skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: A new Stefan equation to characterize the evolution of thermokarst lake and talik geometry
Abstract. Thermokarst lake dynamics, which play an essential role in carbon releasedue to permafrost thaw, are affected by various geomorphological processes.In this study, we derive a three-dimensional (3D) Stefan equation tocharacterize talik geometry under a hypothetical thermokarst lake in thecontinuous permafrost region. Using the Euler equation in the calculus ofvariations, the lower bounds of the talik were determined as an extremum ofthe functional describing the phase boundary area with a fixed total talikvolume. We demonstrate that the semi-ellipsoid geometry of the talik isoptimal for minimizing the total permafrost thaw under the lake for a givenannual heat supply. The model predicting ellipsoidal talik geometry wascompared to talik thickness observations using transient electromagnetic(TEM) soundings in Peatball Lake on the Arctic Coastal Plain (ACP) ofnorthern Alaska. The depth : width ratio of the elliptical sub-lake talik cancharacterize the energy flux anisotropy in the permafrost, although the lakebathymetry cross section may not be elliptic due to the presence ofnear-surface ice-rich permafrost. This theory suggests that talikdevelopment deepens lakes and results in more uniform horizontal lakeexpansion around the perimeter of the lakes, while wind-induced waves andcurrents are likely responsible for the elongation and orientation ofshallow thermokarst lakes without taliks in certain regions such as the ACPof northern Alaska.  more » « less
Award ID(s):
1806213 1806202 1806287 1820883
PAR ID:
10321230
Author(s) / Creator(s):
; ; ; ; ; ; ; ;
Date Published:
Journal Name:
The Cryosphere
Volume:
16
Issue:
4
ISSN:
1994-0424
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; ; et al (, Environmental Research Letters)
    Abstract Thermokarst lakes accelerate deep permafrost thaw and the mobilization of previously frozen soil organic carbon. This leads to microbial decomposition and large releases of carbon dioxide (CO2) and methane (CH4) that enhance climate warming. However, the time scale of permafrost-carbon emissions following thaw is not well known but is important for understanding how abrupt permafrost thaw impacts climate feedback. We combined field measurements and radiocarbon dating of CH4ebullition with (a) an assessment of lake area changes delineated from high-resolution (1–2.5 m) optical imagery and (b) geophysical measurements of thaw bulbs (taliks) to determine the spatiotemporal dynamics of hotspot-seep CH4ebullition in interior Alaska thermokarst lakes. Hotspot seeps are characterized as point-sources of high ebullition that release14C-depleted CH4from deep (up to tens of meters) within lake thaw bulbs year-round. Thermokarst lakes, initiated by a variety of factors, doubled in number and increased 37.5% in area from 1949 to 2009 as climate warmed. Approximately 80% of contemporary CH4hotspot seeps were associated with this recent thermokarst activity, occurring where 60 years of abrupt thaw took place as a result of new and expanded lake areas. Hotspot occurrence diminished with distance from thermokarst lake margins. We attribute older14C ages of CH4released from hotspot seeps in older, expanding thermokarst lakes (14CCH420 079 ± 1227 years BP, mean ± standard error (s.e.m.) years) to deeper taliks (thaw bulbs) compared to younger14CCH4in new lakes (14CCH48526 ± 741 years BP) with shallower taliks. We find that smaller, non-hotspot ebullition seeps have younger14C ages (expanding lakes 7473 ± 1762 years; new lakes 4742 ± 803 years) and that their emissions span a larger historic range. These observations provide a first-order constraint on the magnitude and decadal-scale duration of CH4-hotspot seep emissions following formation of thermokarst lakes as climate warms. 
    more » « less
  2. ; ; ; ; ; (, 18th International Conference on Ground Penetrating Radar)
    This research demonstrates a new measurement and scaling approach to constrain the estimates of methane (CH4) fluxes emitted from permafrost thaw (thermokarst) lakes. Permafrost is estimated to store about 20% of the total terrestrial carbon (C) stock. Permafrost thawing releases C in part as CH4, however, there are large uncertainties in the global CH4 budget that limit the accuracy of climate change projections. Estimating how much C is released from permafrost is critical to overcome this knowledge gap. Lake CH4 fluxes are estimated by combining direct observations, geophysical mapping and satellite remote sensing along with a scaling strategy based on lake expansion rate. This research contributes to advance the understanding of CH4 fluxes from thermokarst lakes and improve atmospheric C models. 
