NASA studying thermokarst lakes - G. Grosse, K. Walter, V. E. Romanovsky

Permafrost Laboratory (University of Alaska)

Project summary

Thermokarst depressions and thermokarst lakes (TKLs) dominate large areas of the arctic land surface and may expand as permafrost continues to warm and thaw, releasing large quantities of methane (CH4) and carbon dioxide (CO2) to the atmosphere. We propose to define the relationship of TKLs to global climate change by developing remote sensing methods to quantify thermokarst and greenhouse gas (GHG) emissions from TKLs in regions (>1 million km2) of organic-rich, icy permafrost and ice-poor permafrost in Siberia and Alaska. We will use fine and broad scale remote sensing and field validation to determine the role of thermokarst as both a source (GHG release) and sink (peat accumulation) for carbon (C), thereby improving understanding of the behavior of a major C pool (icy permafrost) previously poorly considered in global C cycle sciences. Specifically, we will use remote-sensing based land cover classification and change detection to derive information about thermokarst distribution, initiation, and related changes in land surface properties to improve C-cycle and ecosystem models for Northern Hemisphere permafrost regions. We will test new satellite-based techniques: SAR data will be evaluated for upscaling field-measurements of CH4 bubbling from lakes to regional estimates of lake CH4 emissions through the establishment of a Pan-Arctic Lake-Ice Methane Monitoring Network (PALIMMN). By integration of our remotely sensed spatial data, information derived from multi-temporal satellite data (50 years), radiocarbon dated TKL sediment records (up to ~15,000 years old), and available and predicted climatic data, we will inform the sophisticated 2-D and 3-D numerical permafrost models of our collaborators for prediction of spatial and temporal thermokarst dynamics and related GHG emissions in scenarios for up to 200 years into the future as permafrost warms and thaws under global warming.

Thermokarst landscape at one of our main study sites: The Kolyma lowland near Cherskii, Russia

Hypotheses

• Thermokarst results in positive (GHG emissions) and negative (C sequestration) feedbacks to the C cycle, but the release of C from permafrost as GHG's dominates, making thermokarst in high northern latitudes a positive feedback to global climate change.
• Permafrost degradation by thermokarst formation and expansion of TKLs during the next 100-200 years will release tens of gigatons of CH4 through lakes to the atmosphere, increasing the current atmospheric CH4 burden many-fold.
  Objectives and tasks

Research goals

The proposed research has the following four overarching goals:

1. Quantify the current and long-term distribution and dynamics of thermokarst in Siberia and Alaska
2. Quantify GHG emissions from arctic lakes using Synthetic Aperture Radar (SAR)
3. Assess past, present and future impacts of TKL development on the C cycle, including GHG release and C sinks
4. Expand understanding of the role of arctic TKLs in global climate change to broad audiences

PALIMMN

Through international collaboration the proposed research will generate a pulse of activity during the IPY and establish a Pan-Arctic Lake-Ice Methane Monitoring Network (PALIMMN). We will repeat early-winter field surveys, which are simple and fast (~2 hrs/lake) of lake-ice bubbles during 3 years at intensive study sites in Cherskii, interior Alaska and Toolik, and only in one year at additional sites: Northern Seward Peninsula, and Barrow, Alaska. International colleagues with ongoing research at a variety of other arctic and sub-arctic sites have committed to conduct parallel lake-ice bubble surveys on 3-20 lakes during the IPY. The distribution of study sites in PALIMMN will capture variation in arctic and boreal lake types. Data generated through PALIMMN will be made available to the IPY meta-analysis effort of the AON in order to evaluate the significance of lake emissions for regional CH4 budgets. Data will be archived for public access through AON at the Arctic LTER database.

We welcome researchers and non-researchers that would like to join this effort. Please contact Dr. Katey Walter.

Fieldwork

Extensive fieldwork was conducted on the Seward Peninsula, Alaska, in July, August and October 2008. We will have an extended 5 week-expedition in April 2009. Our fieldwork includes ground truthing of remote sensing data, thermokarst basin and lake DGPS surveys, geophysical surveys, fieldspectral measurements, lake ice methane bubble surveys, and sedimentological and biogeochemical studies.

Publications resulting from this project

• Grosse G, Romanovsky V, Walter K, Morgenstern A, Lantuit H, Zimov S (2008): Distribution of Thermokarst Lakes and Ponds at Three Yedoma Sites in Siberia. In: 'Ninth International Conference on Permafrost', Kane DL & Hinkel KM (eds), Institute of Northern Engineering, University of Alaska Fairbanks, pp. 551-556.
• Romanovsky VE, Grosse G (2008): Overview of changes in permafrost in the Northern Hemisphere - Link to Carbon Cycle. NASA LCLUC Program Meeting. Adelphi, Maryland, USA, 1-2 May 2008.
• Grosse G (2008): Changing Permafrost Landscapes in North Eurasia:Remote Sensing Observations and Challenges. ESA User Consultation Workshop, AWI Potsdam, Germany, 20-21 February 2008.

Link to project website: http://www.gi.alaska.edu/snowice/Permafrost-lab/projects/projects_active/proj_thermokarst_NASA.html