Wetter Winters Coincided with Warm Mid-Holocene Summers in Northwestern Russia: Insights from Lipid Biomarkers and Proxy System Modelling
Abstract
As the Arctic warms, models predict an increase in winter precipitation due to sea ice retreat and an increase in summer precipitation due to enhanced poleward moisture transport. Proxy records of past warming can be used to validate these models and better understand the mechanisms causing water cycle changes. However, most Arctic studies have focused on the North Atlantic region. New high-resolution paleohydrology records from across the Arctic are needed to understand the whole region's sensitivity to warming and the spatial pattern of these seasonally different responses. Here, we present a Holocene record of temperature and the seasonal distribution of precipitation from Lake Imandra, on the central Kola Peninsula, Russia. The hydrogen isotopes of n-alkanoic acids from different plant sources (aquatic: C22 and terrestrial: C28) together provide information about the seasonal distribution of precipitation, and summer evapotranspiration (described by ɛC28-C22). We use branched glycerol dialkyl glycerol tetraethers to reconstruct summer temperature. The most prominent features in preliminary results are 1) a rapid 2H-depletion of ~15 per mil in the C22 n-alkanoic acid around 8.7 ka, likely due to a shift in the seasonal distribution of precipitation towards winter as temperatures rose in the Early Holocene, and 2) an increase in ɛC28-C22 after about 6.7 ka, suggesting an increase in summer evapotranspiration coincident with summer cooling following the Holocene Thermal Maximum. We perform sensitivity tests using a lake proxy system model to constrain the effects of changing temperature and precipitation amounts in different seasons on lake water isotope values. The Early Holocene shift to wetter winters is coincident with warmer summers and could be caused by a decline in Barents Sea ice cover and/or a northward shift in the Jet Stream and corresponding storm tracks. Both mechanisms could have been caused by higher regional temperature, which increased rapidly starting at 9 ka.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFMPP15F0715H