[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.

The European Space Agency's CryoSat‐2 satellite mission provides radar altimeter data that are used to derive estimates of sea ice thickness and volume. These data are crucial to understanding recent variability and changes in Arctic sea ice. Sea ice thickness retrievals at the CryoSat‐2 frequency require accurate measurements of sea ice freeboard, assumed to be attainable when the main radar scattering horizon is at the snow/sea ice interface. Using an extensive snow thermophysical property dataset from late winter conditions in the Canadian Arctic, we examine the role of saline snow on first‐year sea ice (FYI), with respect to its effect on the location of the main radar scattering horizon, its ability to decrease radar penetration depth, and its impact on FYI thickness estimates. Based on the dielectric properties of saline snow commonly found on FYI, we quantify the vertical shift in the main scattering horizon. This is found to be approximately 0.07 m. We propose a thickness‐dependent snow salinity correction factor for FYI freeboard estimates. This significantly reduces CryoSat‐2 FYI retrieval error. Relative error reductions of ~11% are found for an ice thickness of 0.95 m and ~25% for 0.7 m. Our method also helps to close the uncertainty gap between SMOS and CryoSat‐2 thin ice thickness retrievals. Our results indicate that snow salinity should be considered for FYI freeboard estimates.

A portable surface-based polarimetric C-band scatterometer for field deployment over sea ice is presented. The scatterometer system, its calibration, signal processing, and near-field correction are described. The near-field correction is shown to be effective for both linear polarized and polarimetric backscatter. Field methods for the scatterometer are described. Sample linear polarized and polarimetric backscatter results are presented for snow-covered first-year sea ice (FYI), multiyear hummock ice, and rough melt pond water on FYI. The magnitude of backscatter signature variability due to system effects is presented, providing the necessary basis for quantitative analysis of field data.

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Although cruise travel to the Canadian Arctic has grown steadily since 1984, some commentators have suggested that growth in this sector of the tourism industry might accelerate, given the warming effects of climate change that are making formerly remote Canadian Arctic communities more accessible to cruise vessels. Using sea-ice charts from the Canadian Ice Service, we argue that Global Climate Model predictions of an ice-free Arctic as early as 2050-70 may lead to a false sense of optimism regarding the potential exploitation of all Canadian Arctic waters for tourism purposes. This is because climate warming is altering the character and distribution of sea ice, increasing the likelihood of hullpenetrating, high-latitude, multi-year ice that could cause major pitfalls for future navigation in some places in Arctic Canada. These changes may have negative implications for cruise tourism in the Canadian Arctic, and, in particular, for tourist transits through the Northwest Passage and High Arctic regions.