APL-UW Home

Jobs
About
Campus Map
Contact
Privacy
Intranet

Ian Joughin

Senior Principal Engineer

Affiliate Professor, Earth and Space Sciences

Email

ian@apl.uw.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

TermPicks: A century of Greenland glacier terminus data for use in scientific and machine learning applications

Goliber, S., and 22 others including T. Black and I. Joughin, "TermPicks: A century of Greenland glacier terminus data for use in scientific and machine learning applications," Cryosphere, 16, 3215-3233, doi:10.5194/tc-16-3215-2022, 2022.

More Info

12 Aug 2022

Marine-terminating outlet glacier terminus traces, mapped from satellite and aerial imagery, have been used extensively in understanding how outlet glaciers adjust to climate change variability over a range of timescales. Numerous studies have digitized termini manually, but this process is labor intensive, and no consistent approach exists. A lack of coordination leads to duplication of efforts, particularly for Greenland, which is a major scientific research focus. At the same time, machine learning techniques are rapidly making progress in their ability to automate accurate extraction of glacier termini, with promising developments across a number of optical and synthetic aperture radar (SAR) satellite sensors. These techniques rely on high-quality, manually digitized terminus traces to be used as training data for robust automatic traces. Here we present a database of manually digitized terminus traces for machine learning and scientific applications. These data have been collected, cleaned, assigned with appropriate metadata including image scenes, and compiled so they can be easily accessed by scientists. The TermPicks data set includes 39 060 individual terminus traces for 278 glaciers with a mean of 136 ± 190 and median of 93 of traces per glacier. Across all glaciers, 32 567 dates have been digitized, of which 4467 have traces from more than one author, and there is a duplication rate of 17%. We find a median error of ~100 m among manually traced termini. Most traces are obtained after 1999, when Landsat 7 was launched. We also provide an overview of an updated version of the Google Earth Engine Digitization Tool (GEEDiT), which has been developed specifically for future manual picking of the Greenland Ice Sheet.

An observation-based approach to calculating ice-shelf calving mass flux

Evans, E., A.D. Fraser, S. Cook, R. Coleman, and J.I. Joughin, "An observation-based approach to calculating ice-shelf calving mass flux," Remote Sens. Environ., 272, doi:10.1016/j.rse.2022.112918, 2022.

More Info

1 Apr 2022

In order to determine whether the calving flux of an ice shelf is changing, the long-term calving flux needs to be established. Methods used to estimate the calving flux either take into account non-steady-state behaviour by capturing movement of the calving-front location (e.g., using satellite observations), or they assume the calving front is stationary and that the ice is in steady state (e.g., flux-gate methods). Non-steady-state methods are hampered by the issue of temporal aliasing, i.e., when the satellite observation frequency is insufficient to capture the cyclic nature of the calving-front position. Methods that assume a steady state to estimate the calving flux accrue uncertainties if the ice shelf changes its physical state. In order to overcome these limitations we propose and implement a new observation-based approach that combines a time series of calving-front locations with a flux-gate method. The approach involves the creation of a unique semi-temporal domain as a mechanism to overcome the issue of temporal aliasing, and only requires easily accessible ice thickness and surface velocity estimates of the ice shelf. This approach allows for complex calving-front geometries and captures calving events of all sizes that are visible within the satellite imagery. Application of the approach allows the long-term average calving flux to be estimated (provided sufficient temporal coverage by satellite imagery), as well as identification of the minimum temporal baseline needed to produce a representative estimate of the long-term average calving flux, for any ice shelf. Implementation of the approach to multiple ice shelves would enable comparisons to be made regarding the spatial variability in the long-term calving flux of Antarctica's ice shelves, thereby highlighting calving regime change around the continent.

Multi-decadal retreat of marine-terminating outlet glaciers in northwest and central-west Greenland

Black, T.E., and I. Joughin, "Multi-decadal retreat of marine-terminating outlet glaciers in northwest and central-west Greenland," Cryosphere, 16, 807-824, doi:10.5194/tc-16-807-2022, 2022.

More Info

10 Mar 2022

The retreat and acceleration of marine-terminating outlet glaciers in Greenland over the past 2 decades have been widely attributed to climate change. Here we present a comprehensive annual record of glacier terminus positions in northwest and central-west Greenland and compare it against local and regional climatology to assess the regional sensitivity of glacier termini to different climatic factors. This record is derived from optical and radar satellite imagery and spans 87 marine-terminating outlet glaciers from 1972 through 2021. We find that in this region, most glaciers have retreated over the observation period and widespread regional retreat accelerated from around 1996. The acceleration of glacier retreat coincides with the timing of sharp shifts in ocean surface temperatures, the duration of the sea-ice season, ice-sheet surface mass balance, and meltwater and runoff production. Regression analysis indicates that terminus retreat is most sensitive to increases in runoff and ocean temperatures, while the effect of offshore sea ice is weak. Because runoff and ocean temperatures can influence terminus positions through several mechanisms, our findings suggest that a variety of processes — such as ocean-interface melting, mélange presence and rigidity, and hydrofracture-induced calving — may contribute to, but do not conclusively dominate, the observed regional retreat.

More Publications

In The News

Giant iceberg blocks scientists' study of 'Doomsday Glacier'

Associate Press, Seth Borenstein

Antarctica's so-called Doomsday Glacier, nicknamed because it is huge and coming apart, is mostly thwarting an international effort to figure out how dangerously vulnerable it is. Glaciologist Ian Joughin comments that the collapse of the Thwaites Glacier ice shelf may occur within the next couple hundred years according to his latest computer modeling.

3 Feb 2022

Fact check: NASA did not deny warming or say polar ice has increased since 1979

USA Today, Kate Petersen

NASA researchers have documented the loss of trillions of tons of ice from Earth's poles due to human-driven climate change. Citing published reports from the Polar Science Center and other sources, popular social media memes claiming an increase in polar ice since 1979 are swatted down.

21 Jan 2022

Why a mighty Antarctic glacier is purging ice into the sea

Mashable, Mark Kaufman

In research recently published in the journal Science Advances, glacier experts found Pine Island — which holds some 180 trillion tons of ice — lost big chunks of ice into the sea over the past few years (2017–2020), and the glacier picked up its pace. This means Pine Island continues to recede, weaken, and expel bounties of ice into the ocean, with the potential to add much more to sea level rise.

22 Jun 2021

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
Close

 

Close