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Ian Joughin

Senior Principal Engineer

Affiliate Professor, Earth and Space Sciences

Email

ian@apl.washington.edu

Phone

206-221-3177

Biosketch

Ian Joughin continues his pioneering research into the use of differential SAR interferometry for the estimation of surface motion and topography of ice sheets. He combines the remote sensing with field work and modeling to solve ice dynamics problems. Solving the problems helps him understand the mass balance of the Greenland and Antarctic Ice Sheets in response to climate change.

In addition to polar research, he also contributed to the development of algorithms that were used to mosaic data for the near-global map of topography from the Shuttle Radar Topography Mission (SRTM).

Department Affiliation

Polar Science Center

Education

B.S. Electrical Engineering, University of Vermont, 1986

M.S. Electrical Engineering, University of Vermont, 1990

Ph.D. Electrical Engineering, University of Washington, 1995

Publications

2000-present and while at APL-UW

Greenland Ice Mapping Project: Ice flow velocity variation at sub-monthly to decadal timescales

Joughin, I., B.E. Smith, and I. Howat, "Greenland Ice Mapping Project: Ice flow velocity variation at sub-monthly to decadal timescales," Cryosphere, 12, 2211-2227, doi:10.5194/tc-12-2211-2018, 2018.

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11 Jul 2018

We describe several new ice velocity maps produced by the Greenland Ice Mapping Project (GIMP) using Landsat 8 and Copernicus Sentinel 1A/B data. We then focus on several sites where we analyse these data in conjunction with earlier data from this project, which extend back to the year 2000. At Jakobshavn Isbræ and Køge Bugt, we find good agreement when comparing results from different sensors. In a change from recent behaviour, Jakobshavn Isbræ began slowing substantially in 2017, with a midsummer peak that was even slower than some previous winter minima. Over the last decade, we identify two major slowdown events at Køge Bugt that coincide with short-term advances of the terminus. We also examined populations of glaciers in north-west and south-west Greenland to produce a record of speed-up since 2000. Collectively these glaciers continue to speed up, but there are regional differences in the timing of periods of peak speed-up. In addition, we computed trends in winter flow speed for much of the south-west margin of the ice sheet and find little in the way of statistically significant changes over the period covered by our data. Finally, although the consistency of the data is generally good over time and across sensors, our analysis indicates that substantial differences can arise in regions with high strain rates (e.g. shear margins) where sensor resolution can become a factor. For applications such as constraining model inversions, users should factor in the impact that the data's resolution has on their results.

Evolving environmental and geometric controls on Columbia Glacier's continued retreat

Enderlin, E.M., S. O'Neel, T.C. Bartholomaus, and I. Joughin, "Evolving environmental and geometric controls on Columbia Glacier's continued retreat," J. Geophys. Res., 123, 1528-1545, doi:10.1029/2017JF004541, 2018.

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1 Jul 2018

Geometry strongly controls the dynamic behavior of marine‐terminating (tidewater) glaciers, significantly influencing advance and retreat cycles independent of climate. Yet the recent, nearly ubiquitous retreat of tidewater glaciers suggests that changes in atmospheric and oceanic forcing may also drive dynamic change. To isolate the influence of geometry on tidewater glacier dynamics, we analyzed detailed observational time series from 2012 to 2016 for two tidewater glaciers with shared dynamic histories and environmental forcing: Columbia Glacier and its former tributary (Post Glacier) in southcentral Alaska. We find that although terminus retreat has driven decadal‐scale changes in dynamics of the Columbia‐Post system, environmental factors contribute to short‐term (i.e., seasonal) dynamic variability. In particular, analysis of force balance time series indicates that observed variations in speed result from seasonal changes to the subglacial hydrologic system and associated changes in basal drag. Variations in terminus position only drive noticeable speed change when the terminus retreats from regions of relatively high basal drag. In agreement with long‐term analyses of Columbia Glacier, we find that terminus geometry can perturb the timing of seasonal ice flow patterns. Specifically, our data support the idea that retreat of a glacier terminus into deeper water is accompanied by a shift in the primary control on frontal ablation. Although our analysis focuses on two Alaskan glaciers, our data suggest that changes in the relative importance of surface meltwater and buoyancy effects on submarine melting and/or calving may manifest as a shift in terminus change seasonality and offer a mechanism to identify frontal ablation controls.

Ice velocity of Jakobshavn Isbrae, Petermann Glacier, Nioghalvfjerdsfjorden, and Zachariae Isstrøm, 2015–2017, from Sentinel 1-a/b SAR imagery

Lemos, A., A. Shepherd, M. McMillan, A.E. Hogg, E. Hatton, and I Joughin, "Ice velocity of Jakobshavn Isbrae, Petermann Glacier, Nioghalvfjerdsfjorden, and Zachariae Isstrøm, 2015–2017, from Sentinel 1-a/b SAR imagery," The Cryosphere, 12, 2087-2097, doi:10.5194/tc-12-2087-2018, 2018.

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18 Jun 2018

Systematically monitoring Greenland's outlet glaciers is central to understanding the timescales over which their flow and sea level contributions evolve. In this study we use data from the new Sentinel-1a/b satellite constellation to generate 187 velocity maps, covering four key outlet glaciers in Greenland: Jakobshavn Isbrae, Petermann Glacier, Nioghalvfjerdsfjorden, and Zachariae Isstrøm. These data provide a new high temporal resolution record (6-day averaged solutions) of each glacier's evolution since 2014, and resolve recent seasonal speedup periods and inter-annual changes in Greenland outlet glacier speed with an estimated certainty of 10%. We find that since 2012, Jakobshavn Isbrae has been decelerating, and now flows approximately 1250 m yr-1 (10%), slower than 5 years previously, thus reversing an increasing trend in ice velocity that has persisted during the last decade. Despite this, we show that seasonal variability in ice velocity remains significant: up to 750 m yr-1 (14%) at a distance of 12 km inland of the terminus. We also use our new dataset to estimate the duration of speedup periods (80–95 days) and to demonstrate a strong relationship between ice front position and ice flow at Jakobshavn Isbrae, with increases in speed of  ~ 1800 m yr-1 in response to 1 km of retreat. Elsewhere, we record significant seasonal changes in flow of up to 25% (2015) and 18% (2016) at Petermann Glacier and Zachariae Isstrøm, respectively. This study provides a first demonstration of the capacity of a new era of operational radar satellites to provide frequent and timely monitoring of ice sheet flow, and to better resolve the timescales over which glacier dynamics evolve.

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In The News

Antarctic'as ice sheet is melting 3 times faster than before

Associate Press, Seth Borenstein

The melting of Antarctica is accelerating at an alarming rate, with about 3 trillion tons of ice disappearing since 1992, an international team of ice experts said in a new study.

14 Jun 2018

Hidden lakes drain below West Antarctica's Thwaites Glacier

UW News and Information, Hannah Hickey

Thwaites Glacier on the edge of West Antarctica is one of the planet’s fastest-moving glaciers. Research shows that it is sliding unstoppably into the ocean, mainly due to warmer seawater lapping at its underside.

8 Feb 2017

Satellite system tracks glaciers' flow in real time

Nature News, Jeff Tollefson

The Global Land Ice Velocity Extraction project (GoLIVE) is the first to provide scientists with regular, semi-automated measurements of ice movement across the entire world. The Landsat 8 satellite covers the planet every 16 days.

16 Dec 2016

More News Items

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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