Histological Identification of Macroalgae from Stomach Contents of the Antarctic Fish Notothenia coriiceps Using Semi-thin Sections

A histological method is described allowing the identification of macro-algal fragments from stomach contents of fish. The rhodophytes Porphyra endiviifolium and Neuroglossum ligulatum were determined from the stomach contents of the Antarctic fish Notothenia coriiceps . The results show P. endiviifolium to be a more important part in the diet of this fish than previously expected. On the basis of the depth distribution of the identified algae it is suggested that N. coriiceps can migrate to very shallow waters for feeding.     

The effective temperature distribution of steady-state, mass-losing accretion discs

Mass loss appears to be a common phenomenon among astrophysical accretion disc systems. An outflow emanating from an accretion disc can act as a sink for mass, angular momentum and energy, and can therefore alter the dissipation rates and effective temperatures across the disc. Here, the radial distributions of dissipation rate and effective temperature across a Keplerian, steady-state, mass-losing accretion disc are derived, using a simple, parametric approach that is sufficiently general to be applicable to many types of dynamical disc–wind models.
Effective temperature distributions for mass-losing accretion discs in cataclysmic variables are shown explicitly, with parameters chosen to describe both radiation-driven and centrifugally driven outflows. For realistic wind mass-loss rates of a few per cent, only centrifugally driven outflows – particularly those in which mass loss is concentrated in the inner disc – are likely to alter the effective temperature distribution of the disc significantly. Accretion discs that drive such outflows could produce spectra and eclipse light curves that are noticeably different from those produced by standard, conservative discs.     

Moraine Exposure Dates Imply Synchronous Younger Dryas Glacier Advances in the European Alps and in the Southern Alps of New Zealand

Samples taken from the top surfaces of boulders on the Lake Misery moraines at Arthur's Pass, in the Southern Alps of New Zealand, were analysed for ¹⁰Be by accelerator mass spectrometry. Exposure ages calculated with the currently accepted production rate, along with scaling corrections for sample latitude and elevation (42°50'S, 960 m), are: 9300 ± 990, 11,000 ± 1360, 11,410 ± 1030, 12,050 ± 960, and 12,410 ± 1180 years. We consider the date of 9300 years to be an outlier, not included in our mean exposure age of 11,720 ± 320 years for the Lake Misery moraines. Based on exposure ages and geomorphologic similarities, we compare the Lake Misery moraines with an Egesen moraine complex at Julier Pass in the Swiss Alps (46°30'N, 2200 m). Based on the ¹⁰Be, ²⁶Al, and ³⁶Cl exposure ages of three boulders, we calculate a mean exposure age of 11,750 ± 140 years for the outer Egesen moraine at Julier Pass. Based solely on ¹⁰Be measurements, we obtain a mean exposure age of 11,860 ± 210 years for this outer moraine. Egesen moraines in the Swiss Alps represent glacier readvance during the Younger Dryas cold reversal, based on regional correlations and on basal radiocarbon dates from bogs located up-valley of Egesen moraines. The exposure dates from Arthur's Pass and Julier Pass show synchronous glacier advances both in the Southern Alps and in the European Alps during the European Younger Dryas chronozone of Mangerud et al .     

Glacially Folded Outwash Near Lago Llanquihue, Southern Lake District, Chile

Folded outwash occurs in four distinct clusters in an arcuate arrangement just west of the terminal Llanquihue moraines deposited by the Lago Llanquihue piedmont ice lobe at the last glacial maximum. These clusters are physically connected along the eastern side to the Llanquihue terminal moraines, and along the western side to the Llanquihue outwash plain. Each cluster consists of three to eleven elongated ridges. The maximum height of individual ridges varies from cluster to cluster beween 18 and 28 m; the maximum length of individual ridges is between 93 and 1074 m. The average orientation of the ridges ranges over a 60° sector relative to former ice-flow direction. The folded out-wash sediments are cut by two distinct internal fault systems with only a faint surface expression below the Holocene top soil.
The folded outwash ridges are interpreted as a push moraine system produced by the same mechanical forces that act in a critically tapered wedge. The folded sediment is a sandy gravel with an angle of friction on the order of φ = 40°. Interpretations of structural data and of mechanical comparisons point to a basal thrust plane in a sand unit with φ between 24° and 30° and with a pore water pressure index of l = 0.7.
It is very unlikely that the observed and analyzed features wereformed under permafrost conditions.     

