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Arctic landfast ice extent and duration are examined from observations, ice assimilations, ocean reanalyses and coupled models. From observations and assimilations, it is shown that in areas where landfast ice conditions last more than 5 months the first-year ice typically grows to more than 2 m and is rarely less than 1 m. The observed spatial distribution of landfast ice closely matches assimilation products but less so for ocean reanalyses and coupled models. Although models generally struggle to represent the landfast ice necessary to emulate the observed import/export of sea ice in regions favourable to landfast ice conditions, some do exhibit both a realistic climatology and a realistic decline of landfast ice extent under an anthropogenic forcing scenario. In these more realistic simulations, projections show that an extensive landfast ice cover should remain for at least 5 months of the year, well into the end of the 21st century. This is in stark contrast with the simulations that have an unrealistic emulation of landfast ice conditions. In these simulations, slow and packed ice conditions shrink markedly over the same period. In all simulations and in areas with landfast ice that lasts more than 5 months, the end-of-winter sea ice thickness remains between 1 and 2 m, well beyond the second half of the century. It is concluded that in the current generation of climate models, projections of winter sea ice conditions in the Canadian Arctic Archipelago and the Laptev Sea are overly sensitive to the representation of landfast ice conditions and that ongoing development in landfast ice parameterization will likely better constrain these projections. [ABSTRACT FROM AUTHOR]

Remarkably low mean September sea ice area in the Canadian Arctic Archipelago (CAA) was observed in 2011 (146×103 km2), a record-breaking level that was nearly exceeded in 2012 (150×103 km2). These values were lower than previous September records set in 1998 (200×103 km2) and 2007 (220×103km2), and are ∼ 60% lower than the 1981-2010 mean September climatology. In this study, the processes contributing to the extreme light years of 2011 and 2012 were investigated, compared to previous extreme minima of 1998 and 2007, and contrasted against historic summer seasons with above average September ice area. The 2011 minimum was associated with positive June through September (JJAS) surface air temperature (SAT) and net solar radiation(K" ) anomalies that facilitated rapid melt, coupled with atmospheric circulation that restricted multi-year ice (MYI) inflow from the Arctic Ocean into the CAA. The 2012 minimum was also associated with positive JJAS SAT and K" anomalies with coincident rapid melt, but further ice decline was temporarily mitigated by atmospheric circulation which drove Arctic Ocean MYI inflow into the CAA. Atmospheric circulation was comparable between 2011 and 1998 (impeding Arctic Ocean MYI inflow) and 2012 and 2007 (inducing Arctic Ocean MYI inflow). However, preconditioning was more apparent leading up to 2011 and 2012 than 1998 and 2007. The rapid melt process in 2011 and 2012 was more intense than observed in 1998 and 2007 because of the thinner ice cover being more susceptible to anomalous thermodynamic forcing. The thinner sea ice cover within the CAA in recent years has also helped counteract the processes that facilitate extreme heavy ice years. The recent extreme light years within the CAA are associated with a longer navigation season within the Northwest Passage. [ABSTRACT FROM AUTHOR]