Variation in the moisture regime of northeastern interior Alaska and possible linkages to the Aleutian Low: Inferences from a late-Holocene δ 18 O record

Melissa L. Chipman, Benjamin Frank Clegg, Feng Sheng Hu

Research output: Contribution to journalArticle

Abstract

Analyses of oxygen and carbon isotopes in bulk carbonate and Chara-stem encrustations, X-ray diffraction, and sediment composition from Keche Lake offer new information on climatic change over the past ~3,400 years in northeastern interior Alaska. The δ 18 O and δD values of water samples from the lake and its inlet streams suggest that evaporation plays an important role in determining the isotopic composition of Keche Lake water at present. However, evaporative enrichment does not appear to be a major driver of the pronounced fluctuations in the bulk-carbonate δ 18 O record on the basis of comparison with Chara-δ 18 O values. The δ 18 O values of bulk carbonate in the Keche Lake sediments vary by up to 10 ‰ over the past 3,400 years, with maximum values of -12 ‰ around 3,400 cal BP and between 2,100 and 1,500 cal BP. High δ 18 O peaks are associated with sediments dominated by quartz, feldspar, and clay minerals suggesting the influence of detrital carbonate. Multi-millennial patterns of δ 18 O variation at Keche Lake appear to be linked with changes in watershed and sediment-depositional processes, which may be driven by varying moisture abundance associated with the position of the Aleutian Low (AL). The increasing trend of carbonate δ 18 O from 3,400 to ~2,100 cal BP probably reflects the increasing importance of a westerly AL, and the high frequency of δ 18 O spikes ~2,100-1,500 cal BP may have resulted from the prevalence of a westerly AL position. Predominance of a westerly AL likely increased snowfall and winter temperature in the region. Such conditions would have promoted soil erosion and thermokarst activity during spring snowmelt, resulting in episodic large influxes of detrital carbonate to Keche Lake and elevating bulk-carbonate δ 18 O. Over the past 1,500 years, bulk-carbonate δ 18 O remained relatively high at Keche Lake but variation was much less pronounced than before. A broad δ 18 O peak centered ~400 cal BP may be related to enhanced winter moisture during the Little Ice Age, although our chronology is inadequate for a rigorous assessment of this interpretation. This study contributes a new δ 18 O record and offers additional information on past moisture-regime shifts associated with changing atmospheric-circulation patterns.

Original languageEnglish (US)
Pages (from-to)69-81
Number of pages13
JournalJournal of Paleolimnology
Volume48
Issue number1
DOIs
StatePublished - Jun 1 2012

Fingerprint

carbonates
moisture
Holocene
carbonate
lakes
westerly
lake
sediments
Chara
sediment
thermokarst
atmospheric circulation
encrustation
winter
snowmelt
Little Ice Age
clay minerals
quartz
X-ray diffraction
soil erosion

Keywords

  • Alaska
  • Aleutian Low
  • Holocene
  • Lake sediment
  • Oxygen isotopes
  • Paleoclimate

ASJC Scopus subject areas

  • Aquatic Science
  • Earth-Surface Processes

Cite this

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title = "Variation in the moisture regime of northeastern interior Alaska and possible linkages to the Aleutian Low: Inferences from a late-Holocene δ 18 O record",
abstract = "Analyses of oxygen and carbon isotopes in bulk carbonate and Chara-stem encrustations, X-ray diffraction, and sediment composition from Keche Lake offer new information on climatic change over the past ~3,400 years in northeastern interior Alaska. The δ 18 O and δD values of water samples from the lake and its inlet streams suggest that evaporation plays an important role in determining the isotopic composition of Keche Lake water at present. However, evaporative enrichment does not appear to be a major driver of the pronounced fluctuations in the bulk-carbonate δ 18 O record on the basis of comparison with Chara-δ 18 O values. The δ 18 O values of bulk carbonate in the Keche Lake sediments vary by up to 10 ‰ over the past 3,400 years, with maximum values of -12 ‰ around 3,400 cal BP and between 2,100 and 1,500 cal BP. High δ 18 O peaks are associated with sediments dominated by quartz, feldspar, and clay minerals suggesting the influence of detrital carbonate. Multi-millennial patterns of δ 18 O variation at Keche Lake appear to be linked with changes in watershed and sediment-depositional processes, which may be driven by varying moisture abundance associated with the position of the Aleutian Low (AL). The increasing trend of carbonate δ 18 O from 3,400 to ~2,100 cal BP probably reflects the increasing importance of a westerly AL, and the high frequency of δ 18 O spikes ~2,100-1,500 cal BP may have resulted from the prevalence of a westerly AL position. Predominance of a westerly AL likely increased snowfall and winter temperature in the region. Such conditions would have promoted soil erosion and thermokarst activity during spring snowmelt, resulting in episodic large influxes of detrital carbonate to Keche Lake and elevating bulk-carbonate δ 18 O. Over the past 1,500 years, bulk-carbonate δ 18 O remained relatively high at Keche Lake but variation was much less pronounced than before. A broad δ 18 O peak centered ~400 cal BP may be related to enhanced winter moisture during the Little Ice Age, although our chronology is inadequate for a rigorous assessment of this interpretation. This study contributes a new δ 18 O record and offers additional information on past moisture-regime shifts associated with changing atmospheric-circulation patterns.",
keywords = "Alaska, Aleutian Low, Holocene, Lake sediment, Oxygen isotopes, Paleoclimate",
author = "Chipman, {Melissa L.} and Clegg, {Benjamin Frank} and Hu, {Feng Sheng}",
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TY - JOUR

T1 - Variation in the moisture regime of northeastern interior Alaska and possible linkages to the Aleutian Low

T2 - Inferences from a late-Holocene δ 18 O record

AU - Chipman, Melissa L.