Orthogonal intersections of megatrends in the Western Pacific ocean basin: a case study of the Mid-Pacific mountains

Present-day tectonic concepts of events on the western paleo-Pacific lithosphere must be assessed relative to new data. Data collected by the newer techniques of geophysical surveying reveal leaky fracture zones, trending NNW–SSE and WSW–ENE; non-sequential in-line ages on most seamount chains; and orthogonal intersections of fracture zones. The fracture zones meander, braid, merge, splay, start and stop at any place, and are generally aligned with, or contain, linear chains of seamount. The combination of these in-line features is called megatrends. When the GEOSAT data are compared to the available bathymetry, this seemingly jumbled tectonic structure is verified. As the pole of rotation changes, the stress field changes alignment to agree with the Chandler wobble of Earth. Younger megatrends, propagating ever eastward, cross the older, already imprinted megatrends. During the Cretaceous, the voluminous outpouring of igneous rock created the large Pacific plateaus and rises where the megatrends, active and inactive, orthogonally intersected. The magma floods at the intersections flowed outwardly, and the outward flooding accounts for the fanning magnetic lineations around the Manihiki, Magellan, Shatskiy, and Hess rises. A case study of the Mid-Pacific Mountains (MPM), lying in the north-central Pacific Ocean basin, shows that the MPM formed about 125–110-Ma by overprinting the orthogonal intersections of fracture zones at the Molokai and Easter/Krusenstern–Emperor megatrends and the Murray and Tubai/Mamua megatrends. The MPM have been undergoing distortion into a vortex structure, a feature which has been confirmed by updated bathymetry, GEOSAT altimetry data, and drillsite information.     

The Antarctic contribution to Holocene global sea level rise

The Holocene glacial and climatic development in Antarctica differed considerably from that in the Northern Hemisphere. Initial deglaciation of inner shelf and adjacent land areas in Antarctica dates back to between 10-8 Kya, when most Northern Hemisphere ice sheets had already disappeared or diminished considerably. The continued deglaciation of currently ice-free land in Antarctica occurred gradually between ca. 8-5 Kya. A large southern portion of the marine-based Ross Ice Sheet disintegrated during this late deglaciation phase. Some currently ice-free areas were deglaciated as late as 3 Kya. Between 8-5 Kya, global glacio-eustatically driven sea level rose by 10-17m, with 4-8 m of this increase occurring after 7 Kya. Since the Northern Hemisphere ice sheets had practically disappeared by 8-7 Kya, we suggest that Antarctic deglaciation caused a considerable part of the global sea level rise between 8-7 Kya, and most of it between 7-5 Kya. The global mid-Holocene sea level high stand, broadly dated to between 8-4 Kya, and the Littorina-Tapes transgressions in Scandinavia and simultaneous transgressions recorded from sites e.g. in Svalbard and Greenland, dated to 7-5 Kya, probably reflect input of meltwater from the Antarctic deglaciation.     

The Energy Balance Experiment EBEX-2000. Part I: overview and energy balance

An overview of the Energy Balance Experiment (EBEX-2000) is given. This experiment studied the ability of state-of-the-art measurements to close the surface energy balance over a surface (a vegetative canopy with large evapotranspiration) where closure has been difficult to obtain. A flood-irrigated cotton field over uniform terrain was used, though aerial imagery and direct flux measurements showed that the surface still was inhomogeneous. All major terms of the surface energy balance were measured at nine sites to characterize the spatial variability across the field. Included in these observations was an estimate of heat storage in the plant canopy. The resultant imbalance still was 10%, which exceeds the estimated measurement error. We speculate that horizontal advection in the layer between the canopy top and our flux measurement height may cause this imbalance, though our estimates of this term using our measurements resulted in values less than what would be required to balance the budget. The National Center for Atmospheric Research is supported by the National Science Foundation