Ice Cover In Spring Research Articles

Sea ice thickness in the Eastern Canadian Arctic: Hudson Bay Complex & Baffin Bay

Past observations of sea ice thickness in the Eastern Canadian Arctic (ECA) have generally been restricted to drill-hole measurements at a few local sites on landfast ice. Here we use data from the laser altimeter ICESat and the radar altimeter Cryosat-2 to present a 14-year record (2003–2016) of high-resolution and spatially extensive ice thickness observations for the ECA and identify 12 sub-regions with distinct patterns. The mean sea ice growth rate within the seasonally ice-covered ECA from November to April is 23cmmo−1 (565km3mo−1), with the fastest increase in thickness occurring through strong ice convergence and deformation in eastern Hudson Bay and Foxe Basin. Our results demonstrate characteristically asymmetrical distributions of sea ice thickness in both Hudson Bay and Baffin Bay, but in opposing directions. In Hudson Bay the spring ice cover is 40cm thicker in the eastern region compared to the northwestern region, whereas in Baffin Bay the ice is 20cm thicker in the western half of the bay compared to the eastern half. In Hudson Bay we find that years with strong and positive ice drift vorticity (i.e. cyclonic and convergent conditions) correlate with increasingly asymmetrical sea ice covers, with the level of west-east asymmetry varying from 2 to 11cm per 100km. However, in Baffin Bay the ice drift vorticity is typically negative (i.e. anticyclonic and divergent) with no obvious link to the asymmetry of the spring ice cover. Finally, we estimate that large interannual variations in spring sea ice volume within the ECA lead to ±15% variations in the volume of freshwater available at the ocean surface during summer.

A geospatial model to determine patterns of ice cover breakup along the Slave River

Spring floods have become less frequent along the Slave River and Slave River Delta. As a result, prolonged dry periods have occurred leading to an influx of invasive vegetation more tolerant to dry conditions (e.g., willows). Ice cover breakup and ice jamming can be important mechanisms in river flooding. A clear understanding of spatial and temporal patterns of the spring ice cover breakup along the Slave River could identify possible causes of reduced flood magnitude and frequency in the Slave River Delta. Few attempts have been made to examine the patterns of ice cover breakup along this river. A geospatial model has been introduced in this study to pinpoint the most likely areas of breakup initiation and persistent ice and ice cover at the end of the breakup period along the river. Relatively narrow river sections are responsible for initiation of breakup and relatively wide sections of the river have a strong predisposition for persistent ice along the Slave River. Daily time series of MODIS satellite images acquired from different years were used to examine the spatial and temporal patterns of ice breakup along the Slave River. In addition to geomorphological influence, air temperature and flow conditions also have strong impacts on the spatial and temporal patterns of the ice cover breakup.

Mechanism of an Abrupt Decrease in Sea-Ice Cover in the Pacific Sector of the Arctic during the Late 1980s

The recent decline in Arctic sea-ice cover (SIC) shows seasonal and regional characteristics. The retreat of summer sea ice has occurred mainly in the Pacific sector of the Arctic. In this study, using the moving t-test, we found an abrupt change event in the long-term sea-ice area in the Pacific sector in summer 1989. This event was linked to the phase shift of the Arctic Oscillation (AO) or the Northern Annular Mode (NAM). Corresponding with the AO/NAM phase shift from negative to positive, the area of the northern hemisphere stratospheric polar vortex decreased abruptly in winter 1988/89. Comparisons of two periods before (1979–1988) and after (1989–1993) the abrupt decrease in sea ice show that an anomalous winter sea level pressure (SLP) was induced by changes in the polar vortex leading to an anomalous cyclonic ice drift in the Pacific sector. The changes in SLP and wind field persisted into the following spring, resulting in a decrease in SIC and warming of the surface air temperature (SAT). The influence of the spring SLP and SAT on ice persisted into the following summer. Meanwhile, the increased summer net surface heat flux over the ocean and sea ice as a result of the decreased spring ice cover further contributed to the summer sea-ice melt.

