Chromosomes of the bowhead whale (Balaena mysticetus linnaeus)

Thesis (M.S.) University of Alaska Fairbanks, 1979The somatic chromosomes of the bowhead whale, Balaena mysticetus, are described for the first time using homogeneous staining and trypsin G-banding. The diploid chromosome number in all cells studied is 42. The bowhead karyotype retains many features of the general 2n = 44 cetacean karyotype from which it is derived, yet it is the first mysticete for which a chromosome number other than 2n = 44 has been reported. The advanced karyotype of the bowhead may reflect greater anatomical specialization of this whale than of other mysticetes. Cytogenetic data for cetaceans are reviewed within the framework of a model of speciation in sympatry

Fear of the dark in children: is stationary night blindness the cause?

No abstract available

Ice Dynamics and Surface Glaciology along US ITASE Traverse Routes in East Antarctica

This award supports a series of field measurements that will improve our understanding of the East Antarctic ice sheet. The objectives of this project are to take advantage of the overland traverse logistics framework provided by US ITASE and to collaborate with other US ITASE investigators to calculate rates of ice sheet thickness change (mass balance) on domes, along elevation contours and along flow lines in East Antarctica using precise global positioning system methods. In addition, the variability (both spatial and temporal) in snow accumulation rates will be assessed using shallow ice cores and ground-penetrating radar profiling, and will provide the capability to deduce true past climate variation in accumulation rates in ~200-year long ice core records by measuring ice motion and upglacier gradients in accumulation rate. Study patterns and causes of the onset of streaming flow in the catchments of selected large outlet glaciers draining through the Transantarctic Mountains will also be determined. The work will be conducted along the proposed US ITASE traverse route from Taylor Dome to South Pole. This route travels across the East Antarctic plateau, roughly parallel to the Transantarctic Mountains. Orthogonal satellite traverses are planned, each of which will follow a flow line of selected major outlet glaciers. The expected results include mass balance determinations for the Ross Ice Shelf sector of the East Antarctic Ice Sheet, an improved snow accumulation map for portions of East Antarctica, the deconvolution of ice dynamics effects from climate effects in ice core records, and an analysis of glaciological conditions near the onset of streaming flow leading to large outlet glaciers. The broader impacts of the proposed work include the collaboration with a multidisciplinary group of polar scientists, support of a graduate student and the production of results that will lead to an improved understanding of the Earth system from which sound planning and policy decisions can be based

Mass Balance and Accumulation Rate Along US ITASE Routes

The primary research activities in this project involved our participation in the four US ITASE field seasons (1999-2003). As part of the field program we collected ~5,500 km of continuous, precise GPS data along the traverse route. These geodetic data are used by ourselves and several other US ITASE investigators. We also installed 15 new mass balance (coffee can) stations in rarely visited regions of West and East Antarctica. Several shallow firn cores were collected to study local variability in snow accumulation around deeper 200-year ice core sites. As part of our collaboration with NASA, we performed detailed 3-dimensional mapping of surface topography and shallow stratigraphy to validate and better interpret results from the ICESat mission. Mass balance marker sites installed during earlier field seasons were visited and resurveyed. Three automatic weather stations close to the proposed Inland WAIS deep drilling site and operated for two years before being removed. The project supported the thesis work of one PhD student. Results were presented at several national and international meetings (WAIS, SCAR/ITASE, MGM, IGS, AGU) and published in peer-reviewed scientific journals

Glaciology of Blue Ice Areas in Antarctica

A \u27horizontal ice core\u27 was collected at the Mount Moulton blue ice field in West Antarctica and preliminary analyses of the sample material suggests that a ~500 kyr climate record is preserved in the ice at this site. This award will contribute to the understanding of the Mt Moulton record by assessing the potential for ice-flow induced deformation of the stratigraphic profile. In addition, this award builds on the recognition of blue ice areas as archives of long climate records by conducting reconnaissance studies for a potential horizontal ice core location at the Allan Hills in East Antarctica. The objectives of this project are to contribute to the glaciological understanding of blue ice areas in Antarctica. Ice flow conditions at the Mt Moulton blue ice field will be studied to assess the possibility that the stratigraphic record has been deformed and reconnaissance of a potential horizontal ice core site in the Allan Hills blue ice field will also be accomplished. Short field programs will be undertaken at each location to collect relevant measurements of ice flow and subglacial topography, and to conduct sampling of material that will enable the preservation of the stratigraphic sequences to be assessed

Exploring site formation and building local contexts through wiggle-match radiocarbon dating: re-dating of the Firth of Clyde Crannogs, Scotland

