In this paper we describe sea ice change and variability during the Canadian International Polar Year (IPY) program and examine several regional and hemispheric causes of this change. In a companion ...paper (Barber et al.,
Climate Change
2012
) we present an overview of the consequences of this observed change and variability on ecosystem function, climatically relevant gas exchange, habitats of primary and apex predators, and impacts on northern peoples. Sea ice-themed research projects within the fourth IPY were designed to be among the most diverse international science programs. They greatly enhanced the exchange of Inuit knowledge and scientific ideas across nations and disciplines. This interdisciplinary and cultural exchange helped to explain and communicate the impacts of a transition of the Arctic Ocean and ecosystem to a seasonally ice-free state, the commensurate replacement of perennial with annual sea ice types and the causes and consequences of this globally significant metamorphosis. This paper presents a synthesis of scientific sea ice research and traditional knowledge results from Canadian-led IPY projects between 2007 and 2009. In particular, a summary of sea ice trends, basin-wide and regional, is presented in conjunction with Inuit knowledge of sea ice, gathered from communities in northern Canada. We focus on the recent observed changes in sea ice and discuss some of the causes of this change including atmospheric and oceanic forcing of both dynamic and thermodynamic forcing on the ice. Pertinent results include: 1) In the Amundsen Gulf, at the western end of the Northwest Passage, open water persists longer than normal and winter sea ice is thinner and more mobile. 2) Large areas of summer sea ice are becoming heavily decayed during summer and can be broken up by long-period waves being generated in the now extensive open water areas of the Chukchi Sea. 3) Cyclones play an important role in flaw leads—regions of open water between pack ice and land-fast ice. They delay the formation of new ice and the growth of multi-year ice. 4) Feedbacks involving the increased period of open water, long-period wave generation, increased open-ocean roughness, and the precipitation of autumn snow are all partially responsible for the observed reduction in multiyear sea ice. 5) The atmosphere is observed as remaining generally stable throughout the winter, preventing vertical entrainment of moisture above the surface.
A decade of instrumented mooring data from Barrow Strait in the eastern Canadian Arctic Archipelago reveals connections between sea ice, water characteristics, and zooplankton dynamics on interannual ...time scales. On the North side of the Strait, the timing of breakup is positively related to the timing of freezeup in the previous year and negatively related to spring water temperature. This suggests that an early freezeup insulates the ocean from a cold autumn atmosphere, allowing heat to be retained until spring when it contributes to early sea ice erosion. There is also a very strong negative association between the timing of freezeup and late summer salinity, suggesting that monitoring of salinity in real time could be used to predict freezeup. A zooplankton biomass index derived from acoustic Doppler current profiler echo intensity data is used to demonstrate that on the North side there are also strong connections between early summer water temperature and the start, length, and productivity of the zooplankton growth season. On the South side of the Strait where currents are stronger, the relationships seen on the North side were not observed. But here integrated zooplankton biomass index and measured currents are used to identify interannual variability in the zooplankton biomass being delivered downstream into Lancaster Sound. Also on the South side, two yearlong records of daily fluorescence profiles reveal a large difference in the phytoplankton biomass being delivered downstream between years and demonstrate a strong relationship between the timing of the spring phytoplankton bloom and that of breakup.
Key Points
Sea ice freezeup and breakup are linked to water column temperature and salinity
A zooplankton biomass index is derived from moored ADCP backscatter data
Key features of the zooplankton growth season are linked to water temperature
The variability of Arctic pack-ice parameters (e.g. extent and ice type) has been monitored by satellite-borne sensors since the early 1960s, and information on ice thickness is now becoming ...available from satellite altimeters. However, the spatial resolution of satellite-derived ice properties is too coarse to validate fine-scale ice variability generated by regional-scale interaction processes that affect the coarse-scale pack-ice albedo, strength and decay. To understand these regional processes, researchers rely on other data-monitoring platforms such as moored upward-looking sonars and helicopter-borne sensors. Backed by observations, two such regional-scale pack-ice decay processes are discussed: the break-up of large pack-ice floes by long-period waves generated by distant storms, and the spring decay of first-year-ice ridges in a diverging pack-ice environment. These two processes, although occurring on regional spatial scales, are important contributors to the evolution of the total pack ice and need to be included in global climate models, especially as the conditions for their occurrence will alter due to climate change.
Sea-ice thicknesses observed in Canadian coastal waters with helicopter-borne electromagnetic–laser sensors show large interannual variability caused by atmospheric fluctuations in two years for two ...areas where surveys were repeated, one in the Amundsen Gulf of the Canadian Beaufort Sea and one over the Labrador Shelf. For the Amundsen Gulf, the bimodal ice thickness peaks shifted by 40 cm to thinner thicknesses for the warmer winter of 2008 compared with 2004. The thinner ice in 2008 can be explained partially by reduced thermodynamic ice growth during the warmer winter of 2008. In addition, winds from the east were more persistent throughout the winter of 2008, increasing ice export from the Amundsen Gulf and thereby creating open-water areas where new ice growth in late winter produced the thinner ice classes. For the Labrador Shelf, the mean ice thicknesses of the warmer winter of 2011 (0.71 m) were much less than those of the near-normal winter of 2009 (1.60 m). Again the difference can be explained by the fact that along the entire Labrador Shelf the winter of 2011 was much warmer, reducing ice growth and resulting in thinner ice locally and thinner ice being transported into the survey region from northern latitudes. In addition, northwesterly winds occurred less frequently during the winter of 2011, reducing the transport of relatively thicker ice into the survey area from northern latitudes.
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