some years show net convergence into the region that is of comparable magnitude to the SIV change attributed to sea-ice growth. In summer, melt/ablation dominates the change each year. In both seasons, 44 year trends in seasonal SIV changes are driven primarily by thermodynamic processes. The inferred thermodynamic growth each year is nearly equal to the inferred melt consistent with SIV at the end of the melt season declining more rapidly than SIV at the end of the growth season. Increased melt season atmospheric heating of the ice-ocean system over 1979–2023, estimated from ERA5 reanalysis, is consistent with the ice-albedo feedback. In the growth season, net cumulative atmospheric heat release from the ice-ocean system shows no trend, suggesting increases in inferred thermodynamic ice growth can be attributed to more rapid growth of thinner ice. In each season, cumulative atmospheric heat input exceeds that required for ice melt/growth resulting in a residual that influences ocean heat content (OHC). Seasonal OHC changes, inferred from ocean observations, are equal to approximately one-third of this residual, although limited ocean observations leave the total heat budget poorly constrained, highlighting a need for more water column observations.