Thermokarst Lakes on the Arctic Coastal Plain of Alaska: Spatial and Temporal Variability in Summer Water Temperature

ABSTRACTIn summer 2010, water temperature profile measurements were made in 12 thermokarst lakes along a 150‐km long north–south transect across the Arctic Coastal Plain of northern Alaska. In shallow lakes, gradual warming of the water column to 1–4°C begins at the lake bed during decay of the ice cover in spring. Rapid warming follows ice‐off, with water temperature responding synchronously to synoptic weather variations across the area. Regionally, ice‐off occurs 2–4 weeks later on lakes near the coast. Inland lakes are warmer (13°C) in mid‐summer than those near the coast (7°C), reflecting the regional climate gradient and the maritime effect. All lakes are well mixed and largely isothermal, with some thermal stratification (< 2°C) occurring during calm, sunny periods in deeper lakes. In deep (6–9 m) lake‐bed depressions that are likely ice‐wedge troughs, water cools by conduction to the colder sediments below, while concurrent warming occurs in the upper water column. A spatially dense sample of near‐surface temperature measurements was collected from one lake over a short period and shows warmer (2–3°C) temperatures on the upwind, sheltered end of the lake. This study demonstrates that climatic gradients, meteorological conditions and basin characteristics impact lake temperature dynamics. Copyright © 2012 John Wiley & Sons, Ltd.

Does spring ice cover influence nest initiation date and clutch size in common eiders?

Understanding how environmental factors affect ecological parameters is important to understanding and predicting impacts of environmental change. Given evidence and anticipated impacts of climate variability, this is especially true with respect to sea ice and its role in animal life history in northern regions. We examined relationships between the extent of consolidated spring ice cover (pack and landfast), nest initiation and clutch size in common eiders (Somateria mollissima) in northern Labrador, a sub-Arctic region on the east coast of Canada. Our initial prediction was that eiders would delay nesting and have smaller clutches in years with more extensive spring ice cover. Between 1998 and 2003, we surveyed coastal islands for breeding eiders and collected information on nest age and clutch size. For those years, we estimated ice cover based on Radarsat-1 images supplied by the Canadian Ice Service during the spring period (approximately June 7–12). We found that spring ice cover was a significant positive predictor of nest initiation date, and the regression equation indicated that if the average extent of ice cover around nesting islands increased by 18 ha, average nesting date was delayed by approximately 1 day. Nest initiation date was a significant negative predictor of clutch size, and the regression equation indicated that a 20 day delay in nesting reduced average clutch size by approximately 1 egg. However, ice cover itself was not a significant predictor of clutch size. Our findings suggest that eiders breed when ice is present, but ice extent may negatively influence aspects of their breeding ecology.

Microzooplankton grazing impact in the Western Arctic Ocean

Abstract Microzooplankton grazing impact on phytoplankton was assessed using the Landry–Hassett dilution technique in the Western Arctic Ocean during spring and summer 2002 and 2004. Forty experiments were completed in a region encompassing productive shelf regions of the Chukchi Sea, mesotrophic slope regions of the Beaufort Sea off the North Slope of Alaska, and oligotrophic deep-water sites in the Canada Basin. A variety of conditions were encountered, from heavy sea-ice cover during both spring cruises, moderate sea-ice cover during summer of 2002, and light to no sea ice during summer of 2004, with a concomitant range of trophic conditions, from low chlorophyll- a (Chl- a ; −1 ) during heavy ice cover in spring and in the open basin, to late spring and summer shelf and slope open-water diatom blooms with Chl- a >5 μg L −1 . The microzooplankton community was dominated by large naked ciliates and heterotrophic gymnodinoid dinoflagellates. Significant, but low, rates of microzooplankton herbivory were found in half of the experiments. The maximum grazing rate was 0.16 d −1 and average grazing rate, including experiments with no significant grazing, was 0.04±0.06 d −1 . Phytoplankton intrinsic growth rates varied from the highest values of about 0.4 d −1 to the lowest values of zero to slightly negative growth, on average 0.16±0.15 d −1 . Light limitation in spring and post-bloom senescence during summer were likely explanations of observed low phytoplankton growth rates. Microzooplankton grazing consumed 0–120% (average 22±26%) of phytoplankton daily growth. Grazing and growth rates found in this study were low compared to rates reported in another Arctic system, the Barents Sea, and in major geographic regions of the world ocean.

