Zmiany zasięgu czoła i geometrii lodowca Renarda (Spitsbergen) na tle zmian klimatycznych XX wieku

W artykule scharakteryzowano reakcję lodowca Renarda na zmiany klimatu w XX wieku. Bezpośrednim ich odzwierciedleniem były zmiany: zasięgu czoła oraz geometrii powierzchni. Lodowiec Renarda położony na obszarze NW części Ziemi Wedela Jarlsberga jest przykładem lodowca, który od końca Małej Epoki Lodowej podlega nieprzerwanej recesji. Charakteryzowała się ona zróżnicowanym tempem, z okresami przys-pieszenia oraz spowolnienia. Przeanalizowano również zmiany geometrii lodowca będące odzwierciedleniem dodatniego lub ujemnego bilansu strefy alimentacyjnej oraz wysokości linii równowagi.

Spitsbergen glaciers react rapidly to the changes in the polar environment. The evidence for that are changes in the extent of fronts and surface geometry. The Renard Glacier, which is situated in the NW part of Wedel Jarlsberg Land, is an example of the glacier that has undergone continuous recession since the Little Ice Age (LIA). The largest size of the Renard Glacier was reached at the end of XIX century (end of LIA) - 38 km2, but in 2006 its area decreased to 31.3 km2 (17.7%). Recession of the Renard Glacier has been characterised by diverse speed, two periods of acceleration: first in 1936-1960 and second since 1990s till now and two periods of slow down in 1960-1990 and 2000-2005. Such types of changes in speed of recession of glacier front were the results from the glacier reaction (with certain delay) to XX century climate changes. The fastest recession has been noted for period 2005-2006: it is 14 ma-1, when the multi-annuals mean for 1936-2006 is 10 ma-1. Following quick climate warming at the beginning of XX century and at the turn of XX and XXI century accelerated reduction of both surface and thickness of glacier while colder weather of 1960s made certain build-up of its surfaces, especially alimentation areas. The reason for that phenomenon was changeable height of equilibrium line which oscillated between 300 and 430 m a.s.l.