Inland thinning of Byrd Glacier, Antarctica, during Ross Ice Shelf formation

• Published in: Earth surface processes and landforms Vol. 48; no. 15; pp. 3363 - 3380
• Main Authors: Stutz, Jamey, Eaves, Shaun, Norton, Kevin, Wilcken, Klaus M., Moore, Claudia, McKay, Rob, Lowry, Dan, Licht, Kathy, Johnson, Katelyn
• Format: Journal Article
• Language: English
• Published: Bognor Regis Wiley Subscription Services, Inc 01.12.2023
• Subjects: Antarctic ice sheet reconstruction; Boundary conditions; Cobblestone; cosmogenic nuclides; data‐model comparison; Exposure; Geology; Geomorphology; glacial geomorphology; Glaciation; Glacier retreat; Glaciers; Holocene; Ice; Ice cover; Ice sheet thickness; Ice sheets; Ice shelves; Land ice; Last Glacial Maximum; Marine geology; Matching; Modelling; Mountain glaciers; Mountains; Nunataks; Records; Sliding; Slumping; Spacecraft recovery; Stability; surface exposure dating; Thickness; Thinning
• ISSN: 0197-9337; 1096-9837
• DOI: 10.1002/esp.5701

Geomorphological records of past ice sheet change offer the opportunity to examine their centennial‐scale response to changing boundary conditions, which are not adequately captured in the satellite record. Here, we present the first reconstruction of ice surface lowering at Byrd Glacier, the largest outlet glacier of the Transantarctic Mountains. Using surface exposure ages from glacial erratic cobbles collected in two vertical transects along the Lonewolf Nunataks, we find the initial emergence of this set of nunataks occurred at ~15 ka, with a rapid pulse of thinning at ~8 ka. We compare our glacier thinning profiles with modelled ice sheet thickness and grounding line histories from two model ensembles to identify key processes responsible for ice sheet change. All model runs from the two ensembles predict grounding line retreat and inland thinning to occur in one rapid step from Last Glacial Maximum to present, in line with marine geology records, our exposure age data and derived glacier thinning rates. Experiments best matching the glacial thickness constraints, reconstructed from the surface exposure data, have faster basal sliding (i.e., promote greater sliding rates resulting in thinner ice). However, experiments best matching the timing and rapid rate of ice thinning derived from the same surface exposure data have higher basal friction. This apparent change in the modelled basal sliding regime, from when the ice surface is at maximum thickness, to the rapid thinning at ~8 ka, occurs as the grounding line retreats towards the Byrd Glacier and Ross Ice Shelf forms during the Holocene. This past context has implications for the stability of the modern grounding line of Byrd Glacier, which is characterised by high basal melt rates at the terminus—a process that has the potential to propagate glacier thinning far inland, impacting the overall (in)stability of the Byrd Glacier and Ross Ice Shelf. Using surface exposure ages from glacial erratic cobbles at two sites within the Lonewolf Nunataks, we find the initial glacial thinning occurred at ~15 ka, with rapid thinning at ~8 ka. Ice sheet model simulations that best match our thickness constraints have faster basal sliding, but models best matching our timing have higher basal friction. This apparent change in basal sliding regime from the Last Glacial Maximum to present may be related to the formation of the Ross Ice Shelf.