Holocene environmental change of Svalbard - multi-proxy climate reconstruction from lake sediments
In order to study past climates from time periods not covered by instrumental observations, we have to rely on indirect climate data. Common sources of this data are ice cores, tree rings, lake sediments and other geological deposits and historical records, which contain proxy information on past environmental conditions.
During the Holocene the climate and other environmental factors have varied on a millennial and centennial scale due to natural factors such as changes in July insolation at 60 °N (Berger & Loutre, 1991). Kaufman et al. (2009) reviewed the Holocene climate development in the Arctic based on tree ring, ice core and lake sediment records. These compiled records of summer and annual temperatures indicate a slight cooling trend during the last 2000 years, peaking in the Little Ice Age and with subsequent warming during the last 150 years.
Most recent climate reconstructions from Svalbard have concentrated on the last ca. 2000 years and are mostly in good accordance to Kaufman’s et al. (2009) findings. E.g. according to ice core records from Svalbard the winter temperatures have been declining during the last 1200 years and started to increase in the region during the industrial era (Devine et al, 2011). A lake sediment record of the last 1760 years, however, indicated only slight decrease in July mean temperatures reconstructed from chironomids, but an increase during the last 70 years (Velle et al., 2011). Furthermore, another lake record for the last 1800 years based on a new method using the alkenone unsaturation index for a lacustrine environment indicates no trend of decreasing late Holocene summer temperatures before the gradual warming A.D. 1660-1900 (D’Andrea et al., 2012). These ice core and lake sediment records might suggest increased seasonality on Svalbard during the last 2000 years and support previous results of accelerated warming in the industrial era.
The aim of this international project is to study the variation of environment and climate in Svalbard during the Holocene. By analysing proxies as chironomids, alkenones, macrofossils, DNA together with stable isotopes of carbon and nitrogen, pollutants of BC and nitrogen in lake sediments and comparing the results with the ice cores records from Svalbard, we hope to answer our objectives. The detailed objectives of this study are:
- To reconstruct the Holocene summer temperatures which are an important complement to winter temperature reconstructions from Svalbard ice cores and more specific to see if climate have experienced increased seasonality the last 1200 years.
- Establish a tephrochronology for Svalbard as a dating method for arctic sediments lacking organic material. A well-developed tephrochronology could enhance comparisons between ice cores from Svalbard but also between other climate archives in the North Atlantic region.
- Examining the fire history for the last 1000 years and the black carbon pollution history during the industrial era and comparison with ice core data from Svalbard
- Study of other environmental conditions affecting the lake such as the source of nutrients, in order to understand the atmospheric influence and internal processes in the lake
- Sedimentology and ITRAX XRF core scanning will be used to identify physical sedimentary changes and determine relative elemental composition in order to reconstruct environmental conditions
- Stable isotopes of carbon and nitrogen of bulk organic matter (bulk organic carbon isotope composition; δ13C organic), total carbon (%TC), total nitrogen (%TN) and C/N to comprehend information of changing vegetation types in lake and catchment system as well as the productivity of the lake.
The following study areas for lake sediment coring have been identified:
Northern Prins-Karls-Forlandet - Blokkvatn