Christophe Kinnard

High‐resolution (1 mm) stratigraphic information was derived from digital image analysis of an ice core from the Prince of Wales (POW) Icefield, Central Ellesmere Island, Canada. Following careful image processing, a profile of ice core transmitted light was derived from the greyscale images and used to reconstruct high‐resolution density variations for the unfractured sections of the core. Images were further classified into infiltration and glacier ice using an automatic thresholding procedure, and were converted to a high‐resolution melt percentage index. The mean annual melt percentage over the last 580 years was 9%, and melting occurred in 8 years out of 10. Melting obliterated most of the original depositional sequence, and seasonal density cycles were mostly unrecognizable. The ice core solid conductivity was greater and more variable in melt features than in glacier ice, owing to washout of strong acids by meltwater (elution) and chemical enrichment upon refreezing. This hindered the identification of acid volcanic layers and further compromised dating by annual layer counting. Comparison of the melt record with those from other Arctic ice caps shows that the melt‐temperature relationship on POW Icefield is site‐specific. We speculate that this is due to the peculiar position of the icefield, which rests on the periphery of the Baffin Bay maritime climate zone, and to the proximity of the North Open Water polynya, which controls snow accumulation variability on the icefield and affects the melt percentage index.

Changes in the extent of seasonal ice were investigated using historical and satellite observations for the period 1870–2003. The seasonal ice zone (SIZ) has been gradually expanding since 1870, with a marked acceleration over the past three decades, and has migrated north to encompass all peripheral Arctic seas. The expansion of the SIZ may be increasing the salinity of the upper Arctic Ocean, consistent with recent observations. The migration of the SIZ over continental shelves may also be enhancing the formation rate and salinity of Arctic deep waters, which are subsequently advected to the convective region of the Greenland‐Iceland‐Norwegian Sea, thereby influencing the formation of North Atlantic deep waters and related global thermohaline circulation.

We present a complete climatic analysis of Sea-ice conditions in the Canadian Arctic based on digitized operational charts from the Canadian Ice Service for the period 1980–2004. The Seasonal climatology, Spatial variance and linear trends in total ice concentrations (CT) were calculated. The maximum reduction rate in CT was found in the Beaufort Sea (>24% decade^–1) and in the Davis Strait/Labrador Sea region (>18% decade^–1) during Spring and Summer. Empirical orthogonal function (EOF) analysis performed on monthly CT deviations yielded four Significant EOF modes explaining 32% of the total variance. The Spatial pattern, temporal behaviour and Seasonality of these four EOF modes are discussed and correlated with fields of Sea-level pressure, Surface winds, Surface air temperature and Sea-surface temperature monthly anomalies. These results point to the dominant influence of the North Atlantic Oscillation on CT decadal anomalies during the cold Season, while climate variability in the Pacific influences CT variations in the Beaufort Sea region during Spring–summer.

Correlation between glaciochemical time Series from an ice core collected on Devon Ice Cap, Nunavut, Canada, and gridded time Series of Sea-ice concentrations reveals Statistically Significant inverse relationships between Sea-salt concentrations (mainly Na⁺, Mg²⁺and Cl^–) in the ice core and Sea-ice cover in Baffin Bay over the period 1980–97. An empirical orthogonal function (Eof) analysis performed on all major ions Shows that the dominant mode of glaciochemical variability (Eof1) represents a Sea-salt Signal, which correlates best with Sea-ice concentration in Baffin Bay. On a Seasonal basis, the Strongest and most Spatially extensive anticorrelations are found in Baffin Bay during the fall, followed by Spring, Summer and winter. These results Support the notion that increased open-water conditions in Baffin Bay during the Stormy Seasons (fall and Spring) promote increased production, transport and deposition of Sea-salt aerosols on Devon Ice Cap. Comparison of ice-core time Series of Eof1, δ¹⁸O and melt percentage, with air temperatures recorded in Upernavik, Greenland, Suggests that ice-cover variations in Baffin Bay over the past ∽145 years were dynamically rather than thermodynamically controlled, with periods of Strengthened cyclonic circulation leading to increased open-water conditions, and a greater Sea-salt flux on Devon Ice Cap.

A turf‐banked solifluction lobe was instrumented for the continuous recording of surface and internal movement, thaw settlement, soil volumetric moisture content and thermal conditions during the spring and summer of 2002. Strain probe measurements showed that gelifluction occurred as a series of discrete and abrupt displacements near the thaw plane, followed by retrograde movement. Most gelifluction events took place when thaw rates were high and the soil was saturated almost to the surface, but rain was also capable of inducing gelifluction at depth. The rapid and localized character of the observed displacements suggests that gelifluction results from micro‐shearing of the soil, possibly along the interface of thawing ice lenses. Copyright © 2005 John Wiley & Sons, Ltd.