(Siberia & Mongolia) and other paleoclimatic indicators
(Vaks et al., 2013).
Cave carbonates (mineral deposits) can be used to analyze past permafrost conditions. Carbonates (Figure 2) originating within a cave's Vadose Zone (unsaturated area above the water table) accumulate from the addition of precipitation percolating into the cave system. When the ground is frozen surrounding (and within) a cave complex, the growth of carbonates terminates – they cannot grow in regions of permafrost. Warm temperatures and available water are two requirements for cave carbonate (speleothem) growth. The speleothems can be dated to reveal past fluctuations in these two parameters. Dr. Anton Vaks used a U-Th dating method to reconstruct 500,000 years of past carbonate fluctuations in Siberia (Figure 1). He found that a particularly extensive period of permafrost melt occurred approximately 400,000 years before present within the Arctic. During this interglacial event, the permafrost boundary was shifted northward, as extensive warming and carbonate growth transpired. Additionally, sea surface levels and temperatures amplified at this time. Moreover, carbonate cave growth has been linked to increased concentrations of atmospheric carbon dioxide, released from thawing permafrost. Overall, it is concluded that an increase in temperature of 1°C will thaw discontinuous permafrost and an increase of 1.5°C has the potential to thaw continuous permafrost within the Arctic (Vaks et al., 2013).
References
Permafrost Links