A new Arctic sea ice regime : causes and consequences. The Tara Arctic Damocles project

The Tara Arctic project, conducted from 2006 to 2008 as part of the EU-funded Damocles (Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies) program, involved the schooner Tara drifting across the Arctic Ocean to assess the impacts of climate change on this critical region. Tara drifted for about 500 days, twice as fast as the Fram more than one century ago, providing a unique drifting observatory that gathered multidisciplinary data on atmospheric, oceanic and sea ice conditions precisely at a time the Arctic sea ice underwent profound and drastic changes as a response to climate changes. The first decade of the XXIst century was characterized by an exceptionnal Arctic sea ice transformation affecting all the main parameters related to sea ice dynamics and thermodynamics such as sea ice thickness, sea ice age, sea ice mobility, sea ice extent , sea ice volume (or mass) and the seasonal sea ice variability. By now the new Arctic sea ice is thinner, younger and moves faster. The Tara Arctic Damocles project documented a decline in multi-year ice, underscoring the transition to a younger (first-year ice), more vulnerable ice cover. Key results from Tara Arctic Damocles highlighted rapid climate-driven changes in the Arctic environment partly caused by warmer winters. The sea ice extent minimum in September, was reduced by half from 8. 10 6 km 2 during the 1980s and 1990s down to 4. 10 6 km 2 for the past 12 years . Over the same time period the sea ice volume decreased by 75% due to a mean sea ice thickness reduction by half from more than 3m down to less than 2m thick. A new stable Arctic sea ice regime has been taking place for the past 12 years. For how long this new Arctic will last in the context of the global warming still very active everywhere and in particular in the Arctic were it is four times faster than anywhere else on the Globe ? This new Arctic sea ice situation is deeply impacting the northern hemisphere weather patterns and has profound implications on both marine and terrestrial Arctic ecosystems.