Accelerated and amplified changes have characterized the northern high latitude climate system in recent decades. While many important processes that are driving, and driven by, Arctic climate change have been extensively studied, one area of research that has received relatively less attention involves quantifying and accounting for large-scale changes in the extent and distribution of frozen ground, both permafrost and seasonally frozen ground. Frozen ground covers up to 50.5% of the Northern Hemisphere land areas, and the near-surface soil freeze/thaw cycle extends over an even larger area. Frozen ground is therefore the single largest component of the cryosphere in terms of maximum area extent. The existence of permafrost and seasonally frozen ground is due to heat exchange between the ground surface and the overlying atmosphere, and the area extent and geographic distribution is therefore primarily forced by climate.
Rather than provide component-based analysis of specific surface/atmosphere interactions, the PIs propose to study how the synoptic-scale circulation of the Northern Hemisphere atmosphere drives, and is driven by, changes in the freeze/thaw cycle in the Russian Arctic. The integrated effects of the atmosphere provide a first-order driver of changes in the distribution of frozen ground. Their work will thus address a missing link in the Arctic climate system, the interactions between the largest cryospheric component, frozen ground, and regional to large-scale variations in the Northern Hemisphere atmosphere.
The PIs hypothesize that (1) atmospheric circulation anomalies over and upstream of the Russian Arctic induce changes in the soil thermal regime, which responds via soil temperature and freeze/thaw depth anomalies; (2) these freeze/thaw cycle anomalies are stored in the soil and alter the surface energy flux during the onset of winter, which results in feedbacks on the overlying atmosphere; (3) snow and vegetation cover, also influenced by the atmosphere, provide further interactions and feedbacks between the ground thermal regime and atmospheric circulation.
Multivariate statistical analyses and modeling approaches will be employed to establish the patterns of variability and covariability in fields of soil temperature and freeze/thaw depth, and a number of atmospheric circulation variables, teleconnections, the polar vortex, and surface and tropospheric circulation fields. Snow cover and vegetation fields will also be analyzed to establish the precise interactions, feedbacks, and pathways linking the soil thermal regime and atmospheric circulation.
