Ice Sheets as Paleoclimate Archives

For an ice sheet of thickness H in equilibrium with a climate supplying accumulation at a rate a (thickness of ice per imit time), the vertical velocity near the ice-sheet surface is a and this velocity decreases to zero at the ice-sheet bed. A characteristic time constant for the ice core is H/a. The longest histories are therefore obtained from the thick and dry interiors of the ice sheets (particularly central East Antarctica, where H/a = 2 X 10 yrs). Unfortunately, records from low a sites are also low resolution, so to obtain a high-resolution record a high a site must be used and duration sacrificed (examples are the Antarctic Peninsula (H/a = 10 ) and southern Greenland H/a = 5 x 10 )). 

A Barnes Ice Cap B Devon Ice Cap Agassiz Ice Cap Camp Century GISP2 GRIP Renland 

I Byrd J Siple Dome K South Pole L Taylor Dome M Vostok N DomeC 0 Law Dome 

Obtaining an accurate and detailed depth-age relationship for an ice core is, of course, a necessary task for learning paleoclimate histories. Approximate time scales can be calculated using numerical models of ice and heat flow for the core site (Reeh, 1989), constrained by estimates of the modem accumulation rate and by measurements of ice thickness from radio-echo-sounding surveys. 

West Antarctica, but not at the very dry sites in East Antarctica. In addition to such continual counting methods, one can determine the absolute age of ice by identifying the fallout from volcanic eruptions of known age. 

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