Sentences with phrase «glacier ablation»

This paper examines whether maximum winter season snowpack, and snowpack and glacier ablation, can be determined for secondary locations from standard locations once baseline data exists for the secondary sites.

This indicates that monitoring of glacier ablation is essential for forecasting of alpine runoff.

Not exact matches

And is the current large scale ablation seen on these glaciers due to these glaciers coming to some equilibrium with a warmer world due to coming out of the LIA and response times associated with the large masses involved?

Evidence from glacial advance / retreat (e.g. the evidence from tropical Andean glaciers you cite above) is often difficult to interpret, because glacial mass balance represents in general a subtle competition between the influences of ablation (determined by changes in temperature thresholds reached) and accumulation (determined by changes in humidity and precipitation).

Our work at Alexander Island is supported by the British Antarctic Survey and involves analysis of valley glacier and ice - shelf moraines at Ablation Point Massif and Fossil Bluff.

The Greenland, and possibly the Antarctic, ice sheets have been losing mass recently, because losses by ablation including outlet glaciers exceed accumulation of snowfall.

Detailed studies of the energy balance and ablation of the Zongo and Chacaltaya glaciers support the importance of air temperature increase, and identify the increase in downward infrared radiation as the main way that the effect of the warmer air is communicated to the glacier surface [Wagnon et al. 1999; Francou et al, 2003].

Therefore, if conditions allow the glacier surface to warm to 0 C, the amount of ablation that can be sustained by a given energy input increases dramatically.

This certainly speaks to the rapid ablation of tropical glaciers.

Though air temperature has so far remained below freezing, melting has begun to occur, and the glacier is suffering net ablation over its entire surface.

If melt - water percolates into the glacier and re-freezes, the effect on ablation is more limited and indirect.

Other pages display maps of individual glaciers, with white regions indicating the «accumulation zone,» where snow falls and adds to the mass, and gray stippled areas showing the «ablation zone,» where melting eats away at the ice.

So long as an ice sheet gains an equal mass through snowfall as it loses through melt, ablation, and calving from glaciers and ice shelves, it is said to be in balance.

On marine terminating outlet glaciers the mechanisms to trigger thinning is surface ablation causing thinning, and potentially basal melting, though not yet observed (though see this recent paper by Holland et al, 2008).

Each ablation triangle is then representative of ablation for other portions of the glacier that lose their snowpack simultaneously.

In addition to the measured retreat we have measured the surface profiles of these glaciers, measured annual snowpack on the glaciers and annual ablation.

There are at least three ablation measurement sites on each glacier.

By mid-summer ablation rates do not vary substantially within the 1600 m - 2400 m elevation band, which is the primary elevation zone for glaciers.

Therefore, the processes of accumulation and ablation are the physical link between glaciers and climate, which explains why these ice bodies are such valuable tracers of climate variability on the scale of decades and centuries.

2) Snowpack ablation from 1984 - 2002 on four glaciers (3 by NCGCP and 1 by USGS).

There is a threshold of glacier extent reduction dependent on the magnitude of ablation rate increase, where glacier runoff declines, the few examples suggest this is in the 10 - 20 % areal extent loss.

Annual ice and firn ablation (firn and ice net balance: Mayo et al., 1972) is determined using ablation stakes drilled into the glacier surface and simultaneously checked on the same date in late September.

In the North Cascades the ablation surface of the previous year is always marked by a 2 - 5 cm thick band of dirty firn or glacier ice.

This does not demonstrate that the glaciers are more sensitive to ablation season conditions.

The correlation from glacier to glacier for the same time periods is 0.86 - 0.99, indicating that ablation conditions are becoming increasingly consistent on glaciers as the summer melt season develops.

Ablation peaks in May at low elevation Snotel sites, in June at high elevation Snotel sites, and in August on glaciers.

Ablation is measured by emplacing stakes in the glacier at the end of the previous melt season or the beginning of the melt season.

Comparison between net annual balance for each glacier, and accumulation season and ablation season conditions at NOAA Washington State Division 5 weather stations is presented in Table 5.

From July - September glaciers are the primary area of residual snow and ice ablation.

The changes in accumulation and ablation with location and during recent years indicates the importance of monitoring multiple glaciers as they are unique.

This narrow range indicates that late in the ablation season the density of snowpack on North Cascade glaciers is uniform, and need not be measured to determine mass balance.

The amount of runoff provided by a glacier is the product of its surface area and ablation rate.

NCGCP (Pelto, 1996; Pelto and Riedel, 2001) and the USGS (Krimmel, 1998) measurements on glaciers do provide a direct measure of ablation in this elevation band at multiple locations over the last 20 years.

Ablation has been measured for periods of at least two weeks with on site temperature measurement at numerous Snotel and glacier sites.

The resulting relationship is consistent and indicates that on - site temperature provides a good estimate of ablation over a multi-week period regardless of location at a Snotel site or on a glacier.

Ablation measurement on nine North Cascade glaciers for twenty - nine discrete two to six week periods during this part of the ablation season yield mean ablation rates of 0.036 m / day, 0.038 m / day and 0.028 m / day for July, August and September respeAblation measurement on nine North Cascade glaciers for twenty - nine discrete two to six week periods during this part of the ablation season yield mean ablation rates of 0.036 m / day, 0.038 m / day and 0.028 m / day for July, August and September respeablation season yield mean ablation rates of 0.036 m / day, 0.038 m / day and 0.028 m / day for July, August and September respeablation rates of 0.036 m / day, 0.038 m / day and 0.028 m / day for July, August and September respectively.

Each program monitors ablation during specific time periods using stakes emplaced in the glacier surface.

This glacier runoff is best determined by direct measurement of ablation on glaciers.

The four primary climatic variables affecting North Cascade glaciers are ablation season temperature, accumulation season precipitation, summer cloud cover and May and October freezing levels (Tangborn, 1980; Pelto, 1988).

Ablation measurements were made at a minimum of six stakes on each glacier.

Equilibrium line - The boundary between the region on a glacier where there is a net annual loss of ice mass (ablation area) and that where there is a net annual gain (accumulation area).

Dear Kenneth, when it warms, glaciers retreat until either a new equilibrium between ablation and accumulation is found or until they disappear.

By the way Kenneth, you were commented on the line «when it warms, glaciers retreat until either a new equilibrium between ablation and accumulation is found or until they disappear.»

When it is warm, ice melts faster and the glacier will retreat until it reaches a new equilibrium between accumulation and ablation.

Accumulation and ablation both primarily take place during the warm season and the formation of superimposed ice on this continental - type glacier is important.

In the North Cascades the warmer temperatures have increased summer ablation on the glaciers (Pelto, 2006).

A glacier is divided into an ablation zone where all accumulated snow is lost from the winter and an accumulation zone where snowpack is retained to the end of the summer.

Glaciers exist because accumulation exceeds ablation (melting) in a location.

In Glacier National Park, North Cascades, Helm Glacier and Place Glacier frequent loss of the entire snowcover by the end of the ablation season has become commonplace (WGMS, 2005 The result is in net ablation throughout the accumulation area causing thinning of the glacier in the accumulation zone.

The equilibrium line is the elevation on a glacier at which annual accumulation equals ablation.