Michael J. Willis

Michael J. Willis
Virginia Tech (Virginia Polytechnic Institute and State University) | VT · Department of Geosciences

PhD

About

72
Publications
15,555
Reads
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1,761
Citations
Citations since 2017
27 Research Items
1418 Citations
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2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300
Introduction
I am a geodesy and remote sensing specialist with a deep interest in time varying topography, glacier dynamics and natural hazards.
Additional affiliations
January 2009 - September 2016
Cornell University
Position
  • PostDoc Position

Publications

Publications (72)
Article
Full-text available
The 2019 Ridgecrest earthquake sequence manifested as one of the most complex fault surface ruptures observed in California in modern times. The M6.4 foreshock and M7.1 mainshock occurred on an intricate network of orthogonal and sub‐parallel faults resulting in observable surface displacement and surface rupture captured by geodetic data. Here we...
Article
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The Patagonia Icefields (PIF) are the largest non-polar ice mass in the southern hemisphere. The icefields cover an area of approximately 16,500 km ² and are divided into the northern and southern icefields, which are ~ 4000 km ² and ~ 12,500 km ² , respectively. While both icefields have been losing mass rapidly, their responsiveness to various cl...
Article
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Deep learning has been used for mapping retrogressive thaw slumps and other periglacial landforms but its application is still limited to local study areas. To understand the accuracy, efficiency, and transferability of a deep learning model (i.e., DeepLabv3+) when applied to large areas or multiple regions, we conducted several experiments using t...
Article
On 17 October 2015, a large landslide entered the marine waters of Taan Fiord, Alaska, and generated a displacement wave with a 193 m runup. The wave scoured the surrounding hillslopes of soil and vegetation and deposited significant volumes of material into the fjord, onto hillslopes on the opposite side of the fjord, and on top of Tyndall Glacier...
Article
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To advance monitoring of surface water resources, new remote sensing technologies including the forthcoming Surface Water and Ocean Topography (SWOT) satellite (expected launch 2022) and its experimental airborne prototype AirSWOT are being developed to repeatedly map water surface elevation (WSE) and slope (WSS) of the world’s rivers, lakes, and r...
Article
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Global sea level provides an important indicator of the state of the warming climate, but changes in regional sea level are most relevant for coastal communities around the world. With improvements to the sea-level observing system, the knowledge of regional sea-level change has advanced dramatically in recent years. Satellite measurements coupled...
Article
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Plain Language Summary A glacier surge is a sudden speedup of glacier flow coinciding with a large advance of the ice front. Some glaciers surge periodically every 10–100 years, and so surge mechanism is thought to be independent of climate change. However, some recent surges have evacuated so much ice that another surge is unlikely to occur in the...
Article
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Wind abrasion is important for planetary landscape evolution, and wind‐abraded bedrock landscapes contain many landforms that are difficult to interpret. Here we exploit a natural experiment in Chile where topographic shielding by an upwind lava flow yields diverse erosional landforms in a downwind ignimbrite. Using a 3‐D topographic wind model, we...
Article
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Evolution of the 2014 Vulcan Creek landslide-dammed lake, Yukon, Canada, using field and remote survey techniques Abstract The Vulcan Creek landslide is a 1 to 2 × 10^6 m^3 landslide that occurred in southwest Yukon between 15 August and 9 September 2014. The elevation difference between the landslide headscarp and distal extent of the deposit is 3...
Article
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Significance The recent deglaciation of Greenland is a response to both oceanic and atmospheric forcings. From 2000 to 2010, ice loss was concentrated in the southeast and northwest margins of the ice sheet, in large part due to the increasing discharge of marine-terminating outlet glaciers, emphasizing the importance of oceanic forcing. However, t...
Article
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Ice caps that are mostly frozen at the bedrock-ice interface are thought to be stable and respond slowly to changes in climate. We use remote sensing to measure velocity and thickness changes that occur when the margin of the largely cold-based Vavilov Ice Cap in the Russian High Arctic advances over weak marine sediments. We show that cold-based t...
