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.

Sea ice deforms under convergent and Shear motion, causing rafting and ridging. This results in thicker ice than could be formed by thermodynamic growth only. Three different approaches to Simulating the formation of pressure ridges in a dynamic–thermodynamic continuum model are considered. They are compared with and evaluated by airborne laser profiles of the Sea-ice Surface roughness. The respective characteristic of each of the three ridging Schemes is (1) a prognostic equation for deformation energy from which ridge parameters are derived; (2) a redistribution function, Shifting ice between two categories, level and ridged, combined with a Monte Carlo Simulation for ridge parameters; and (3) prognostic equations for ridge density and height, resulting in the formation of ridged-ice volume. The model results Show that the ridge density is typically related to the State of ice motion, whereas the mean Sail height is related to the parent ice thickness. In general, all of the three models produce realistic distributions of ridges. Finally, the Second ridging Scheme is regarded as the most appropriate for climate modelling, while the third Scheme has advantages in Short-term Sea-ice forecasting.

During February and March 2004, Satellite-tracked ice beacons and helicopter-borne Sensors collected ice-drift and ice-thickness data from the Southern Gulf of St Lawrence, Canada, to Study the region’s ice-thickness evolution and ice-drift behavior in response to winter Storms. Three northeasterly Storms passed through the area during the observation period, pushing the pack ice against the north Shore of Prince Edward Island. The resulting Severe ice deformation caused major changes in the ice-thickness distribution of two pack-ice areas tracked by ice beacons that Survived the Storms. The ice drift ranged from 1.4% to 2.9% of the wind Speed during free ice-drift conditions, decreasing to 0% when the pack ice compacted against the Shoreline. Most of the thinner ice deformed first, increasing the mean ice thickness over 6–8 km line Sections around the beacons from 0.6 and 0.3 m before the Storms to 1.9 and 2.0 m after the Storms. The ice-thickness increases can be accounted for by the reduced pack-ice area due to ice ridging. Over the next 4weeks, deformation continued and the mean ice thickness around the beacons increased to 2.8 m, well in excess of the maximum undeformed possible ice growth of 65 cm. Ice charts captured the ice thickness of undeformed and composite ice floes but did not capture the ice volume in ice-rubble fields.

Semi-diurnal oscillations are a ubiquitous feature of polar Sea-ice motion. Over much of the Arctic basin, inertial and Semi-diurnal tidal variability have Similar frequencies So that periodicity alone is inadequate to determine the Source of oscillations. We investigate the relative roles of tidal and inertial variability in Arctic Sea ice using a barotropic ice–ocean model with Sea ice embedded in an upper boundary layer. Results from this model are compared with ‘levitated’ ice–ocean coupling used in many models. In levitated models the mechanical buoyancy effect of Sea ice is neglected So that convergence of ice, for example, does not affect the oceanic Ekman flux. We use rotary Spectral analysis to compare Simulated and observed results. This helps to interpret the rotation Sense of Sea-ice drift and deformation at the Semi-diurnal period and is a useful discriminator between tidal and inertial effects. Results indicate that the levitated model generates an artificial inertial resonance in the presence of tidal and wind forcing, contrary to the embedded Sea-ice model. We conclude that Sea-ice mechanics can cause the rotational response of ice motion to change Sign even in the presence of Strong and opposing local tidal forcing when a physically consistent dynamic ice–ocean coupling is employed.

Sea ice plays an important role in ocean–atmosphere heat exchange, global albedo and the marine ecosystem. Knowledge of variation in Sea-ice extent is essential in order to understand past climates, and to model possible future climate Scenarios. This paper presents results from a Short firn core Spanning 15 years collected from near Mount Brown, Wilhelm II Land, East Antarctica. Variations of methanesulphonic acid (MSA) at Mount Brown were positively correlated with Sea-ice extent from the coastal region Surrounding Mount Brown (60–120˚ E) and from around the entire Antarctic coast (0–360˚ E). Previous results from Law Dome identified this MSA–sea-ice relationship and proposed it as an Antarctic Sea-ice proxy (Curran and others, 2003), with the Strongest results found for the local Law Dome region. Our data provide Supporting evidence for the Law Dome proxy (at another Site in East Antarctica), but a deeper Mount Brown ice core is required to confirm the Sea-ice decline Suggested by Curran and others (2003). Results also indicate that this deeper record may also provide a more circum-Antarctic Sea-ice proxy.

Passive microwave imagery indicates a decreasing trend in Arctic Summer Sea-ice extent Since 1979. The Summers of 2002–05 have exhibited particularly reduced extent and have reinforced the downward trend. Even the winter periods have now Shown decreasing trends. At the local level, Arctic residents are also noticing changes in Sea ice. In particular, indigenous elders and hunters report changes Such as earlier break-up, later freeze-up and thinner ice. The changing conditions have profound implications for Arctic-wide climate, but there is also regional variability in the extent trends. These can have important ramifications for wildlife and indigenous communities in the affected regions. Here we bring together observations from remote Sensing with observations and knowledge of Inuit who live in the Baffin Bay region. Weaving the complementary perspectives of Science and Inuit knowledge, we investigate the processes driving changes in Baffin Bay Sea-ice extent and discuss the present and potential future effects of changing Sea ice on local activities.