Holocene Hydroclimatic Reorganizations in Northwest Canada Inferred from Lacustrine Carbonate Oxygen Isotopes

Authors: LASHER, EVERETT - University Of Pittsburgh; ABBOTT, MARK - University Of Pittsburgh; ANDERSON, LESLEIGH - Us Geological Survey (USGS); Witthaus, Lindsey; FINNEY, BRUCE - Idaho State University

Submitted to: Geophysical Research Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2021
Publication Date: 8/20/2021
Citation: Lasher, E., Abbott, M.B., Anderson, L., Witthaus, L.M., Finney, B.P. 2021. Holocene Hydroclimatic Reorganizations in Northwest Canada Inferred from Lacustrine Carbonate Oxygen Isotopes . Geophysical Research Letters. 48:e2021GL092948. https://doi.org/10.1029/2021GL092948.
DOI: https://doi.org/10.1029/2021GL092948

Interpretive Summary: In order to understand recent climate changes around the Arctic, it is useful to document hydroclimate change during the early Holocene, a recent period warmer than present. A sub-centennial isotope record from the southern Yukon Territory at Squanga Lake of the past 11,000 years provides evidence of hydroclimatic extremes and post-glacial changes. Squanga Lake is a deep through-flowing system that discharges runoff from a ~284 km2 watershed to the Teslin River, a tributary of the Yukon River. Sediment cores were dated using radiometric methods and oxygen and carbon isotopes were measured in calcite as well as ostrocod shells to estimate past climatic changes. The bulk calcite oxygen isotope values of the sediment record are similar to modern lake water and annual precipitation values. At 11 ka BP (thousands of years before 1950), higher oxygen isotope values are interpreted to reflect the combined effects of severe aridity and weak influence by the Aleutian Low. A steady decline in oxygen isotope values by 8 ka BP reflects a gradual change to wetter conditions, likely related to increased winter precipitation. Results illustrate the magnitude of hydroclimatic states at high latitudes and that they have varied widely over the Holocene.

Technical Abstract: To place recent climate changes around the Arctic in context, it is useful to document hydroclimate change during the early Holocene, a recent period warmer than present. A sub-centennial isotope record from the southern Yukon Territory at Squanga Lake of the past 11,000 years provides evidence of hydroclimatic extremes and post-glacial reorganization. Squanga Lake is a deep through-flowing system that discharges runoff from a ~284 km2 watershed to the Teslin River, a tributary of the Yukon River. Marl sediment cores were measured for oxygen (d18O) and carbon (d13C) isotopes of ostracod and bulk calcite, including modern surface sediments, and dated by radiometric methods. The bulk calcite d18O values of the sediment record range from –16 to –21‰ which are similar to modern lake water and annual precipitation values. At 11 ka BP (thousands of years before 1950), higher d18O values are interpreted to reflect the combined effects of severe aridity and weak influence by the Aleutian Low. A steady decline to lower d18O values by 8 ka BP reflects a gradual reorganization to wetter conditions, likely related to increased winter precipitation by enhanced Aleutian Low activity. Results illustrate the magnitude of hydroclimatic states at high latitudes and that they have varied widely over the Holocene.