Article
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Glacial retreat in recent decades has exposed unstable slopes and allowed deep water to extend beneath some of those slopes. Slope failure at the terminus of Tyndall Glacier on 17 October 2015 sent 180 million tons of rock into Taan Fiord, Alaska. The resulting tsunami reached elevations as high as 193 m, one of the highest tsunami runups ever docu...
Article
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A quick rebound for Antarctic crust Earth's crust deforms under the load of glaciers and ice sheets. When these masses are removed, the crust rebounds at a time scale determined by the viscosity of the upper mantle. Using GPS, Barletta et al. found that the viscosity of the mantle under the West Antarctic Ice Sheet is much lower than expected. This...
Article
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The glaciers of the Franz Josef Land (FJL) archipelago in the Russian Arctic are subjected to rapidly-warming temperatures but are small contributors to sea level. We analyze ice surface elevation data derived from satellite stereo imagery (WorldView and SPOT), radar altimetry (CryoSat-2), and a digitized 1953 cartographic map to calculate elevatio...
Article
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This paper describes a collaboration between a visual artist and geoscientists, who together viewed the same rugged, high mountain landscape through different, yet complementary, lenses. We pair scientific mapping and historic comparative photography with a series of site-specific sculptural installations to interpret the dramatic geological change...
Article
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The large Juneau and Stikine icefields (Alaska) lost mass rapidly in the second part of the 20th century. Laser altimetry, gravimetry and field measurements suggest continuing mass loss in the early 21st century. However, two recent studies based on time series of Shuttle Radar Topographic Mission (SRTM) and Advanced Spaceborne Thermal Emission and...
Article
On 17 October 2015, a landslide of roughly 60×10⁶ m³ occurred at the terminus of Tyndall Glacier in Taan Fiord, southeastern Alaska. It caused a tsunami that inundated an area over 20km², whereas the landslide debris itself deposited within a much smaller area of approximately 2km². It is a unique event in that the landslide debris was deposited in...
Article
Full-text available
The large Juneau and Stikine icefields (Alaska, JIF and SIF) lost mass rapidly in the second part of the 20th century. Laser altimetry, gravimetry and sparse field measurements suggest continuing mass loss in the early 21st century. However, two recent studies based on time series of SRTM and ASTER digital elevation models (DEMs) indicate a slowdow...
Article
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Significance Meltwater runoff is an important hydrological process operating on the Greenland ice sheet surface that is rarely studied directly. By combining satellite and drone remote sensing with continuous field measurements of discharge in a large supraglacial river, we obtained 72 h of runoff observations suitable for comparison with climate m...
Article
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River piracy—the diversion of the headwaters of one stream into another one—can dramatically change the routing of water and sediment, with a profound e�ect on landscape evolution. Stream piracy has been investigated in glacial environments, but so far it has mainly been studied over Quaternary or longer timescales. Here we document how retreat of...
Article
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Since 1990, Yahtse Glacier in southern Alaska has advanced at an average rate of ~100 m year−1 despite a negative mass balance, widespread thinning in its accumulation area, and a low accumulation-area ratio. To better understand the interannual and seasonal changes at Yahtse and the processes driving these changes, we construct velocity and ice su...
Article
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We calculate thinning rates (dhdt) at the 5800 km2 Stikine Icefield of southeast Alaska from stacked digital elevation models (DEMs) acquired between 2000 and 2013/2014, and glacier velocities between 1985 and 2014 from feature tracking on optical image pairs. We find a mass change rate of −3.3 ± 1.1 Gt yr−1 between 2000 and 2014, equivalent to an...
Article
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Accurate quantification of the millennial-scale mass balance of the Greenland ice sheet (GrIS) and its contribution to global sea-level rise remain challenging because of sparse in situ observations in key regions. Glacial isostatic adjustment (GIA) is the ongoing response of the solid Earth to ice and ocean load changes occurring since the Last Gl...
Article
Ice loss from the glaciers of Novaya Zemlya (NVZ) is the dominant contributor to sea level for the Russian Arctic. Here we present maps of glacier elevation change rates (dhdt) and velocities at Novaya Zemlya that reveal evidence of the impact of both calving flux and surface melt on ice mass loss.dhdt are calculated by applying a weighted linear r...
