The present study contains a calculation and discussion of meridional advection of water vapour on a daily basis across three latitude circles (65°N., 70°N., 80°N.) for the months of January and July, 1958. [...]

No description available.

No description available.

The seasonal cycle of snow and sea ice is a fundamental feature of the Arctic climate system. In the Northern Hemisphere, about 55 million km2 of sea ice and snow undergo complete melt and freeze processes every year. Because snow and sea ice are much brighter (higher albedo) than the underlying surface, their presence reduces absorption of incoming solar energy at high latitudes. Therefore, changes of the sea-ice and snow cover have a large impact on the Arctic climate and possibly at lower latitudes. One of the most important determining factors of the seasonal snow and sea-ice cover is the timing of the seasonal melt-freeze transitions. Hence, in order to better understand Arctic climate variability, it is key to continuously monitor these transitions. This thesis presents an algorithm for obtaining melt-freeze transitions using scatterometers over both the land and sea-ice domains. These satellite-borne instruments emit radiation at microwave wavelengths and measure the returned signal. Several scatterometers are employed: QuikSCAT (1999–2009), ASCAT (2009–present), and OSCAT (2009–present). QuikSCAT and OSCAT operate at Ku-band (λ=2.2 cm) and ASCAT at C-band (λ=5.7 cm), resulting in slightly different surface interactions. This thesis discusses these dissimilarities over the Arctic sea-ice domain, and juxtaposes the time series of seasonal melt-freeze transitions from the three scatterometers and compares them with other, independent datasets. The interactions of snow and sea ice with other components of the Arctic climate system are complex. Models are commonly employed to disentangle these interactions. But this hinges upon robust and well-formulated models, reached by perpetual testing against observations. This thesis also presents an evaluation of how well eleven state-of-the-art global climate models reproduce the Arctic sea-ice cover and the summer length—given by the melt-freeze transitions—using surface observations of air temperature. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: In press. Paper 4: Submitted.</p>

This thesis characterizes the cycling of carbon, nitrogen and silicon by marine polar diatoms through the aid of a field study and a laboratory study. Field studies were conducted along a transect from Victoria, Canada to Barrow, Alaska and particulate carbon, nitrogen and silicon, chlorophyll a, nitrate, phosphate, silicic acid, and carbon and nitrogen incorporation, along with biogenic silica net incorporation were measured. Total primary production was lowest in the NE Pacific (0.3 to 1.0 mmol m-3 day-1), with new production contributing 17 to 38% of total production. Biogenic silica net incorporation in the upper 250 m of the water column in the NE Pacific was relatively low (0 to 0.12 mmol m-3 day-1), but positive, indicating the opportunity for export from the euphotic zone. Total primary, new production and production by siliceous plankton was highest in the Chukchi Sea, due to the influence of nutrient influx from the Anadyr Stream. Total primary production ranged from 1.0 to 3.2 mmol m-3 day-1, new production contributed as much as 56% of total production, and the production by siliceous phytoplankton was as high as 5.6 mmol m-3 day-1. Siliceous biomass was usually recycled in the upper water column of the Bering and the Chukchi Seas, in contrast to the NE Pacific. The interference of lithogenic material on the measurement of biogenic silica was explored using data from the Bering and Chukchi Seas. Results show that lithogenic interference is location specific. Sediment clay composition data should be considered when high concentrations of lithogenic silica are present. The laboratory study examined the effects of different irradiance and temperature conditions on two polar diatom species: Thalassiosira antarctica and Porosira glacialis. Temperature and irradiance had species-specific effects on the cellular content of carbon, nitrogen and silicon. The relationship between growth rate and silicon content for T. antarctica showed that silicon content increased as growth rate decreased, which is in agreement with previous studies. However, this relationship did not hold for P. glacialis at low temperatures. These species-specific effects complicate the understanding of how environmental change will influence phytoplankton populations in Arctic and sub-Arctic marine areas. In general, primary production was lower in the Bering and Chukchi Seas when compared to previous studies, however it is unknown whether differences are due to interannual variability or a trend of decreasing production. Data from both the field and laboratory component indicate a high amount of biological silicon cycling in polar environments. This study represents the first time net silicon incorporation has been measured as far north as the Chukchi Sea.

