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Observations of terrestrial locomotion in Antarctic seals

first_imgObservations are reported on the modes of terrestrial locomotion among Antarctic members of the Phocidae. An account is given of the sinuous (or “swimming”) type of progression found most developed in the crabeater seal Lobodon carcinophagus (Hombron and Jacquinot), and of its occurrence in the leopard seal Hydrurga leptonyx (Blainville). This type of movement has not been seen in the Weddell seal Leptonychotes weddelli Lesson, where the undulatory (caterpillar‐like) method is the normal locomotory pattern on land. The fore‐flippers are not used by the adult Weddell seal in terrestrial locomotion, but the pup does make some use of the fore‐flippers during the first 10 to 15 days of postnatal life. The locomotory patterns used by the elephant seal Mirounga leonina Linn, and the probable methods used by the Ross seal Ommatophoca rossi Gray, are noted. The observation that the harp seal Pagophilus groenlandicus (Erxleben) shows the sinuous type of movement under stress is recorded.last_img read more

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Relative effect of taphonomy on calcification temperature estimates from fossil planktonic foraminfera

first_imgThis paper explores the effects of preservation and taphonomy on the ultrastructure of recent and fossil (Quaternary and Neogene) Globigerinoides using scanning electron microscopy and thin section petrography. We show preservation states from: pristine (plankton tow) specimens that are “glassy”, have a microcrystalline test structure, and bear sharply defined interpore ridges with delicate spines; through core top and fossil specimens that have gametogenic calcite veneers of euhedral or lumpy deposits covering the interpore ridges and spine bases; to fossil material with extensive dissolution of the test wall and diagenetic calcite formed during shallow burial (less than 300 m below the sea floor). The latter produce it “grainy” texture to the test. Although we cannot unravel the precise effects of ecology and taphonomy on calcification temperature at every site, we show that for well-preserved fossil material with gametogenic calcite, temperature estimates are typically 2-3 degrees C cooler than modern sea surface, and are similar to those recorded using the delta(18)Oof core top material from tropical latitudes. In contrast, at tropical sites with poor fossil preservation, estimates of calcification temperature are significantly cooler, sometimes by more than 10 degrees C than expected From present observations.last_img read more

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On the association between northward turnings of the interplanetary magnetic field and substorm onsets

first_imgWe re-examine whether substorms are triggered by solar wind fluctuations or an internal magnetospheric instability by comparing the statistical associations between substorm onsets and (1) an external trigger definition, (2) a simple internal trigger definition of only prior loading of solar wind energy that is a subset of the external trigger definition. Statistical associations are calculated both for observed substorm onsets and onsets generated by a Minimal Substorm Model in which substorms are purely internally triggered. Thence we argue that a minimum interval of prior loading is a necessary condition for substorm onset, a subsequent northward IMF turning is not necessary, and consequently that an internal trigger from a magnetospheric instability is a necessary and sufficient condition for substorm onset. We discuss how this result may explain a report that externally triggered substorms are systematically larger than non-externally triggered substorms.last_img read more

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Crustal thickening along the West Antarctic Gondwana margin during mid-Cretaceous deformation of the Triassic intra-oceanic Dyer Arc

first_imgSubduction-related Mesozoic mafic dykes in eastern Palmer Land, Antarctic Peninsula, record the developmentof an intra-oceanic arc terrane, the Dyer Arc, probably of late Permian–Triassic age, represented by atholeiitic dyke group. Arc rocks were deformed in late Triassic–early Jurassic and mid-Cretaceous times onthe Gondwana margin. Eruption of syn- to post-mid-Cretaceous orogenesis magmatism is represented by acalc–alkaline group of dykes. The tholeiitic dykes intruded immature granitic crust of the Eastern Zonesub-terrane of the Central Domain, one of the magmatic terranes of the Pacific margin of Gondwana. Thecalc–alkaline dykes straddle the major tectonic boundary between the Central Domain and the continentalmargin Eastern Domain. 132 dykes were studied, 82 of which are calc–alkaline, 48 tholeiitic and two shoshonitic,across an area of approximately 4000 km2. Tholeiitic dykes strike broadly NNW–SSE, transposed intoparallelism with the strike of the tectonic boundary during Cretaceous orogenesis whereas calc–alkalinedykes strike tightly ESE–WNW at a high angle to the boundary. The tholeiites pre-date late Triassic deformationand metamorphism, and are interpreted as dominantly Triassic in age, whereas Ar–Ar dated calc–alkalinedykes are younger (~100 Ma and ~97 Ma) and field relations indicate that they overlap with the waning phaseof the mid-Cretaceous Palmer Land Event. The tholeiites have trace element abundances similar to, but moredepleted than, those of modern intra-oceanic arcs, as recorded by Zr/Hf ratios. Nb/Yb versus TiO2*/Yb andSm/Yb versus La/Sm plots are used to model depths of partial melting. The tholeiites were mostly generatedat shallow depths corresponding to 2.5 and certainly less than 3.0 GPa in largely garnet-free mantle. Thecalc–alkaline magmas were generated at pressures greater than 3.0 to possibly >3.5 GPa, in the garnet zone.The deepening of the mantle source, and onset of calc–alkaline magmatism are interpreted to have beencaused by deformation of the intra-oceanic arc terrane on the Gondwana margin, and lithospheric thickeningduring the Palmer Land Event.last_img read more

