New research in Nature reveals 85 years of glacier growth and stability in East Antarctica – Watts Up With That?

From CLIMATE ARCHIVES
Early aerial exploration photos reveal 85 years of glacier growth and stability in East Antarctica

Publication date: May 25, 2024 – Mads Dømgaard, Anders Schomacker, Elisabeth Isaksson, Romain Millan, Huiban Flora, Amaury Dehecq, Amanda Fleischer, Geir Moholdt, Jonas K. Andersen & Anders A. Bjørk

Nature Communications: Our results demonstrate that the stability and growth in ice elevation observed in terrestrial basins over the past few decades is part of a trend lasting at least a century and highlights the the importance of understanding long-term changes when explaining current dynamics. … However, in Antarctica, the scarcity of historical climate data makes estimates of climate reanalysis before the 1970s largely uncertain.^ten,23and the observed trends cannot be clearly distinguished from natural variation^24,25.

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By Marc Morano

https://www.nature.com/articles/s41467-024-48886-x

Early aerial exploration photos reveal 85 years of glacier growth and stability in East Antarctica

Published: May 25, 2024 – Mads Dømgaard, Anders Schomacker, Elisabeth Isaksson, Romain Millan, Huiban Flora, Amaury Dehecq, Amanda Fleischer, Geir Moholdt, Jonas K. Andersen & Anders A. Bjørk

Nature communication

Summary (Emphasis added)

Over the past few decades, some regions of Antarctica have shifted from a state of glacial mass balance to mass loss. To determine whether recent trends exceed the scale of natural variation, long-term observations are important. Here we explore the archive of Antarctica’s earliest, large-scale, aerial imagery to provide a unique record of 21 glaciers along the East Antarctic coast since the 1930s. In Lützow Bay -Holm, our results show that ice surface elevation has remained constant since the 1930s and signs that local land-bound sea ice conditions are weakening. Along the Kemp and Mac Robertson Coasts, and the Ingrid Christensen Coast, we observe moderate long-term thickening of glaciers since 1937 and 1960 with cyclical variability and decadal thinning . In all regions, long-term changes in ice thickness correspond to snowfall trends since 1940. Our results demonstrate that the stability and growth in ice elevation observed in terrestrial basins over the past few decades is part of a trend lasting at least a century and highlights the the importance of understanding long-term changes when explaining current dynamics.

Introduce

The East Antarctic Ice Sheet (EAIS) contains more than 52 m of potential sea level (SLE)^first. Recent observations suggest that the EAIS is more vulnerable than previously anticipated²and has contributed significantly to continent-wide mass loss over the past decades³. Damage mainly occurred in some coastal watersheds in Wilkes Land⁴and is largely due to Modified Circulating Deep Water (CDW) intrusion.². Terrestrial basins, where most of the ice lies above sea level, have recently shown an increase in volume due to increased accumulation.^5,6,7,8partially balanced the overall mass loss^9,ten. Time series observations of East Antarctic glaciers before the satellite era are rare¹¹ and therefore not long enough to determine whether recent trends are independent of natural fluctuations^2,twelfth. Historical datasets from early expeditions serve as a vital link connecting records from the pre-satellite era, such as those derived from ice cores¹³ or geology¹⁴ and geomorphological evidence¹⁵to quantitative observations of mass changes obtained from satellites^5,6,7. While geological and geomorphological records cover longer time ranges with temporal uncertainties of up to thousands of years.^14,15SMB estimates from ice cores are generally very local and spatially limited¹⁶. In contrast, data from historical aerial expeditions often provide coverage over large areas, with detailed information in time and space.^17,18,19. Additionally, historical data provide an important basis for forward modeling of glacier dynamics, allowing for long-term reanalysis data and more accurate model calibration.²⁰. In Greenland and Svalbard, long-term observations from historical aerial images have been important in determining the historical response of glaciers to climate change.^18,19,21,22. However, in Antarctica, the scarcity of historical climate data makes estimates of climate reanalysis before the 1970s largely uncertain.^ten,23and the observed trends cannot be clearly distinguished from natural variation^24,25.

Here, we rediscover and use images from the earliest large-scale aerial photography campaign conducted over the Antarctic continent, allowing us to extend the era of observational records of the Glacier evolution since the 1930s. Since the beginning of the 20th century^th This century, several expeditions have been deployed to Antarctica for the purpose of exploration and aerial photography to create geographical maps.^{26,27,28,29,30}. However, only a handful of previous studies have used these data to create digital elevation models (DEMs), and only for glaciers located in West Antarctica and the Antarctic Peninsula.^{11,thirty first,32}since 1947³². On the Antarctic Peninsula, these observations show widespread near-frontal surface lowering and inland stability since 1960^{thirty first}. On the other hand, historical observations of Byrd Glacier over the past 40 years show constant surface elevation, stable grounding, and surface flow rates¹¹.

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Currently, the earliest extensive mass balance estimates of the ice sheet date back to the late 1970s^3,6,7and since then, all subregions considered in this study have shown overall or relatively unchanged mass gains.

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Regardless of potential climate changes, our results indicate that glaciers in Kemp and Mac Robertson Land and along the Ingrid Christensen Coast, have accumulated mass over the past 85 years, which has certainly partially mitigate recent mass loss from East Antarctica marine basins. and the West Antarctic Ice Sheet (WAIS). This positive mass balance and accumulation trend is predicted to persist as snowfall is expected to increase across the entire EAIS over the next century.^54,55and projected ice sheet modeling studies estimate positive mass balance in all three subregions under all future RCP scenarios⁵⁶.

Finally, we determine the frontal changes of 21 glaciers from 1937 to 2023 (Table S1 and picture. S11). From 85 years of observations, we find two distinct regional patterns; one where the glacier surface elevation remains constant and one where the ice thickens.

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