AGW Observer

Observations of anthropogenic global warming

Papers on polar ice sheets

Posted by Ari Jokimäki on November 24, 2009

This is a list of papers on the modern observations of Greenland and Antarctic ice sheets. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (December 9, 2009): van den Broeke et al. (2009) added.
UPDATE (November 25, 2009): Chen et al. (2009) added, thanks to John Cook for pointing it out, see the comment section below.

Polar ice sheets

Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE – Velicogna (2009) “We use monthly measurements of time-variable gravity from the GRACE (Gravity Recovery and Climate Experiment) satellite gravity mission to determine the ice mass-loss for the Greenland and Antarctic Ice Sheets during the period between April 2002 and February 2009. We find that during this time period the mass loss of the ice sheets is not a constant, but accelerating with time, i.e., that the GRACE observations are better represented by a quadratic trend than by a linear one, implying that the ice sheets contribution to sea level becomes larger with time. In Greenland, the mass loss increased from 137 Gt/yr in 2002–2003 to 286 Gt/yr in 2007–2009, i.e., an acceleration of −30 ± 11 Gt/yr2 in 2002–2009. In Antarctica the mass loss increased from 104 Gt/yr in 2002–2006 to 246 Gt/yr in 2006–2009, i.e., an acceleration of −26 ± 14 Gt/yr2 in 2002–2009.” [Link to PDF]

Recent Sea-Level Contributions of the Antarctic and Greenland Ice Sheets – Shepherd & Wingham (2007) A review article. “As global temperatures have risen, so have rates of snowfall, ice melting, and glacier flow. Although the balance between these opposing processes has varied considerably on a regional scale, data show that Antarctica and Greenland are each losing mass overall. Our best estimate of their combined imbalance is about 125 gigatons per year of ice, enough to raise sea level by 0.35 millimeters per year.” [Link to PDF]

Interannual variations of the mass balance of the Antarctica and Greenland ice sheets from GRACE – Ramillien et al. (2006) “We use new GRACE geoid solutions provided by the Groupe de Recherche en Géodésie Spatiale (GRGS/CNES), at the resolution of ~400 km and sampled at 10-day interval. In the three regions, significant interannual variations are observed, which we approximate as linear trends over the short time span of analysis. Over Greenland, an apparent total volume loss of 119 +/− 10 cu km/yr water is observed. For the Antarctica ice sheet, a bimodal behaviour is apparent, with volume loss amounting to 88 +/− 10 cu km/yr water in the West, and increase in the East amounting to 72 +/− 20 cu km/yr water.” [Link to PDF]

Mass changes of the Greenland and Antarctic ice sheets and shelves and contributions to sea-level rise: 1992-2002 – Zwally et al. (2005) “Changes in ice mass are estimated from elevation changes derived from 10.5 years (Greenland) and 9 years (Antarctica) of satellite radar altimetry data from the European Remote-sensing Satellites ERS-1 and -2. … The Greenland ice sheet is thinning at the margins (−42 ± 2 Gt a−1 below the equilibrium-line altitude (ELA)) and growing inland (+53 ± 2 Gt a−1 above the ELA) with a small overall mass gain (+11 ± 3 Gt a−1; −0.03 mm a−1 SLE (sea-level equivalent)). The ice sheet in West Antarctica (WA) is losing mass (−47 ± 4 Gt a−1) and the ice sheet in East Antarctica (EA) shows a small mass gain (+16 ± 11 Gt a−1) for a combined net change of −31 ± 12 Gt a−1 (+0.08 mm a−1 SLE).” [Link to PDF]

Mass Balance of Polar Ice Sheets – Rignot & Thomas (2002) “Recent advances in the determination of the mass balance of polar ice sheets show that the Greenland Ice Sheet is losing mass by near-coastal thinning, and that the West Antarctic Ice Sheet, with thickening in the west and thinning in the north, is probably thinning overall.” [Link to PDF]

Greenland ice sheet

Partitioning Recent Greenland Mass Loss – van den Broeke et al. (2009) “Mass budget calculations, validated with satellite gravity observations [from the Gravity Recovery and Climate Experiment (GRACE) satellites], enable us to quantify the individual components of recent Greenland mass loss. The total 2000–2008 mass loss of ~1500 gigatons, equivalent to 0.46 millimeters per year of global sea level rise, is equally split between surface processes (runoff and precipitation) and ice dynamics.” [Link to PDF]

Large and Rapid Melt-Induced Velocity Changes in the Ablation Zone of the Greenland Ice Sheet – van de Wal et al. (2008) “Continuous Global Positioning System observations reveal rapid and large ice velocity fluctuations in the western ablation zone of the Greenland Ice Sheet. Within days, ice velocity reacts to increased meltwater production and increases by a factor of 4. Such a response is much stronger and much faster than previously reported. Over a longer period of 17 years, annual ice velocities have decreased slightly, which suggests that the englacial hydraulic system adjusts constantly to the variable meltwater input, which results in a more or less constant ice flux over the years.” [Link to PDF]

