From AAAS online:
Widespread Persistent Thickening of the East Antarctic Ice Sheet by Freezing from the Base
Abstract
An International Polar Year aerogeophysical investigation of the high interior of East Antarctica reveals widespread freeze-on that drives significant mass redistribution at the bottom of the ice sheet. While surface accumulation of snow remains the primary mechanism for ice sheet growth, beneath Dome A 24% of the base by area is frozen-on ice. In some places, up to half the ice thickness has been added from below.
These ice packages result from conductive cooling of water ponded near the Gamburtsev Subglacial Mountain ridges and supercooling of water forced up steep valley walls. Persistent freeze-on thickens the ice column, alters basal ice rheology and fabric and upwarps the overlying ice sheet, including the oldest atmospheric climate archive, and drives flow behavior not captured in present models.
- Received for publication 8 November 2010.
- Accepted for publication 18 February 2011.
- Robin E. Bell1,
- Fausto Ferraccioli2,
- Timothy T. Creyts1,
- David Braaten3,
- Hugh Corr2,
- Indrani Das1,
- Detlef Damaske4,
- Nicholas Frearson1,
- Thomas Jordan2,
- Kathryn Rose2,
- Michael Studinger5, and
- Michael Wolovick1
+ Author Affiliations
1Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA.
2British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK.
3Center for the Remote Sensing of Ice Sheets, Kansas University, Lawrence, KS, USA.
4Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover, Germany.
5Goddard Earth Science and Technology Center, University of Maryland Baltimore County, MD, and NASA Goddard Space Flight Center, MD, USA.
I was simply pointing out that the existence of liquid water at the base of ice sheets does not require mysterious flows from oceans (see George E. Smith’s comment on March 8, 2011 at 5:10 pm) or even springs. It can be there simply because of dynamical processes involving pressure and geothermal heat acting at the base of the ice sheet. No doubt springs exist, but the source of water from those would ultimately be from ice sheet melt too.
kadaka (KD Knoebel) says: “3. This makes bottom of sheet grow thicker, without any new water added? Some clarification of your comment seems warranted.”
Maybe there is some confusion about *localized* growth at the bottom of the ice sheet by the refreezing of water transported from elsewhere (either at the rock-ice interface or beneath it via aquifers). This is not the same as thinking there might be an *overall* increase in the amount of Antarctic ice because it is growing from beneath. The “new” water would still have come from ice sheet melt somewhere else.
Tapeats creek (http://web.mst.edu/~rogersda/cp_megalandslides/tapeats_cave_canyon.htm) is entirely spring fed, is a relatively small creek yet it continuously discharges an estimated 70 million gallons a day 24/7-365 days a year. Who can say what is happening under the icecap. I dare say it is not a simple answer. Volcanoes discharge “new” water that has never been part of the surface water cycle before. There are volcanoes under the icecap. We cannot simply assume the ice cap only gains water from precipitation. The polar world is a cold desert. We know little of the geology under the ice. Estimates of ice mass are WAGs.