Britta Jensen

Current research:

Sub-continental correlation of past megadroughts using volcanic ash in peat
I am presently working with Gill Plunkett and Robert Booth (Lehigh University, Bethlehem, PA, USA) on the feasibility of using cryptotephra (volcanic ash deposits not visible to the naked eye) in correlating Holocene ombrotrophic peat bogs from the mid-west and east coast of North America. Our interest in doing so is two-fold:

(1) While tephrostratigraphy has been used for many decades in western North America to correlate and date various sedimentary deposits, very little work has examined whether cryptotephra can be used at more distal sites (i.e. the east coast). European tephrostratigraphic frameworks are built almost entirely on cryptotephra, and there is no a priori reason why we should not be able to successfully build similar networks in eastern North America.

(2) Multi-decadal droughts (i.e. megadroughts) have been a recurrent feature of the climate system throughout the mid to late Holocene, but most paleo-drought reconstructions are based on tree-rings, which are largely limited to western North America. Ombrotrophic peatlands are alternative sources for paleo-drought records in more humid regions of central and eastern North America; they are particularly sensitive to moisture changes since they are atmospherically-fed. Peatland records indicate that ecologically significant droughts, although relatively uncommon in historical times, have occurred in the past in these regions. However, because peat cores are dated using radiometric techniques (14C, 210Pb), the precision and accuracy of peat paleo-drought records can be insufficient to evaluate broad spatial-temporal patterns of drought, and associated climate forcing mechanisms. Tephra, because they are typically deposited over days to weeks and thus represent an isochronous horizon, can correlate and date these sites with a level of precision and accuracy that far exceeds other methods.

Other active projects:

I am continuing research that builds on my dissertation, which is focused on sediments ranging in age between ca. 3 Ma to the latest Pleistocene. This includes refining the tephrostratigraphic framework for eastern Beringia (unglaciated Alaska and Yukon) and linking the terrestrial paleoenvironmental record of this region to the marine realm. I am also actively collaborating with Vadim Kravchinsky and Ted Evans (Geophysics, University of Alberta) on applying various geomagnetic methods to the long loess deposits that blanket the region. We are attempting to improve correlations of these deposits to one another and to other, more established, global paleo-records through paleointensity, paleomagnetic and magnetic susceptibility measurements. We are also hoping to extract wind-direction data, that when combined with geochemical data, should provide some insight into broad-scale synoptic wind patterns over the Quaternary in this region, something that is presently poorly understood. This research has also provided new insight into the depositional models for loess in Yukon and Alaska.