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Benjamin Smith

Senior Principal Physicist

Affiliate Associate Professor, Earth and Space Sciences

Email

bsmith@apl.washington.edu

Phone

206-616-9176

Department Affiliation

Polar Science Center

Education

B.S. Physics, University of Chicago, 1997

M.S. Geology & Geophysics, University of Wisconsin - Madison, 1999

Ph.D. Earth & Space Sciences/Geophysics, University of Washington - Seattle, 2005

Publications

2000-present and while at APL-UW

Simulating the processes controlling ice-shelf rift paths using damage mechanics

Huth, A., R. Dudu, B. Smith, and O. Sergienko, "Simulating the processes controlling ice-shelf rift paths using damage mechanics," J. Glaciol., EOR, doi:10.1017/jog.2023.71, 2023.

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21 Sep 2023

Rifts are full-thickness fractures that propagate laterally across an ice shelf. They cause ice-shelf weakening and calving of tabular icebergs, and control the initial size of calved icebergs. Here, we present a joint inverse and forward computational modeling framework to capture rifting by combining the vertically integrated momentum balance and anisotropic continuum damage mechanics formulations. We incorporate rift–flank boundary processes to investigate how the rift path is influenced by the pressure on rift–flank walls from seawater, contact between flanks, and ice mélange that may also transmit stress between flanks. To illustrate the viability of the framework, we simulate the final 2 years of rift propagation associated with the calving of tabular iceberg A68 in 2017. We find that the rift path can change with varying ice mélange conditions and the extent of contact between rift flanks. Combinations of parameters associated with slower rift widening rates yield simulated rift paths that best match observations. Our modeling framework lays the foundation for robust simulation of rifting and tabular calving processes, which can enable future studies on ice-sheet–climate interactions, and the effects of ice-shelf buttressing on land ice flow.

Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020

Otosaka, I.N., and 67 others including I. Joughin, M.D. King, B.E. Smith, and T.C. Sutterley, "Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020," Earth Syst. Sci. Data, 15, 1297-1616, doi:10.5194/essd-15-1597-2023, 2023.

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20 Apr 2023

Ice losses from the Greenland and Antarctic ice sheets have accelerated since the 1990s, accounting for a significant increase in the global mean sea level. Here, we present a new 29-year record of ice sheet mass balance from 1992 to 2020 from the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE). We compare and combine 50 independent estimates of ice sheet mass balance derived from satellite observations of temporal changes in ice sheet flow, in ice sheet volume, and in Earth's gravity field. Between 1992 and 2020, the ice sheets contributed 21.0±1.9 mm to global mean sea level, with the rate of mass loss rising from 105 Gt yr−1 between 1992 and 1996 to 372 Gt yr−1 between 2016 and 2020. In Greenland, the rate of mass loss is 169±9 Gt yr−1 between 1992 and 2020, but there are large inter-annual variations in mass balance, with mass loss ranging from 86 Gt yr−1 in 2017 to 444 Gt yr−1 in 2019 due to large variability in surface mass balance. In Antarctica, ice losses continue to be dominated by mass loss from West Antarctica (82±9 Gt yr−1) and, to a lesser extent, from the Antarctic Peninsula (13±5 Gt yr−1). East Antarctica remains close to a state of balance, with a small gain of 3±15 Gt yr−1, but is the most uncertain component of Antarctica's mass balance.

Evaluating Greenland surface-mass-balance and firn-densification data using ICESat-2 altimetry

Smith, B.E., B. Medley, X. Fettweis, T. Sutterley, P. Alexander, D. Porter, and M. Tedesco, "Evaluating Greenland surface-mass-balance and firn-densification data using ICESat-2 altimetry," Cryosphere, 17, 789-808, doi:10.5194/tc-17-789-2023, 2023.

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16 Feb 2023

Surface-mass-balance (SMB) and firn-densification (FD) models are widely used in altimetry studies as a tool to separate atmospheric-driven from ice-dynamics-driven ice-sheet mass changes and to partition observed volume changes into ice-mass changes and firn-air-content changes. Until now, SMB models have been principally validated based on comparison with ice core and weather station data or comparison with widely separated flight radar-survey flight lines. Firn-densification models have been primarily validated based on their ability to match net densification over decades, as recorded in firn cores, and the short-term time-dependent component of densification has rarely been evaluated at all. The advent of systematic ice-sheet-wide repeated ice-surface-height measurements from ICESat-2 (the Ice Cloud, and land Elevation Satellite, 2) allows us to measure the net surface-height change of the Greenland ice sheet at quarterly resolution and compare the measured surface-height differences directly with those predicted by three FD–SMB models: MARv3.5.11 and GSFCv1.1 and GSFCv1.2. By segregating the data by season and elevation, and based on the timing and magnitude of modelled processes in areas where we expect minimal ice-dynamics-driven height changes, we investigate the models' accuracy in predicting atmospherically driven height changes. We find that while all three models do well in predicting the large seasonal changes in the low-elevation parts of the ice sheet where melt rates are highest, two of the models (MARv3.5.11 and GSFCv1.1) systematically overpredict, by around a factor of 2, the magnitude of height changes in the high-elevation parts of the ice sheet, particularly those associated with melt events. This overprediction seems to be associated with the melt sensitivity of the models in the high-elevation part of the ice sheet. The third model, GSFCv1.2, which has an updated high-elevation melt parameterization, avoids this overprediction.

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In The News

How ants inspired a new way to measure snow with space lasers

Wired, Matt Simon

Glaciologist Ben Smith comments on a clever new technique to measure fluffy snow on the Earth's surface with the orbiting ICESat-2 lidar instrument.

31 May 2022

Edge of Pine Island Glacier’s ice shelf is ripping apart, causing key Antarctic glacier to gain speed

UW News, Hannah Hickey

For decades, the ice shelf helping to hold back one of the fastest-moving glaciers in Antarctica has gradually thinned. Analysis of satellite images reveals a more dramatic process in recent years: From 2017 to 2020, large icebergs at the ice shelf’s edge broke off, and the glacier sped up.

11 Jun 2021

Shrinking ice sheets lifted global sea level 14 millimeters

Eos (American Geophysical Union), Tim Hornyak

Researchers measure both grounded and floating ice sheets using satellite data spanning a 16-year period.

15 May 2020

More News Items

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