Estimation and Effects of Internal Accumulation on Five Glaciers in Alaska

Abstract

Estimates of internal accumulation for five Alaskan glaciers in different climates suggests that internal accumulation occurs in glaciers throughout Alaska. A method of estimating the quantity of internal accumulation is based on the annual minimum temperature ?Γ the snow-firn interface. The consistency of the estimates suggests that valid approximations of internal accumulation can be made over large areas. The estimates have not been confirmed by measurements of mass change, but are believed to be accurate within 10 percent. Point balance quantities of internal accumulation range from 0.65 m a-1, which is 64% of the annual accumulation on McCall Glacier, to 0.12 m a-1, 7% of the annual accumulation on Wolverine Glacier. The amount of internal accumulation decreases rapidly from north to south in Alaska; however it should be expected worldwide where sub-freezing, porous firn is invaded by water.Internal accumulation occurs in temperate glaciers in strongly maritime climates as well as glaciers in cold continental climates where it delays the onset of runoff, accelerates the process of converting snow into glacier ice, and explains the occurrence of temperate glaciers in permafrost areas.

Albedo decline on Greenland's Mittivakkat Gletscher in a warming climate

“…Subsequent increases of melt/rain water content have been shown to reduce snowpack cold content (due to release of latent heat) (e.g. Trabant and Mayo, ; Kane et al , ; Conway and Benedict, ) and change snow grain size/shape and snow liquid content (e.g. Dumont et al , ), again resulting in albedo lowering.…”

Reanalysing glacier mass balance measurement series

“…> 10 % contribution from basal melt to the total ablation of Franz Josef Glacier, which they explain by the strongly maritime environment of the glacier. Some of the proposed corrections for internal accumulation seem to be very large: Trabant and Mayo (1985) for Alaskan glaciers report 7-64 %, Trabant and Benson (1986) for Mc-Call report 40 %, Schneider and Jansson (2004) for STO report 3-5 %, and Reijmer and Hock (2008) for STO report 20 % (all relative to annual accumulation).…”

Observations of pronounced Greenland ice sheet firn warming and implications for runoff production

“…'s [] observations. Examining a range of published observations shows that this pattern of near‐freezing firn temperature at the runoff limit is typical across subpolar and polar glacier sites despite a range of mean annual surface temperatures and annual accumulation at the runoff limits of various glaciers [ Trabant and Mayo , ; Maohuan , ; Müller , ; Bamber , ; Schytt , ; Blatter and Kappenberger , ]. In cases where glaciers do produce runoff from lower temperature firn [e.g., Müller , ], steeper elevation gradients are typically present.…”

“…This makes the 10 m firn temperature a variable of interest for climate study, because this single measurement can characterize a site's recent temperature history. While the 10 m firn temperature can represent a mean annual snow surface temperature under some conditions, and was originally pursued for this purpose [e.g., Benson , ], it frequently deviates from the mean annual surface temperature observed at the surface for a variety of reasons [e.g., Schytt , ; Benson , ; Trabant and Mayo , ; Paterson , ; Müller , ; Ohmura , ; Steffen and Box , ]. Instead, shallow borehole temperatures represent an integration of recent energy balance at the site, transported to depth by three mechanisms of heat transfer: conduction, convection, and percolation.…”