New Methods to Reconstruct Holocene Temperature Variations Close to the Ice Sheet Margin in Southwest Greenland
Supervised by Dr Sarah Woodroffe & Professor Erin McClymont
Our understanding of the response of the southern half of the Greenland Ice Sheet (GIS) to warm and cool phases during the Holocene is limited in part because there are very few long climate records from the terrestrial margins of the ice sheet. Because of this, geophysical models used to predict past ice sheet history have no alternative but to use borehole and δ18O temperature records from ice cores from the centre of the ice sheet (GRIP and DYE3) to infer temperature changes across the whole of the ice sheet surface (e.g. Simpson et al., 2009; Tarasov and Peltier, 2002). One important problem with this approach is that the ice core records are dominated by winter temperature signals, whilst melting at the margins is most sensitive to summer temperature variability.
To improve glaciological model predictions of future ice sheet change under a variety of climate change scenarios we require new records of past temperature and climate changes at marginal locations. The ice sheet in the south west region is particularly sensitive to climate changes because of its relatively low latitude, the low gradient of the ice sheet surface (which means for a small temperature change a large area of ice is affected), the presence of several low-elevation sectors and terrestrial as well as marine termini, several of which have retreated significantly since the Little Ice Age (LIA).
Previous environmental reconstructions have relied on pollen, diatoms, biogenic silica, Loss on Ignition and chironomids preserved in lakes along the ice free corridor in southwest Greenland to reconstruct temperature fluctuations during the Holocene. Other than chironomids these proxy methods provide evidence for broad environmental changes only, as catchment processes, vegetation development and changes in lake water chemistry through the Holocene complicate their relationship to air temperature fluctuations. Chironomid training sets have been developed in Greenland and elsewhere which are capable of providing quantitative temperature reconstructions, but they have not been widely applied yet in Greenland (e.g. Brooks and Birks 2001, Brodersen and Anderson 2002). In addition, a recent study of two closely spaced lakes in Southwest Greenland shows that a new proxy based on alkenone unsaturation in lake sediments can quantitatively predict Holocene temperature fluctuations with an error of 1.3 °C (D’Andrea et al., 2011). This is a new proxy that has yet to be tested in other lakes in Southwest Greenland.
This project aims to use both of these recently-developed quantitative proxy methods to reconstruct Holocene temperature variability from lakes close to the ice sheet margin in Southwest Greenland. We already have core material from a lake close to Nuuk which could be studied as part of an MSc by Research project, and if the project was taken on as a PhD it would also involve fieldwork to additional site / sites in Southwest Greenland during year 2 to collect new core material to allow regional comparisons.
Brodersen, K.P., Anderson, N.J., 2002. Freshwater Biol., 47, 1137-1157.
Brooks, S.J., Birks, H.J.B. 2001. Quat. Sci. Rev., 20, 1723-1741.
D’Andrea, W.J., et al., 2011. Proc. Nat. Acad. Sci., doi/10.1073/pnas.1101708108.
Simpson, M.J.R., et al., 2009. Quat. Sci. Rev., 28, 1631-1657.
Tarasov, L., Peltier, W. R., 2002. Geophys. J. Int., 150, 198-229.