Vertical Land Motion From Present‐Day Deglaciation in the Wider Arctic

• Published in: Geophysical research letters 2020-10, Vol.47 (19), p.n/a
• Main Authors: Ludwigsen, Carsten Ankjær, Khan, Shfaqat Abbas, Andersen, Ole Baltazar, Marzeion, Ben
• Format: Article
• Language: English
• Subjects: Ablation; Arctic; Arctic glaciers; Arctic ice; coastal sea level; Coastal zone; Deformation; Deglaciation; Earth surface; Glaciers; Global positioning systems; Global sea level; GPS; Greenland; Ice ages; Land ice; Mean sea level; Meltwater; Northern Hemisphere; Sea level; Sea level changes; Sea level rise; Uplift; vertical land motion
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL088144

Vertical land motion (VLM) from past and ongoing glacial changes can amplify or mitigate ongoing relative sea level change. We present a high‐resolution VLM model for the wider Arctic, that includes both present‐day ice loading (PDIL) and glacial isostatic adjustment (GIA). The study shows that the nonlinear elastic uplift from PDIL is significant (0.5–1 mm yr−1) in most of the wider Arctic and exceeds GIA at 15 of 54 Arctic GNSS sites, including sites in nonglaciated areas of the North Sea region and the east coast of North America. Thereby the sea level change from PDIL (1.85 mm yr−1) is significantly mitigated from VLM caused by PDIL. The combined VLM model was consistent with measured VLM at 85% of the GNSS sites ( R=0.77) and outperformed a GIA‐only model ( R=0.64). Deviations from GNSS‐measured VLM can be attributed to local circumstances causing VLM. Plain Language Summary From 2003 to 2015, the Northern Hemisphere lost more than 6,000 gigatons of land ice, which added nearly 18 mm to the global mean sea level rise. Loss of land‐based ice results in the vertical deformation of the Earth's surface. Ongoing rebounding or subsidence caused by the end of the last ice age is often assumed to govern vertical deformation. However, present‐day ice loss from Greenland and Arctic glaciers also cause an immediate vertical deformation. By using an vertical deformation model, that includes both components, we can explain GPS‐measured deformation occurring in the Arctic. Our results show that the present‐day Arctic ice loss contribution to vertical deformation is ∼0.5 to 1 mm yr−1 in the wider northern region. This exceeds deformation caused by the disappearance of the last ice ages at many coastal regions, including the North Sea region and the North American Atlantic coast. The Arctic present‐day ice loss included in the VLM model equals a global sea level rise of 1.5 mm yr−1, which means that 30–80% of the sea level rise caused by Arctic ice loss is mitigated by surface uplift caused by the same ice loss. Key Points Elastic VLM from present‐day ice loss in the Arctic causes significant uplift of coastlines in North America and Northern Europe A combined VLM model that includes GIA and elastic VLM yields good agreement with GNSS stations in the wider Arctic Residuals between GNSS and modeled VLM provide an approximation of extraordinary VLM caused by local circumstances