DE-NT0005665

Goal
The goals of this research are to characterize the source, magnitude and temporal variability of methane seepage from two representative thermokarst lake areas within the Alaskan North Slope gas hydrate province and to assess the vulnerability of these areas to ongoing and future arctic climate change.

Performer
Institute of Northern Engineering, University of Alaska Fairbanks, Fairbanks, AK 99775-5860
US Geological Survey, Woods Hole, MA 02543

Maps: a) Alaska North Slope Gas Hydrate stability zone extent (Courtesy of USGS); b) The locations of the three study sites in the Alaska.

Background
Atmospheric methane is a potent greenhouse gas. Predicted increases in methane flux, connected in large part to expected changes in the thickness of permafrost, will in turn affect atmospheric methane concentrations. However, knowledge gaps remain regarding nearly all aspects of past and present methane emissions from terrestrial arctic sites thus limiting the accuracy of climate change models used to predict fluctuations in methane flux under various climate warming scenarios. Assessing changes in the size or intensity of terrestrial arctic methane seeps as both a possible cause and a probable effect of future climate change requires a baseline understanding of (a) the contemporary factors controlling the spatial distribution and temporal frequency of arctic methane emissions; (b) the key methane sources; and (c) the associated methane flux. This research program is largely designed to address these critical needs.

Related to the overarching issue of present and future arctic methane emissions is the more focused problem of the susceptibility of arctic methane hydrate deposits to global climate change. Much of the published research on methane hydrates purports to be partially motivated by the potential that global warming could lead to dissociation of a portion of the global hydrate reservoir, which may in turn exacerbate warming if/once the methane reaches the atmosphere. Terrestrial permafrost gas hydrates are thought to be particularly susceptible to climate forcing since the overlying thermal buffer of ocean water is absent. At the same time, the absence of ocean water, where much of the methane emitted at the seafloor may dissolve or be oxidized, also means that dissociation of permafrost hydrates could lead to more direct and presumably more efficient methane transfer to the atmosphere. To date, no study has proved that dissociating methane hydrates contribute to arctic methane emissions, nor have sufficient field data been acquired to assess the potential for such a contribution in the future. This issue is central to the evaluation of the role of methane hydrates in climate change and will be directly, systematically, and quantitatively addressed in this project.

Predicted changes in thickness of active layer (the soil above permafrost that melts each year in the summer sun) by 2050 (from Anisimov et al., 1997) under some global warming scenarios. The Alaskan North Slope is expected to experience some of the most profound changes in permafrost conditions.

Potential Impacts
This project will be among the first to acquire direct, targeted data to assess whether permafrost gas hydrates are among the most susceptible to climate change. In the process of acquiring such data, methane fingerprinting techniques will be used that are at the cutting edge and extend these methods to the terrestrial hydrate system for the first time. Such developments will also advance the potential for methane source characterization in conventional methane systems and in the marine hydrate system and be of potential use to researchers on other DOE-NETL hydrates projects. This research will also provide robust data about contemporary methane flux from some of the most perturbed areas (thermokarst lakes and their thaw bulbs) of the Alaskan North Slope. This baseline data will be invaluable in decades to come as potential climate warming scenarios play out. At the same time, the methane flux data will help to further refine climate modeling and the contribution of atmospheric methane derived from arctic sources. Lastly, this project will increase the understanding of the relative roles of diffuse and discrete (seep) methane flux in terrestrial settings—a necessity for making progress on aspects of climate change and gas hydrate reservoir dynamics linked to climate change. In short, this project will have benefits in terms of broaching first-order scientific questions, developing new techniques and extending existing techniques to new environments, and building critical collaborations and knowledge sharing between marine and terrestrial methane seep and gas hydrate communities.

Accomplishments
This award began on October 1, 2008. On December 8, 2008 the principal investigator met with USGS scientists in Woods Hole, Massachusetts to discuss geophysical imaging of the thaw bulb and geochemical analyses that the USGS will be conducting. On December 9, 2008 the principal investigator attended a kick-off meeting at NETL in Morgantown. The project is moving ahead with plans for the first field sampling excursion this spring. The University of Alaska led multidisciplinary team will conduct field work May 5th through May 15th. During this time, field-based measurements and direct sampling/surveying will be done at the Qalluuraq Lake seep near Atqasuk on the North Slope and at the Fairbanks-area control site. Both gas and lake sediment samples will be collected for subsequent laboratory-based analysis to assess the potential and nature of methane sinks and the long-term record of methane emissions.

Current Status
During the first year the focus of this project will be field-based measurements and direct sampling/surveying of the Qalluuraq Lake seep near Atqasuk on the North Slope and the Fairbanks-area control site. Gas and lake sediment samples for subsequent laboratory-based analysis to assess the potential and nature of methane sinks and the long-term record of methane emissions. Laboratory analyses and synthesis activities will draw upon the unique strengths and backgrounds of our multidisciplinary team from the University of Alaska and the US Geological Survey as well as other US and international scientists, with expertise in limnology, methane biogeochemistry, organic chemistry, microbiology, geophysics, hydrology, arctic permafrost dynamics, and gas hydrate systems. In addition, geophysical imaging will be conducted to gain a better understanding of the interaction among geologic structures, permeable lithologies, and fluid migration pathways; to image the thickness of the thaw bulbs beneath the lake; and to potentially capture an image of active seepage from a lake bottom and of trapped/migrating gas in the lake bottom sediments.

Project Start: October 1, 2008
Project End: September 30, 2011

Project Cost Information for UAF NT0005665:
Phase 1: DOE Contribution: $290,803, Performer Contribution: $90,753
Phase 2: DOE Contribution: $361,355, Performer Contribution: $92,703
Phase 3: DOE Contribution: $98,763, Performer Contribution: $95,508
Planned Total Funding (if project continues through all project phases):
DOE Contribution: $750,921, Performer Contribution: $278,964

Associated Cost Information for USGS NT0006147:
Phase 1: DOE Contribution: $92,508
Phase 2: DOE Contribution: $87,863
Phase 3: DOE Contribution: $90,577
Planned Total Funding (if project continues through all project phases):
DOE Contribution: $270,948

Contact Information:
NETL - Robert Vagnetti (Robert.Vagnetti@netl.doe.gov or 304-285-1334)
University of Alaska Fairbanks - Mathew Wooller (ffmjw@uaf.edu or 907-474-6738)
USGS - Carolyn Ruppel (cruppel@usgs.gov or 508-457-2339)

Additional Information:

Technology Status Assessment [PDF-90KB] - October, 2008

Kick-off Meeting Presentation [PDF - 2.47MB] - December, 2008