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The presence of the sea ice biomarker IP25 in Arctic marine sediments has previously been used as a proxy measure of past sea ice conditions in the Arctic. Although the sea ice diatom origin of IP25 was established previously, the nature of its production within sea ice, along with its transport through the water column to underlying sediments and its short-term preservation therein, had not been investigated in any significant detail. Variations in the concentration of the sea ice diatom biomarker IP25, were measured in sea ice collected from the eastern Beaufort Sea and Amundsen Gulf from January to June 2008. Temporal and vertical changes in IP25 concentrations were compared against other established indicators of sea ice algal production to determine, for the first time, that approximately 90% of the total sea ice IP25 accumulation occurred coincident with the ice algal bloom period. It was further established that IP25 biosynthesis was restricted, by sea ice porosity, to within the lower few centimetres of the sea ice and specifically to where brine volume fractions were >5%. Concentration differences of IP25 between sea ice and filtered seawater samples were also compared with those of established lipid indicators of algal production to estimate the dispersion of these lipids following seasonal sea ice melt. The largest concentration differences between sea ice and seawater samples were observed for IP25 and some other HBIs, consistent with a sea ice origin, while concentrations of fatty acids and sterols suggested contributions from both sea ice and phytoplankton. A novel analysis of a range of macrofaunal species revealed the presence of IP25 and other HBIs, with distributions somewhat resembling those observed in sea ice but more closely reflecting distributions of HBIs measured in sediments. As such, it is hypothesised that IP25 and HBI distributions in macrofaunal species reflect those of the sediments in which they live. The presence of IP25 and HBIs in macrofaunal species revealed, for the first time, a significant potential for biological cycling and storage of IP25 and other HBIs in the Arctic resulting from exposure during transport of the biomarker between sea ice and sediment. The observed presence of IP25 in 75% of the specimens investigated has presented important evidence for the potential of IP25 to act as a tracer of Arctic sea ice diet in the marine food web. Measurement of the downcore profiles of IP25 in shallow marine sediments alongside other biogeochemical parameters provided new evidence for the early diagenesis of this biomarker. Statistical correlations between some IP25 and Mn/Ti profiles (Station 405b; r = 0.89), that aid determination of the oxygen penetration depth, provided novel evidence for the partial degradation of IP25 (and other HBIs) in the upper sediment sections considered to be oxic. As such, it is suggested here, for the first time, that reactions under oxic conditions could be responsible for degradation of HBIs in some Arctic marine sediments, with the supply of organic carbon influential on the depth of oxygen penetration. The observations recorded in this thesis have therefore offered a much greater understanding of the concentration and distribution of IP25 and related lipids in a wide range of Arctic environments including sea ice, seawater, macrofauna and sediments, than was previously known. Since in most cases these observations represent the first of their kind, it is anticipated that the work carried out here will play an important role, forming the foundation of many important future studies.

Approved for public release; distribution is unlimited. / This study evaluates the latest Navy Operational Global Atmospheric Prediction System (NOGAPS) version 4.0 with a comparison to data collected during the Surface Heat Budget of the Arctic (SHEBA) project from October 1997 to October 1998. In particular, three periods from this year long study were the focus and included, a winter, spring, and summer case. For each of these cases the first 24-hour period of the forecasts were analyzed for any bias and root mean square difference from the SHEBA data. NOGAPS had no significant biases in pressure and wind speed. During the winter case, the NOPGAPS surface temperature remained near -28 C while observed temperature varied in response to cloud cover changes and was lower by 5.3 C on the average. During the spring the NOGAPS temperatures had a steady increase from -11 C until reaching the melt season temperature of 0 C 11 days earlier than observed. As a result of too warm a surface and less downwelling longwave radiation, the net longwave flux cooling was greater than observed, by an average of -12.4 Wm-2. The NOGAPS net shortwave radiation was greater than observed by an average of 62 Wm-2 for spring and 22.6 Wm-2 for summer. / Lieutenant, United States Navy