Article
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In order to model and predict future behavior of marine terminating glaciers, it is essential to understand the different factors that control a glaciers response to climate change. Here we present a detailed study of the asynchronous changes in dynamic behavior of four adjacent marine-terminating glaciers at Upernavik Isstrøm (UI), Northwest Green...
Article
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Liquid water stored on the surface of ice sheets and glaciers impacts surface mass balance, ice dynamics, and heat transport. Multispectral remote sensing can be used to detect supraglacial lakes and estimate their depth and area. In this study, we use in situ spectral and bathymetric data to assess lake depth retrieval using the recently launched...
Article
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We identified co-seismic ionospheric disturbances (CID) in Antarctica generated by the 2010 Maule and the 2011 Tohoku-Oki earthquakes analyzing TEC data with a modified beamforming technique. Beamforming in Antarctica, however, is not straightforward due to the effects of array deformation and atmospheric neutral wave-ionospheric plasma coupling. W...
Article
The Matusevich Ice Shelf (MIS), located within the Severnaya Zemlya Archipelago in the Russian Arctic, rapidly broke apart between August 10th and September 7th 2012. We examine the response of the outlet glaciers that fed the MIS from local ice caps to the removal of the ice shelf. We use spaceborne laser altimetry, and multiple optically derived...
Article
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Liquid water stored on the surface of ice sheets and glaciers impacts surface mass balance, ice dynamics, and heat transport. Supraglacial lakes, therefore, play a significant role in ice sheet behavior as a surface expression of the glacial hydrological system. Multispectral remote sensing can be used to detect supraglacial lakes and estimate thei...
Article
In a warming climate, surface meltwater production on large ice sheets is expected to increase. If this water is delivered to the ice sheet base it may have important consequences for ice dynamics. For example, basal water distributed in a diffuse network can decrease basal friction and accelerate ice flow, whereas channelized basal water can move...
Article
We provide a high-resolution map of elevation change rates dh/dt at the Juneau Icefield (JIF), southeastern Alaska, in order to quantify its contribution to sea-level rise between 2000 and 2009/2013. We also produce the first high-resolution map of ice speeds at the JIF, which we use to constrain flux and look for acceleration. We calculate dh/dt u...
Conference Paper
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GPS total electron content (TEC) measurements are commonly used to study ionospheric disturbances in the near and far field. For co-seismic ionospheric disturbances (CIDs) the apparent velocity of the signal can be calculated from distance travel-time plots or interferometric stacking techniques. To date, signals related to solid earth-atmosphere c...
Article
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We produce the first icefield-wide volume change rate and glacier velocity estimates for the Cordillera Darwin Icefield (CDI), a 2605 km2 temperate icefield in southern Chile (69.6° W, 54.6° S). Velocities are measured from optical and radar imagery between 2001-2011. Thirty-six digital elevation models (DEMs) from ASTER and the SRTM DEM are stacke...
Article
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A time-series composed of 156 ASTER derived Digital Elevation Models (DEMs) and a radar-penetration-bias corrected version of the Shuttle Radar Topography Mission (SRTM) DEM is used to derive ice surface height and volume changes at the Southern Patagonian Ice Field (SPI) in southern South America. The observations, made between February 2000 and M...
Article
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We produce the first icefield-wide volume change rate and glacier velocity estimates for the Cordillera Darwin Icefield (CDI), a 2605 km<sup>2</sup> temperate icefield in Southern Chile (69.6° W, 54.6° S). Velocities are measured from optical and radar imagery between 2001–2011. Thirty-seven digital elevation models (DEMs) from ASTER and the SRTM a...
Article
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The Greenland GPS Network (GNET) uses the Global Positioning System (GPS) to measure the displacement of bedrock exposed near the margins of the Greenland ice sheet. The entire network is uplifting in response to past and present-day changes in ice mass. Crustal displacement is largely accounted for by an annual oscillation superimposed on a sustai...
