接地帯の発見がグリーンランドの氷河の融解加速を説明する(Grounding zone discovery explains accelerated melting under Greenland’s glaciers)

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2024-03-13 カリフォルニア大学校アーバイン校(UCI)

カリフォルニア大学アーバイン校とNASAジェット推進研究所の研究者は、グリーンランド北西部のピーターマン氷河に関する初の大規模な観測およびモデリング研究を行いました。その結果、氷河の加速された融解の原因は、21世紀初頭以来、氷下の温かい海水の侵入であることが明らかになりました。彼らのコンピュータ予測によれば、潜在的な海面上昇はこれまでの予測よりもはるかに悪化する可能性があることが示されました。研究では、ピーターマン氷河の潮汐運動をマッピングするために欧州の衛星ミッションからのレーダー干渉データを使用し、気候変動の影響を推定するためにマサチューセッツ工科大学の一般的な計算モデルを使用しました。

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グリーンランド、ペテルマン・グレッチャー接地帯の海水侵入による氷の融解速度のモデル化 Modeling Ice Melt Rates From Seawater Intrusions in the Grounding Zone of Petermann Gletscher, Greenland

R. Gadi, E. Rignot, D. Menemenlis
Geophysical Research Letters  Published: 22 December 2023
DOI:https://doi.org/10.1029/2023GL105869

接地帯の発見がグリーンランドの氷河の融解加速を説明する(Grounding zone discovery explains accelerated melting under Greenland’s glaciers)

Abstract

Satellite radar interferometry data reveals that the grounding line of Petermann Glacier, Greenland migrates by several kilometers during the tidal cycle, bringing pressurized, subsurface, warm ocean waters in regular contact with a large sector of grounded ice. We use the Massachusetts Institute of Technology general circulation model in two dimensions to calculate the ice melt rates as a function of grounding zone (GZ) length and ocean Thermal Forcing (TF). Ice melt rates are found to be higher in the GZ cavity than anywhere else in the ice shelf cavity. The melt rates increase sub-linearly with the length of the GZ and ocean TF. The model results agree well with remote sensing estimates of ice melt. High basal ice melt rates in tidally flushed grounding zones imply that marine-terminating glaciers are more sensitive to ocean TF than anticipated, which will increase their projected contribution to sea level rise.

Key Points

  • First modeling of ice melt rates from seawater intrusions in the kilometer-size grounding zone (GZ) of Petermann Glacier using an ocean model
  • Modeled melt rates are highest in the GZ and increase linearly with GZ width and ocean thermal forcing
  • High melt rates in kilometer-size grounding zones imply a higher sensitivity of glaciers to ocean warming than anticipated

Plain Language Summary

The traditional view of ice melting in contact with ocean waters is that melt rates drop to zero at the grounding line, which is a semi-fixed boundary at the junction between grounded ice and the ocean. In reality, the grounding line migrates by kilometers during the tidal cycle, more than 10 times beyond the range expected from hydrostatic equilibrium, which brings warm, saline water in rapid contact with broad sectors of grounded ice. We use an ocean model to calculate the melt rates caused by seawater intrusions. We find that the melt rates in the GZ are higher than anywhere else in the ice shelf cavity and increase as the GZ becomes wider and the ocean gets warmer. Ice melt in kilometer-size grounding zones will reduce the basal resistance to flow and will increase the sensitivity of the glacier flow to ocean warming, hence projections of sea level rise from the glacier will go up.

1702地球物理及び地球化学
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