About the project
Ocean Controls on high-latitude Climate sensitivity – a Pliocene case study (OCCP)
OCCP addresses the role of the Nordic Seas during the Pliocene through a fully integrated multi-proxy and model study, such as has not been carried out to date. According to our pilot study, the Nordic Seas was not as warm during the Pliocene as previously proposed, and the pattern of ocean circulation was very different from modern conditions.
The Pliocene Epoch (5.3-2.6 million years ago) is a warm period of particular interest, when boundary conditions of the climate system were similar to the present, but sea level was higher and today’s polar and subpolar regions were as warm as or warmer than predicted in future scenarios. High northern latitudes are thought to have been especially warm; however, how these warm, high-latitude conditions were maintained is an open question, in part given the apparently contradictory observational evidence in the Nordic Seas.
The Nordic Seas link the North Atlantic and Arctic Oceans, and is a small but dynamically important part of the global ocean. In today’s climate, they form a region of strong atmosphere-ocean exchange, vigorous mixing of water masses and deep convection. The Nordic Seas offer a unique opportunity to study the exchange of salt, heat and mass between the North Atlantic and Arctic oceans in situations with a warmer climate than at present. OCCP aims to resolve conflicting views on the role of the Nordic Seas in determining high northern latitude climate and the degree of Arctic amplification during a key warm period in Earth’s history, the Pliocene. We will adopt a multidisciplinary approach. New, multi-proxy data characterizing the Nordic Seas water column during the Pliocene will be generated and combined with published data from the North Atlantic/Arctic region. The reconstructions will be combined with results from model experiments designed to investigate the large-scale dynamics of the region. The model results will be used to identify key processes responsible for the observed high latitude climate of the Pliocene and the role of the Nordic Seas “gateway” between the North Atlantic and Arctic. This approach will enable us to make substantial progress towards understanding the mechanisms behind the apparent high sensitivity of the Arctic in warm climates, the role of the Nordic Seas in the arctic amplification of Pliocene warming, and will ultimately help constrain the long-term sensitivity of the climate system in a warming world.
The guiding hypotheses to be tested in this project are whether:
- the ocean circulation and northern limb of the AMOC may operate differently from today under climatic boundary conditions close to modern.
- prior estimates of Pliocene oceanic warmth and oceanic heat advection towards the Arctic are overestimated, and earlier estimates of Pliocene Arctic amplification may have been too high.
Resolve the role of the Nordic Seas in determining climate conditions at high northern latitudes during a warmer than present climate state.
Objective 1 -
Determine Pliocene temperature, stratification, ocean circulation and ventilation in the eastern Nordic Seas.
Objective 2 -
Apply climate models to investigate the dynamical processes governing Pliocene high northern latitude climate.
Objective 3 -
Identify the forcing(s) most important for creating observed high latitude Pliocene climate states.
A schematic illustration of planned output from reconstructions and model sensitivity experiments.
Project leader: Bjørg Risebrobakken1
Project team: Eystein Jansen1,2, Carin Andersson1,2, Paul Bachem1, Camille Li3, Kerim Nisancioglu3, Stijn De Schepper1, Zhongshi Zhang1, Camille Contoux1, Erin McClymont4, Gilles Ramstein5
1Uni Research Climate
2Departhment of Earth Science, University of Bergen
3Centre for Climate Dynamics at the Bjerknes Centre, University of Bergen
4Durham University, UK