4.2 Changes in the sea ice regime of the Canadian Arctic Archipelago

Tuesday, 3 May 2011: 1:45 PM
Rooftop Ballroom (15th Floor) (Omni Parker House )
Stephen Howell, Canadian Meteorological Service, Toronto, ON, Canada; and T. Agnew, A. Tivy, and C. Derksen

It has been suggested that a warmer climate may not immediately result in lighter sea ice conditions in the Canadian Arctic Archipelago (CAA) because warming facilitates increased MYI dynamic import from the Arctic Ocean. This process has held true until 2005. However since 2005 a steady decrease in the MYI component of the CAA ice matrix has occurred. The decreases have not been caused by a dramatic single year event but have been gradual with less monthly variability compared to the historical ice chart record for the region which goes back to 1968.

At the same time, surface air temperature over the CAA has shown considerable warming caused in part by a change in large scale atmospheric circulation. This appears to have shifted the two main sources of MYI in the CAA: a) import from the Arctic Ocean and b) promotion of sea ice which has survived the melt season. Since 2005, this shift has increased ice area flux from the Arctic Ocean into the more northern Queen Elizabeth Islands but decreased influx in M'Clure Strait in the summer months. Along with reduced amounts of ice surviving summer melt, this has prevented MYI replenishment in the southerly regions particularly M'Clure Strait, Western Parry Channel and the M'Clintock Channel during fall.

The main conclusion is increased warming and reduced import from the Arctic Ocean via the M'Clure Strait has prevented appreciable MYI replenishment during the summer months since 2005. The replenishment of the inventory of MYI normally occurs during the summer months and export always takes place during the fall months. With near-zero replenishment of MYI during the summer, the export processes that occur during the fall result in an overall net loss. This combination of dynamic and thermodynamic processes have dominated since 2005 and produced consistent year over year MYI decreases in the CAA. If these processes continue, easier navigation through the channels of the Northwest Passage may occur faster than previously thought.

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