Seasonal Speedup Along the Western Flank of the Greenland Ice Sheet – Joughin et al. (2008) “It has been widely hypothesized that a warmer climate in Greenland would increase the volume of lubricating surface meltwater reaching the ice-bedrock interface, accelerating ice flow and increasing mass loss. We have assembled a data set that provides a synoptic-scale view, spanning ice-sheet to outlet-glacier flow, with which to evaluate this hypothesis. On the ice sheet, these data reveal summer speedups (50 to 100%) consistent with, but somewhat larger than, earlier observations. The relative speedup of outlet glaciers, however, is far smaller (<15%). Furthermore, the dominant seasonal influence on Jakobshavn Isbrae's flow is the calving front's annual advance and retreat. With other effects producing outlet-glacier speedups an order of magnitude larger, seasonal melt's influence on ice flow is likely confined to those regions dominated by ice-sheet flow."

Changes in the Velocity Structure of the Greenland Ice Sheet – Rignot & Kanagaratnam (2006) “Using satellite radar interferometry observations of Greenland, we detected widespread glacier acceleration below 66° north between 1996 and 2000, which rapidly expanded to 70° north in 2005. Accelerated ice discharge in the west and particularly in the east doubled the ice sheet mass deficit in the last decade from 90 to 220 cubic kilometers per year. As more glaciers accelerate farther north, the contribution of Greenland to sea-level rise will continue to increase.”

Satellite Gravity Measurements Confirm Accelerated Melting of Greenland Ice Sheet – Chen et al. (2006) “Using time-variable gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) satellite mission, we estimate ice mass changes over Greenland during the period April 2002 to November 2005. After correcting for the effects of spatial filtering and limited resolution of GRACE data, the estimated total ice melting rate over Greenland is –239 ± 23 cubic kilometers per year, mostly from East Greenland. This estimate agrees remarkably well with a recent assessment of –224 ± 41 cubic kilometers per year, based on satellite radar interferometry data. GRACE estimates in southeast Greenland suggest accelerated melting since the summer of 2004, consistent with the latest remote sensing measurements.” [Link to PDF]

Surface Melt-Induced Acceleration of Greenland Ice-Sheet Flow – Zwally et al. (2002) “The near coincidence of the ice acceleration with the duration of surface melting, followed by deceleration after the melting ceases, indicates that glacial sliding is enhanced by rapid migration of surface meltwater to the ice-bedrock interface. … The indicated coupling between surface melting and ice-sheet flow provides a mechanism for rapid, large-scale, dynamic responses of ice sheets to climate warming.” [Link to PDF]

Antarctic ice sheet

Accelerated Antarctic ice loss from satellite gravity measurements – Chen et al. (2009) “The Gravity Recovery and Climate Experiment5 (GRACE) offers the opportunity of quantifying polar ice-sheet mass balance from a different perspective6, 7. Here we use an extended record of GRACE data spanning the period April 2002 to January 2009 to quantify the rates of Antarctic ice loss. In agreement with an independent earlier assessment4, we estimate a total loss of 190±77 Gt yr-1, with 132±26 Gt yr-1 coming from West Antarctica. However, in contrast with previous GRACE estimates, our data suggest that East Antarctica is losing mass, mostly in coastal regions, at a rate of -57±52 Gt yr-1, apparently caused by increased ice loss since the year 2006.”

West Antarctic Ice Sheet collapse – the fall and rise of a paradigm – Vaughan (2008) “It is now almost 30 years since John Mercer (1978) first presented the idea that climate change could eventually cause a rapid deglaciation, or “collapse,” of a large part of the West Antarctic ice sheet (WAIS), raising world sea levels by 5 m and causing untold economic and social impacts. This idea, apparently simple and scientifically plausible, created a vision of the future, sufficiently alarming that it became a paradigm for a generation of researchers and provided an icon for the green movement. Through the 1990s, however, a lack of observational evidence for ongoing retreat in WAIS and improved understanding of the complex dynamics of ice streams meant that estimates of likelihood of collapse seemed to be diminishing. In the last few years, however, satellite studies over the relatively inaccessible Amundsen Sea sector of West Antarctica have shown clear evidence of ice sheet retreat showing all the features that might have been predicted for emergent collapse. These studies are re-invigorating the paradigm, albeit in a modified form, and debate about the future stability of WAIS. Since much of WAIS appears to be unchanging, it may, no longer be reasonable to suggest there is an imminent threat of a 5-m rise in sea level resulting from complete collapse of the West Antarctic ice sheet, but there is strong evidence that the Amundsen Sea embayment is changing rapidly. This area alone, contains the potential to raise sea level by around ~1.5 m, but more importantly it seems likely that it could, alter rapidly enough, to make a significant addition to the rate of sea-level rise over coming two centuries. Furthermore, a plausible connection between contemporary climate change and the fate of the ice sheet appears to be developing. The return of the paradigm presents a dilemma for policy-makers, and establishes a renewed set of priorities for the glaciological community. In particular, we must establish whether the hypothesized instability in WAIS is real, or simply an oversimplification resulting from inadequate understanding of the feedbacks that allow ice sheets to achieve equilibrium: and whether there is any likelihood that contemporary climate change could initiate collapse.” David G. Vaughan, Climatic Change, Volume 91, Numbers 1-2, 65-79, DOI: 10.1007/s10584-008-9448-3 [Full text]