There are at least four wooden intertidal platforms, also known as marine crannogs, in the Firth of Clyde, on the west coast of Scotland. The interpretation of these sites partly depends on their dating and, if coeval, they could point to the presence of a native maritime hub. Furthermore, the spatial coincidence with the terminus of the Antonine Wall has led to speculation about the role they may have played in Roman-native interaction during the occupation of southern Scotland in the early first millennium cal ad. Hence, a better absolute chronology is essential to evaluate whether the marine crannogs were contemporary with one another and whether they related to any known historic events. This article presents results of a wiggle-match dating project aimed at resolving these uncertainties at two of the sites in question, Dumbuck and Erskine Bridge crannogs. The results show that the construction of these sites pre-date direct Roman influence in Scotland. Furthermore, the results indicate that the two sites were built at least 300 years apart, forcing us to consider the possibility that they may have functioned in very different historical contexts. Other findings include technical observations on the fine shape of the radiocarbon calibration curve near the turn of the first millennia bc/ad and potential evidence for persistent contamination in decayed and exposed sections of waterlogged alder

Collaborative Research: High-resolution studies of glacier dynamics at two major outlet glaciers in East Greenland

The Principal Investigators request support for an interdisciplinary, high-resolution study involving remote sensing and field investigations at two of Greenland\u27s largest outlet glaciers. The study of the Helheim and Kangerdlugssuaq Glaciers will integrate seismological, glaciological, and geodetic observations to build an understanding of flow dynamics at major outlet glaciers, which represent a critical junction between the atmosphere, cryosphere, and hydrosphere. The project would be the first long-term occupation of an outlet glacier by a GPS receiver network, and would address questions of flow variation on earthquake to interannual time scales. Recent discoveries have made it clear that our understanding of the dynamics of flow at large outlet glaciers is limited and inadequate for understanding the ways in which the outlet glaciers, and the ice sheets they drain, respond to external forcings. The spectrum of timescales over which significant velocity variations in outlet glacier flow can occur appears to be much broader than previously believed, with significant variations occurring on timescales of 10s of seconds to several years. Analysis of glacial earthquakes suggests that significant volumes of ice may move at speeds 1000 times faster than their average annual velocities for periods of a minute or two and a doubling of average annual flow speeds over only a few years has been observed at some glaciers. Multiple observations now indicate that glacier flow behavior can respond quickly to environmental changes, including rapid climate change. It is not currently clear, however, what mechanisms or combination of mechanisms allow for, or drive, the temporal variations, nor is it clear how variations in flow behavior at different timescales are related to one another. Understanding the changes in force balance that control variations across the range of timescales from minutes to years requires observations at higher resolution in both space and time than are currently available, and achieving a comprehensive picture of the interactions between short- and long-timescale processes, and between external forcings and glacier flow behavior, requires the integration of data and expertise from several traditionally separate disciplines.. Intellectual Merit. The research will lead to a greatly improved understanding of the dynamics of flow at the large, fast-moving outlet glaciers that drain the Greenland ice sheet and of the temporal variability in their rates and modes of flow. It will provide insight into the processes controlling glacial earthquakes and possible connections between glacial-earthquake activity and global climate change.Broader Impacts. Understanding the controls on flow configuration at major outlet glaciers, and the timescales over which they may respond to climatic forcing, is of great importance for proper modeling of systems affected by the transfer of fresh polar meltwater to the world\u27s oceans. A better understanding of glacier and ice-sheet response to climate change will allow for improvements in modeling of the coupled ice ocean atmosphere system, and of its interactions with the solid Earth. The geodetic instrumentation and processing techniques developed under this proposal will benefit researchers in a variety of environments such as glacier and volcano monitoring involving rapid, large-scale motions and the risk of instrument loss

