Past and present permafrost distribution in the Northern and Southern Hemisphere: comparison of the GCM-based mapping with the observations

SAITO KAZUYUKI; MARCHENKO SERGEI; TROMBOTTO LIAUDAT DARIO; BIGELOW NANCY; ROMANOVSKY VLADIMIR; YOSHIKAWA KENJI; WALSH JOHN

Bern

Congreso; INQUA - Quaternary Sciences, the view from the mountains; 2011

INQUA

Freeze/thaw dynamics of soil is a decisive factor in the cold-regions eco-climate systems. Changes in the subsurface thermal regimes and the distribution of frozen ground in time and space are important in understanding the attribution and consequence of Quaternary climate change. A combined modelling of the large-scale climate and land processes with physically-based freeze/thaw dynamics have not extensively employed yet. As a preliminary step, we constructed a FG mapping from the near-surface atmospheric thermal conditions (freeze and thaw indices), that could reasonably reconstruct the large-scale FG distribution in the NH despite simplifications of the determining factors in the reality (e.g., vegetation, soil, snow, and topography). It was applied to the late Quaternary conditions of the both hemispheres for 0ka (pre-industrial), 6ka (mid-Holocene), and 21ka (the last glacial maximum; LGM), modelled by global climate models (GCMs) participating the Paleoclimate Model Intercomparison Project 2 (PMIP2). The NH results were compared against reconstruction maps by Frenzel et al. (1992) and Velichko (1984), while the SH results were compared with the evidence obtained by observations in Patagonia and the Andean region (Trombotto 2002), and a map of winter freeze in Patagonia. The Holocene results (0ka and 6ka) were largely similar to each other with common cool biases. The LGM showed substantial increase of the permafrost, but also insufficient cooling during the cold season in some regions (e.g., north of the Alps). The majority of the models produced no freezing in the SH or, at most, seasonal frost in the Andes for 0ka, partly due to coarse topographic resolution (similar to the Himalayas for NH). Use of high-resolution topography data improved the regional details of the FG distributions such as Andean permafrost for 0ka, but still failed to reconstruct lowland permafrost in the high- and mid-latitude regions.