Article
We use a satellite-based survey of glacier surface elevation changes, speeds and surface melt conditions between 2000 and 2011 to quantify mass loss from the Northern Patagonian Icefield (NPI), Chile. A history of ice elevation change is found by differencing ASTER Digital Elevation Models (DEMs) relative to a void-filled version of the DEM collect...
Article
The Greenland GPS Network (GNET) uses GPS geodesy to measure the displacement of bedrock exposed near the margins of the Greenland Ice Sheet. The amplitudes of the observed vertical velocities indicate that over most of coastal Greenland these displacements are dominated by the solid earth's instantaneous elastic response to contemporary losses in...
Article
We present a successful example of sub-pixel tracking applied to high-resolution (~0.5 meter) optical imagery to image earthquake surface deformation. We examine the 2010-Sept-4 Mw 7.1 Darfield and 2011-Feb-22 Mw 6.3 Christchurch, New Zealand earthquakes using space-based interferometric synthetic aperture radar (InSAR) and high-resolution optical...
Article
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Our study used space-based interferometric synthetic aperture radar (InSAR) and feature tracking on sub-meter-resolution optical imagery pairs to characterize surface deformation resulting from the 4 September 2010 Mw 7.1 Darfield, 22 February 2011 Mw 6.3 Christchurch, and 13 June 2011 Christchurch earthquakes (dates in local time), each of which o...
Article
We use satellite imagery and imagery-derived digital elevation models (DEMs) from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) onboard the Terra satellite to examine glacier speeds and elevation change rates (ECRs) for the Juneau Icefield (134.1° W, 58.7° N) from 2000 to 2010, with the goal of using these results to es...
Article
The 4000 km2 Northern Patagonian Icefield (NPI), 13,000 km2 Southern Patagonian Icefield (SPI) and the 2500 km2 Cordillera Darwin Icefields (CDI) form the main ice bodies of the Patagonian Icefields of South America. Analysis of satellite imagery, derived digital elevation models (DEMs) and spaceborne laser altimetry confirm that each of the icefie...
Article
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Few measurements have been made on the outlet glaciers of the Northern, Southern and Cordillera Darwin Icefields of Patagonia due to difficult access and pervasive bad weather. During the early 1990s' many glaciers around the periphery of the low-latitude temperate icefields thinned and retreated rapidly providing a disproportionately large contrib...
Article
Newly installed polar geodetic networks such as the Greenland GPS Network (GNET) and the Antarctic GPS Network (ANET) provide a means to determine the movement of the Earth's crust in response to past and present changes in ice mass. It is possible to distinguish between bedrock motions driven by glacial isostatic adjustment (GIA) - the response of...
Article
The IJ05 Antarctic ice sheet history is employed to drive a suite of approximately one thousand two-layered, laterally-homogeneous spherical Earth models and generate predictions of Antarctic crustal uplift due to glacial isostatic adjustment (GIA). GPS data collected between 1996 and 2010 on the flanks of the West Antarctic Rift System are used to...
Article
Mass-loss from small icefields is the greatest contributor from the cryosphere to sea level rise at present. The Juneau Icefield is a small low-latitude glacier system in southeast Alaska. Remote-sensing data from SAR and optical instruments is examined for inter-annual and seasonal changes in glacier elevation and velocity. We use subpixel offset...
Article
We examine the annual vertical oscillations in the GNET time series and compare these with the oscillations observed in the GRACE mass change time series, as well as with the seasonal fluctuations expected on the basis of meteorological and glaciological studies. Seasonal signals in crustal displacement, which are usually dominantly developed in th...
Article
The IJ05 Antarctic ice sheet history is employed to drive a suite of approximately one thousand two-layered, laterally-homogeneous spherical Earth models and generate predictions of Antarctic crustal uplift due to glacial isostatic adjustment (GIA). Comparison of the predictions with GPS-derived crustal uplift rates, mainly from southern Victoria L...
Article
The low altitude and latitude of the 4000 km2 Northern Patagonian Ice Field (NPIF) make it relatively sensitive to changing climate. Existing work on the icefield suggest that mass loss has accelerated over the last decade, but these studies are spatially and temporally incomplete. We use a combination of subpixel offset tracking of ASTER and SAR i...
