Derivation and analysis of a high-resolution estimate of global permafrost zonation

Abstract

Abstract. Permafrost underlies much of Earth's surface and interacts with climate, eco-systems and human systems. It is a complex phenomenon controlled by climate and (sub-) surface properties and reacts to change with variable delay. Heterogeneity and sparse data challenge the modeling of its spatial distribution. Currently, there is no data set to adequately inform global studies of permafrost. The available data set for the Northern Hemisphere is frequently used for model evaluation, but its quality and consistency are difficult to assess. Here, a global model of permafrost extent and dataset of permafrost zonation are presented and discussed, extending earlier studies by including the Southern Hemisphere, by consistent data and methods, by attention to uncertainty and scaling. Established relationships between air temperature and the occurrence of permafrost are re-formulated into a model that is parametrized using published estimates. It is run with a high-resolution (< 1 km) global elevation data and air temperatures based on the NCAR-NCEP reanalysis and CRU TS 2.0. The resulting data provide more spatial detail and a consistent extrapolation to remote regions, while aggregated values resemble previous studies. The estimated uncertainties affect regional patterns and aggregate number, and provide interesting insight. The permafrost area, i.e. the actual surface area underlain by permafrost, north of 60 • S is estimated to be 13-18 × 10 6 km 2 or 9-14 % of the exposed land surface. The global permafrost area including Antarctic and sub-sea permafrost is estimated to be 16-21 × 10 6 km 2 . The global permafrost region, i.e. the exposed land surface below which some permafrost can be expected, is estimated to be 22 ± 3 × 10 6 km 2 . A large proportion of this exhibits considerable topography and spatially-discontinuous permafrost, underscoring the importance of attention to scaling issues and heterogeneity in large-area models.

A new map of permafrost distribution on the Tibetan Plateau

“…These models link permafrost temperature with surface temperature using seasonal surface transfer functions and subsurface thermal properties, which can provide reasonable assessments of permafrost distribution when the permafrost upper boundary conditions and regional soil thermal properties are satisfied. Recently, a global permafrost zonation index (PZI) was established based on the relationships between the air temperature and the occurrence of permafrost (Gruber, 2012). The PZI can represent broad spatial patterns but does not provide the actual extent of the permafrost.…”

“…Permafrost is a major component of the cryosphere and is sensitive to climate changes (Wu et al, 2002b;Haeberli and Hohmann, 2008;Li et al, 2008;Gruber, 2012). Due to its unique and extremely high altitude (mean elevation over 4000 m) and low mean annual air temperatures (generally lower than −2 • C with an intra-annual amplitude over 20 • C in the permafrost region), the Tibetan Plateau (TP) possesses the largest areas of permafrost in the mid-and lowlatitude regions of the world Zhao et al, 2004Zhao et al, , 2010Yang et al, 2010).…”

Simulating high-latitude permafrost regions by the JSBACH terrestrial ecosystem model

“…Based on a simple relationship between air temperature and the permafrost probability, Gruber (2012) estimated that around 22 % (±3 %) of the Northern Hemisphere land is underlain by permafrost. During the past glacial/interglacial cycles vast amounts of organic matter have been accumulated in these soils (Zimov et al, 2006).…”

Large-area land surface simulations in heterogeneous terrain driven by global data sets: application to mountain permafrost

“…Wood et al, 2011;Barnett et al, 2005;Gruber, 2012). In addition, numerical methods allow for transient assessment of past and future states, an essential step for change detection of (near-)surface conditions (Etzelmüller, 2013).…”