The IPCC report from 2013 predicts radical temperature changes in the world the coming years, with a melting ice cap in the Arctic as consequence. According to geological research made by institutes and scholars from the Arctic states the Arctic is likely to hold the last remaining oil and gas resources of the world. The melting ice cap opens up for resource exploitation and for new naval transportation routes between Asia and Europe and North America. There is a debate over what geopolitical implications these natural resources and the new transportation routes will get for the surrounding Arctic states since the existing international regulations in some areas are inadequate. This debate is divided into two camps; one side argues that the Arctic states will act cooperatively when exploiting the resources and navigating the new transportation routes, while the other side predicts violent and conflictive state behavior. The objective of this study is to analyze existing and potential conflicts in the Arctic through the perspective of leading international relations theories in order to make projections of potential Arctic developments. As analytical tool the study applies a conflict analysis framework to structure and categorize both the findings and the analytical chapter. In this qualitative and abductive study the data has been collected through mainly official state and private documents and text analysis of these documents have been used as method. The study concludes that a combination of both cooperation and competition is likely to occur in the Arctic in future, but cooperation will be the first alternative of choice for states rather than conflict.

The Arctic charr (Salvelinus alpinus) is a top predator in northern lakes and accumulates persistent lipophilic contaminants. Toxaphene, a major organochlorine contaminant in Arctic charr, is known to be acutely toxic to fish but the effects of dietary exposure have not been examined. Furthermore, lake-resident Arctic charr are frequently infected with larvae of the cestode, Diphyllobothrium dendriticum. The objective of this study was to investigate the effects of toxaphene exposure on Arctic charr growth, nutritional quality, physiology, and susceptibility to infections of D. dendriticum. A preliminary experiment found no effect of toxaphene on charr visceral organ and fat weights, plasma Vitamin A and E and plasma cortisol, although dominance hierarchies within groups may have masked treatment effects. For the main experiment, hatchery-reared Arctic charr were subjected to one of four treatments: (i) a single oral dose of corn oil (control); (ii) a single oral dose of 10 mug/g wet weight toxaphene dissolved in corn oil; (iii) exposure to 15 larval D. dendriticum; and (iv) a combination of both. (Abstract shortened by UMI.)

No description available.

Given the pace of climate change in the Arctic, it is vital to better constrain terrigenous dissolved organic matter (tDOM) fluctuations in large Arctic Rivers and the role that climate change may bring to tDOM inputs into the Arctic Ocean and to the global carbon cycle. This project uses the optical properties of chromophoric dissolved organic matter (CDOM) to investigate the quality, quantity and fate of dissolved organic matter (DOM) in large Arctic Rivers and the interior Arctic Basin. In large rivers surrounding the Arctic, peak discharge CDOM is largely derived from fresh terrestrial plant material whereas during base flow the CDOM pool has a greater microbial imprint, particularly in the Mackenzie. The higher microbial imprint in the Mackenzie can be explained by longer water residence times, which may be important in a warming climate where increased precipitation rates will likely lead to increased hydrological connectivity and therefore longer water residence times. In surface waters of the Canadian Archipelago, 17 % of the DOM pool is of terrestrial origin, even though waters are diluted with sea ice melt, suggesting the likelihood of a subsurface plume of tDOM entrained within river runoff from Arctic Rivers. In the interior Arctic, an elevated terrestrial CDOM signal in the Eurasian Basin (EB) points to the presence of Eurasian river CDOM entrained within river runoff in the Transpolar Drift. In contrast, autochthonous/microbial CDOM sources become more important the Canadian Basin (CB) and the terrestrial CDOM signal is much lower relative to the EB. A good constraint on the nature and distributions of freshwater (FW) in the Arctic Ocean is paramount to understand the role climate change may play for the Arctic’s hydrological cycle. During this study, we used the spatial patterns of terrestrially derived CDOM to better understand the distribution and nature of river runoff across the upper Arctic Basin. This study illustrates the usefulness of CDOM to finger-print water masses within the Arctic Ocean and shows promise to improve our understanding of upper Arctic Ocean ventilation patterns.

The predicted increase in atmospheric temperatures is expected to affect the turnover of soil organic carbon in permafrost soils through modifications of the soil thermal regime. However, the tundra biome is formed of a mosaic of diverse landscape types with differing patterns of soil organic carbon storage and partitioning. Among these, differences in e.g. vegetation diversity and soil movements due to freeze-thaw processes are of main importance for assessing potential C remobilization under a changing climate. In this study, we described the storage of soil organic carbon (SOC) and the aboveground phytomass carbon in relation to geomorphology and periglacial features for two areas on Taymir Peninsula (Arctic Russia). An average of 29.5 kg C m-2, calculated by upscaling with a land cover classification, is stored in the upper soil meter at these two study sites. The mean C phytomass storage amounts to ca.0.406 Kg C m-2, or only 1.38% of the total SOC storage. The topography, at different scales, plays an important role in the carbon partitioning. High amounts of soil organic carbon are found in highland areas and within the patterned ground features found in peatlands. The highest amounts of aboveground phytomass carbon are found in deciduous shrubs and moss layers. The large variability in carbon distribution within land cover types among the sites reveals the challenge of upscaling the carbon storage values over the Arctic and thus highlight the necessity to carry out detailed field inventories in this region.