NOAA/WDS Paleoclimatology - North Slope, Alaska 6,000 Year Lake Sediment Geochemical Data

STUDY NOTES: Geochemical data from 2 lakes on the North Slope of Alaska, USA for the past 6,000 years. Data for Lake Ne14 include elemental counts per second and ratios from X-ray fluourescence, mineralogical proportion from X-ray diffraction, %CaCO3 from loss-on-ignition (950 degrees C), bulk-sediment strontium isotopes, and bulk-sediment carbon isotopes (before and after acid-fumigation). Data from Perch Lake include elemental counts per second and ratios from X-ray fluourescence, and %CaCO3 from loss-on-ignition (950 degrees C). Provided Keywords: thermo-erosion, retrogressive thaw slump, permafrost, Arctic, Alaska
ABSTRACT SUPPLIED BY ORIGINATOR: Anthropogenic warming may promote rapid permafrost thaw in the Arctic and alter the global carbon cycle. Although several studies suggest increased thermo-erosion as a result of recent warming, a long-term context is necessary to assess the linkages of thermokarst processes with climate variability. We analyzed sediment cores from two lakes on the Alaskan North Slope (USA), one with (Lake NE14) and one without (Perch Lake) watershed thermo-erosion. Distinct geochemical and lithological characteristics provide evidence for sedimentary input from carbonate-rich permafrost soils associated with past retrogressive thaw slumping at Lake NE14 but not at Perch Lake. These characteristics include increases in Ca:Sr, Ca:K, carbonate:[feldspar + clay minerals], percent CaCO3, and d13C, and decreases in 87Sr:86Sr. At least ten episodes of thermo-erosion occurred over the past 6000 yr at Lake NE14. Most of these episodes coincided with periods of elevated summer temperatures, but moisture variation and geomorphic factors likely played a role in driving their occurrence. Our results suggest that positive feedbacks facilitate reactivation of thermo-erosion in ice-rich terrain, adding to the growing body of evidence that these Arctic landscapes are unstable in a changing climate.