[A-CG42] 北極域の科学

[ACG42-15] 西グリーンランド域の領域モデル開発 〜大西洋起源水変動及び氷河融解変動の理解〜

*大谷 若葉¹、中山 佳洋²、Michael Wood⁴、Fenty Ian³、Mensah Vigan² (1.北海道大学環境科学院、2.北海道大学低温科学研究所、3.NASAジェット推進研究所、4.Moss Landing Marine Laboratories)

キーワード：グリーンランド、大西洋起源水

The North Atlantic subpolar gyre carries Atlantic Water (AW) towards the margins of western Greenland, which intrudes into fjords and contributes to the recent retreat and acceleration of Greenland Glaciers. The AW transport by subpolar gyre towards West Greenland Current(WGC) is suggested to be controlled by the North Atlantic Oscillation. During sustained positive NAO index, an increase in westerly winds enhances AW advection from the Irminger Sea. However, it is still unclear how AW intrudes onto the continental shelf, travels over the continental shelf, and flows into fjords and towards glaciers. This may generate uncertainty in understanding the glacier melting. Here, we develop a regional ocean model in West Greenland downscaled from ECCO LLC 270 global state estimate for 26 years (1992-2017) using the Massachusetts Institute of Technology general circulation model (MITgcm). Horizontal grid spacing is 3-4km. The vertical discretization comprises 50 levels varying in thickness. We employ the iceplume model and force the model using the subglacial freshwater discharge calculated by Model Atmospheric Regional(MAR) over the land and ice areas of Greenland.We compare our simulated output with existing ship-based observations, Argo floats, and moorings. We further investigate AW variability along WGC by comparing the model and observations focusing on the water mass distributions, properties, and variabilities. Our model simulates the warming trend of 0.18℃ per year at the front of Jakobshavn Glacier. The model also simulates high seasonal variabilities from Davis Strait to Jakobshavn Glacier with temperature peaks identified from November to July.The simulated temperature fluctuates seasonally and interannually.We also conduct sensitivity experiments with ice plume parameterization and with an equal amount of freshwater flux only at the surface. These sensitivity experiments highlight the importance of subglacial freshwater discharge in enhancing the AW inflow into West Greenland fjords.