In the Queen Elizabeth Islands, regional distributions of vegetation and many summer climate patterns show similar, distinctive S-shaped patterns, a response to the interaction between regional topography and persistent northwesterly flow from the central Arctic Ocean. The cool and cloudy central polar pack ice climate bulges almost unimpeded into the low-lying islands of the northwest and north-central sector. This region has the least vascular plant diversity and is dominated almost entirely by herbaceous species. The mountains of Axel Heiberg and Ellesmere islands create a barrier that effectively shelters an intermontane region from both the central Arctic Ocean climate and travelling cyclonic systems. In this large intermontane zone regional minimums of cloud cover and maximums of temperatures and melt season duration are found. This area contains the most dense and diverse vascular plant assemblages. Woody species and sedges dominate, and many species with more southerly limits occur as disjuncts. The plateaus and highlands in the southern islands modify the central Arctic Ocean climate sufficiently to produce an intermediate climate. Woody species and sedges also dominate this area; however, the density and diversity are less than that of the intermontane area. Several phytogeographic limits occur in the Queen Elizabeth Islands, including the northern limits of woody plants and sedges, and the northern limits of the dominance of woody plants and sedges. These regional boundaries roughly coincide with regional mean July isotherms of 3 and 4°C respectively.

[1] The Canadian Ice Service Digital Archive (CISDA) is a compilation of weekly ice charts covering Canadian waters from the early 1960s to present. The main sources of uncertainty in the database are reviewed and the data are validated for use in climate studies before trends and variability in summer averaged sea ice cover are investigated. These data revealed that between 1968 and 2008, summer sea ice cover has decreased by 11.3% ± 2.6% decade −1 in Hudson Bay, 2.9% ± 1.2% decade −1 in the Canadian Arctic Archipelago (CAA), 8.9% ± 3.1% decade −1 in Baffin Bay, and 5.2% ± 2.4% decade −1 in the Beaufort Sea with no significant reductions in multiyear ice. Reductions in sea ice cover are linked to increases in early summer surface air temperature (SAT); significant increases in SAT were observed in every season and they are consistently greater than the pan-Arctic change by up to ∼0.2°C decade −1 . Within the CAA and Baffin Bay, the El Niño-Southern Oscillation index correlates well with multiyear ice coverage (positive) and first-year ice coverage (negative) suggesting that El Niño episodes precede summers with more multiyear ice and less first-year ice. Extending the trend calculations back to 1960 along the major shipping routes revealed significant decreases in summer sea ice coverage ranging between 11% and 15% decade −1 along the route through Hudson Bay and 6% and 10% decade −1 along the southern route of the Northwest Passage, the latter is linked to increases in SAT. Between 1960 and2008, no significant trends were found along the northern western Parry Channel route of the Northwest Passage.

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A study of pollen grain concentration in surface snow and ice cores at 15 sites in the Canadian high Arctic and one site near the tree line, together with published pollen deposition rates south of the tree line has shown long-range dispersal of pollen from the boreal forest to the limits of our area on the Arctic Ocean close to Svalbard and the North Pole. There are no discernible trends of deposition rates within the high Arctic which suggests extremely long trajectories with strong zonal components; some of the pollen may have an Eurasian source. We relate the trajectories to synoptic patterns in the mid-and high Arctic.