NSF Org:	OPP Office of Polar Programs (OPP)
Recipient:	UNIVERSITY OF ALASKA FAIRBANKS
Initial Amendment Date:	July 27, 2020
Latest Amendment Date:	July 27, 2020
Award Number:	1914668
Award Instrument:	Standard Grant
Program Manager:	Michael E. Jackson OPP  Office of Polar Programs (OPP) GEO  Directorate for Geosciences
Start Date:	August 15, 2020
End Date:	July 31, 2022 (Estimated)
Total Intended Award Amount:	$140,928.00
Total Awarded Amount to Date:	$140,928.00
Funds Obligated to Date:	FY 2020 = $140,928.00
History of Investigator:	Andy Aschwanden (Principal Investigator) aaschwanden@alaska.edu
Recipient Sponsored Research Office:	University of Alaska Fairbanks Campus 2145 N TANANA LOOP FAIRBANKS AK  US  99775-0001 (907)474-7301
Sponsor Congressional District:	00
Primary Place of Performance:	University of Alaska Fairbanks Campus AK  US  99775-7880
Primary Place of Performance Congressional District:	00
Unique Entity Identifier (UEI):	FDLEQSJ8FF63
Parent UEI:
NSF Program(s):	Unallocated Program Costs
Primary Program Source:	0100XXXXDB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s):	9150
Program Element Code(s):	919900
Award Agency Code:	4900
Fund Agency Code:	4900
Assistance Listing Number(s):	47.078

ABSTRACT

Part I: Nontechnical
Earths warming climate has the potential to drive widespread collapse of glaciers and ice sheets across the planet, driving global sea-level rise. Understanding both the rate and magnitude of such changes is essential for predicting future sea-level and how it will impact infrastructure and property. Collapse of the ice sheets of Antarctica has the potential to raise global sea-level by up to 60 meters. However, not all regions of Antarctica are equally suspectable to collapse. One area with potential for collapse is the Wilkes Subglacial Basin in East Antarctica, a region twice the size of California's Central Valley. Geologic evidence indicates that the ice-sheet in this region has retreated significantly in response to past global warming events. While the geologic record clearly indicates ice-sheets in this area are vulnerable, the rate and magnitude of any future retreat will be influenced significantly by geology of the region. In particular, ice-sheets sitting above warm Earth will collapse more quickly during warming climate. Constraining the geologic controls on the stability of the ice-sheets of the Wilkes Subglacial Basin remains challenging since the ice-sheet hides the geology beneath kilometers of ice. As a step in understanding the potential for future ice loss in the Wilkes Subglacial Basin this project will conduct geophysical analysis of existing data to better constrain the geology of the region. These results will constrain new models designed to understand the tectonics that control the behavior of the ice-sheets in the region. These new models will highlight the geological properties that exert the most significant control on the future of the ice-sheets of the Wilkes Subglacial Basin. Such insights are critical to guide future efforts aimed at collecting in-situ observations needed to more fully constrain Antarctica's potential for future sea-level.

Part II: Technical Description
In polar environments, inward-sloping marine basins are susceptible to an effect known as the marine ice-sheet instability (MISI): run-away ice stream drainage caused by warm ocean water eroding the ice shelf from below. The magnitude and time-scale of the ice-sheet response strongly depend on the physical conditions along the ice-bed interface, which are, to a first order, controlled by the tectonic evolution of the basin. Topography, sedimentology, geothermal heat flux, and mantle viscosity all play critical roles in ice-sheet stability. However, in most cases, these solid-Earth parameters for regions susceptible to the MISI are largely unknown. One region with potential susceptibility to MISI is the Wilkes Subglacial Basin of East Antarctica. The project will provide an integrated investigation of the Wilkes Subglacial Basin, combining geophysical analyses with both mantle flow and ice-sheet modeling to understand the stability of the ice sheet in this region, and the associated potential sea level rise. The work will be focused on four primary objectives: (1) to develop an improved tectonic model for the region based on existing seismic observations as well as existing geophysical and geological data; (2) to use the new tectonic model and seismic data to estimate the thermal, density, and viscosity structure of the upper mantle and to develop a heat flow map for the WSB; (3) to simulate mantle flow and to assess paleotopography based on our density and viscosity constraints; and (4) to assess ice-sheet behavior by modeling (a) past ice-sheet stability using our paleotopography estimates and (b) future ice-sheet stability using our heat flow and mantle viscosity estimates. Ultimately, the project will generate improved images of the geophysical structure beneath the WSB that will allow us to assess the geodynamic origin for this region and to assess the influence of geologic parameters on past, current, and future ice-sheet behavior. These efforts will then highlight areas and geophysical properties that should be the focus of future geophysical deployments.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

PROJECT OUTCOMES REPORT

Disclaimer

This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.

Climate change and sea-level rise are among the biggest challenges of the 21st century. While the models we use to predict how much is Antarctica will use in the future have become substantially better in recent years, the models are still not as good as they should be to make reliable predictions. A careful analysis of the models that have been used to estimate sea-level rise from Greenland and Antarctica for the sixth Assessment Report of the Intergovernmental Panel on Climate Change revealed that most models struggle with simulation the recent past. There are many reasons why this is the case. Having a good starting point is key. Here we use a method from the field of machine learning to better estimate model parameters which are difficult to measure. We simulate how fast the ice flows for a large number of parameter combinations and each simulated velocity field is then compared to satellite observations of ice flow. However, instead of blindly trying out all possible parameter combinations, machine learning is used to find the best fitting parameter combinations in an efficient way. The calibration process can be efficiently done on modern graphics card, which is much faster than on CPUs.
We applied the calibration method to Antarctica and calibrated eight parameters of the Parallel Ice Sheet Model, an open-source computer model that simulates the flow of glacier ice. The Parallel Ice Sheet Model or PISM is one of the most successful ice sheet models out there and has been used in over 170 scientific publications. Simulations made with the calibrated parameters now show good agreement with observations.
The method we used is quite general. It has already been applied to PISM and the Greenland Ice Sheet, and it can be easily adapted to work with other computer models.

Last Modified: 12/23/2022
Modified by: Andy Aschwanden

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