    more » « less
  3. ; ; ; ; ; (, Communications Earth & Environment)
    Abstract Climate-driven permafrost thaw can release ancient carbon to the atmosphere, begetting further warming in a positive feedback loop. Polar ice core data and young radiocarbon ages of dissolved methane in thermokarst lakes have challenged the importance of this feedback, but field studies did not adequately account for older methane released from permafrost through bubbling. We synthesized panarctic isotope and emissions datasets to derive integrated ages of panarctic lake methane fluxes. Methane age in modern thermokarst lakes (3132 ± 731 years before present) reflects remobilization of ancient carbon. Thermokarst-lake methane emissions fit within the constraints imposed by polar ice core data. Younger, albeit ultimately larger sources of methane from glacial lakes, estimated here, lagged those from thermokarst lakes. Our results imply that panarctic lake methane release was a small positive feedback to climate warming, comprising up to 17% of total northern hemisphere sources during the deglacial period. 
    more » « less
  4. ; ; ; ; ; (, Journal of Geophysical Research: Earth Surface)
    Abstract The impact of permafrost thaw on hydrologic, thermal, and biotic processes remains uncertain, in part due to limitations in subsurface measurement capabilities. To better understand subsurface processes in thermokarst environments, we collocated geophysical and biogeochemical instruments along a thaw gradient between forested permafrost and collapse‐scar bogs at the Alaska Peatland Experiment site near Fairbanks, Alaska. Ambient seismic noise monitoring provided continuous high‐temporal resolution measurements of water and ice saturation changes. Maps of seismic velocity change identified areas of large summertime velocity reductions nearest the youngest bog, indicating potential thaw and expansion at the bog margin. These results corresponded well with complementary borehole nuclear magnetic resonance measurements of unfrozen water content with depth, which showed permafrost soils nearest the bog edges contained the largest amount of unfrozen water along the study transect, up to 25% by volume. In situ measurements of methane within permafrost soils revealed high concentrations at these bog‐edge locations, up to 30% soil gas. Supra‐permafrost talik zones were observed at the bog margins, indicating talik formation and perennial liquid water may drive lateral bog expansion and enhanced permafrost carbon losses preceding thaw. Comparison of seismic monitoring with wintertime surface carbon dioxide fluxes revealed differential responses depending on time and proximity to the bogs, capturing the controlling influence of subsurface water and ice on microbial activity and surficial emissions. This study demonstrates a multidisciplinary approach for gaining new understanding of how subsurface physical properties influence greenhouse gas production, emissions, and thermokarst development. 
    more » « less
  5. ; ; ; ; ; ; ; (, EGUshpere)
    The rapid climate warming is affecting the Arctic which is rich in aquatic systems. As a result of permafrost thaw, thermokarst lakes and ponds are either shrinking due to lake drainage or expanding due to lake shore erosion. This process in turn mobilizes organic carbon, which is released by permafrost deposits and active layer material that slips into the lake. In this study, we combine hydrochemical measurements and remote sensing data to analyze the influence of lake change processes, especially lake growth, on lake hydrochemical parameters such as DOC, EC, pH as well as stable oxygen and hydrogen isotopes in the Arctic Coastal Plain. For our entire dataset of 97 water samples from 82 water bodies, we found significantly higher CH4 concentrations in lakes with a floating-ice regime and significantly higher DOC concentrations in lakes with a bedfast-ice regime. We show significantly lower CH4 concentrations in lagoons compared to lakes as a result of an effective CH4 oxidation that increased with a seawater connection. For our detailed lake sampling of two thermokarst lakes, we found a significant positive correlation for lake shore erosion and DOC for one of the lakes. Our detailed lake sampling approach indicates that the generally shallow thermokarst lakes are overall well mixed and that single hydrochemical samples are representative for the entire lake. Finally, our study confirms that DOC concentrations correlates with lake size, ecoregion type and underlying deposits. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email