Publications
EOS Harig, Christopher and Frederik J. Simons. Ice mass loss in Greenland, the Gulf of Alaska, and the Canadian Archipelago: Seasonal cycles and decadal trends.
Geophys. Res. Let., 43 (7), 3150-3159, 2016.
Online: http://dx.doi.org/10.1002/2016GL067759
Print: Reprint (pdf)

Abstract: Over the past several decades mountain glaciers and ice caps have been significant contributors to sea level rise. Here we estimate the ice mass changes in the Canadian Archipelago, the Gulf of Alaska, and Greenland since 2003 by analyzing time-varying gravimetry data from the Gravity Recovery and Climate Experiment. Prior to 2013, interannual ice mass variability in the Gulf of Alaska and in regions around Greenland remains within the average estimated over the whole data span. Beginning in summer 2013, ice mass in regions around Greenland departs positively from its long-term trend. Over Greenland this anomaly reached almost 500 Gt through the end of 2014. Overall, long-term ice mass loss from Greenland and the Canadian Archipelago continues to accelerate, while losses around the Gulf of Alaska region continue but remain steady with no significant acceleration.



EPSL Harig, Christopher and Frederik J. Simons. Accelerated West Antarctic ice mass loss continues to outpace East Antarctica gains. Earth Planet. Sci. Let., 415, 134-141, 2015. http://dx.doi.org/10.1016/j.epsl.2015.01.029 Reprint (pdf)

Abstract: While multiple data sources have confirmed that Antarctica is losing ice at an accelerating rate, different measurement techniques estimate the details of its geographically highly variable mass balance with different levels of accuracy, spatio-temporal resolution, and coverage. Some scope remains for methodological improvements using a single data type. In this study we report our progress in increasing the accuracy and spatial resolution of time-variable gravimetry. We determine the geographic pattern of ice mass change in Antarctica between January 2003 and June 2014, accounting for glacio-isostatic adjustment using the IJ05_R2 model. Expressing the unknown signal in a sparse Slepian basis constructed by optimization to prevent leakage out of the regions of interest, we use robust signal processing and statistical estimation methods. Applying those to the latest time series of data from the Gravity Recovery and Climate Experiment (GRACE) we map Antarctica's mass loss in space and time as well as can be recovered from satellite gravity alone. West Antarctica is losing ice mass at a rate of -121 +- 8 Gt/yr and has experienced large acceleration of ice mass losses along the Amundsen Sea coast of -18 +- 5 Gt/yr^2, doubling the mass loss in the past six years. The Antarctic Peninsula shows slightly accelerating ice mass loss, with larger accelerated losses in the southern half of the Peninsula. Ice mass gains due to snowfall in Dronning Maud Land have continued to add about half the amount of West Antarctica's loss back into the continent over the last decade. We estimate the overall mass losses from Antarctica since January 2003 at a rate of -92 +- 10 Gt/yr.

Media:
Ice loss in west Antarctica is speeding up, by John Abraham, The Guardian, 05/11/2015 (web)

Melting Antarctic: Failure to act now on emissions could rause oceans by metres, by Graham Readfearn, The Guardian, 05/05/2015 (web)

Sea level: Past and present melting rates point to 3m by end of century, by Jayalakshmi K, International Business Times 05/05/2015 (web)

Scientists horrified by speed of glaciers melting, by Russell Jackson, The Scotsman 05/04/2015 (web)

Gravity data shows Antarctic ice sheet is melting much faster, Delhi Daily News 05/02/2015 (web)

Antarctica is melting ever faster, by Jenna Iacurci, Nature World News 05/01/2015 (web)

Satellite data helps pinpoint Antarctic ice loss, by Bob Berwyn, Summit County Voice 05/04/2015 (web)

Gravity data show that Antarctic ice sheet is melting increasingly faster,
by Morgan Kelly, News@Princeton, 04/30/2015 (web)
Also reported in,
Phys.org, 04/30/2015 (web)
Science 2.0, 05/01/2015 (web)
e Science News, 05/01/2015 (web)
Daily News and Analysis, 05/01/2015 (web)
ENCmag.com, 05/01/2015 (web)
R & D Magazine, 05/01/2015 (web)
Sierra Leone Times, 05/01/2015 (web)
Web India, 05/01/2015 (web)
Deccan Herald, 05/01/2015 (web)
Reporting Climate Science.com, 05/03/2015 (web)
Noticiasdelaciencia.com, 05/04/2015 (web, in Spanish)

Climat: la Terre perd son congelateur, by Sylvestre Huet, Liberation 04/02/2015 (web)





EOS Harig, Christopher, Kevin W. Lewis, Alain Plattner, and Frederik J. Simons. A suite of software analyzes data on the sphere.
Eos, 96, 2015.
Online: http://dx.doi.org/10.1029/2015EO025851
Print: Reprint (pdf)

Description: The software improves data analysis over small portions of a spherical planetary surface. Among other applications, it has helped track Greenland's ice loss over time.

