My current research can be divided into three main themes: (1) analytical development related to XRF core scanning; (2) paleoenvironmental reconstructions based on geochemical records from lake sediments; and (3) reconstructing atmospheric dust deposition using peatland archives.
The ITRAX XRF Core Scanner is a relatively new arrangement of a classic analytical technique and is part of the S:LAM Lab at the Department of Geological Sciences. (S:LAM stands for Sediments: Lacustrine and Marine but slam in Swedish means silt, ooze, slime, etc.). We routinely run lake and marine sediments on this instrument but have also analysed speleothems, soils, peats, meteorites and rocks. My analytical development work looks at calibration of XRF core scanning data and novel sample introduction methods. The latter has involved the analysis of dry sediments from (1) sediment trap systems where material is limited and precious and (2) ashed peats where the organic matrix otherwise interferes with analysis.
Looking for flood layers in a speleothem from Kapsia Cave in Greece using XRF core scanning (figure by Martin Finné).
By understanding the fundamental processes occurring in the lake catchment, within the water column, and in the sediment we can better extract the climate signals archived in lake sediments. One way to study these is to compare elemental data from sediment traps with corresponding varves in sediment cores. This provides information on sediment deposition and within lake processes that control this deposition. I have had the privilege of working with samples from Nylandsjön in central Sweden, which has decades of archived sediment cores to work with.
XRF core scanning data provides only relative concentration information and multi-proxy approaches are necessary to get full environmental data from a sequence. I have recently, or am currently working on, sequences from Nightingale Island in the mid-Atlantic; Sokli in northern Finland; and Lake Vuoksjávrátje in northwestern Sweden, to reconstruct past changes in precipitation, productivity, weathering and erosion.
The beautiful varves from Nylandsjön collected in 2011.
I also work on reconstructing mineral dust fluxes using peats in attempts to improve the current spatial coverage of terrestrial dust records. To do this I am studying a suite of bogs from central Sweden including Store Mosse (the “Great Bog”), a national park. In and around the studied transect are impressive aeolian deposits that attest to a time when Sweden was much dustier than today. The idea is to produce the first records of mineral dust deposition in Scandinavia and test the use of peat bogs are dust archives. Along with my PhD student Jenny Sjöström, we are developing new proxies and approaches to these types of records. Results to date indicate that Scandinavia has experienced variations in dust deposition (amount and source), during the mid-Holocene in particular, and that this can affect carbon accumulation rates in northern ecosystems.
Store Mosse is a massive bog system covering 77 km2, which has been studied by Swedish researchers for decades. Significant aeolian deposits are found in the area telling us about Sweden's much dustier past.
Since Sweden isn’t a very dusty place, I have initiated a sister project in South Africa and Lesotho. You can read about our first field season on a blog written for school children and hosted by the Bolin Centre for Climate Research. Geochemical, diatom, 14C and bulk density analysis on the material we collected in Lesotho are presently in full swing by my Masters student Caroline Bringensparr. Several other sites were explored for our dust work including Dartmoor in the South African midlands.
Jenny Sjöström (my PhD student) gets ready for the ascent up to Lesotho. A spring fed peatland found on the high plateau of Lesotho (ca 2900 mabsl).
South Africa Dartmoor: With colleagues Jemma Finch and Trevor Hill (both left) from the University of KwaZulu-Natal checking the material at Dartmoor wetland (Caroline Bringensparr, back right).