2023-05-08 カリフォルニア大学校アーバイン校(UCI)
◆ペテルマン氷河のグラウンディングラインは、潮汐サイクル中に大きく変化し、温かい海水が侵入して氷が加速度的に融解するようになることがわかりました。新しい研究では、海に向かっている氷河のグラウンディングラインは、潮汐サイクル中に移動せず、氷が融解することはないという従来の考え方を置き換えます。これらのダイナミックスをモデルに含めると、ピーターマン氷河だけでなく、海に面したほとんどの北グリーンランドの氷河および南極大陸の氷河について、海面上昇の予測が最大200％増加する可能性があるとされています。
＜関連情報＞
- https://news.uci.edu/2023/05/08/uc-irvine-nasa-jpl-researchers-discover-a-cause-of-rapid-ice-melting-in-greenland/
- https://www.pnas.org/doi/10.1073/pnas.2220924120
グリーンランド、ペテルマン氷河のキロメートル規模の接地帯における後退前と後退中の融解速度 Melt rates in the kilometer-size grounding zone of Petermann Glacier, Greenland, before and during a retreat
Enrico Ciracì, Eric Rignot, Bernd Scheuchl, Valentyn Tolpekin, Michael Wollersheim, Lu An, Pietro Milillo, Jose-Luis Bueso-Bello, Paola Rizzoli and Luigi Dini
Proceedings of the National Academy of Sciences Published:May 8, 2023
DOI:https://doi.org/10.1073/pnas.2220924120
Significance
We present a record of glacier ice dynamics and ice melt rate at the boundary between grounded ice and ocean—or grounding line—of Petermann Glacier, a major outlet glacier in Northwest Greenland. The traditional view of grounding lines implemented in ice sheet models in charge of projecting sea level rise is that they not migrate during the tidal cycle and experiences no ice melt. Instead, the satellite record reveals kilometer-size grounding line migrations—or grounding zones—with preferential intrusions along preexisting subglacial channels. The highest melt rates of ice are recorded within the grounding zone. Vigorous ice-ocean interaction in kilometer-wide grounding zone will make projections of sea level rise from glaciers potentially double.
Abstract
Warming of the ocean waters surrounding Greenland plays a major role in driving glacier retreat and the contribution of glaciers to sea level rise. The melt rate at the junction of the ocean with grounded ice—or grounding line—is, however, not well known. Here, we employ a time series of satellite radar interferometry data from the German TanDEM-X mission, the Italian COSMO-SkyMed constellation, and the Finnish ICEYE constellation to document the grounding line migration and basal melt rates of Petermann Glacier, a major marine-based glacier of Northwest Greenland. We find that the grounding line migrates at tidal frequencies over a kilometer-wide (2 to 6 km) grounding zone, which is one order of magnitude larger than expected for grounding lines on a rigid bed. The highest ice shelf melt rates are recorded within the grounding zone with values from 60 ± 13 to 80 ± 15 m/y along laterally confined channels. As the grounding line retreated by 3.8 km in 2016 to 2022, it carved a cavity about 204 m in height where melt rates increased from 40 ± 11 m/y in 2016 to 2019 to 60 ± 15 m/y in 2020 to 2021. In 2022, the cavity remained open during the entire tidal cycle. Such high melt rates concentrated in kilometer-wide grounding zones contrast with the traditional plume model of grounding line melt which predicts zero melt. High rates of simulated basal melting in grounded glacier ice in numerical models will increase the glacier sensitivity to ocean warming and potentially double projections of sea level rise.
