A Multi-Decadal 11.5 ka Sedimentary Pigment Record of Aquatic Productivity and Landscape Stability from Torfadalsvatn, North Iceland.

Abstract:

North Iceland is located in a climatically sensitive region at the interface between the warm Irminger Current and the cold East Greenland Current. Torfadalsvatn (66° 3'41.73"N, 20°23'14.26"W) is a relatively small (0.4 km²) and shallow (z=5.8 m) lake that lies on the Skagi peninsula of northern Iceland approximately 0.5 km from the modern coastline and is ideally situated to compare with regional climate records of nearby marine cores from the North Iceland Shelf. We have employed a multi-proxy approach to reconstruct Holocene terrestrial climate from an 8.4 m sediment core at 15-30 year resolution using sedimentary pigments, organic carbon flux, C:N and their stable isotopes, and biogenic silica measured by Fourier Transform Infrared Spectroscopy. Several proxies show peak values shortly after 8 ka suggesting peak Holocene warmth may have occurred at this time. Elevated canthaxanthin, produced by cyanobacteria, and lutein (green algae and higher plants), along with less negative δ¹³C and high C:N suggest a productive aquatic environment with abundant aquatic macrophytes. The mid Holocene is characterized by elevated diatom pigment concentration, reduced C:N and lutein concentration suggesting a shift toward a diatom dominated system with continued high aquatic productivity. At ~1.5 ka influx of terrestrial organic matter increases associated with a decrease in aquatic productivity. Terrestrial organic matter continues to increase during the late Holocene, peaking at ~1750 AD potentially associated with minimum local Little Ice Age temperatures. Aquatic productivity, however, continues to decrease until ~1900 AD suggesting that the landscape destabilization signal may have become saturated before minimum temperatures occurred. A comparison of the data from this core with other high-resolution regional climate records will not only increase our understanding of differences in climate histories between north and south Iceland, but will also allow for a better understanding of the manifestation of variable Irminger Current strength on terrestrial climate.