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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

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.

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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.

Ocean-induced melt volume directly paces ice loss from Pine Island Glacier

Joughin, I., D. Shapero, P. Dutrieux, and B. Smith, "Ocean-induced melt volume directly paces ice loss from Pine Island Glacier," Sci. Adv., 7, doi:10.1126/sciadv.abi5738, 2021.

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22 Oct 2021

The spatial distribution of ocean-induced melting beneath buttressing ice shelves is often cited as an important factor controlling Antarctica’s sea-level contribution. Using numerical simulations, we investigate the relative sensitivity of grounded-ice loss to the spatial distribution and overall volume of ice-shelf melt over two centuries. Contrary to earlier work, we find only minor sensitivity to melt distribution (<6%), with a linear dependence of ice loss on the total melt. Thus, less complex models that need not reproduce the detailed melt distribution may simplify the projection of future sea level. The linear sensitivity suggests a contribution of up to 5.1 cm from Pine Island Glacier over the next two centuries given anticipated levels of ocean warming, provided its ice shelf does not collapse because of other causes.

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

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