Stratigraphic Features of Firn as Proxy Climate Signals at the Summit Ice Cap of Usnkovsky Volcano, Kamchatka, Russia

Abstract

Field observations were conducted at the summit ice cap of the Usnkovsky volcano, central Kamchatka, in the summer of 1996, in order to evaluate the potential of the ice cap for reconstruction of the past climate over Kamchatka. A 27-m-long firn-core contains an approximate 27-yr record of net balance with an average accumulation rate of 0.57 m a⁻¹ water equivalent. The temperature of the firn is −16.5°C at 10-m depth. Average annual accumulation rates are calculated by reference to dated ash layers and amount to between 0.38 and 0.88 m a⁻¹ during six fixed periods. Depth and age of pore close-off are calculated as 58 m and 66 yr at this site by empirical formulas. Comparisons of the accumulation rates with winter precipitation at lowland stations indicate that there is a positive relationship with winter precipitation on the eastern and western coasts of the peninsula. We cannot find a clear relation between the rates and annual average sea-ice extent in the Sea of Okhotsk, which implies the vapor source to the ice cap could have been the North Pacific. Melt feature percentage in the firn core displays a clear positive relationship with summer air temperature at 700 hPa over Kamchatka. The result obtained suggests that the ice cap has potential for the reconstruction of paleoclimate over the Kamchatka Peninsula.