Landscape features and sea ice influence nesting common eider abundance and dispersion

Factors that influence individual and colony spacing are still not well understood in many organisms. Common eiders ( Somateria mollissima (L. 1758)) nest on coastal islands and forage in intertidal and shallow subtidal waters. We considered several biotic and abiotic factors, their interactions, and how these might influence the distribution of eider colonies at several spatial scales in Labrador, Canada. At the island level, nest abundance was not related to intertidal prey density. At the 104 km2grid scale, eider nest abundance and the coefficient of dispersion (CD; the variance to mean ratio of colony size or grid cell, where CD indicates population dispersion) were negatively related to the number of islands. Spring ice cover was positively related to the number of islands but was negatively related to eider nest abundance and to CD. Ice cover – abundance and ice cover – CD were significant at two spatial scales (104 and 455 km2, respectively), but other relationships were weaker at the larger spatial scale. We hypothesize that during the spring, archipelagos with many islands trap ice, providing terrestrial predators access to nesting islands by acting as bridges and that increased predation reduces habitat quality causing nesting eiders to disperse. Our findings suggest that eiders respond to landscape features, including ice cover, a feature that is being influenced by climate change.

Seasonal and regional patterns in egg production of Calanus glacialis/marshallae in the Chukchi and Beaufort Seas during spring and summer, 2002

Understanding the physical and biogeochemical processes that control the exchange of biogenic carbon within and between the arctic shelves, slopes, and deep basins is a key objective of the Western Arctic Shelf-Basin Interaction program (SBI). Here, egg production (EP) of the dominant copepod Calanus glacialis/marshallae was used as an indicator of food limitation for the mesozooplankton community in the Chukchi and Beaufort Seas in spring and summer, 2002. Both C. glacialis and C. marshallae may occur in this region but the two cannot easily be differentiated visually. Four oceanographic regions were objectively identified that roughly corresponded to the different pathways in circulation of nutrient-rich Pacific water. A ‘transition’ region characterized by ‘older’ Pacific water was located at the shelfbreak and separated the nutrient-rich shelf water and the low-nutrient waters of the deep basin. The observed spatial pattern in EP in C. glacialis/marshallae in spring and summer resulted both from the different water mass environments and from the reproductive cycle of the species. EP was greater on the shelf than in the basin, corresponding to differences in body size and nitrogen condition factor (NCF) in females, while the egg viability was generally high throughout the study area. EP showed no relationship with low-chlorophyll a biomass under heavy ice-cover in spring, while a significant relationship was observed in the more open water in summer. Adult female carbon condition factor (CCF) was much higher in summer, reflecting the accumulation of lipids during the growth season. Small animals with a markedly greater NCF dominated on the shelf. The shelfbreak region contained a mixture of females from the shelf and the basin with intermediate sizes, conditions, and EP rates. The occurrence of water typical of the ‘transition’ shelfbreak region and elevated EP in C. glacialis/marshallae offshore on the Barrow Canyon and East Barrow sections indicated offshore transport of productive shelf water and the associated plankton community. The input of nutrient-rich Pacific water and accompanying elevated production to the northern Chukchi Sea and the Chukchi-Beaufort shelfbreak region may contribute to the reproductive success of C. glacialis/marshallae in this region.

Evaluation of North Water Spring Ice Cover from Satellite Photographs

Satellite photographs for 2 years (March-September) have been used to study ice cover in the polynia called "North Water," and to determine whether reliable ice maps could be made from satellite data without computer analysis. After early July the clouds became opaque and distinction between cloud and ice is impossible. It was concluded that ice distribution for short periods could best be obtained by careful photograph interpretation. The most persistent open water is found at the northern edge, at about 78° N. The southern ice edge is diffuse. The changes in ice cover in the North are mainly caused by freezing and melting, whereas ice transport is important in the southern area.