PERICLIMv1.0: a model deriving palaeo-air temperatures from thaw depth in past permafrost regions

Abstract

Abstract. Periglacial features, such as various kinds of patterned ground, cryoturbations, frost wedges, solifluction structures, and blockfields, are among the most common relics of cold climate periods, which repetitively occurred throughout the Quaternary. As such, they are widespread archives of past environmental conditions. Climate controls on the development of most periglacial features, however, remain poorly known, and thus empirical palaeo-climate reconstructions based on them have limited validity. This study presents and evaluates a simple new inverse modelling scheme called PERICLIMv1.0 (PERIglacial CLIMate) that derives palaeo-air temperature characteristics related to the palaeo-active-layer thickness, which can be recognized using many relict periglacial features found in past permafrost regions. The evaluation against modern temperature records showed that the model reproduces air temperature characteristics with average errors ≤1.3 ∘C. The past mean annual air temperature modelled experimentally for two sites in the Czech Republic hosting relict cryoturbation structures was between -7.0±1.9 and -3.2±1.5 ∘C, which is well in line with earlier reconstructions utilizing various palaeo-archives. These initial results are promising and suggest that the model could become a useful tool for reconstructing Quaternary palaeo-environments across vast areas of mid-latitudes and low latitudes where relict periglacial assemblages frequently occur, but their full potential remains to be exploited.

Optically‐Stimulated‐Luminescence Ages and Paleo‐Environmental Implications of Relict Frost Wedges in North–Central Bohemia, Czech Republic

“…Since the present-day MAAT at the frost-wedge sites is ~9-10°C, the LGM temperature reduction likely attained ~−17°C to ~−12°C (cf. [75][76][77]117]), which is in line with previous estimates based on various relict periglacial features from the central and western European lowlands [3,11,26,[119][120][121][122].…”

“…The LGM active‐layer thickness in lowland soils probably attained ~1–2 m [23, 77]. Around this time, there were also the lowest MAGTs and MAATs inferred from borehole logs and former active‐layer thickness, respectively, of ~−6°C to ~−4°C [75, 76, 117] and ~−7°C to ~−3°C [77], as well as a pronounced decline in noble gas recharge temperatures to values close to zero [118], which signal cold‐climate conditions and the existence of permafrost. Since the present‐day MAAT at the frost‐wedge sites is ~9–10°C, the LGM temperature reduction likely attained ~−17°C to ~−12°C (cf.…”

“…Only higher-elevated areas of the Czech Republic above ~1200 m asl favored local mountain glaciations (not shown in the map scale of Figure 1) in the last glacial period [71][72][73]. Situated between the Fennoscandian and Alpine ice sheets, the Bohemian and Most basins have mostly been dominated by tundra vegetation during cold stages of the Pleistocene [74] when MAATs and MAGTs likely declined by at least ~12-17°C compared with the present based on model estimates [75][76][77]. Cold climates at these times promoted the growth of permafrost at least 70-130 m thick [76,78] and intense periglacial processes, which gave rise to widespread sedimentary structures and landforms such as frost wedges and polygons, cryoturbations, dells, or dry and asymmetric valleys [53,54,79].…”

“…Frost-weathering features and cryogenic carbonates in caves indicated that permafrost in and around the Bohemian and Most basins was at least 30-65 m thick at elevations <450 m asl [55,115] and model simulations suggested that its maximum thickness was 70-130 m [76,78]. The LGM active-layer thickness in lowland soils probably attained ~1-2 m [23,77]. Around this time, there were also the lowest MAGTs and MAATs inferred from borehole logs and former active-layer thickness, respectively, of ~−6°C to ~−4°C [75,76,117] and ~−7°C to ~−3°C [77], as well as a pronounced decline in noble gas recharge temperatures to values close to zero [118], which signal coldclimate conditions and the existence of permafrost.…”