Broad-band electromagnetic seismographs with maximum sensitivity     

Vladimír Tobyáš 《Studia Geophysica et Geodaetica》1967,11(1):34-47

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Radio‐echo layering in West Antarctica: a spreadsheet dataset     

Martin J. Siegert  Magdeline Pokar  Julian A. Dowdeswell  Toby Benham 《地球表面变化过程与地形》2005,30(12):1583-1591

Of the various information recovered from radio‐echo sounding (RES) of polar ice sheets, internal layering is currently under‐utilized by glaciologists, due in part to a lack of available data. Here, RES layering of the West Antarctic Ice Sheet, from the 1970s RES survey of approximately 70 per cent of this ice mass, is made available in a series of spreadsheets. Three types of internal layers are evident in the dataset. The first is continuous layers that have a stratigraphic appearance and can often be traced easily for hundreds of kilometres. The second is buckled layering, which also resembles stratigraphy and can sometimes be traced over tens of kilometres (although layer identification can often be difficult). The roughness of these layers is often greater than the bed at the same wavelength. The third is highly distorted or absent layering, which is not possible to trace laterally. Despite debate concerning the origin of RES layers, they are thought by most glaciologists to represent isochronous surfaces. The pattern of internal layering is potentially of importance to glaciologists for three reasons. (1) The position of undeformed layers below the ice surface is a function of accumulation rate, ice flow and basal melting conditions. Numerical modelling (including new ‘data assimilation’ techniques) could be used to discriminate between these processes, so revealing important information about the ice sheet and its environment. (2) Buckled layers are deformed by ice flow process, and so their occurrence can be related to the flow dynamics of the ice sheet. (3) Very buckled layers are often associated with ice stream flow, which allows their location to mark the positions of past and present fast‐flowing ice. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Submesoscale features and their interaction with fronts and internal tides in a high-resolution coupled atmosphere-ocean-wave model of the Bay of Bengal   总被引：1，自引：1，他引：0  

Tommy G. Jensen  Igor Shulman  Hemantha W. Wijesekera  Stephanie Anderson  Sherwin Ladner 《Ocean Dynamics》2018,68(3):391-410

Large freshwater fluxes into the Bay of Bengal by rainfall and river discharges result in strong salinity fronts in the bay. In this study, a high-resolution coupled atmosphere-ocean-wave model with comprehensive physics is used to model the weather, ocean circulation, and wave field in the Bay of Bengal. Our objective is to explore the submesoscale activity that occurs in a realistic coupled model that resolves mesoscales and allows part of the submesoscale field. Horizontal resolution in the atmosphere varies from 2 to 6 km and is 13 km for surface waves, while the ocean model is submesoscale permitting with resolutions as high as 1.5 km and a vertical resolution of 0.5 m in the upper 10 m. In this paper, three different cases of oceanic submesoscale features are discussed. In the first case, heavy rainfall and intense downdrafts produced by atmospheric convection are found to force submesoscale currents, temperature, and salinity anomalies in the oceanic mixed layer and impact the mesoscale flow. In a second case, strong solitary-like waves are generated by semidiurnal tides in the Andaman Sea and interact with mesoscale flows and fronts and affect submesoscale features generated along fronts. A third source of submesoscale variability is found further north in the Bay of Bengal where river outflows help maintain strong salinity gradients throughout the year. For that case, a comparison with satellite observations of sea surface height anomalies, sea surface temperature, and chlorophyll shows that the model captures the observed mesoscale eddy features of the flow field, but in addition, submesoscale upwelling and downwelling patterns associated with ageostrophic secondary circulations along density fronts are also captured by the model.  相似文献   

Reply to discussion of ‘Gisbornian (Caradoc) graptolites from New South Wales,Australia: systematics,biostratigraphy and evolution’ by B. Rickards,L. Sherwin and P. Williamson     

Barrie Rickards  Lawrence Sherwin  Penelope L. Williamson 《Geological Journal》2003,38(2):181-183

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Gisbornian (Caradoc) graptolites from New South Wales,Australia: systematics,biostratigraphy and evolution     

Barrie Rickards  Lawrence Sherwin  Penelope Williamson 《Geological Journal》2001,36(1):59-86

The biodiversity record of graptolites from the Cheeseman's Creek Formation, considered herein as late Gisbornian (Caradoc) in age, has been substantially increased to fifteen taxa, including the new species Dicellograptus praemorrisi sp. nov. and Climacograptus vandenbergi sp. nov. Some of the records have global correlative significance enabling us to identify the wilsoni Biozone ( = calcaratus Biozone of eastern Australia). Several evolutionary lineages have been recognized:

• 1 Dicellograptus moffatensis (Carruthers, 1858) → D. praemorrisi sp. nov → D. morrisi Hopkinson, 1871
• 2 Glossograptus hincksi Hopkinson, 1872 → Glossograptus? sp.
• 3 Climacograptus bicornis (J. Hall, 1847) → C. vandenbergi sp. nov. → C. lanceolatus VandenBerg, 1990.

Copyright © 2001 John Wiley & Sons, Ltd.  相似文献