Contribution of Snow to Arctic First-Year and Multi-Year Sea Ice Mass Balance Within the Last Ice Area

Abstract

We present the δ18O isotope composition of 16 multi-year ice (MYI) and eight first-year ice (FYI) cores collected during spring from the Lincoln Sea, a region within the Last Ice Area, which is expected to retain MYI longest into the future. Isotopic signatures were used to quantify the contribution of snow to sea ice mass. These estimates yield a higher total snow contribution in MYI (10 ± 5%) than to FYI (4 ± 2%). Converted to Snow Depth Equivalent (SDE), MYI had five times larger SDE (0.79 ± 0.38 m) than FYI (0.16 ± 0.11 m). The difference is explained by the contribution of refrozen surface and under-ice melt ponds as well as superimposed/interposed ice for MYI resulting from higher accumulation of snow over multiple, longer accumulation seasons compared to FYI. Given the impending replacement of MYI by FYI, the large difference in absolute snow contributions between MYI and FYI highlights the potential implications in terms of the redistribution of precipitation-derived (meteoric) freshwater throughout the Arctic Ocean. Furthermore, we observed high relative snow contributions to ice mass in the surface of one-third of older FYI cores, which we attributed to flooding and formation of snow-ice. Our results support the premise that flooding events on FYI may be more prevalent throughout the Arctic Ocean than previously assumed.