Article
Full-text available
We present preliminary geodetic estimates for vertical bedrock velocity at twelve survey GPS stations in the West Antarctic GPS Network, an additional survey station in the northern Antarctic Peninsula, and eleven continuous GPS stations distributed across the continent. The spatial pattern of these velocities is not consistent with any postglacial...
Article
We present the initial results of the West Antarctic GPS Network (WAGN), which was initiated in the 2002/03 Antarctic field season. Specifically we present vertical velocity estimates for all WAGN stations with a total occupational time span of 3 years or more. Most of these station have been observed for at least four years, and many for 5 years o...
Article
The effect of relatively high fidelity regional ocean loading in Antarctica on predicted rates of glacial isostatic adjustment (GIA) is quantified for the IJ05 surface loading history. The recently developed IJ05 model was designed to incorporate the growing compilation of geological and glaciological constraints on the evolution of the Antarctic i...
Article
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Continuous GPS data are required in order to provide major advances in the understanding of ongoing polar ice mass change. Glacial Isostatic Adjustment (GIA) is the largest source of uncertainty for the Gravity Recovery and Climate Experiment (GRACE). GIA is currently observed with 50 bedrock continuous GPS sites in Antarctica and around Greenland....
Article
Data from the Gravity Recovery and Climate Experiment (GRACE) have recently been used to infer mass change rates of the Antarctic ice sheet. A leading source of uncertainty in interpretation of the GRACE measurements is the poorly constrained Glacial Isostatic Adjustment (GIA) correction. We use the recent IJ05 ice sheet history to load a suite of...
Article
A decade of Global Positioning System (GPS) data have been collected at bedrock sites in southern Victoria Land, Antarctica. Measured motions of the crust have been examined to determine if ongoing tectonic deformation occurs within the study area, across the structural boundary between East and West Antarctica. Crustal motions are used to test for...
Chapter
The POLar Earth observing NETwork(POLENET) is an ambitious international project to deploy geophysical instruments at very remote high-latitude sites during the International Polar Year (IPY). One of the goals of the project is to run instruments year round with as little maintenance as possible. POLENET will be installed using robust lightweight s...
Article
POLENET is an IPY-endorsed science initiative aimed at dramatically improving the coverage in geodetic, seismic, and other geophysical data across the polar regions. The POLENET science team, in collaboration with UNAVCO and IRIS E&O staff, are developing multimedia materials about POLENET science for dissemination to the public and to educators an...
Article
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Several years of continuous data have been collected at remote bedrock Global Positioning System (GPS) sites in southern Victoria Land, Antarctica. Annual to sub-annual variations are observed in the position time-series. An atmospheric pressure loading (APL) effect is calculated from pressure field anomalies supplied by the European Centre for Med...
Article
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The Transantarctic Mountains Deformation (TAMDEF) network is a relatively dense GPS array deployed on bedrock throughout the Victoria Land region of Antarctica. The network covers nearly a quarter million square kilometers, extending approximately 675 km N-S and 350 km E-W. It spans the uplifted Transantarctic Mountains rift-flank block, the boundi...
Article
A decade of GPS data has been used to derive strongly constrained bedrock motions over southern Victoria Land, Antarctica. The measurements have been made from 74°S at Terra Nova Bay to 82°S at the Byrd Glacier and have bracketed the most easterly and westerly outcrops of bedrock available. Station spacing is ~70km with the network covering about 2...
Article
Campaign GPS measurements made between 1996 and 2004 are used to describe the crustal velocity field in southern Victoria Land, Antarctica. The GPS network stretches along the Transantarctic Mountains from the region of the David Glacier near 75° S to the Byrd Glacier region at 81.5° S and encompasses volcanic islands within the adjacent West Antar...
Article
The Transantarctic Mountain Deformation (TAMDEF) GPS network has been constructed over Victoria Land, Antarctica. After new station deployments in 2003, the TAMDEF network extends 670 km north-south and 400 km east-west. The network crosses gradients in predicted vertical motion due to glacial-isostatic rebound and spans the Terror Rift in the west...