| NSF Org: |
OPP Office of Polar Programs (OPP) |
| Recipient: |
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| Initial Amendment Date: | May 1, 2018 |
| Latest Amendment Date: | May 1, 2018 |
| Award Number: | 1744958 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Paul Cutler
pcutler@nsf.gov (703)292-4961 OPP Office of Polar Programs (OPP) GEO Directorate for Geosciences |
| Start Date: | June 1, 2018 |
| End Date: | May 31, 2021 (Estimated) |
| Total Intended Award Amount: | $90,640.00 |
| Total Awarded Amount to Date: | $90,640.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
4333 BROOKLYN AVE NE SEATTLE WA US 98195-1016 (206)543-4043 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
7600 Sand Point Way Seattle WA US 98195-5672 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): |
PREEVENTS - Prediction of and, ANT Glaciology, ANT Integrated System Science |
| Primary Program Source: |
0100XXXXDB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.078 |
ABSTRACT
Understanding and being able to more reliably forecast ice mass loss from Antarctica is a critical research priority for Antarctic Science. Massive ice shelves buttress marine terminating glaciers, slowing the rate that land ice reaches the sea and, in turn, restraining the rate of sea level rise. To date, most work has focused on the destabilizing impacts of warmer air and water temperatures, resulting in melting that thins and weakens ice shelves. However, recent findings indicate that sea ice does not protect ice shelves from wave impacts as much as previously thought, which has raised the possibility that tsunamis and other ocean waves could affect shelf stability. This project will assess the potential for increased shelf fracturing from the impact of tsunamis and from heightened wave activity due to climate-driven changes in storm patterns and reduced sea-ice extent by developing models to investigate how wave impacts damage ice shelves. The modeling effort will allow for regional comparisons between large and small ice shelves, and provide an evaluation of the impacts of changing climate and storm patterns on ice shelves, ice sheets, glaciers, and, ultimately, sea level rise. This project will train graduate students in mathematical modeling and interdisciplinary approaches to Earth and ocean sciences.
This project takes a four-pronged approach to estimating the impact of vibrations on ice shelves at the grounding zone due to tsunamis, very long period, infragravity, and storm-driven waves. First, the team will use high-resolution tsunami modeling to investigate the response of ice shelves along the West Antarctic coast to waves originating in different regions of the Pacific Ocean. Second, it will compare the response to wave impacts on grounding zones of narrow and wide ice shelves. Third, it will assess the exposure risk due to storm forcing through a reanalysis of weather and wave model data; and, finally, the team will model the propagation of ocean-wave-induced vibrations in the ice from the shelf front to and across the grounding zone. In combination, this project aims to identify locations along the Antarctic coast that are subject to enhanced, bathymetrically-focused, long-period ocean-wave impacts. Linkages between wave impacts and climate arise from potential changes in sea-ice extent in front of shelves, and changes in the magnitude, frequency, and tracks of storms. Understanding the effects of ocean waves and climate on ice-shelf integrity is critical to anticipate their contribution to the amplitude and timing of sea-level rise. Wave-driven reductions in ice-shelf stability may enhance shelf fragmentation and iceberg calving, reducing ice shelf buttressing and eventually accelerating sea-level rise.
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.
The proposed research activities of the element of tsunami modeling have been fully fulfilled throughout the performance period between 02/01/2018 and 06/01/2020. The major goal of UW?s research of this project is to model the propagation of a suite of the strongest historical and synthetic Pacific tsunamis to the West Antarctica Coast (WAC) to identify locations where bathymetry of the West Antarctic continental shelf focuses tsunami energy at particular grounding zone locations of ice shelves. The modeled tsunamis at the front of the WAC ice shelves will be used as source functions (or boundary conditions) for a flexural-gravity wave model (developed and conducted by collaborators at Stanford University) to understand the mechanical response of ice shelves to tsunami wave forcing.
The main outcomes obtained from the UW research activities are summarized below:
1. A two-level tsunami propagation simulation from earthquake sources in the Pacific to the West Antarctica ice shelf has been developed based on the up-to-date MEaSUREs BedMachine Antarctica V2 500-m bathymetric DEM (https://nsidc.org/data/nsidc-0756/versions/2). The developed tsunami model is validated using observational data in the Antarctica ice shelf, for examples, the Cope Roberts tide station data from the 2011 Tohoku tsunami event (Fig. 1), and the spectrogram of the hydrophone records during the 2015 Illapel, Chile tsunami. This is the first model that we know to research tsunami impact over the Antarctica ice shelf at 500 m grid resolution, and gives excellent results in simulating tsunami propagation over the Antarctica Ice Shelf.
2. A suite of historical tsunami events has been numerically investigated to assess their impact on the West Antarctica Ice Shelf. These historical events include the 2011 M9.1 Tohoku, 1964 M9.2 Alaska, 1960 M9.5 Chile, 2009 M8.1 Samoa, and 2015 M8.3 Chile. Specifically for the 2015 Illapel, Chile event, a variety of published tsunami sources were inspected in terms of the frequency content of the Infra-Gravity (IG) waves comparing to the observations at a deep-ocean tsunameter near the source. The main outcomes of these model simulations prove the tsunamis generated along Chile?s coastline produce distinct IG waves affecting the Antarctica Ice Shelf all the way from the source (Fig. 2).
3. The 2015 Illapel, Chile tsunami (Fig. 2) and the 2011 Tohoki tsunami (Fig. 3) are simulated with both nondispersive and dispersive tsunami models to gain insights in the frequency content of the waves obtained from the two types of models. In addition, sensitivity tests were conducted to ensure model convergence from different grid resolutions for basin-scale tsunami propagation simulation. The main outcomes are that the dispersive model conserves more infra-gravity wave energy than the nondispersive model does, and the grid resolution of > 1 arc min (~ 1.8 km) captures more IG frequencies in both dispersive and nondispersive models.
4. A suite of synthetic tsunamis generated by earthquakes with different magnitudes (M8.2, M8.6, and M9.1) in all major subduction zones in the Pacific are simulated to identify the most possible tsunami sources regions that can potentially produce wave excitation on the grounding zone of WAC. The main outcomes show that the Ross Sea ? Thwaites ice shelves are more vulnerable to tsunamis generated from South America, New Zealand, and Central America (Mexico) than other subduction zones in the Pacific (Fig. 4).
5. Guided by the results obtained in 4, simulations of M8.6 tsunami events generated from the most-hazardous subduction zones were conducted using the 2-level model developed in 1. The main outcomes of these simulations indicate the tsunamis originated from Central America and Kermadec subduction zones pose more severe tsunami threats to the Ross Sea ice shelf than others, while tsunamis generated from the south end of the South America Subduction Zone are the most threatening to Thwaites (Fig. 5).
6. The model simulation results are provided to the Stanford University team as boundary condition input to their flexural-gravity wave model to study wave excitation on the ice shelf.
7. The UW modeling studies offer a useful modeling database of tsunami impact on West Antarctica ice shelf as results of tsunamis generated from earthquake origins around the Pacific rim. It provides valuable model data for researchers to investigate further the tsunami-induced ice shelf vibrations in the grounding zones. The model outcomes help improve modeling of ice shelf evolution and reduce the uncertainty in projections of impending increases in the rate and magnitude of sea level rise.
Last Modified: 11/23/2021
Modified by: Yong Wei
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