The University of Southampton
University of Southampton Institutional Repository

Holocene thermokarst lake dynamics in northern interior Alaska: the interplay of climate, fire, and subsurface hydrology

Holocene thermokarst lake dynamics in northern interior Alaska: the interplay of climate, fire, and subsurface hydrology
Holocene thermokarst lake dynamics in northern interior Alaska: the interplay of climate, fire, and subsurface hydrology
The current state of permafrost in Alaska and meaningful expectations for its future evolution are informed by long-term perspectives on previous permafrost degradation. Thermokarst processes in permafrost landscapes often lead to widespread lake formation and the spatial and temporal evolution of thermokarst lake landscapes reflects the combined effects of climate, ground conditions, vegetation, and fire. This study provides detailed analyses of thermokarst lake sediments of Holocene age from the southern loess uplands of the Yukon Flats, including bathymetry and sediment core analyses across a water depth transect. The sediment core results, dated by radiocarbon and 210Pb, indicate the permanent onset of finely laminated lacustrine sedimentation by ∼8,000 cal yr BP, which followed basin development through inferred thermokarst processes. Thermokarst expansion to modern shoreline configurations continued until ∼5000 cal yr BP and may have been influenced by increased fire. Between ∼5000 and 2000 cal yr BP, the preservation of fine laminations at intermediate and deep-water depths indicate higher lake levels than present. At that time, the lake likely overflowed into an over-deepened gully system that is no longer occupied by perennial streams. By ∼2000 cal yr BP, a shift to massive sedimentation at intermediate water depths indicates that lake levels lowered, which is interpreted to reflect a response to drier conditions based on correspondence with Yukon Flats regional fire and local paleoclimate reconstructions. Consideration of additional contributing mechanisms include the possible influence of catastrophic lake drainages on down-gradient base-flow levels that may have enhanced subsurface water loss, although this mechanism is untested. The overall consistency between the millennial lake-level trends documented here with regional paleoclimate trends indicates that after thermokarst lakes formed, their size and depth has been affected by North Pacific atmospheric circulation in addition to the evolution of permafrost, ground ice, and subsurface hydrology. As the first detailed study of a Holocene thermokarst basin that links expansion, stabilization and subsequent climate-driven lake level variations in a loess upland, these results provide a framework for future investigations of paleoclimatic signals from similar lake systems that characterize large regions of Alaska and Siberia.
Alaska, HOLOCENE, permafrost, thermokarst lakes, lake levels, paleoclimate
Edwards, Mary
4b6a3389-f3a4-4933-b8fd-acdfef72200e
lesleigh, anderson
5f41c2fb-ad93-442d-942a-3989ab1e49c4
shapley, mark
bc6ab743-9736-4aee-b3ac-d8b5ba2efcbd
finney, bruce
a3ed686d-391c-438e-91c1-5848e097283f
Langdon, Catherine
628b8ce9-a413-4ebb-924f-fbeb7193a021
Edwards, Mary
4b6a3389-f3a4-4933-b8fd-acdfef72200e
lesleigh, anderson
5f41c2fb-ad93-442d-942a-3989ab1e49c4
shapley, mark
bc6ab743-9736-4aee-b3ac-d8b5ba2efcbd
finney, bruce
a3ed686d-391c-438e-91c1-5848e097283f
Langdon, Catherine
628b8ce9-a413-4ebb-924f-fbeb7193a021

Edwards, Mary, lesleigh, anderson, shapley, mark, finney, bruce and Langdon, Catherine (2019) Holocene thermokarst lake dynamics in northern interior Alaska: the interplay of climate, fire, and subsurface hydrology. Frontiers in Earth Science, 7 (53). (doi:10.3389/feart.2019.00053).

Record type: Article

Abstract

The current state of permafrost in Alaska and meaningful expectations for its future evolution are informed by long-term perspectives on previous permafrost degradation. Thermokarst processes in permafrost landscapes often lead to widespread lake formation and the spatial and temporal evolution of thermokarst lake landscapes reflects the combined effects of climate, ground conditions, vegetation, and fire. This study provides detailed analyses of thermokarst lake sediments of Holocene age from the southern loess uplands of the Yukon Flats, including bathymetry and sediment core analyses across a water depth transect. The sediment core results, dated by radiocarbon and 210Pb, indicate the permanent onset of finely laminated lacustrine sedimentation by ∼8,000 cal yr BP, which followed basin development through inferred thermokarst processes. Thermokarst expansion to modern shoreline configurations continued until ∼5000 cal yr BP and may have been influenced by increased fire. Between ∼5000 and 2000 cal yr BP, the preservation of fine laminations at intermediate and deep-water depths indicate higher lake levels than present. At that time, the lake likely overflowed into an over-deepened gully system that is no longer occupied by perennial streams. By ∼2000 cal yr BP, a shift to massive sedimentation at intermediate water depths indicates that lake levels lowered, which is interpreted to reflect a response to drier conditions based on correspondence with Yukon Flats regional fire and local paleoclimate reconstructions. Consideration of additional contributing mechanisms include the possible influence of catastrophic lake drainages on down-gradient base-flow levels that may have enhanced subsurface water loss, although this mechanism is untested. The overall consistency between the millennial lake-level trends documented here with regional paleoclimate trends indicates that after thermokarst lakes formed, their size and depth has been affected by North Pacific atmospheric circulation in addition to the evolution of permafrost, ground ice, and subsurface hydrology. As the first detailed study of a Holocene thermokarst basin that links expansion, stabilization and subsequent climate-driven lake level variations in a loess upland, these results provide a framework for future investigations of paleoclimatic signals from similar lake systems that characterize large regions of Alaska and Siberia.

Text
feart-07-00053 - Version of Record
Available under License Creative Commons Attribution.
Download (5MB)

More information

Accepted/In Press date: 6 March 2019
Published date: 3 April 2019
Keywords: Alaska, HOLOCENE, permafrost, thermokarst lakes, lake levels, paleoclimate

Identifiers

Local EPrints ID: 429660
URI: https://eprints.soton.ac.uk/id/eprint/429660
PURE UUID: 56c04b9a-b06e-4866-9443-8166fb089acf
ORCID for Mary Edwards: ORCID iD orcid.org/0000-0002-3490-6682

Catalogue record

Date deposited: 03 Apr 2019 16:30
Last modified: 04 Apr 2019 00:35

Export record

Altmetrics

Contributors

Author: Mary Edwards ORCID iD
Author: anderson lesleigh
Author: mark shapley
Author: bruce finney
Author: Catherine Langdon

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×