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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

icepack: A new glacier flow modeling package in Python, version 1.0

Shapero, D.R., J.A. Badgeley, A.O. Hoffman, and I.R. Joughin, "icepack: A new glacier flow modeling package in Python, version 1.0," Geosci. Model Dev., 14, 4593-4616, doi:10.5194/gmd-14-4593-2021, 2021.

More Info

26 Jul 2021

We introduce a new software package called 'icepack' for modeling the flow of glaciers and ice sheets. The icepack package is built on the finite element modeling library Firedrake, which uses the Unified Form Language (UFL), a domain-specific language embedded into Python for describing weak forms of partial differential equations. The diagnostic models in icepack are formulated through action principles that are specified in UFL. The components of each action functional can be substituted for different forms of the user's choosing, which makes it easy to experiment with the model physics. The action functional itself can be used to define a solver convergence criterion that is independent of the mesh and requires little tuning on the part of the user. The icepack package includes the 2D shallow ice and shallow stream models. We have also defined a 3D hybrid model based on spectral semi-discretization of the Blatter–Pattyn equations. Finally, icepack includes a Gauss–Newton solver for inverse problems that runs substantially faster than the Broyden–Fletcher–Goldfarb–Shanno (BFGS) method often used in the glaciological literature. The overall design philosophy of icepack is to be as usable as possible for a wide a swath of the glaciological community, including both experts and novices in computational science.

Ice-shelf retreat drives recent Pine Island Glacier speedup

Joughin, I., D. Shapero, B. Smith, P. Dutrieux, and M. Barham, "Ice-shelf retreat drives recent Pine Island Glacier speedup," Sci. Adv., 7, doi:10.1126/sciadv.abg3080, 2021.

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11 Jun 2021

Speedup of Pine Island Glacier over the past several decades has made it Antarctica's largest contributor to sea-level rise. The past speedup is largely due to grounding-line retreat in response to ocean-induced thinning that reduced ice-shelf buttressing. While speeds remained fairly steady from 2009 to late 2017, our Copernicus Sentinel 1A/B-derived velocity data show a >12% speedup over the past 3 years, coincident with a 19-km retreat of the ice shelf. We use an ice-flow model to simulate this loss, finding that accelerated calving can explain the recent speedup, independent of the grounding-line, melt-driven processes responsible for past speedups. If the ice shelf’s rapid retreat continues, it could further destabilize the glacier far sooner than would be expected due to surface- or ocean-melting processes.

Observing traveling waves in glaciers with remote sensing: new flexible time series methods and application to Sermeq Kujalleq (Jakobshavn Isbræ), Greenland

Riel, B., B. Minchew, and I. Joughin, "Observing traveling waves in glaciers with remote sensing: new flexible time series methods and application to Sermeq Kujalleq (Jakobshavn Isbræ), Greenland," Cryosphere, 15, 407-439, doi:10.5194/tc-15-407-2021, 2021.

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28 Jan 2021

The recent influx of remote sensing data provides new opportunities for quantifying spatiotemporal variations in glacier surface velocity and elevation fields. Here, we introduce a flexible time series reconstruction and decomposition technique for forming continuous, time-dependent surface velocity and elevation fields from discontinuous data and partitioning these time series into short- and long-term variations. The time series reconstruction consists of a sparsity-regularized least-squares regression for modeling time series as a linear combination of generic basis functions of multiple temporal scales, allowing us to capture complex variations in the data using simple functions. We apply this method to the multitemporal evolution of Sermeq Kujalleq (Jakobshavn Isbræ), Greenland. Using 555 ice velocity maps generated by the Greenland Ice Mapping Project and covering the period 2009–2019, we show that the amplification in seasonal velocity variations in 2012–2016 was coincident with a longer-term speedup initiating in 2012. Similarly, the reduction in post-2017 seasonal velocity variations was coincident with a longer-term slowdown initiating around 2017. To understand how these perturbations propagate through the glacier, we introduce an approach for quantifying the spatially varying and frequency-dependent phase velocities and attenuation length scales of the resulting traveling waves. We hypothesize that these traveling waves are predominantly kinematic waves based on their long periods, coincident changes in surface velocity and elevation, and connection with variations in the terminus position. This ability to quantify wave propagation enables an entirely new framework for studying glacier dynamics using remote sensing data.

More Publications

In The News

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

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

Ice shelf protecting Antarctic glacier is breaking up faster

Associated Press, Seth Borenstein

A critical Antarctic glacier is looking more vulnerable as satellite images show the ice shelf that blocks it from collapsing into the sea is breaking up much faster than before and spawning huge icebergs, a new study says.

11 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
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