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.
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.
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.
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.
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.
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.
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.