Resiliency of Arctic sea ice to warming from southerly advection in early spring

Summertime surface melt over sea ice was observed in situ by the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) on May 25, 2020. The melt was initiated by longwave radiative forcing from a warm, cloudy air mass advected from lower latitudes, similar to that observed in 1998 during the Surface Heat Budget of the Arctic Ocean in the Beaufort Sea. In addition to triggering melt onset, research suggests that springtime atmospheric advection may also precondition Arctic sea ice for melt onset by rapidly increasing its internal energy. In keeping with this, we find that an advection event in April 2020 delivered 42% of the springtime increase in internal energy the MOSAiC ice floes underwent prior to melt onset. However, we argue that the potential for this preconditioning to affect the melt onset date is limited. We test whether the energy retained within the snow/ice column from the event was significant relative to the hypothetical scenario that the event did not reach MOSAiC. We apply both observed surface temperatures and counterfactual (simulated) ones characterized by the event’s absence to a diffusion model representing the snow and ice. We find that the energy storage anomaly in the ice from the event decays rapidly relative to the scenario that omits advection (e-folding time 6.9 days). This diminishing impact is because the initial warming reduces the temperature gradient in the ice column, creating a negative feedback that suppresses heating thereafter. The influence of the April advection dissipated in the ice several weeks prior to melt onset. A more important precursor to melt onset may be the date of persistently positive atmospheric forcing, which causes convergence of flux within the ice. These results imply that negative feedbacks associated with heat conduction are a moderating factor to the beginning of the melt season.