Graduation date: 1998

Graduation date: 1997

Graduation date: 1969

I studied the occurrence of two sympatric morphs of arctic charr, Salvelinus alpinus (L.) in Vatnshlidarvatn, a small shallow lake in NW Iceland. The arctic charr were subjectively distinguished by colour and appearance as brown morph or silver morph, and measured for morphological and life history characters. The study revealed the presence of two growth forms represented by the two morphs that differed in age and size at sexual maturation, reproductive investment, and time and place of spawning. The morphs differed significantly in gill raker number and morphometric characters related to manoeuvrability and cruising ability. Morphological segregation was established early in life and is most readily explained as developmental heterochrony. Both morphs were benthivorous, but could be segregated as diet specialist and generalist, with diet segregation being important only when food (especially the benthic crustacean Eurycercus spp.) was scarce, The occurrence of one abundant food resource, and lack of interspecific competition (no other fish species are present) may explain the different feeding strategies. The presence of "empty" niche should induce variability and divergence in morphology and life history to occupy available niche space. / Graduation date: 1997

A total of 5065 specimens (5018 valves of bivalve and 47 gastropod shells) have been identified and classified into 27 species from 55 samples collected from raised glaciomarine and estuarine sediments, and glacial tills. The bivalves <i>Hiatella arctica</i>, <i>Mya truncate</i>, <i>Astarte borealis</i>, and <i>Serripes groenlandicus</i> are the most common species. Our samples record the dominance of infaunal suspension-feeders that are most abundant on soft substrates typically occurring in nearshore environments. The dominance of bivalves with respect to gastropods reflects an averaged record of the fossil assemblages inhabiting the high latitude nearshore environments. Six unique associations, which are comparable to the composition of modern communities inhabiting in fiords and on continental shelf from Canadian high arctic, and three distinctive taxa groups (deposit feeders, suspension-feeders, and rare taxa) are recognized by cluster analysis and Multidimensional Scaling conducted on presence-absence data. The trophic composition of paleocommunities in this study is as follows: suspension-feeders > deposit feeders > carnivores > browsers. The occurrence of <i>Mya pseudoarenaria</i> in fossil assemblages indicates an age of the fossils around early Holocene. <p>Most of the samples are not substantially transported nor significantly reworked. Shell disarticulation and fragmentation can result from sea ice scouring of the seafloor and the development of permafrost in raised marine sediments. The degree of shell disarticulation for the four most common taxa is generally low which likely reflects high sedimentation rates and rapid burial in nearshore environments, especially those from glaciomarine silts and estuarine deposits. Four common species exhibit different preservation potential based the degree of fragmentation and disarticulation (Serripes < Mya < Hiatella < Astarte). Shells with high (or low) degree of fragmentation for single species (i.e. Hiatella) also correspond to different energy conditions of the associated sediments facies from which the shells are recovered. The general absence of strongly bioeroded or encrusted shells among samples suggests rapid burial of the shells with only limited exposure on the sediment surface, or the absence of grazing, boring or encrusting taxa in the environment that is dominated by infaunal habit of most of the taxa represented in the shell assemblages. <p>Four taphofacies are recognized by cluster analysis on the basis of four taphonomic variables (fragmentation, corrasion, bioerosion, and encrustation) characterized by poor preservation, fair preservation, fair-good preservation, and fair preservation with poor corrasion respectively. Faunal succession and paleo-marine environments during the deglaciation in early Holocene are reconstructed from the seven sedimentation facies (glacial, beaches, shallow marine, proglacial, shallow marine or estuarine - pebbly sand and gravel with algal debris, shallow marine or estuarine - pebbly silt with algal debris, shallow marine or estuarine - interbedded silt and sand).

