Sarah Watkins

Dr Sarah Watkins

My research interests are in environmental magnetism and in particular, its application to the fields of palaeoceanography and palaeoclimatology.

My Ph.D. (below), “Geological ground-truthing of modelling iceberg trajectories in the North Atlantic: Present day and Last Glacial Maximum”, involved the use of magnetic proxies to reconstruct ice-rafted debris (IRD) patterns and hence iceberg trajectories. These reconstructed IRD patterns were then used to validate the results of an iceberg model for the Last Glacial Maximum (LGM), allowing identification of the circulation state in the North Atlantic during the LGM.

My publications etc.

Abstract from my PhD.

An increasing number of ocean modelling and proxy studies has provided evidence that, during the past, the thermohaline circulation may have existed in a different configuration to the present-day. Here, a twin approach is adopted, combining ocean model results and sediment proxy data, to investigate North Atlantic circulation at the present day and Last Glacial Maximum (LGM). Forcing fields from ocean general circulation models (OGCM) are used to drive an iceberg trajectory model, which investigates the effect of the surface circulation patterns on iceberg drift. Magnetic measurements of deep-sea sediments have been used to identify ice-rafted detritus (IRD), allowing reconstruction of iceberg trajectories. The magnetic properties of 321 present-day samples and 154 LGM samples have been measured, together with samples from potential source areas. Multivariate analysis of selected, diagnostic magnetic parameters is used to characterise the sediment and identify the main controls on sedimentation. For both time periods the clustering distinguishes lower-latitude, aeolian input west of Africa from other detrital sediment inputs to the north and west North Atlantic. Present-day inter-calibration of the iceberg model and magnetic data indicate that the iceberg model performs reasonably well. Three possible stable ocean circulation states during the LGM are investigated. Two states have formation of intermediate/deep water in the North Atlantic (with different formation sites, rates and sinking depths), the third has all deep water formation in the Southern Ocean. Of the three modelled ocean circulation states, the magnetic data support that with dominant deep water formation in the Southern Ocean. Both the LGM iceberg model results and the magnetic data question the dominant role of Hudson Bay in delivering large amounts of IRD to the LGM North Atlantic (outside of Heinrich events), instead indicating the greater importance of European and St. Lawrence sourced IRD.

Telephone: + 44 (0)1524 592378.
Fax: + 44 (0)1525 847099.
email: sarah.watkins using univ address of @lancaster.ac.uk