To reconstruct conditions throughout the water column at the site of the Sirius Water polynya several types of analysis were conducted on discrete one-centimetre slices of sediment. Changes in primary productivity were ascertained using measurements of organic carbon and nitrogen, as well as biogenic silica content of the sediments. The latter indicates levels of (diatom) primary production, an important ecosystem function in polynya settings and the analyses represented a new skill for the researcher. Benthic (bottom dwelling) foraminifera, whose calcareous shells are preserved as fossils in marine sediments, were counted and as different species have different environmental preferences inferences were made about the bottom water conditions in which they lived. The age of the sediment was established using radiocarbon dating of these same shells and indicated that these marine sediments were deposited between 0 – 12000 years ago. The amount of sediment deposited in the earlier part of the record was much larger and from 12000 to 7500 years ago, that translates to sub-centennial resolution of reconstructions. Conditions changed rapidly at the transition between the previous Younger Dryas cold period, that lasted until 11,700 years before present, and the current Holocene warm epoch. This multi-proxy study will be published in a peer-review manuscript to evaluate the impact of wider Arctic and North Atlantic Ocean circulation and atmospheric regimes on the evolution of marine conditions on the North-East Greenland shelf.
For the North Water polynya marine sediment core, a specific benthic foraminifera species was extracted from samples. The stable oxygen isotopic signature contained in these shells reflects the salinity and temperature of the water masses in which the shells were formed. The ratio of magnesium to calcium in the shells reflects primarily water temperature and using a species-specific calibration, these ratios can be transformed into water temperature. This quantitative analysis will also be published in a peer-review article and builds on qualitative work already completed. The results will be used to compare past time intervals when it is known that polynya formation was strong (or weak) and the impact this may have had on ocean circulation and ocean heat transport into northern Baffin Bay.
