Role of Snowfall Versus Air Temperatures for Greenland Ice Sheet Melt‐Albedo Feedbacks

Abstract

The Greenland Ice Sheet is a leading contributor to global sea‐level rise because climate warming has enhanced surface meltwater runoff. Melt rates are particularly sensitive to air temperatures due to feedbacks with albedo. The primary melt‐albedo feedback, fluctuation of seasonal snowlines, however, is determined not only by melt but also by antecedent snowfall which could delay the onset of dark glacier ice exposure. Here we investigate the role of snowfall versus air temperatures on ice sheet melt‐albedo feedbacks using satellite remote sensing and atmospheric reanalysis data. We find several lines of evidence that snowline fluctuations are driven primarily by air temperatures and that snowfall is a secondary control. First, standardized linear regressions indicate that the timing of glacier ice exposure is nearly twice as sensitive to air temperatures than antecedent snowfall. Second, in 74% of the ablation zone by area, winter snowfall rates are not significantly correlated with winter air temperatures. This relationship implies that ice sheet melt due to climate warming is unlikely to be compensated by higher snowfall rates in the ablation zone. Third, we find no significant change in snowfall rates in the ablation zone during our 1981–2021 study period. Our findings demonstrate that snowfall is unlikely to reduce future ice sheet melt and that ice sheet meltwater runoff should be accurately predicted by air temperatures. Although given the importance of melt‐albedo feedbacks, ice sheet models that parameterize albedo or are coupled with regional climate models are likely to provide the most accurate projections of mass loss.

Impacts of emissions uncertainty on Antarctic instability and sea-level rise

“…More rapid near-term emissions growth increases the amount of time ice sheets are exposed to warmer air and ocean waters. Two mechanisms may contribute to a nonlinear response to this increased exposure: reduction in ice sheet buttressing and melt-elevation feedbacks [20][21][22][23]. As a result, two pathways with the same cumulative emissions may yield different GMSLR levels by a given year, depending on the interactions between the emissions pathway and the geophysical sensitivity to those emissions.…”