1. Culturing Lab and proxy development

One of ARCLIMs primary objectives is to develop new geochemical proxies for palaeoceanographic reconstruction at high latitudes as the existing proxies have significant limitations for use at high latitudes such as not being calibrated for low temperatures. We aim to establish new and develop existing proxies. This includes exploring the possibility of using Na/Ca as a salinity-proxy, Ba/Ca as a proxy for freshwater circulation, namely river input, and using B/Ca and U/Ca as proxies for carbonate chemistry as well as extending the temperature range of the calibration of the existing paleothermometer Mg/Ca for both sub-polar and polar temperatures.

The developed proxy calibrations will be based on culturing planktic foraminifera in our newly establish culturing lab at UiT. Our lab is optimised for culturing in conditions that mimics the sup-polar and polar conditions, such as the polar summer of low temperature and 24-hour light with variable intensity. Our samples are all collected during summer cruises in the Nordic Seas

The proxies will be developed separately for the sup-polar (to sub-tropical) species Globigerina bulloides and the polar species Neogloboquadrina pachyderma. As different species have different geochemical uptake at different conditions, it is important to calibrate the proxies for the species it is intended to be applied to. This is one of the current limitations of proxy calibrations, due to challenges of culturing experiments, proxies have been calibrated for a limited number of species, particularly biased towards tropical and sub-tropical species. For G. bulloides we aim to extend the existing Mg/Ca calibration to the lower temperature range (below 16°C) with the 2022 experiments at 6, 9, and 13°C. Whereas for N. pachyderma we have performed culturing experiments at 2, 4.5, 6, 7, and 9°C over the two culturing experiments in 2021 and 2022. Development of proxies for salinity and carbonate chemistry (e.g., pH and carbonate ion) will be applied to both species.

For both species we will user laser-ablation ICP-MS which allows us to analyse single chambers, hence the method will be applicable to samples with few foraminifera specimens which is a common challenge at high latitudes. In additions, laser-ablation provides the opportunity to constrain intra-shell geochemical variability which affects the proxy calibrations. Using both species in our proxy-development allows us to reconstruct complete palaeoceanographic records in sub-polar and polar environments, particularly during past warm periods.

2. Earth system model development

Alongside culturing and proxy-development, ARCLIM also aim to use climate modelling together with proxy data to further explore the mechanisms of deep-water formation in the Nordic Seas and the North Atlantic with the help of the neodymium (Nd) seawater isotopic composition (εNd), in order to track the provenance of the water masses. In that scope, the oceanic neodymium concentration as well as the εNd will be implemented in the Earth System Model of intermediate complexity, iLOVECLIM. iLOVECLIM is a suitable model to simulate past periods of time such as the Last Interglacial and the Last deglaciation with “reasonable” computation resources. Taking advantage of a very recent modelling effort to better simulate and understand the marine Nd cycling, our modelling implementation will also aim to disentangle the processes on how seawater acquires its εNd signature.

3. Arctic Amplification and ocean circulation during past warmer-than-present time periods

The Arctic regions are heating at a rate up to four times faster than the global average, making them disproportionately susceptible to the effects of anthropogenic climate change. This discrepancy in warming between the northern high latitudes and the rest of the globe is referred to as Arctic amplification. Being the northern terminus of a worldwide system of ocean currents, changes within the Arctic Ocean are inherently linked to changes across the rest of the globe, and the Atlantic in particular. Investigating changes to ocean circulation in past warmer-than-present time periods (interglacials) is one way to better understand these complicated systems and in doing so constrain predictions for future responses to contemporary climate change. For example, during the Earth’s last complete interglacial cycle, multiple records have suggested that the Atlantic currents transporting Equational heat northwards strengthened and encroached deeper into the Arctic basin, amplifying high latitude warming, similar to modern observations. Further studies have suggested however that the increased Arctic freshwater input, whether through melting sea ice and glaciers or increased rainfall, ultimately disrupted and weakened this northwards heat transfer, resulting in regional cooling over the Nordic Seas and northern Europe. This development is still disputed however, demonstrating the need for further research into past ocean circulation if we wish to use it as an analogue for a future warm Arctic.

4. The role of the polar ocean in the past abrupt changes in climate and the carbon cycle