Constraining the Impact of Arctic Amplification in the Nordic Sea: A biogeochemical approach (CIAAN)
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Audrey Morley(1), Ulyssess Ninnemann(2), Peter Croot(1), Rachel Cave(1), Gavin Foster(3), Julie Meilland(4)
(1)National University of Ireland Galway (NUIG), (2)University of Bergen, (3)University of Southampton, (4)MARUM, Bremen University
Climate Change, Oceanography
Palaeoceanography, Marine Geochemistry
One of the key challenges in climate change science is to assess the magnitude of future climate change. Uncertainties associated with predictions remain large due to the shortness of our observational records (at best 150 years) and the absence of high-impact climate events therein to serve as an analogue for future change. This is especially problematic when estimating Arctic climate change because the response in the Arctic is amplified relative to the global mean, making the Arctic the most sensitive and vulnerable environment with regards to global warming. The North Atlantic and Nordic Seas are also one of the most important regions throughout the global oceans for the uptake of atmospheric carbon dioxide (pCO2) having absorbed one fourth of the total fossil fuel emissions since preindustrial times. In the Nordic Seas, the uptake of CO2 is linked to the formation of cold North Atlantic Deepwater (NADW) and thereby the Atlantic Meridional Overturning Circulation. While it is evident that the removal of CO2 from the atmosphere is crucial when considering future climate change, it remains uncertain how (if) a warmer than present ocean will continue to moderate the effect of anthropogenic greenhouse gas emissions. This fundamental question remains to be answered especially since changing rates in CO2 absorptions are not considered in future climate change scenarios. Equally concerning is the potential of acidification and de-oxygenation of North Atlantic deep waters that may irreversibly damage vulnerable deep-sea habitats and their biodiversity.
A research survey of the Nordic Seas with the RV Celtic Explorer allowed us to collect water, plankton, and sediment samples. Water samples will be analysed for climate relevant dissolved gases (O2, N2, Ar, CO2 and DMS) alongside temperature, salinity, and the carbonate chemistry of the water column. In addition, we will assess the biogeochemical processes pertinent to pico- and nanoplankton distributions that will inform us on primary production and food webs in the upper ocean and how these are evolving due to climate change. Plankton tow samples will allow us to assess the spatial distribution of planktonic foraminifera a climate sensitive unicellular organism that builds a shell out of calcium carbonate during its lifetime. Their spatial distribution is closely linked to sea surface temperature and the chemistry of their shells records ECVs during their lifetime. Marine sediment samples provide an archive of past foraminifera populations. Analysing the chemistry preserved in their shells therefore allows us to reconstruct past changes in climate relevant parameters such as sea surface temperature and pH beyond the observational period (e.g. 150 years. These reconstructions are crucial to assess natural variability and the sensitivity of the climate system to anthropogenic warming.
The Cruise to the Nordic Seas took place from August 24th to September 16th 2020. Samples collected from the Nordic Seas are currently being analysed at NUI Galway and partner institutions.
Essential Climate Variables (ECVs); North Atlantic Deepwater formation; Atlantification of Nordic Seas