In this study, total As (T-As) levels in superpermafrost groundwater at a site in the High Arctic doubled over the course of the summer thaw. This increase was not due to snow input, as levels in snow were negligible. This increase in T-As did not correspond with a decrease in Eh, nor a rise in soluble Fe(II). It did, however, correspond with a shift in As speciation from arsenate to arsenite suggestive of reducing conditions. In the absence of predominant reducing conditions, the highly alkaline nature of the melting snow and concomitant large input of HCO3- may have played an important role in the increase of As in groundwater during the summer thaw. <p>Laboratory studies found that dissolved As (D-As) release under anaerobic conditions depended on the organic matter content of soil, with organic soils releasing D-As under reducing conditions and mineral soils sequestering D-As. In temperate soils, the release of D-As from organic soils is greatly accelerated due to the activity of anaerobic microbes. In northern soils, the same phenomenon may occur, with greater microbiological activity in organic soils where there is more labile C and nutrients than in mineral soil. <p>The sequestration of As in mineral soil is postulated to have occurred due to preferential sorption of arsenite to ferrihydrite or possibly to green rust minerals present under anaerobic conditions. Supporting this, arsenite sequestration occurred to a greater extent compared to arsenate, which is in agreement with the relative affinities of these two species for ferrihydrite. <p>Evidence from this study suggests that the As cycle on Truelove Lowland is dominated by the desorption of As due to HCO3- input each year during the spring melt linked to the sorption of As to ferrihydrite or green rust present in underlying mineral soils. The sequential thawing of the soils active layer and large inputs of HCO3- are unique to northern environments. Thus, this delicate balance of two sorbing processes should be born in mind in northern development. Large inputs of soluble organic matter or nutrients could cause increased solubilization and mobility of D-As during the summer thaw when soils become flooded.

A total of 5065 specimens (5018 valves of bivalve and 47 gastropod shells) have been identified and classified into 27 species from 55 samples collected from raised glaciomarine and estuarine sediments, and glacial tills. The bivalves <i>Hiatella arctica</i>, <i>Mya truncate</i>, <i>Astarte borealis</i>, and <i>Serripes groenlandicus</i> are the most common species. Our samples record the dominance of infaunal suspension-feeders that are most abundant on soft substrates typically occurring in nearshore environments. The dominance of bivalves with respect to gastropods reflects an averaged record of the fossil assemblages inhabiting the high latitude nearshore environments. Six unique associations, which are comparable to the composition of modern communities inhabiting in fiords and on continental shelf from Canadian high arctic, and three distinctive taxa groups (deposit feeders, suspension-feeders, and rare taxa) are recognized by cluster analysis and Multidimensional Scaling conducted on presence-absence data. The trophic composition of paleocommunities in this study is as follows: suspension-feeders > deposit feeders > carnivores > browsers. The occurrence of <i>Mya pseudoarenaria</i> in fossil assemblages indicates an age of the fossils around early Holocene. <p>Most of the samples are not substantially transported nor significantly reworked. Shell disarticulation and fragmentation can result from sea ice scouring of the seafloor and the development of permafrost in raised marine sediments. The degree of shell disarticulation for the four most common taxa is generally low which likely reflects high sedimentation rates and rapid burial in nearshore environments, especially those from glaciomarine silts and estuarine deposits. Four common species exhibit different preservation potential based the degree of fragmentation and disarticulation (Serripes < Mya < Hiatella < Astarte). Shells with high (or low) degree of fragmentation for single species (i.e. Hiatella) also correspond to different energy conditions of the associated sediments facies from which the shells are recovered. The general absence of strongly bioeroded or encrusted shells among samples suggests rapid burial of the shells with only limited exposure on the sediment surface, or the absence of grazing, boring or encrusting taxa in the environment that is dominated by infaunal habit of most of the taxa represented in the shell assemblages. <p>Four taphofacies are recognized by cluster analysis on the basis of four taphonomic variables (fragmentation, corrasion, bioerosion, and encrustation) characterized by poor preservation, fair preservation, fair-good preservation, and fair preservation with poor corrasion respectively. Faunal succession and paleo-marine environments during the deglaciation in early Holocene are reconstructed from the seven sedimentation facies (glacial, beaches, shallow marine, proglacial, shallow marine or estuarine - pebbly sand and gravel with algal debris, shallow marine or estuarine - pebbly silt with algal debris, shallow marine or estuarine - interbedded silt and sand).