Figures:
Figure 01 pdf png, Figure 02 pdf png, Figure 03 pdf png, Magazine Art pdf

Figures files (code):
On the way...



PNAS Harig, Christopher and Frederik J. Simons. Mapping Greeenland's mass loss in space and time. Proc. Natl. Acad. Sc., 109(49), 19934-19937. doi:10.1073/pnas.1206785109, 2012. Reprint (pdf) Supporting Information (pdf)

Abstract: The melting of polar ice sheets is a major contributor to global sea-level rise. Early estimates of the mass lost from the Greenland ice cap, based on satellite gravity data collected by the Gravity Recovery And Climate Experiment (GRACE), have widely varied. While the continentally and decadally averaged estimated trends have now more or less converged, to this date there has been little clarity on the detailed spatial distribution of Greenland's mass loss, nor on how the geographical pattern has varied on relatively shorter time scales. Here we present a spatially and temporally resolved estimation of the ice mass change over Greenland between April 2002 and August 2011. While the total mass loss trend has remained linear, actively changing areas of mass loss were concentrated on the southeastern and northwestern coasts, with ice mass in the center of Greenland steadily increasing over the decade.

Media:
Climate Change 2013: The Physical Science Basis, Intergovernmental Panel on Climate Change, Fifth Assessment Report (AR5-WG1), 2013

New science upsets calculations on sea level rise, climate change, by Lewis Page, The Register, 11/28/2012 (web)

El hielo de Groenlandia no se derrite tan rapidamente como se habia estimado, cienciaaldia.com, 11/28/2012 (web, in Spanish)

Embracing data `noise' bring Greenland's complex ice melt into focus, by M. Kelly, News@Princeton, 11/27/2012 (web)

Anderungen in der Schwerkraft verraten Eisschmelze, derStandard.at, 11/24/2012 (web, in German)

Le Groenland fond avec gravite, by Sylvestre Huet, Liberation, 11/22/2012 (web, in French)

De rafelranden van de ijskap, by Elmar Veerman, Wetenschap24.nl, 11/21/2012 (web, in Dutch)

Eisschild schrumpft jahrlich um 200 Mrd. Tonnen, Science@ORF.at, 11/20/2012 (web, in German)

Schwerkraft-Messung zeigt massive Eisschmelze, Die Welt, 11/20/2012 (web, in German)

Greenland ice loss is accelerating, by Sunanda Creagh, TheConversation.edu.au, 11/20/2012 (web)

Greenland ice is melting at ever faster rates, by Laura Sinpetru, Softpedia.com, 11/20/2012 (web)

Geoscientists report Greenland ice sheet melting rate is increasing, by Bob Yirka, Phys.org, 11/20/2012 (web)

Greenland ice melt accelerating, by Larry O'Hanlon, ABC.net.au, 11/20/2012 (web)

Coste della Groenlandia sempre piu povere di ghiacci, Sciolti 200 miliardi di tonnellate in 10 anni, Meteoleontinoi, 11/20/2012 (web, in Italian)

Degelo na Gronelandia mapeado, CienciaHoje, 11/20/2012 (web, in Portuguese)

Groenlandia ha perdido 200.000 millones de toneladas de hielo en la ultima decada, ABC.es, 11/20/2012 (web, in Spanish)

Wechselnde Schwerkraft zeigt Schmelzen des Gronlandeises, Focus.de, 11/19/2012 (web, in German)

Eispanzer Gronlands schmilzt ungleichmassig ab,
Reported in,
Sudostschweiz.ch, 11/19/2012 (web, in German)
Blick.ch, 11/19/2012 (web, in German)

Greenland ice melt is accelerating, by Douglas Main,
Reported in,
CBSNews.com, 11/19/2012 (web)
OurAmazingPlanet.com, 11/19/2012 (web)

Greenland is losing 200 billion tons of ice every year, by Randy Astaiza, BusinessInsider.com, 11/19/2012 (web)

Greenland loses 200 billion tons ice per year, by Larry O'Hanlon,
Reported in,
MSNBC.msn.com, 12/03/2012 (web)
Discovery.com, 11/19/2012 (web)
LiveScience.com, 11/19/2012 (web)

Other Relevant Publications:

Christopher Harig, Shijie Zhong & Frederik J. Simons Constraints on upper-mantle viscosity from the flow-induced pressure gradient across the Australian continental keel
Geochem., Geophys., Geosys., 2010, 11, Q06004 doi:10.1029/2010GC003038

Frederik J. Simons & F. A. Dahlen Spherical Slepian functions and the polar gap in geodesy Geoph. J. Int., 2006, 166 (3), 1039-1061 doi:10.1111/j.1365-246X.2006.03065.x