University of Maine

About: University of Maine is a education organization based out in Orono, Maine, United States. It is known for research contribution in the topics: Population & Ice sheet. The organization has 8637 authors who have published 16932 publications receiving 590124 citations. The organization is also known as: University of Maine at Orono.

Paleoclimatology and paleo‐oceanography of the Norwegian and Greenland seas: glacial‐interglacial contrasts

Abstract: Synoptically mapped faunal abundance and faunal composition data, derived from a suite of 24 Norwegian Sea cores, were used to derive sea-surface temperatures for the last glacial maximum (18,000 B.P.), the last interglacial (120,000 B.P.), and isotope stage 5a (82,000 B.P.). Surface circulation and ice cover reconstructions for these three times, deduced from the sea-surface temperatures, suggest the following conclusions: (1) During glacial periods, Norwegian Sea surface circulation formed a single, sluggish, counterclockwise gyre that was caused by wind drag on the ubiquitous sea ice cover; (2) the last interglacial was characterized by a circulation pattern similar to that of today except that the two counterclockwise gyres were displaced toward the east and were more vigorous than they are today. This circulation pattern forced the Norwegian Current into a position close to the coast of Norway and permitted formation of a strong east-west temperature gradient close to the Scandinavian landmass; (3) interglacial periods prior to 120,000 B.P. had similar climatic conditions to the 82,000 B.P. level and were characterized by a weak two-gyre circulation pattern. The southern gyre, driven by wind stress in summer months, was ice covered in winters. The northern gyre had little open water even in summers and was primarily formed by wind drag on sea ice. Atmospheric modifications resulting from these circulation patterns and sea ice conditions produced varying climatic conditions in Scandinavia during interglacials prior to the Holocene. The climate was probably warmer and moister during the last interglacial (Eemian) than it is today. Other interglacials during the last 450,000 years, but prior to the Eemian, were probably colder and drier as the Norwegian Sea was not an important source of heat and moisture.

Results from the EISMINT model intercomparison : the effects of thermomechanical coupling

Abstract: This paper discusses results from the second phase of the European Ice sheet Modelling Initiative (EISMINT). It reports the intercompartison of ten operational ice-sheet models and uses a series of experiments to examine the implications of thermomechanical coupling for model behaviour. A schematic, circular ice sheet is used in the work which investigates both steady states and the response to stepped changes in climate. The major finding is that radial symmetry implied in the experimental design can, under certain circumstances, break down with the formation of distinct, regularly spaced spokes of cold ice which extended from the interior of the ice sheet outward to the surrounding zone of basal melt. These features also manifest themselves in the thickness and velocity distributions predicted by the models. They appear to be a common feature to all of the models which took part in the intercomparison, and may stem from interactions between ice temperature, flow and surface form. The exact nature of these features varies between models, and their existence appears to be controlled by the overall thermal regimne of the ice sheet. A second result is that there is considerable agreement between the models in their predictions of global-scale response to imposed climate change.

Bioavailable amino acids in sediments: A biomimetic, kinetics-based approach

Abstract: We developed a biomimetic approach, based on direct incubation with proteolytic enzymes, to measure bioavailable amino acids in sediments. The kinetics of release of monomers and oligopeptides, which are amenable to absorption by cells, is measured as either individual or total amino acids. Microbial proteases incubated with fresh sediments yield amino acids at a similar rate as gut juices from a deposit-feeding holothuroid. Amino acid release from fresh sediment was dominated by a slow hydrolysis step from a refractory substrate, which can be described with a first-order rate law. Typical rate constants for release were in the range 0.15-0.52 h-l, consistent with gut residence times of deposit feeders. The bioavailable pool of peptides had a composition resembling that of average biological tissue, but comparisons with tissue composition suggested dietary deficiency of some essential amino acids. The early stages of release exhibited significant contributions from osmolytes (e.g. glutamic acid and taurine), while a larger, more slowly released pool was anomalously low in methionine, suggesting a contribution from microbial coat proteins. Freezing the sediment led to greater yields of amino acids, which reduced the simulation of a deposit feeder’s gut but indicated a larger pool of potentially bioavailable substrate protected by some kind of matrix. This larger pool of peptide substrate was usually dominated by higher molecular weight polypeptides as measured by the Coomassie Blue method.