Climatic signal of ice melt features in southern Greenland

Acceleration of snow melt in an Antarctic Peninsula ice core during the twentieth century

“…Water equivalence of annual snow layers used a snow-water depth conversion based on density measurements along the length of the core, and for melt layer width used the 0.917 g cm −3 density of ice. Expressing melt as a percentage relative to annual accumulation, and assuming that ice-sheet thinning with depth affects melt layers in the same way as the annual water-equivalent layers, removes the need to apply a thinning correction to the melt thickness data 17 , which is desirable as thinning corrections become more uncertain with depth down an ice core. There is no long-term trend or deviation in the thinning-corrected annual accumulation at the JRI site over the 200 years spanning the annual chronology of the JRI core, indicating that the twentieth-century intensification of melt is not affected by its expression relative to annual layer thickness.…”

“…In this paper, we present the melt layer data back to ad 1000, which corresponds to a depth of 283.2 m in the JRI ice core and an annual layer thickness of 7.1 cm based on the JRI-1 chronology 19 . The position and thickness of the melt layers were used to calculated the percentage of the summer-centred (July-June) annual accumulation that was comprised of melt after conversion of both parameters to water-equivalent lengths 17 . Water equivalence of annual snow layers used a snow-water depth conversion based on density measurements along the length of the core, and for melt layer width used the 0.917 g cm −3 density of ice.…”

“…Although stable-isotope records from ice cores can provide quantified reconstructions of mean temperature, the isotopic diffusion 11,12 that occurs after snow deposition obscures the seasonal components except in the most highly resolved records. Instead, ice-core records of melt can be used to gain information about past summer temperatures and surface snow melt, using either the occurrence of melt layers at sites where melt is rare [13][14][15] or the thickness of melt layers where melt occurs more frequently 16,17 . Such ice-core melt records have been used to reconstruct the history of summer melting at various sites across the Arctic [15][16][17] ; however, only one extended melt reconstruction so far exists for the Antarctic continent 14 .…”

Summer temperature trend over the past two millennia using air content in Himalayan ice

“…Instead, the ER ice core δ 18 O record is significantly and inversely correlated to the Southwest Indian Monsoon intensity Zhang et al, 2005), suggesting the dominance of a "precipitation amount effect" on stable isotopes (Hoffmann and Heimann, 1997;Araguás-Araguás et al, 1998). Here we present a novel attempt to reconstruct the summer temperature trend using a physical proxy, the ice core gas content, that reflects relative frequency and intensity of melt phenomena, thus providing valuable data on past summer climate (Herron et al, 1981).…”

Pollen evidence for increased summer rainfall in the medieval warm period at Maili, northeast China

“…Evidence for climate changes in the Medieval warm period have been widely found in Europe (Lamb, 1977), North America (Bernabo, 1981;Koerner, 1977;Scuderi, 1993;Stine, 1994: Davis, 1994), Russian Arctic (Graybill andShiyatov, 1992: Shiyatov, 1995), Greenland (Herron et al, 1981), the Sargasso Sea (Keigwin, 1996) and Patagonia (Villalba, 1990• Stine, 1994. According to the work by Zhu (1973), however, the temperature variation in eastern China is a little ditt•rent, with the warm period occurring some 200-300 years earlier, and it was rather cold in the 13th century corresponding to the peak warming in Europe (Zhu, 1973;Crowley and North, 1991 ).…”