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Configuration of the northern Antarctic Peninsula Ice Sheet at LGM based on a new synthesis of seabed imagery

first_imgWe present a new seafloor map for the northern Antarctic Peninsula (AP), including swath multibeam data sets from five national programs. Our map allows for the examination and interpretation of Last Glacial Maximum (LGM) paleo-ice sheet/stream flow directions developed upon the seafloor from the preservation of: mega-scale glacial lineations, drumlinized features, and selective linear erosion. We combine this with terrestrial observations of flow direction to place constraints on ice divides and accumulation centers (ice domes) on the AP continental shelf. The results show a flow bifurcation as ice exits the Larsen-B embayment. Flow emanating off the Seal Nunataks (including Robertson Island) is directed toward the southeast, then eastward as the flow transits toward the Robertson Trough. A second, stronger “streaming flow” is directed toward the southeast then southward, as ice overflowed the tip of the Jason Peninsula to reach the southern perimeter of the embayment. Our reconstruction also refines the extent of at least five other distinct paleo-ice stream systems which, in turn, serve to delineate seven broad regions where contemporaneous ice domes must have been centered on the continental shelf during the LGM time interval. Our reconstruction is more detailed than other recent compilations because we followed specific flow indicators and have kept tributary flow paths parallellast_img read more

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A new continuous planar fit method for calculating fluxes in complex, forested terrain

first_imgThe planar fit (PF) method is often recommended for long-term eddy covariance flux measurements because it offers a number of advantages over rotating into streamwise coordinates. For sites over complex, forested terrain a single PF may not account for complex variations in slope and canopy cover with wind direction. An alternative to the PF method is presented where the tilt angle is fitted as a continuous function of the wind direction. This retains many of the benefits of the PF method, while at the same time better representing local variations in tilt with wind direction.last_img

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Simulation study for ground-based Ku-band microwaveobservations of ozone and hydroxyl in the polar middle atmosphere

first_imgThe Ku-band microwave frequencies (10.70–14.25 GHz) overlap emissions from ozone (O3) at 11.072 GHz and hydroxyl radical (OH) at 13.441 GHz. These important chemical species in the polar middle atmosphere respond strongly to high-latitude geomagnetic activity associated with space weather. Atmospheric model calculations predict that energetic electron precipitation (EEP) driven by magnetospheric substorms produces large changes in polar mesospheric O3 and OH. The EEP typically peaks at geomagnetic latitudes of ∼65∘ and evolves rapidly with time longitudinally and over the geomagnetic latitude range 60–80∘. Previous atmospheric modelling studies have shown that during substorms OH abundance can increase by more than an order of magnitude at 64–84 km and mesospheric O3 losses can exceed 50 %. In this work, an atmospheric simulation and retrieval study has been performed to determine the requirements for passive microwave radiometers capable of measuring diurnal variations in O3 and OH profiles from high-latitude Northern Hemisphere and Antarctic locations to verify model predictions. We show that, for a 11.072 GHz radiometer making 6 h spectral measurements with 10 kHz frequency resolution and root-mean-square baseline noise of 1 mK, O3 could be profiled over 8×10−4–0.22 hPa (∼98–58 km) with 10–17 km height resolution and ∼1 ppmv uncertainty. For the equivalent 13.441 GHz measurements with vertical sensor polarisation, OH could be profiled over 3×10−3–0.29 hPa (∼90–56 km) with 10–17 km height resolution and ∼3 ppbv uncertainty. The proposed observations would be highly applicable to studies of EEP, atmospheric dynamics, planetary-scale circulation, chemical transport, and the representation of these processes in polar and global climate models. Such observations would provide a relatively low-cost alternative to increasingly sparse satellite measurements of the polar middle atmosphere, extending long-term data records and also providing “ground truth” calibration data.last_img read more

