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The U.S. Geological Survey Gas Hydrates Project

Climate-Hydrate Interactions

Climate studies in the USGS Gas Hydrates Project have become increasingly important since 2007 and focus on the impact of Late Pleistocene to contemporary climate change on the stability of methane hydrate deposits. The goal is to determine how much, if any, methane hydrate is currently dissociating on Earth in response to climate change processes and to estimate the amount of methane that would directly reach the atmosphere from such degassing. It is postulated that methane reaching the atmosphere from degassing gas hydrates could exacerbate climate change and could have contributed to significant warming during other periods of Earth's history. An additional interest of the USGS Gas Hydrates Project is the possible role of deep marine cold seeps in exporting aged carbon to the oceans.

An introduction and overview provides the USGS Gas Hydrates Project’s perspective on gas hydrates and climate change issues. Additional reading is given below. The Arctic is experiencing climate change at a rapid rate compared to most other places on Earth. The USGS Gas Hydrates Project has therefore focused on studying both permafrost-associated and deepwater marine gas hydrates in the US Arctic.

schematic of synergy
Schematic depicting the possible synergy among climate warming and increased methane emissions (including from gas hydrate dissociation) in the Arctic.
cross section from onshore to deepwater ocean basin
On this cross-section from onshore to deepwater ocean basin, gas hydrates occur in and beneath permafrost onshore and on continental shelves flooded over the past 15,000 years of sea level rise. For the deepwater system, the gas hydrate zone vanishes on upper continental slopes before thickening seaward in the shallow sediments with increasing water depth. On contemporary Earth, gas hydrates are most likely to be breaking down in Sectors 2 and 3. From Ruppel, Nature Knowledge, 2011.

Thermokarst Lakes Emitting Methane

In 2009 and 2010, the USGS Gas Hydrates Project collaborated with the University of Alaska-Fairbanks to conduct geochemical, geophysical, and microbiological studies of thermokarst lakes (Lake Qalluuraq , Teshekpuk Lake, and others) that are releasing methane from the Alaskan North Slope. The methane that is venting from these lakes is unlikely to be derived from dissociating gas hydrates.

methane seep
A methane seep in shallow Lake Qalluuraq on the Alaskan North Slope near the Native Village of Atqasuk breaks the water’s surface during 2009 geophysical surveys
Ukpik data collection 2011
Collecting seismic data aboard the R/V Ukpik on the inner shelf of the US Beaufort Sea in 2011.

Subsea Permafrost and Continental Shelf Methane Emissions: US Beaufort Sea

With the involvement of a postdoctoral fellow sponsored by the US Department of Energy (DOE) and the National Research Council, the USGS Gas Hydrates Project produced the first regional map of (relict) subsea permafrost on the US Beaufort Sea continental shelf, based on an analysis of legacy seismic data. The permafrost formed beneath unglaciated Arctic coastal plains during the Late Pleistocene and was subsequently inundated by sea level rise through to the present. Areas where the subsea permafrost is degrading now are most likely to be associated with methane emissions at least partially derived from intra- or subpermafrost gas hydrates.

In 2010 and 2011, we conducted geophysical surveys on the inner shelf of the US Beaufort Sea to validate regional subsea permafrost findings, map seafloor morphology affected by ice and methane, and determine shallow subseafloor methane distributions.

Mapping Methane Fluxes on the Beaufort Continental Shelf

The USGS Gas Hydrates Project mapped seawater and atmospheric methane and carbon dioxide concentrations on the US Beaufort Sea shelf and upper continental slope in 2011 and 2012 using cavity ringdown spectroscopy (CRDS). The 2012 program also included real-time mapping of the carbon isotopic signature of methane and carbon dioxide in seawater (CRDS), determination of water column methane oxidation rates, and water sampling as a function of depth for direct determination of methane concentrations. The oxidation rate measurements were carried out in collaboration with University of California-Irvine.

In October 2012, the Gas Hydrates Project conducted sampling of seawater and multiple levels of air to determine methane and carbon dioxide concentrations and fluxes from the Chukchi Sea to the Mackenzie Delta aboard the USCG Healy.

Tracking Gas Hydrate Dynamics on the Upper Continental Slope of the US Beaufort Sea

In August 2012, the USGS Gas Hydrates Project acquired ~500 km of multichannel seismic data and Chirp data from the shelf to upper continental slope in the US Beaufort Sea. These were the first non-industry seismic surveys of this area in the modern era and provide an unprecedented data set to constrain the morphology of the upper feather edge of gas hydrate stability, thermal regimes on the upper continental slope, the location of possible relict gas hydrate beneath the shelf, and the loci of initiation of large-scale slope failures.

The USGS Gas Hydrates Project is also collaborating with academic partners on numerical modeling of gas hydrate dynamics in these areas and will conduct extensive 2014 coring across the upper feather edge of gas hydrate stability on the Beaufort continental slope with sponsorship from DOE.

This research serves as site survey for a proposed multiplatform Integrated Ocean Drilling Program study of Late Pleistocene to contemporary climate change on the US Beaufort continental shelf and slope. The pre-proposal (#797), which highlights catching climate change in progress through the tool of the drill, was led by USGS Gas Hydrates Project personnel.

image of seafloor and shallow subseafloor imagery
Seafloor and shallow subseafloor imagery collected on the US Beaufort Shelf in the area of subsea permafrost in 2010
Beaufort relative methane concentrations measured in real time
Relative methane concentrations measured in real-time in near-surface seawater by CRDS technology in 2011 between Harrison Bay and Prudhoe Bay, Beaufort Sea, Alaska.

Methane Emission Mechanisms

With NSF sponsorship, the Gas Hydrates Project is collaborating with MIT Parsons Lab on the mechanisms for methane release from fine-grained sediments and the net flux of methane from temperate lakes. This work is conducted in a kettle lake close to Boston, where MIT has nearly 2 decades’ worth of data.

Fingerprinting Dissociating Gas Hydrate with Noble Gases

A major challenge to researchers is the lack of a technique able to distinguish methane released from recently dissociated gas hydrate from other populations of methane. This is particularly important on circum-Arctic continental shelves, where there are many possible sources of methane and where dissociation of methane hydrates would imply more serious perturbation of the sedimentary section during warming and inundation than would methane release from other sources. With Andrew Hunt of the USGS Noble Gas Facility in Denver, the USGS Gas Hydrates Project has been investigating the potential for noble gas characteristics to distinguish between gas recently dissociated from gas hydrates and other gas populations. The research has underscored the need for careful handling of hydrate samples, whose noble gas signatures change significantly during storage in liquid nitrogen.

methane plume imaged by a fishfinder
A methane plume imaged by a fishfinder operated at 200 kHz in Upper Mystic Lake near Boston.
noble gas analyses
Using noble gas signatures to fingerprint gases emitted from dissociating gas hydrate and from other sources.

Further Reading

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This page last modified on Monday, 14-Jan-2013 04:50:53 EST