Hypsometric control on glacier mass balance sensitivity in Alaska and northwest Canada

Abstract

Glacier hypsometry provides a first-order approach for assessing a glacier's response to climate forcings. We couple the Randolph Glacier Inventory to a suite of in situ observations and climate model output to examine potential change for the ∼27,000 glaciers in Alaska and northwest Canada through the end of the 21st century. By 2100, based on Representative Concentration Pathways (RCPs) 4.5-8.5 forcings, summer temperatures are predicted to increase between +2.1 and +4.6 ∘ C, while solid precipitation (snow) is predicted to decrease by −6 to −11%, despite a +9 to +21% increase in total precipitation. Snow is predicted to undergo a pronounced decrease in the fall, shifting the start of the accumulation season back by ∼1 month. In response to these forcings, the regional equilibrium line altitude (ELA) may increase by +105 to +225 m by 2100. The mass balance sensitivity to this increase is highly variable, with the most substantive impact for glaciers with either limited elevation ranges (often small (<1 km 2 ) glaciers, which account for 80% of glaciers in the region) or those with top-heavy geometries, like icefields. For more than 20% of glaciers, future ELAs, given RCP 6.0 forcings, will exceed the maximum elevation of the glacier, resulting in their eventual demise, while for others, accumulation area ratios will decrease by >60%. Our results highlight the first-order control of hypsometry on individual glacier response to climate change, and the variability that hypsometry introduces to a regional response to a coherent climate perturbation.

Hydrologic impacts of changes in climate and glacier extent in the Gulf of Alaska watershed

“…The glaciers in the GOA are anticipated to retreat significantly by the end of the century [e.g., Huss and Hock , ; McGrath et al ., ]. Given that the timing and magnitude of runoff from glacier catchments depend strongly on the areal extent of glacier ice, it is necessary to model future glacier extent prior to conducting studies to forecast hydrologic responses.…”

“…Climate models predict that the GOA will become warmer and wetter in the future [ McAfee et al ., ], leading to significant reductions in snowpack and glacier extent [ Bliss et al ., ; Huss and Hock , ; McGrath et al ., ]. Increased precipitation and air temperature, decreased snow/rain fraction [ McAfee et al ., ], changes in land cover [ Bieniek et al ., ; McGrath et al ., ], and glacier‐derived runoff [ O'Neel et al ., ] have the potential to drive large downstream changes in the timing, magnitude, and composition of the freshwater discharge to the GOA.…”

Glacierized headwater streams as aquifer recharge corridors, subarctic Alaska

“…Mountain glacier mass loss is ubiquitous in recent decades [ Gardner et al ., ], with some of the most rapid rates of change in Alaska [ Jacob et al ., ; Larsen et al ., ; Radić and Hock , ] and in the Arctic [ Dyurgerov et al ., ; Geck et al ., ; Nuth et al ., ; Shahgedanova et al ., ]. Glaciers in continental regions are generally losing volume at an accelerating rate [ Dyurgerov and Meier , ; McGrath et al ., ] and small mountain glaciers (~1 km 2 ) are some of the most sensitive to climate and significant contributors to total glacier coverage loss [ Bolch et al ., ; McGrath et al ., ; Paul et al ., ]. High‐latitude mountain glaciers, which represent about 50% of the world's mountain glacier area [ Björnsson et al ., ], have been identified via glacier mass balance studies to be a major source of the increased freshwater inflow to the Arctic Ocean [ Bring and Destouni , ; Dyurgerov et al ., ; Dyurgerov and Carter , ; Neal et al ., ; Weingartner et al ., ].…”

Hydrologic Diversity in Glacier Bay Alaska: Spatial Patterns and Temporal Change

“…The steady-state AAR (AAR0) was chosen to be 0.65, based on the observations of several benchmark Alaskan glaciers by Mernild et al (2013). While some studies have suggested that AAR0 values change in the future, Beamer et al (2017) found that the assumption of a steady-state AAR (i.e., keeping AAR fixed at 0.65 for the future runs) provided estimates of future glacier changes that are in accord with other published values (Huss and Hock, 2015;their figure S10;McGrath et al, 2017). As a result, we similarly assume AAR0 to be equal to 0.65 10 for the future runs.…”