TY - JOUR
T1 - Blue-ice moraines formation in the Heritage Range, West Antarctica
T2 - Implications for ice sheet history and climate reconstruction
AU - Woodward, John
AU - Hein, Andrew S.
AU - Winter, Kate
AU - Westoby, Matthew J.
AU - Marrero, Shasta M.
AU - Dunning, Stuart A.
AU - Lim, Michael
AU - Rivera, Andrés
AU - Sugden, David E.
N1 - Funding Information: The research was funded by the UK Natural Environment Research Council grant numbers NE/I025840/1 , NE/I027576/1 , NE/I024194/1 and NE/I025263/1 . We thank the British Antarctic Survey for logistical support and Scott Webster, Malcolm Airey and Phil Stevens for field support. Reed Scherer kindly checked till samples for marine diatoms.
PY - 2022/4/1
Y1 - 2022/4/1
N2 - Blue ice is found in areas of Antarctica where katabatic winds, focussed by steep surface slopes or by topography around nunataks, cause enhanced surface ablation. This process draws up deeper, older ice to the ice sheet surface, often bringing with it englacial sediment. Prevailing theories for dynamically stable moraine surfaces in East Antarctica suggest that: (i) it is this material, once concentrated, that forms blue-ice moraines (BIM), (ii) that the moraine formation can be dated using cosmogenic isotope approaches, and that, (iii) since we expect an increase in exposure age moving away from the ice margin towards bedrock, dating across the moraine can be used to constrain ice-sheet history. To test this lateral accretion model for BIM formation we visited Patriot, Marble and Independence Hills in the southern Heritage Range, West Antarctica. Detailed field surveys of surface form, sediment and moraine dynamics were combined with geophysical surveys of the englacial structure of the moraines and cosmogenic nuclide analysis of surface clasts. Results suggest sediment is supplied mainly by basal entrainment, supplemented by debris-covered valley glaciers transferring material onto the ice sheet surface, direct deposition from rock-fall and slope processes from nunataks. We find that once sediment coalesces in BIM, significant reworking occurs through differential ablation, slope and periglacial processes. We bring these processes together in a conceptual model, concluding that many BIM in West Antarctica are dynamic and, whilst they persist through glacial cycles, they do not always neatly record ice sheet retreat patterns since linear distance from the ice margin does not always relate to increased clast exposure age. Understanding the dynamic processes involved in moraine formation is critical to the effective interpretation of the typically large scatter of cosmogenic nuclide exposure ages, opening a deep window into the million-year history of the West Antarctic Ice Sheet.
AB - Blue ice is found in areas of Antarctica where katabatic winds, focussed by steep surface slopes or by topography around nunataks, cause enhanced surface ablation. This process draws up deeper, older ice to the ice sheet surface, often bringing with it englacial sediment. Prevailing theories for dynamically stable moraine surfaces in East Antarctica suggest that: (i) it is this material, once concentrated, that forms blue-ice moraines (BIM), (ii) that the moraine formation can be dated using cosmogenic isotope approaches, and that, (iii) since we expect an increase in exposure age moving away from the ice margin towards bedrock, dating across the moraine can be used to constrain ice-sheet history. To test this lateral accretion model for BIM formation we visited Patriot, Marble and Independence Hills in the southern Heritage Range, West Antarctica. Detailed field surveys of surface form, sediment and moraine dynamics were combined with geophysical surveys of the englacial structure of the moraines and cosmogenic nuclide analysis of surface clasts. Results suggest sediment is supplied mainly by basal entrainment, supplemented by debris-covered valley glaciers transferring material onto the ice sheet surface, direct deposition from rock-fall and slope processes from nunataks. We find that once sediment coalesces in BIM, significant reworking occurs through differential ablation, slope and periglacial processes. We bring these processes together in a conceptual model, concluding that many BIM in West Antarctica are dynamic and, whilst they persist through glacial cycles, they do not always neatly record ice sheet retreat patterns since linear distance from the ice margin does not always relate to increased clast exposure age. Understanding the dynamic processes involved in moraine formation is critical to the effective interpretation of the typically large scatter of cosmogenic nuclide exposure ages, opening a deep window into the million-year history of the West Antarctic Ice Sheet.
KW - Blue ice moraine
KW - Cosmogenic nuclide dating
KW - Geophysical surveys
KW - Ice sheet history
KW - West Antarctic ice sheet
UR - http://www.scopus.com/inward/record.url?scp=85125868740&partnerID=8YFLogxK
U2 - 10.1016/j.qsa.2022.100051
DO - 10.1016/j.qsa.2022.100051
M3 - Article
AN - SCOPUS:85125868740
SN - 2666-0334
VL - 6
JO - Quaternary Science Advances
JF - Quaternary Science Advances
M1 - 100051
ER -