AU - Clegg, Benjamin Frank

AU - Hu, Feng Sheng

PY - 2012/6/1

Y1 - 2012/6/1

N2 - Analyses of oxygen and carbon isotopes in bulk carbonate and Chara-stem encrustations, X-ray diffraction, and sediment composition from Keche Lake offer new information on climatic change over the past ~3,400 years in northeastern interior Alaska. The δ 18 O and δD values of water samples from the lake and its inlet streams suggest that evaporation plays an important role in determining the isotopic composition of Keche Lake water at present. However, evaporative enrichment does not appear to be a major driver of the pronounced fluctuations in the bulk-carbonate δ 18 O record on the basis of comparison with Chara-δ 18 O values. The δ 18 O values of bulk carbonate in the Keche Lake sediments vary by up to 10 ‰ over the past 3,400 years, with maximum values of -12 ‰ around 3,400 cal BP and between 2,100 and 1,500 cal BP. High δ 18 O peaks are associated with sediments dominated by quartz, feldspar, and clay minerals suggesting the influence of detrital carbonate. Multi-millennial patterns of δ 18 O variation at Keche Lake appear to be linked with changes in watershed and sediment-depositional processes, which may be driven by varying moisture abundance associated with the position of the Aleutian Low (AL). The increasing trend of carbonate δ 18 O from 3,400 to ~2,100 cal BP probably reflects the increasing importance of a westerly AL, and the high frequency of δ 18 O spikes ~2,100-1,500 cal BP may have resulted from the prevalence of a westerly AL position. Predominance of a westerly AL likely increased snowfall and winter temperature in the region. Such conditions would have promoted soil erosion and thermokarst activity during spring snowmelt, resulting in episodic large influxes of detrital carbonate to Keche Lake and elevating bulk-carbonate δ 18 O. Over the past 1,500 years, bulk-carbonate δ 18 O remained relatively high at Keche Lake but variation was much less pronounced than before. A broad δ 18 O peak centered ~400 cal BP may be related to enhanced winter moisture during the Little Ice Age, although our chronology is inadequate for a rigorous assessment of this interpretation. This study contributes a new δ 18 O record and offers additional information on past moisture-regime shifts associated with changing atmospheric-circulation patterns.

AB - Analyses of oxygen and carbon isotopes in bulk carbonate and Chara-stem encrustations, X-ray diffraction, and sediment composition from Keche Lake offer new information on climatic change over the past ~3,400 years in northeastern interior Alaska. The δ 18 O and δD values of water samples from the lake and its inlet streams suggest that evaporation plays an important role in determining the isotopic composition of Keche Lake water at present. However, evaporative enrichment does not appear to be a major driver of the pronounced fluctuations in the bulk-carbonate δ 18 O record on the basis of comparison with Chara-δ 18 O values. The δ 18 O values of bulk carbonate in the Keche Lake sediments vary by up to 10 ‰ over the past 3,400 years, with maximum values of -12 ‰ around 3,400 cal BP and between 2,100 and 1,500 cal BP. High δ 18 O peaks are associated with sediments dominated by quartz, feldspar, and clay minerals suggesting the influence of detrital carbonate. Multi-millennial patterns of δ 18 O variation at Keche Lake appear to be linked with changes in watershed and sediment-depositional processes, which may be driven by varying moisture abundance associated with the position of the Aleutian Low (AL). The increasing trend of carbonate δ 18 O from 3,400 to ~2,100 cal BP probably reflects the increasing importance of a westerly AL, and the high frequency of δ 18 O spikes ~2,100-1,500 cal BP may have resulted from the prevalence of a westerly AL position. Predominance of a westerly AL likely increased snowfall and winter temperature in the region. Such conditions would have promoted soil erosion and thermokarst activity during spring snowmelt, resulting in episodic large influxes of detrital carbonate to Keche Lake and elevating bulk-carbonate δ 18 O. Over the past 1,500 years, bulk-carbonate δ 18 O remained relatively high at Keche Lake but variation was much less pronounced than before. A broad δ 18 O peak centered ~400 cal BP may be related to enhanced winter moisture during the Little Ice Age, although our chronology is inadequate for a rigorous assessment of this interpretation. This study contributes a new δ 18 O record and offers additional information on past moisture-regime shifts associated with changing atmospheric-circulation patterns.

KW - Alaska

KW - Aleutian Low

KW - Holocene

KW - Lake sediment

KW - Oxygen isotopes

KW - Paleoclimate

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