Measurements of Time-Variable Gravity Show Mass Loss in Antarctica – Velicogna & Wahr (2006) “Using measurements of time-variable gravity from the Gravity Recovery and Climate Experiment satellites, we determined mass variations of the Antarctic ice sheet during 2002–2005. We found that the mass of the ice sheet decreased significantly, at a rate of 152 ± 80 cubic kilometers of ice per year, which is equivalent to 0.4 ± 0.2 millimeters of global sea-level rise per year. Most of this mass loss came from the West Antarctic Ice Sheet.” [Link to PDF]

Mass balance of the Antarctic ice sheet – Wingham et al. (2006) “Here, we use satellite radar altimetry to measure the elevation change of 72% of the grounded ice sheet during the period 1992–2003. Depending on the density of the snow giving rise to the observed elevation fluctuations, the ice sheet mass trend falls in the range −5-+85 Gt yr−1. … Mass gains from accumulating snow, particularly on the Antarctic Peninsula and within East Antarctica, exceed the ice dynamic mass loss from West Antarctica.” [Link to PDF]

Widespread Complex Flow in the Interior of the Antarctic Ice Sheet – Bamber et al. (2000) “It has been suggested that as much as 90% of the discharge from the Antarctic Ice Sheet is drained through a small number of fast-moving ice streams and outlet glaciers fed by relatively stable and inactive catchment areas. Here, evidence obtained from balance velocity estimates suggests that each major drainage basin is fed by complex systems of tributaries that penetrate up to 1000 kilometers from the grounding line into the interior of the ice sheet.” [Link to PDF]

Satellite Radar Interferometry for Monitoring Ice Sheet Motion: Application to an Antarctic Ice Stream – Goldstein et al. (1993) “The SRI velocities and grounding line of the Rutford Ice Stream, Antarctica, agree fairly well with earlier ground-based data. The combined use of SRI and other satellite methods is expected to provide data that will enhance the understanding of ice stream mechanics and help make possible the prediction of ice sheet behavior.” [Link to PDF]

West Antarctic ice sheet and CO2 greenhouse effect: a threat of disaster – Mercer (1978) Not an observational paper but is included here because it seems to be a classic on this subject. “If the global consumption of fossil fuels continues to grow at its present rate, atmospheric CO2 content will double in about 50 years. Climatic models suggest that the resultant greenhouse-warming effect will be greatly magnified in high latitudes. The computed temperature rise at lat 80° S could start rapid deglaciation of West Antarctica, leading to a 5 m rise in sea level.” [Link to PDF]

5 Responses to “Papers on polar ice sheets”

  1. John Cook said

    This one’s hot off the press (just blogged on it at http://www.skepticalscience.com/East-Antarctica-is-now-losing-ice.html)

    Accelerated Antarctic ice loss from satellite gravity measurements – Chen et al (2009) – Accurate quantification of Antarctic ice-sheet mass balance and its contribution to global sea-level rise remains challenging, because in situ measurements over both space and time are sparse. Satellite remote-sensing data of ice elevations and ice motion show significant ice loss in the range of -31 to -196 Gt yr-1 in West Antarctica in recent years, whereas East Antarctica seems to remain in balance or slightly gain mass, with estimated rates of mass change in the range of -4 to 22 Gt yr-1. The Gravity Recovery and Climate Experiment5 (GRACE) offers the opportunity of quantifying polar ice-sheet mass balance from a different perspective. Here we use an extended record of GRACE data spanning the period April 2002 to January 2009 to quantify the rates of Antarctic ice loss. In agreement with an independent earlier assessment, we estimate a total loss of 19077 Gt yr-1, with 13226 Gt yr-1 coming from West Antarctica. However, in contrast with previous GRACE estimates, our data suggest that East Antarctica is losing mass, mostly in coastal regions, at a rate of -5752 Gt yr-1, apparently caused by increased ice loss since the year 2006.

  2. John Cook said

    Accidentally left a paragraph on the end of my URL which is:
    http://www.skepticalscience.com/East-Antarctica-is-now-losing-ice.html

  3. Ari Jokimäki said

    Thanks, John. I was aware (by reading your article) that there was a recent paper on this that used GRACE, but I confused it with Velicogna (2009), not realizing that there were two recent papers doing similar thing with GRACE. :)

  4. Ari Jokimäki said

    I just realised that your article was a new one (and good one as usual)! It’s hard to keep track with all these new studies coming in. ;)

  5. Ari Jokimäki said

    I added van den Broeke et al. (2009).

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