Preprints
https://doi.org/10.5194/egusphere-2024-522
https://doi.org/10.5194/egusphere-2024-522
01 Mar 2024
 | 01 Mar 2024
Status: this preprint is open for discussion.

Arctic glacier snowline altitudes rise 150 meters over the last four decades

Laura J. Larocca, James M. Lea, Michael P. Erb, Nicholas P. McKay, Megan Phillips, Kara A. Lamantia, and Darrell S. Kaufman

Abstract. The number of Arctic glaciers with direct, long–term measurements of mass balance is limited. Here we used satellite–based observations of the glacier snowline altitude (SLA), the location of the transition between snow cover and ice late in the summer, to approximate the position of the equilibrium line altitude (ELA)–a parameter important for mass balance assessment and for understanding the response of glaciers to climate change. We mapped the snowline (SL) on a subset of 269 land–terminating glaciers above 60 °N latitude in the latest available summer, clear–sky Landsat satellite image between 1984 and 2022. The mean SLA was extracted using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM). We compare remotely–observed SLA observations with available long–term field–based measurements of ELA and with ERA5–Land reanalysis climate data. Over the last four decades, Arctic glacier SLAs have risen an average of ~152 m (3.9±0.4 m yr–1; R2=0.74, p<0.001), with a corresponding summer (June, July, August) temperature shift of +1.2 °C at the glacier locations. This equates to a 127±5 m shift per 1 °C of summer warming. However, along with warming, we observe an overall decrease in snowfall, an increase in rainfall, and a decrease in the total number of days in which the mean daily temperature is less than or equal to 0 °C. Glacier SLA is most strongly correlated with the number of freezing days, emphasizing the dual effect of multi–decadal trends in mean annual temperature on both ablation (increasing melt) and accumulation processes (reducing the number of days in which snow can fall). Although we find evidence for a negative morpho–topographic feedback that occurs as glaciers retreat to higher elevations, we show that more than 50 % of the glaciers studied here could be entirely below the SLA by 2100, assuming the pace of global warming and the mean rate of SLA rise is maintained.

Laura J. Larocca, James M. Lea, Michael P. Erb, Nicholas P. McKay, Megan Phillips, Kara A. Lamantia, and Darrell S. Kaufman

Status: open (until 02 May 2024)

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Laura J. Larocca, James M. Lea, Michael P. Erb, Nicholas P. McKay, Megan Phillips, Kara A. Lamantia, and Darrell S. Kaufman
Laura J. Larocca, James M. Lea, Michael P. Erb, Nicholas P. McKay, Megan Phillips, Kara A. Lamantia, and Darrell S. Kaufman

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Short summary
Here we present summer snowline altitude (SLA) timeseries for 269 Arctic glaciers. Between 1984 and 2022, SLAs rose ~150 m, equating to a ~127 m shift per 1 °C of summer warming. SLA is most strongly correlated with annual temperature variables, highlighting their dual effect on ablation and accumulation processes. We show that SLAs are rising fastest on low elevation glaciers, and that >50 % of the studied glaciers may be doomed to disappear by 2100 if the mean rate of SLA rise is maintained.