Larocca Laura, Assistant Professor, School of Ocean Futures in the Rob Walton College of Global Futures, Julie Ann Wrigley Global Futures Laboratory, is lead author on Glacier Equilibrium‐Line Altitude Change Across Alaska and Adjacent Canada Indicates a Cold, Dry Little Ice Age and Weaker Aleutian Low, a new publication in Geophysical Research Letters.
Glaciers respond sensitively to changes in climate, particularly to shifts in temperature and precipitation. In this study, measured how much the altitude of the glacier equilibrium line (the boundary between snow accumulation and melt) has changed since the Little Ice Age (LIA), a cool period from year ∼1250–1900. Across 215 glaciers in Alaska, the equilibrium line has risen by an average of ∼170 m. This change is roughly equivalent to ∼1.6°C of summer warming or an increase of ∼250 mm in annual precipitation. Factors such as glacier orientation, slope, and topographic setting (elevation), explain about one‐ third of the variation in how much equilibrium lines have shifted, likely reflecting differences in glacier sensitivity to climate changes and stronger warming at higher elevations. After accounting for these effects, the remaining changes correlate more strongly with climate variables, particularly with winter precipitation. Overall, the magnitude and spatial pattern of equilibrium line shifts across Alaska indicate (a) climate during the LIA was colder and drier than today, consistent with a positive coupling between temperature and precipitation over the past several centuries, and (b) a weaker, westward‐shifted Aleutian Low pressure system during the LIA, which has since strengthened and migrated eastward.
Says Laura: New paleo–glacier evidence indicates that Arctic warming since the Little Ice Age was accompanied by overall wetting, reflecting a positive long-term coupling between temperature and precipitation. An Alaska-wide reconstruction of equilibrium-line altitude changes across 215 glaciers shows that warming coincided with increased precipitation linked to changes in the Aleutian Low, a semi-permanent low-pressure system. The results further suggest that, as warming progresses, increased precipitation is becoming less effective at limiting glacier mass loss as snowfall shifts to rain, highlighting constraints on future precipitation-driven buffering of glacier loss.