Holocene climate inferred from glacier extent, lake sediment and tree rings at Goat Lake, Kenai Mountains, Alaska, USA

Thomas A. Daigle, Darrell S Kaufman

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20 Citations (Scopus)

Abstract

Lake sediment, glacier extent and tree rings were used to reconstruct Holocene climate changes from Goat Lake at 550 m asl in the Kenai Mountains, south-central Alaska. Radiocarbon-dated sediment cores taken at 55 m water depth show glacial-lacustrine conditions until about 9500 cal. yr BP, followed by organic-rich sedimentation with an overall increasing trend in organic matter and biogenic silica content leading up to the Little Ice Age (LIA). Through most of the Holocene, the northern outlet of the Harding Ice. eld remained below the drainage divide that currently separates it from Goat Lake. A sharp transition from gyttja to inorganic mud about AD 1660 signifies the reappearance of glacier meltwater into Goat Lake during the LIA, marking the maximum Holocene (postglacial) extent. Meltwater continued to discharge into the lake until about AD 1900. A 207 yr tree-ring series from 25 mountain hemlocks growing in the Goat Lake watershed correlates with other regional tree-ring series that indicate an average summer temperature reduction of about 1°C during the 19th century compared with the early-mid 20th century. Cirque glaciers around Goat Lake reached their maximum LIA extent in the late 19th century. Assuming that glacier equilibrium-line altitudes (ELA) are controlled solely by summer temperature, then the cooling of 1°C combined with the local environmental lapse rate would indicate an ELA lowering of 170 m. In contrast, reconstructed ELAs of 12 cirque glaciers near Goat Lake average only 34 ± 18 m lower during the LIA. The restricted ELA lowering can be explained by a reduction in accumulation-season precipitation caused by a weakening of the Aleutian low-pressure system during the late LIA.

Original languageEnglish (US)
Pages (from-to)33-45
Number of pages13
JournalJournal of Quaternary Science
Volume24
Issue number1
DOIs
StatePublished - 2009

Fingerprint

goat
tree ring
lacustrine deposit
glacier
Little Ice Age
Holocene
mountain
lake
climate
equilibrium line
cirque
meltwater
gyttja
low pressure system
summer
Mountains
Glacier
Lake Sediments
Goat
Tree Rings

Keywords

  • Alaska
  • Equilibrium-line altitude
  • Holocene climate change
  • Lake sediment
  • Little Ice Age
  • Tree rings

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Palaeontology

Cite this

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title = "Holocene climate inferred from glacier extent, lake sediment and tree rings at Goat Lake, Kenai Mountains, Alaska, USA",
abstract = "Lake sediment, glacier extent and tree rings were used to reconstruct Holocene climate changes from Goat Lake at 550 m asl in the Kenai Mountains, south-central Alaska. Radiocarbon-dated sediment cores taken at 55 m water depth show glacial-lacustrine conditions until about 9500 cal. yr BP, followed by organic-rich sedimentation with an overall increasing trend in organic matter and biogenic silica content leading up to the Little Ice Age (LIA). Through most of the Holocene, the northern outlet of the Harding Ice. eld remained below the drainage divide that currently separates it from Goat Lake. A sharp transition from gyttja to inorganic mud about AD 1660 signifies the reappearance of glacier meltwater into Goat Lake during the LIA, marking the maximum Holocene (postglacial) extent. Meltwater continued to discharge into the lake until about AD 1900. A 207 yr tree-ring series from 25 mountain hemlocks growing in the Goat Lake watershed correlates with other regional tree-ring series that indicate an average summer temperature reduction of about 1°C during the 19th century compared with the early-mid 20th century. Cirque glaciers around Goat Lake reached their maximum LIA extent in the late 19th century. Assuming that glacier equilibrium-line altitudes (ELA) are controlled solely by summer temperature, then the cooling of 1°C combined with the local environmental lapse rate would indicate an ELA lowering of 170 m. In contrast, reconstructed ELAs of 12 cirque glaciers near Goat Lake average only 34 ± 18 m lower during the LIA. The restricted ELA lowering can be explained by a reduction in accumulation-season precipitation caused by a weakening of the Aleutian low-pressure system during the late LIA.",
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AB - Lake sediment, glacier extent and tree rings were used to reconstruct Holocene climate changes from Goat Lake at 550 m asl in the Kenai Mountains, south-central Alaska. Radiocarbon-dated sediment cores taken at 55 m water depth show glacial-lacustrine conditions until about 9500 cal. yr BP, followed by organic-rich sedimentation with an overall increasing trend in organic matter and biogenic silica content leading up to the Little Ice Age (LIA). Through most of the Holocene, the northern outlet of the Harding Ice. eld remained below the drainage divide that currently separates it from Goat Lake. A sharp transition from gyttja to inorganic mud about AD 1660 signifies the reappearance of glacier meltwater into Goat Lake during the LIA, marking the maximum Holocene (postglacial) extent. Meltwater continued to discharge into the lake until about AD 1900. A 207 yr tree-ring series from 25 mountain hemlocks growing in the Goat Lake watershed correlates with other regional tree-ring series that indicate an average summer temperature reduction of about 1°C during the 19th century compared with the early-mid 20th century. Cirque glaciers around Goat Lake reached their maximum LIA extent in the late 19th century. Assuming that glacier equilibrium-line altitudes (ELA) are controlled solely by summer temperature, then the cooling of 1°C combined with the local environmental lapse rate would indicate an ELA lowering of 170 m. In contrast, reconstructed ELAs of 12 cirque glaciers near Goat Lake average only 34 ± 18 m lower during the LIA. The restricted ELA lowering can be explained by a reduction in accumulation-season precipitation caused by a weakening of the Aleutian low-pressure system during the late LIA.

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