Upper Mantle Viscosity Underneath Northern Marguerite Bay, Antarctic Peninsula Constrained by Bedrock Uplift and Ice Mass Variability. Issue 24 (24th December 2021)

• Record Type: Journal Article
• Authors: Samrat, Nahidul Hoque; King, Matt A.; Watson, Christopher; Hay, Andrea; Barletta, Valentina R.; Bordoni, Andrea
• Is Part Of: Geophysical research letters. Volume 48:Issue 24(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-12-24
• Subjects: satellite geodesy -- space geodetic surveys -- Antarctica -- dynamics of lithosphere and mantle -- ice mass -- rheology: lithosphere and mantle; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL097065
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: We constrain viscoelastic Earth rheology and recent ice‐mass change in the northern Marguerite Bay region of the Antarctic Peninsula. Global Positioning System (GPS) time series from Rothera and San Martin stations show bedrock uplift range of ∼−0.8–1.8 mm/year over 1999–2005 and 2016–2020 but ∼3.5–6.0 mm/year over ∼2005–2016. Digital elevation models reveal substantial surface lowering, but at a lower rate since ∼2009. Using these data, we show that an elastic‐only model cannot explain the non‐linear uplift of the GPS sites but that a layered viscoelastic model can. We show close agreement between GPS uplift changes and viscoelastic models with effective elastic lithosphere thickness and upper‐mantle viscosity ∼10–95 km and ∼0.1−9 × 10 18 Pa s, respectively. Our viscosity estimate is consistent with a north‐south gradient in viscosity suggested by previous studies focused on specific regions within the Antarctic Peninsula and adds further evidence of the low viscosity upper mantle in the northern Antarctic Peninsula. Plain Language Summary: Over the last few decades, the glaciers of the Antarctic Peninsula have thinned tens to hundreds of meters. This unloading of the solid Earth has produced a viscoelastic response of the solid Earth. By observing this response and comparing it to viscoelastic models combined with ice unloading models, we may infer the viscoelastic properties of the Earth in this region. In this study, we estimate ice mass changes over 15 years using satellite images. Then we analyze estimates of solid Earth displacement from continuous Global Positioning System (GPS) stations attached to bedrock. When compared to the predictions of deformation from viscoelastic models with different Earth properties and ice mass change rates, we find the rate of glacier thinning must have slowed since around 2009–2010 and suggests a thin elastic lithosphere with a lower‐viscosity upper mantle underneath this region. Key Points: GPS‐measured time‐varying uplift rates ranging between ∼1.6 ± 0.8 and ∼6.0 ± 0.6 mm/year over 1999.1–2016.0 in Northern Marguerite Bay Glaciers in the region generally show a reduced rate of surface lowering since ∼2009 Comparing GPS and modeled viscoelastic deformation suggests a lower‐viscosity upper mantle for this region with possible thin lithosphere