Global glacier contributions to sea level rise

[Anne]

While 99 percent of Earth's land ice is locked up in the Greenland and Antarctic ice sheets, the remaining ice in the world's glaciers contributed just as much to sea rise as the two ice sheets combined from 2003 to 2009, according to a new study by a team led by Professor Alex Gardner of Clark University. The study compared traditional ground measurements to satellite data from ICESat and GRACE missions.  The processing and interpretation of the GRACE satellite observations was carried out by Dr Wouters of Bristol's School of Geographical Sciences with Professor John Wahr of the University of Colorado.

Professor Gardner says, "Traditional estimates of glacier mass loss, based solely on field measurements and localized observations, can sometimes overestimate ice loss when the findings are extrapolated over larger regions with few observations, like entire mountain ranges.

"Although ICESat and GRACE each have their own limitations, their estimates of mass change for large glacierised regions agree very well which gives us strong confidence in our results.''

An article about the paper is in Science Daily.

The paper itself is in Science, behind a paywall.

A RECONCILED ESTIMATE OF GLACIER CONTRIBUTIONS TO SEA LEVEL RISE: 2003 TO 2009
Abstract
Glaciers distinct from the Greenland and Antarctic Ice Sheets are losing large amounts of water to the world’s oceans. However, estimates of their contribution to sea level rise disagree. We provide a consensus estimate by standardizing existing, and creating new, mass-budget estimates from satellite gravimetry and altimetry and from local glaciological records. In many regions, local measurements are more negative than satellite-based estimates. All regions lost mass during 2003–2009, with the largest losses from Arctic Canada, Alaska, coastal Greenland, the southern Andes, and high-mountain Asia, but there was little loss from glaciers in Antarctica. Over this period, the global mass budget was –259 ± 28 gigatons per year, equivalent to the combined loss from both ice sheets and accounting for 29 ± 13% of the observed sea level rise.

Science 17 May 2013:
Vol. 340 no. 6134 pp. 852-857
DOI:10.1126/science.1234532

(Not sure if this post should be here, or under Glaciers.)

[F.Tnioli]

One thing i wonder about is whether mass loss of _ice_ in Greenland and Antarctica could be massively underestimated due to the the fact that not all liquid water which is created by melting of ice in Greenland and Antarctica end up in the ocean; substantial (perhaps even main?) fraction of melt waters end up, for now - i guess, - not in the ocean, but in under-ice lakes and pockets, which can grow to a huge size. Under-ice lake Vostok is one well known example of such a body of under-ice water, but not the only one; nearly 400 subglacial lakes are already found in Antarctica, and i see no reason why similar bodies of under-ice water couldn't exist in Greenland as well.

Which means, at some point, with such lakes "full" in terms of rockbed and more melt water arriving, and ice barriers between within-ice water bodies and the ocean failing, we'll see large discharges and "sudden" acceleration of "mass loss" of Greenland and Antarctic ice masses. No?