Long-term Circumpolar Active Layer Monitoring (CALM) program observations in Northern Alaskan tundra

ABSTRACT

The Circumpolar Active Layer Monitoring (CALM) network is an ongoing international effort to collect and disseminate standardized measurements of active-layer dynamics to monitor the response of near-surface permafrost parameters to climate change. This work presents a distillation of 25 years (1995–2019) of observations from three north–south transects of CALM sites in tundra environments of Alaska. Transects examined in this work bisect tundra regions of discontinuous permafrost on the Seward Peninsula, and the continuous permafrost zone on the western and eastern sections of the Arctic Foothills and Arctic Coastal Plain. These transects represent regional climatic gradients, several physiographic provinces, and regionally characteristic landcover associations. Total active-layer thickening at observed sites ranged from 7 to 26 cm; more significant thaw occurred in the foothills despite less pronounced warming air temperature trends. This summary highlights several regional active layer responses to climate warming, complicated by distinct thermal landscape sensitivities, landscape variability, and documented thaw subsidence. Data summarized in this report are publicly available and represent an important validation resource for earth-system models that include regions in the continuous and discontinuous permafrost zones of northern and western Alaska.

KEYWORDS:

• Circumpolar Active Layer Monitoring
• active layer
• permafrost
• monitoring
• climate change
• Alaska

Acknowledgements

The CALM network has been supported by U.S. National Science Foundation (NSF) awards OPP-9732051 to the University of Cincinnati, OPP-0352958 to the University of Delaware, and ARC-1002119, OPP-1304555, and OPP-1836377 to the George Washington University, and OPP-1836381 to Northern Michigan University and Michigan State University. Any opinions, findings, conclusions, or recommendations expressed in this work are those of the authors and do not necessarily reflect the views of the NSF. The mention of specific product names does not constitute an endorsement by the NSF. We are grateful to the numerous researchers and students who assisted in the field by conducting CALM observations and providing data. Dr. Jerry Brown has been a guiding force in the CALM program from its inception in the early 1990s; the influence of his conceptual constructs and their implementation are pervasive in this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by U.S. National Science Foundation (NSF) [grant number ARC-1002119,OPP-0352958,OPP-1304555,OPP-1836377,OPP-1836381,OPP-9732051].