Our proposal was to generate records of Arctic Ocean change from the western Canadian Basin (Northwind Ridge) through analyses of radiogenic isotopes preserved in sediments.  The use of neodymium (Nd) isotopes in chemically leachable metal-oxide coatings on these sediments allowed us to generate records suitable to interpretation of changes in deep Arctic circulation on both long (Pleistocene to modern) timescales, and on glacial-interglacial timescales.  Our data demonstrate that the early Pleistocene deep Canadian Basin was influenced significantly by water sourced from the Pacific Ocean: a situation that is not seen in the modern dominantly Atlantic-influenced Arctic basin.  That deep water in the Canadian Basin was influenced by the Pacific implicates a down-welling mechanism of deep water formation that is not seen today, and that Atlantic waters were restricted from penetrating the Arctic as efficiently as they do today.  That is, the deep ocean circulation of the Arctic was significantly different in the early Pleistocene compared to the modern.  We can further predict that the heat and salt budget within and out of the Arctic was different in the early Pleistocene compared to the modern, which has important climatic feedbacks.  We found that the change from the apparently stable early Pleistocene circulation to that of the modern has been associated with an increase in variance.  Specifically, the advent of large glaciations of the Mid-Pleistocene appears to be associated with dramatic directional change in deep water Canadian Basin circulation.  These observations suggest that a possible warm future climate may see the return of the deep Arctic circulation to conditions similar to the (warmer) early Pleistocene.  

We also conducted a core-top study that allowed us to estimate pre-modern, late Quaternary, deep ocean circulation in the Arctic - as a means to establish a "baseline" for changes that observations demonstrate are currently underway in the Arctic.  This study indicated that even the pre-modern (interglacial, latest Quaternary) Canadian Basin had some contribution of deep water from the Pacific; something that is not seen in the limited modern observations available to date.  These data imply that the deep Arctic may be approaching a new deep water circulation configuration not seen at least in the past million years (contrary to a return to a state similar to the early Pleistocene).

Both of these studies indicate dramatic changes have occurred in deep Arctic circulation over the latest Pleistocene into the Holocene.  Change is also seen in the provenance of the sediments delivered to the western Canadian Basin, as found from isotopic composition of the sediments themselves.  That is, the source and delivery of the sediments - dominantly a function of surface land and ocean processes - changed dramatically over the Holocene from a remarkably stable early Pleistocene condition.  This change, measured in this work using radiogenic isotopic tracers, is indicative of glacial-interglacial changes superimposed over a directional change in erosion and transport of sediment to the Northwind Ridge.  These data imply the (surface) Arctic has been changing erosive regime for many thousands of years.

We discuss where future conditions may align with these observed natural changes in presentations and publications (one thesis, one manuscript published; two manuscripts in preparation; several general and specialized conferences).  

This work has supported the successful M.Sc. of a young female geoscientist, the introduction of two undergraduate students to cutting-edge science,  the continuity of expertise in scientific techniques through our lab technician and the early career of the PI (first grant).

Last Modified: 08/29/2013...

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