TY - JOUR
T1 - A geomorphology based reconstruction of ice volume distribution at the Last Glacial Maximum across the Southern Alps of New Zealand
AU - James, William H. M.
AU - Carrivick, Jonathan L.
AU - Quincey, Duncan Joseph
AU - Glasser, Neil
N1 - Funding Information:
WJ was funded by a NERC PhD studentship ( NE/K500847/1 ). JC and WJ thanks the School of Geography, University of Leeds, for assistance with fieldwork costs. Trevor Chinn commented on an early version of the manuscript.
Publisher Copyright:
© 2019 The Authors
PY - 2019/9/1
Y1 - 2019/9/1
N2 - We present a 3D reconstruction of ice thickness distribution across the New Zealand Southern Alps at the Last Glacial Maximum (LGM, c. 30–18 ka). To achieve this, we used a perfect plasticity model which could easily be applied to other regions, hereafter termed REVOLTA (Reconstruction of Volume and Topography Automation). REVOLTA is driven by a Digital Elevation Model (DEM), which was modified to best represent LGM bed topography. Specifically, we removed contemporary ice, integrated offshore bathymetry and removed contemporary lakes. A review of valley in-fill sediments, uplift and denudation was also undertaken. Down-valley ice extents were constrained to an updated geo-database of LGM ice limits, whilst the model was tuned to best-fit known vertical limits from geomorphological and geochronological dating studies. We estimate a total LGM ice volume of 6,800 km3, characterised predominantly by valley style glaciation but with an ice cap across Fiordland. With a contemporary ice volume of approximately 50 km3, this represents a loss of 99.25% since the LGM. Using the newly created ice surface, equilibrium line altitudes (ELAs) for each glacier were reconstructed, revealing an average ELA depression of approximately 950 m from present. Analysis of the spatial variation of glacier-specific ELAs and their depression relative to today shows that whilst an east-west ELA gradient existed during the LGM it was less pronounced than at present. The reduced ELA gradient is attributed to an overall weakening of westerlies, a conclusion consistent with those derived from the latest independent climate models
AB - We present a 3D reconstruction of ice thickness distribution across the New Zealand Southern Alps at the Last Glacial Maximum (LGM, c. 30–18 ka). To achieve this, we used a perfect plasticity model which could easily be applied to other regions, hereafter termed REVOLTA (Reconstruction of Volume and Topography Automation). REVOLTA is driven by a Digital Elevation Model (DEM), which was modified to best represent LGM bed topography. Specifically, we removed contemporary ice, integrated offshore bathymetry and removed contemporary lakes. A review of valley in-fill sediments, uplift and denudation was also undertaken. Down-valley ice extents were constrained to an updated geo-database of LGM ice limits, whilst the model was tuned to best-fit known vertical limits from geomorphological and geochronological dating studies. We estimate a total LGM ice volume of 6,800 km3, characterised predominantly by valley style glaciation but with an ice cap across Fiordland. With a contemporary ice volume of approximately 50 km3, this represents a loss of 99.25% since the LGM. Using the newly created ice surface, equilibrium line altitudes (ELAs) for each glacier were reconstructed, revealing an average ELA depression of approximately 950 m from present. Analysis of the spatial variation of glacier-specific ELAs and their depression relative to today shows that whilst an east-west ELA gradient existed during the LGM it was less pronounced than at present. The reduced ELA gradient is attributed to an overall weakening of westerlies, a conclusion consistent with those derived from the latest independent climate models
KW - geomorphology
KW - glacial
KW - glaciation
KW - glaciology
KW - quaternary
KW - Southern pacific
KW - Glaciation
KW - Glaciology
KW - Geomorphology
KW - Quaternary
KW - Glacial
UR - http://www.scopus.com/inward/record.url?scp=85068842380&partnerID=8YFLogxK
U2 - 10.1016/j.quascirev.2019.06.035
DO - 10.1016/j.quascirev.2019.06.035
M3 - Article
SN - 0277-3791
VL - 219
SP - 20
EP - 35
JO - Quaternary Science Reviews
JF - Quaternary Science Reviews
ER -