Thinning out: A new study suggests that these glaciers may be thinning, endangering water resources…

[OKIsItJustMe]

http://www.nature.com/climate/2009/0901/full/climate.2008.136.html

Research Highlights

Nature Reports Climate Change
Published online: 11 December 2008 | doi:10.1038/climate.2008.136

Thinning out

Anna Armstrong

Geophys. Res. Lett. 35, L22503 (2008)

High elevation glaciers in the Himalayas release meltwater into the Indus, Ganges and Brahmaputra Rivers, contributing up to half of their total river flow. A new study suggests that these glaciers may be thinning, endangering water resources in one of the most populous regions of the world.

Natalie Kehrwald of the Ohio State University and colleagues collected ice cores from the summit of Naimona'nyi Glacier in Tibet. The team measured the level of beta radioactivity and the concentration of two radioactive isotopes, chlorine-36 and hydrogen-3, in the ice. These isotopes are common signatures of nuclear weapons testing in the 1950s and 60s. The notable absence of any radioactive signal in the cores, together with negligible concentrations of radioactive isotopes, indicates that the glacier contains no ice deposited since the 1950s; lead dating confirmed this finding. The authors suggest that increased ice melt resulting from recent warming may be responsible.

Current estimates of the impact of Himalayan glacial retreat on water resources have failed to account for high elevation glacial thinning. If Naimona'nyi is characteristic of other glaciers in the region, meltwater supply is likely to shrink much faster than currently predicted, with considerable negative consequences for up to half a billion people.

[Idealism]

1. I thought this was a male-pattern baldness study

Damn misleading titles *grumble*

[gristy]

2. "new" would be relative, I guess

I've been hearing this for what, years? :(

[OKIsItJustMe]

3. You've been hearing about the lack of certain isotopes in the glaciers? The researchers hadn't.

http://www.agu.org/pubs/crossref/2008/2008GL035556.shtml

…

Abstract

Ice cores drilled from glaciers around the world generally contain horizons with elevated levels of beta radioactivity including ³⁶Cl and ³H associated with atmospheric thermonuclear bomb testing in the 1950s and 1960s. Ice cores collected in 2006 from Naimona'nyi Glacier in the Himalaya (Tibet) lack these distinctive marker horizons suggesting no net accumulation of mass (ice) since at least 1950. Naimona'nyi is the highest glacier (6050 masl) documented to be losing mass annually suggesting the possibility of similar mass loss on other high-elevation glaciers in low and mid-latitudes under a warmer Earth scenario. If climatic conditions dominating the mass balance of Naimona'nyi extend to other glaciers in the region, the implications for water resources could be serious as these glaciers feed the headwaters of the Indus, Ganges, and Brahmaputra Rivers that sustain one of the world's most populous regions.
…

3. Results and Discussion

…
<7> The measurement of accumulation stakes revealed that the surface had lowered 0.675 m a⁻¹ at the summit and 1.425 m a⁻¹ at 4800 masl between 2004 and 2006 . This ablation was unexpected as Naimona'nyi (6050 masl) is of similar or higher elevation than two of the four Tibetan glaciers drilled by BPRC that all contained prominent beta radioactivity peaks or horizons indicating a net positive accumulation when drilled .
…
<10> Naimona'nyi is very anomalous as its ice cores do not contain horizons with elevated beta radioactivity, ³⁶Cl or ³H (Figures 2a and 2b). Only one beta sample is elevated (995.3 dph kg⁻¹) compared to the average activity for the upper 14.01 meters of the core (92.1 dph kg⁻¹). This sample is from a near-surface (0.4 to 0.74 m depth) layer of superimposed ice which comprises the firn-ice transition and physically differs from the ice below as it contains a prominent dust layer. This layer contains very little tritium (2.65 TU) suggesting that it was deposited before 1963. The virtual absence on Naimona'nyi of any ice or snow strata containing beta radioactivity including ³H and ³⁶Cl from post-1950 thermonuclear tests provides strong evidence for a net negative mass balance from 1950 to the present.
…