Research axes

Projections of future climate suggest that high latitudes of the Northern Hemisphere will experience a larger environmental response than the global mean. Arctic regions are already characterized by an acceleration of climatic and environmental change. Loss of sea ice and melting of continental ice caps are dramatic and the rate of change unprecedented.

This is particularly critical since climate change in the Arctic can trigger a series of feedback processes affecting the global climate. Firstly, the accelerated loss of the Greenland ice mass in response to atmospheric and oceanic warming may lead to a significant increase in global sea level. Also, the Arctic sea-ice cover directly impacts the Earth’s heat budget through albedo and freshwater export. The excess meltwater routed towards the North Atlantic and Labrador Sea may interfere with the formation of deep ocean water and the strength of the Atlantic meridional overturning circulation (AMOC), thus affecting the global ocean circulation.

Forecasting the evolution of the Arctic-subarctic ecosystem is thus of utmost importance, not only for sustainable development of high latitude regions, but also for the prediction of global sea-level and climate changes. Such predictions will in turn help stakeholders in the mitigation and adaptation process for human populations and communities that are most at risk. The feedback processes that link the Arctic ice, the ocean and atmosphere, however, remain incompletely documented from observations and are imperfectly quantified as state-of-the-art climate models still fail to reproduce observed instrumental trends of Arctic ice decline. One way of getting around these issues is to use paleoceanographic data so as to extend observations from physical oceanography beyond the instrumental records. Such approaches can help to assess the natural variability of the ocean circulation and weigh the actual impact of anthropogenically driven global warming.

The goals of ArcTrain are thus i) to better understand interactions between ice, land and the ocean in the Arctic-subarctic domain, on time scales ranging from seasons to millennia, ii) to provide benchmarks for current trends and iii) to evaluate the ability of climate models to assess the impact of climate changes on Arctic-subarctic environments, mostly based on synopses of warmer climate intervals in the past. The overall research program will be conducted through sub-projects grouped in three interconnected areas: sea ice, ocean circulation and ice sheets. For each topic, investigation of processes, feedbacks and variability will combine observational data, reconstructions from proxies and modelling. The study areas, which focus on the eastern Canadian Arctic, Baffin Bay, Labrador Sea and Greenland Sea.

Sea Ice

Sea ice is a key component of the Arctic climate and ocean systems. While satellite observations indicate a dramatic decrease of the areal extent of sea ice cover in the Arctic Ocean and a thinning of multi-year ice over the last three decades, predictive climate models underestimate the current rate of sea-ice decline. In addition, there is still a need to discriminate between natural and anthropogenic forcing of sea ice dynamics.

These two issues will be addressed through:

1. Improving algorithms for the analysis of satellite data in order to better understand the evolution of the proportion of multi-year vs first-year ice, due to the large effec of this ratio on the ocean-atmosphere heat exchange and marine biological productivity, and to establish a consistent and reliable time series of the Arctic multiyear sea ice. 
2. Studying sea-ice time series that extend further back in time than instrumental/observation records, with the use of biogenic proxies (e.g. IP25, dinocysts)

The combined information on sea-ice variability and sea-ice processes in timescales ranging from years to millennia will be used to benchmark and improve the representation of sea-ice dynamics in climate models.

Ocean circulation

The subpolar North Atlantic is one of the key regions in the climate system because formation of deep waters contributes to the AMOC, as well as the uptake of CO₂ from the atmosphere.  Paleoceanographic reconstructions and climate model studies imply a key role of Labrador Sea circulation in driving millennial-scale climate variability. On shorter timescales, comprehensive hydrographic data also reveal considerable variations in convection and deep-water formation in the central Labrador Sea, which are only partly understood. Future changes in the strength of the AMOC depend critically on the distribution of heat and salt in the North Atlantic. ArcTrain projects will contribute to establish climatologies for the subpolar North Atlantic and extended time series from paleoclimate archives for benchmarking and improving ocean-circulation models and understanding the physical processes associated with heat and salt transfer in the ocean.

Land Ice

The fate of the Greenland ice sheet during the coming centuries is a major issue. Ice sheet decline will likely continue into the future, but it is unclear whether the current rate of mass loss will accelerate with ongoing oceanic and atmospheric warming. A shrinking ice sheet will not only result in rising sea level but will also inject meltwater into boundary currents near to the deep water formation areas (Hu et al. 2011). The current generation of climate models has a spatial resolution that may be insufficient to capture adequately the response of the ocean circulation to meltwater injections. Natural variations of ice volume during the deglaciation provide a means to test the performance of ice-sheet models and the response of the ocean to meltwater perturbations in high versus low-resolution models.

Projects conducted within ArcTrain will generate new and compile existing meltwater histories from paleoclimate archives and use the resulting information to test the behaviour of ice sheet and climate models. Ice sheet model development is also crucial to improve the representation of ice sheet-ocean coupling, marine ice sheet instabilities, and the effects of increased meltwater on ice sheet dynamics.