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A global database of Holocene paleotemperature records

first_imgA comprehensive database of paleoclimate records is needed to place recent warming into the longer-term context of natural climate variability. We present a global compilation of quality-controlled, published, temperature-sensitive proxy records extending back 12,000 years through the Holocene. Data were compiled from 679 sites where time series cover at least 4000 years, are resolved at sub-millennial scale (median spacing of 400 years or finer) and have at least one age control point every 3000 years, with cut-off values slackened in data-sparse regions. The data derive from lake sediment (51%), marine sediment (31%), peat (11%), glacier ice (3%), and other natural archives. The database contains 1319 records, including 157 from the Southern Hemisphere. The multi-proxy database comprises paleotemperature time series based on ecological assemblages, as well as biophysical and geochemical indicators that reflect mean annual or seasonal temperatures, as encoded in the database. This database can be used to reconstruct the spatiotemporal evolution of Holocene temperature at global to regional scales, and is publicly available in Linked Paleo Data (LiPD) format.last_img read more

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Utah State Football Hosts New Mexico State Saturday

first_img Written by FacebookTwitterLinkedInEmailLOGAN, Utah-Saturday, Utah State will host New Mexico State in the Aggies’ home opener at Maverik Stadium.After dropping a 38-31 decision to nationally-ranked Michigan State, Utah State plays NMSU for the 39th time in history, the sixth-most played series in USU football history.USU leads NMSU 30-8 all-time, including a 14-3 lead at Logan.With Matt Wells at the helm of USU football, the Aggies are 17-12 after a loss and USU has not started a season at 0-2 since 2009. Tags: Matt Wells/Maverik Stadium/Michigan State/NMSU Football/USU Football September 3, 2018 /Sports News – Local Utah State Football Hosts New Mexico State Saturday Brad Jameslast_img

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Tampa Bay gets OK from MLB to explore Montreal

first_img Beau Lund FacebookTwitterLinkedInEmail33ft/iStock(NEW YORK) — Starved for fans despite success on the field, the Tampa Bay Rays have been given the go-ahead by Major League Baseball to look into playing a split season in Montreal.No timetable for the possible plan was announced. An idea under consideration is for the Rays to play early in the season in Tampa Bay and finish up in Montreal, the former home of the Expos.Commissioner Rob Manfred made the announcement Thursday at the end of the owners’ meetings, saying the executive council had granted the Rays “broad permission to explore what’s available.”Manfred said it’s too soon to detail the particulars — as in where the team would play postseason games, or in what stadiums. He did not address whether this would be a step toward a full move.“It’s an interesting kind of idea,” Rays outfielder/infielder Brandon Lowe said before playing at Oakland on Thursday night. “It’s in the future. It’s so far ahead of us that it’s going to be big news right now, but I feel like a lot of us are just kind of, ‘it happened, we saw it,’ but that’s really all it is.”Still, that was plenty enough to spark excitement in Canada, where the Expos played from 1969-2004 before moving to Washington and becoming the Nationals.With their introductions in French and English, jaunty organ music, goofy mascot Youppi! and fun tricolor logo, Les Expos flourished for years with a truly international flair.Rays principal owner Stu Sternberg, in a statement, said: “My priority remains the same, I am committed to keeping baseball in Tampa Bay for generations to come.”“I believe this concept is worthy of serious exploration,” he added.Forget it, St. Petersburg Mayor Rick Kriseman said. Tropicana Field is located in his city.“I want to be crystal clear. The Rays cannot explore playing any Major League Baseball games in Montreal, or anywhere else for that matter, prior to 2028 without reaching a formal memorandum of understanding with the city of St. Petersburg,” he said.Tampa Bay is averaging 14,546 fans per home game, ahead of only the Miami Marlins. The Rays have played at Tropicana Field since their inception in 1998 and drew their lowest home crowd of 5,786 against Toronto last month.Copyright © 2019, ABC Radio. All rights reserved. June 21, 2019 /Sports News – National Tampa Bay gets OK from MLB to explore Montrealcenter_img Written bylast_img read more