Collaborative Research: Byrd Glacier Flow Dynamics

This award supports a project to understand the flow dynamics of large, fast-moving outlet glaciers that drain the East Antarctic Ice Sheet. The project includes an integrated field, remote sensing and modeling study of Byrd Glacier which is a major pathway for the discharge of mass from the East Antarctic Ice Sheet (EAIS) to the ocean. Recent work has shown that the glacier can undergo short-lived but significant changes in flow speed in response to perturbations in its boundary conditions. Because outlet glacier speeds exert a major control on ice sheet mass balance and modulate the ice sheet contribution to sea level rise, it is essential that their sensitivity to a range of dynamic processes is properly understood and incorporated into prognostic ice sheet models. The intellectual merit of the project is that the results from this study will provide critically important information regarding the flow dynamics of large EAIS outlet glaciers. The proposed study is designed to address variations in glacier behavior on timescales of minutes to years. A dense network of global positioning satellite (GPS) instruments on the grounded trunk and floating portions of the glacier will provide continuous, high-resolution time series of horizontal and vertical motions over a 26-month period. These results will be placed in the context of a longer record of remote sensing observations covering a larger spatial extent, and the combined datasets will be used to constrain a numerical model of the glacier\u27s flow dynamics. The broader impacts of the work are that this project will generate results which are likely to be a significant component of next-generation ice sheet models seeking to predict the evolution of the Antarctic Ice Sheet and future rates of sea level rise. The most recent report from the Intergovernmental Panel on Climate Change (IPCC) highlights the imperfect understanding of outlet glacier dynamics as a major obstacle to the production of an accurate sea level rise projections. This project will provide significant research opportunities for several early-career scientists, including the lead PI for this proposal (she is both a new investigator and a junior faculty member at a large research university) and two PhD-level graduate students. The students will be trained in glaciology, geodesy and numerical modeling, contributing to society\u27s need for experts in those fields. In addition, this project will strengthen international collaboration between polar scientists and geodesists in the US and Spain. The research team will work closely with science educators in the Center for Remote Sensing of Ice Sheets (CReSIS) outreach program to disseminate project results to non-specialist audiences

Topographic Control of Regional Accumulation Rate Variability at South Pole and Implications for Ice-Core Interpretation

Snow-accumulation rates are known to be sensitive to local changes in ice-sheet surface slope because of the effect of katabatic winds. These topographic effects can be preserved in ice cores that are collected at non-ice-divide locations. The trajectory of an ice-core site at South Pole is reconstructed using measurements of ice-sheet motion to show that snow was probably deposited at places of different surface slope during the past 1000 years. Recent accumulation rates, derived from shallow firn cores, vary along this trajectory according to surface topography, so that on a relatively steep flank mean annual accumulation is similar to 18% smaller than on a nearby topographic depression. These modern accumulation rates are used to reinterpret the cause of accumulation rate variability with time in the long ice-core record as an ice-dynamics effect and not a climate-change signal. The results highlight the importance of conducting ancillary ice-dynamics measurements as part of ice-coring programs so that topographic effects can be deconvolved from potential climate signals

Cytogenetics and sex determination in collared lemmings

Thesis (Ph.D.) University of Alaska Fairbanks, 1989Collared lemmings (Dicrostonyx groenlandicus rubricatus) from northeastern Alaska were found to have sex chromosomes that differ from those of their Siberian congeners, because of fusion to a particular pair of autosomes. But, as in Siberian lemmings, breeding experiments showed that sex determination involves an X-linked "male-repressor," which causes carriers to develop as fertile females, despite the presence of a Y chromosome. Genotypic frequencies in offspring are consistent with Mendelian expectations of such a system, hence natal sex ratios normally favor females. X-linkage of the male-repressor in Siberia and in Alaska indicates that the gene is probably located on the "original" arms of the X chromosome rather than on the fused autosomal arms, which differ on the two continents. One consequence of the autosomal fusion to the sex chromosomes is that deleterious recessive alleles on the autosome fused to the X chromosome are more resistant to selection than at truly autosomal loci. Another consequence is that, because males are heterozygous for loci fused to the sex chromosomes, they are more resistant to inbreeding depression than XX females. One inbred line produced a natal sex ratio of 67% males. The male-bias probably resulted from loss of the male-repressor and from a lethal carried on the formerly autosomal arm of the X chromosome. As inbreeding coefficients approached 0.3, the lethal would have been homozygous in half of the homogametic (female) zygotes. This phenomenon may explain the excess of males and XY females observed in earlier work. Also, if under the natural mating system, inbreeding depression limits fitness, then fusions of autosomal chromatin to the heterochromosomes could be an adaptation to reduce inbreeding depression in heterogametic individuals. Some other genetic features of collared lemmings do suggest endogamy. Female-biased sex ratios can evolve when mating occurs between neighboring individuals who are more related than if mating occurred randomly. Two proposed sources of such "viscous" gene flow in lemmings are cyclical changes in population density and mosaic habitat. Alternatively, could climate may favor winter aggregation and inhibit the dispersal of winter-born offspring, which would mature and mate with close relatives; dispersal and outbreeding would occur in summer. Thus, inbreeding would be seasonal rather than density-dependent and it is unnecessary to suppose discontinuous habitat