Browsing by Subject "Arctic"
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Item Alternative methods for monitoring polar bears in the North American arctic(2013-12) Stapleton, SethBecause polar bears (Ursus maritimus) are dependent on sea ice, climate change poses a significant threat to their long-term existence. The forecasted impacts of sea ice loss are circumpolar, but to date, effects have been documented in only a few, well-studied populations. Data demonstrating the impacts of climate change are less conclusive or simply lacking elsewhere. In general, current inventory regimes do not enable monitoring with enough regularity to meet the information needs of decision-makers. This reality, combined with pressures from northern communities to reform invasive research techniques (i.e., capture and marking), provided the backdrop for my dissertation. My objective was to implement and evaluate novel, efficient and broadly applicable methods for monitoring polar bears. I first conducted comprehensive aerial (helicopter) surveys of the Foxe Basin population in Nunavut, Canada during the summer, ice-free season. This work demonstrated the utility of the method for estimating the abundance of polar bear populations on land and provided a model for applications in other seasonally ice-free populations. I applied this framework to a neighboring population (Western Hudson Bay) and compared the result to an estimate obtained from physical mark-recapture. This comparison suggested negative bias in the mark-recapture estimate due to spatially limited sampling and resultant capture heterogeneity. Next, I assessed the potential for employing aerial surveys on sea ice in springtime. Although results suggest that detection can be estimated with adequate precision, logistical constraints may hinder the ability to obtain a representative density estimate during springtime. Monitoring programs based on aerial surveys can be designed with sufficient power (>0.8) to detect declines of 40% and 50% over 15- and 30-year periods, with costs comparable to mark-recapture. Costs may be significantly diminished and safety concerns alleviated, however, if bears could be monitored with satellite imagery. I evaluated this technique in a low topography, ice-free setting. Results indicate that bears were reliably identified on imagery, and an estimate of abundance was highly consistent with an independent aerial survey.Item Effect of topography and glaciation history on the movement of carbon and nitrogen within arctic hillsides.(2010-04) Whittinghill, Kyle A.The transport of dissolved organic matter (DOM) down hillslopes to aquatic ecosystems has important implications for both terrestrial and aquatic primary productivity. DOM is an important energy and nutrient source for both terrestrial and aquatic microbes. Within watersheds, physical, chemical, and biological processes transform DOM, but it not well known how landscape heterogeneity may affect these processes in arctic watersheds. In the northern foothills of the Brooks Range, expansion and contraction of mountain glaciers over the last several ice ages have created a mosaic of landscape ages with similar climate and vegetation. My research indicates that younger landscapes (<50,000yrs) have significantly lower pH, 10x higher exchangeable base cation concentrations, and significantly lower rates of DOM production and microbial respiration than older landscapes, which could significantly affect fluxes of carbon and nutrients across the landscape. At the watershed scale, I examined patterns in soil and stream water concentrations of DOM within hillslopes across the chronosequence. I found that while concentrations of dissolved organic carbon decreased significantly moving downslope from the hilltop to the stream; dissolved organic nitrogen concentrations remain similar within the hillslope, but are significantly different among landscape ages. I also used a variety of indices to examine spatial patterns in the biodegradability of DOM within hillslopes and among landscape ages in northern Alaska. My results suggest the low biodegradability of DOM found in streams and rivers in the region is not due to microbial processing of labile DOM in terrestrial ecosystems, but rather to production of recalcitrant DOM throughout the landscape.Item Effects of environmental temperature on biology of cold-adapted Chironomidae (Diptera) from Minnesota and Iceland(2022-10) Nyquist, CorrieChironomids are an abundant and speciose family of aquatic flies which dominate freshwater environments globally. Additionally, chironomids are important food sources for fish and can be used as bioindicators of water quality. This family includes species that are adapted to emerge as adults in winter and under cold conditions across the globe. Both air and water temperatures influence these insects since they grow in aquatic habitats and then emerge as terrestrial adults. However, little research has focused on the effects of thermal heterogeneity in shaping community structure along stream length, how stream temperatures may influence thermal acclimatization in adult chironomids, and the impacts of warm temperature exposure on biology of Arctic, winter-active chironomids. These questions become significant considering climate change since warming temperatures will threaten aquatic systems and cold-adapted organisms including cold-adapted chironomids. The goal of this dissertation was to investigate the influence of water temperature on winter emerging chironomid species composition and air temperature on adult Arctic chironomid lifespan and reproduction. Field work investigating thermal heterogeneity in streams was conducted in Minnesota. Collections of pupal exuviae along the length of thermally variable groundwater-fed streams revealed thermal portioning in taxa along stream length. Thermal partitioning in chironomids indicates that chironomids develop in and emerge from different thermal regimes, and, thus, may display developmental acclimatization to warm temperatures if they emerge from warm springs. Chironomids were collected from geothermally heated and cold springs in southwestern Iceland and placed into warm and cold incubation treatments. Results indicate that chironomids with long degree-day requirements emerging from warm springs have a maximized lifespan under both cold and warm air temperatures. Investigations of winter-active chironomids have been conducted in Europe and North America with little work focused on the Arctic. Iceland, a near Arctic country, faces increasing climate change threats and, thus, documenting warming effects on cold-adapted biota is essential. Winter-active chironomids were documented in Iceland for the first time and investigations of longevity and oviposition timing revealed susceptibility to warm air temperatures in winter emerging Icelandic chironomids. Chironomids comprise a large portion of aquatic food webs, and in Arctic regions, are the predominant aquatic insects. Investigating how environmental conditions control both community composition and population dynamics will further the conservation of cold-water systems by increasing the understanding of how climate change may impact cold-adapted biota.Item The Vulnerability of Northern High-Latitude Ecosystems to Climate and Disturbance-Induced Change(2018-06) Pastick, NealArctic and boreal regions have experienced unprecedented changes in recent decades as the result of climate change. Increasing air temperatures have led to widespread warming and degradation of permafrost, significant shifts in vegetation composition and productivity, and increases in disturbance frequency and extent that can have profound impacts on ecosystems and human populations across the globe. Despite a legacy of studies describing the heightened sensitivity of arctic and boreal ecosystems to change, there has not been a comprehensive assessment of historical and projected trends in landscape properties, disturbances, and drivers of change throughout all of Alaska. Such an assessment is immensely challenging because of spatially-heterogeneous dynamics and interactions among numerous factors that influence ecosystems throughout the State. Consequently, additional research is needed to better characterize permafrost-affected landscapes and their potential response to further perturbations. This dissertation presents important improvements in the mechanistic understanding and characterization capabilities of changing permafrost landscapes by combining field measurements, time series analyses, climate reanalysis data, and remote sensing into an integrated modeling framework. The primary goal is to improve understanding of how and why globally significant permafrost landscapes are changing by means of: (1) Characterizing climate, permafrost, disturbance, and vegetation dynamics that exert strong controls on energy, water, and biogeochemical cycling; (2) Quantifying underlying drivers of change related to contemporary trends in land and water surfaces observed by remote sensing; and; (3) Providing novel approaches and baseline information to fill critical observational gaps identified by the remote sensing community and permafrost and ecosystem scientists. This research supports the science priorities of federal agencies (e.g. United States Geological Survey, National Aeronautics and Space Administration) and techniques and results are highly relevant to climatic, hydrologic, ecologic, topographic, and cryospheric studies. This research provides critically needed information on the temporal and regional distribution of landscape properties and conditions, which is instrumental in determining the vulnerability and resilience of northern high-latitudes regions to climate and disturbance-induced change, and benefits both the research community and the policy community in the management of Arctic and boreal landscapes.