Outcrops and cores of the Sirius Group sediments were studied at Table Mountain, Dry Valleys area, Antarctica. These sediments form a surficial veneer at least 9.5 m thick. Three facies — a gravelly sandstone, a sandstone, and a sandy conglomerate — are mapped and described from 13 outcrops and three cores. The gravelly sandstone, constituting 13%of all cored material, is bimodal with matrix-supported clasts comprising 5–33%of the facies. Fabric analysis indicates that it was deposited primarily by lodgment from glacial ice but with minor elements of meltout and flow. The sandstone facies, constituting 77%of all cored material, is a well-sorted, fine- to medium-grained sand, which commonly has laminated bedding. It is predominantly a glaciofluvial deposit but has some glaciolacustrine elements. The sandy conglomerate, constituting 10%of all cored material, is a minor facies. It is massive and clast-supported. It was deposited in a high-energy environment suggestive of subglacial meltwater channels. Sirius Group sediments at Table Mountain are the result of wet-based ice advancing and retreating over waterlain deposits. This is consistent with an advancing ice mass in climatic conditions that were warmer than present. The majority of the sediments were deposited by alpine ice following a similar pathway to the present-day Ferrar Glacier and as such the depositional environment is one that concurs with evidence of a stable East Antarctic Ice Sheet approach. At Table Mountain, the predominantly glaciofluvial and glaciolacustrine facies is inferred to represent a more distal part of the Sirius Group environment than that seen at other outcrops in the Dry Valleys. 相似文献
The heat balance of the surface layer in the vicinity of the former Ocean Weather Station “Tango” (OWS-T; 29°N, 135°E), where
a large amount of heat is transported by the Kuroshio and transferred to the atmosphere, was studied by during Ocean Mixed
Layer Experiment (OMLET) as an oceanographic component of the Japanese World Climate Research Program (1987–1991). Temperature
and velocity in the upper ocean measured using a surface moored buoy system deployed by the Ocean Research Institute, the
University of Tokyo, in total 668 days of four time series namely the periods of April 1988–November 1988 (OMELET-88), August
1989–February 1990 (OMLET-89), April 1990–September 1990 (OMLET-901) and September 1990–January 1991 (OMLET-902). We have
analyzed the moored buoy data of the upper 100 m for the latter three time series (OMLET-89, -901 and -902) and here we discuss
the heat balance of the upper 100 m, in combination with surface heat flux and oceanographic data provided by the Japan Meteorological
Agency. A large fluctuation of oceanic heat convergence/divergence of 200–300 W/m2 in amplitude with predominant period of 20–30 days occurred in the first half of OMLET-89 period, which was just the early
stage in the formation process of a large meander path of the Kuroshio. A large amount of heat convergence of 71 and 79 W/m2 on average was detected in observation period of OMLET-89 and -901, respectively. During OMLET-902, relatively small heat
convergence of 13 W/m2 was obtained. It is suggested that these variations of oceanic heat convergence in this region were closely related to the
fluctuation of the Kuroshio axis to the south of Japan.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
In the southwestern part of the Okhotsk Sea, oceanographic and sea-ice observations on board the icebreaker Soya were carried out in February 1997. A mixed layer of uniform temperature nearly at the freezing point extending down to a
depth of about 300 m was observed. This is much deeper than has previously been reported. It is suggested that this deep mixed
layer originated from the north (off East Sakhalin), being advected along the shelf slope via the East Sakhalin Current, accompanied
with the thick first-year ice (average thickness 0.6 m). This vertically uniform winter water, through mixing with the surrounding
water, makes the surface water more saline (losing a characteristic of East Sakhalin Current Water) and the water in the 100–300
m depth zone less saline, colder, and richer in oxygen (a characteristic of the intermediate Okhotsk Sea water). The oceanographic
structure and a heat budget analysis suggest that new ice zone, which often appears at ice edges, can be formed through preconditioning
of thick ice advection and subsequent cooling by the latent heat release due to its melting.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
It has recently been realized that the Arctic undergoes drastic changes, probably resulting from global change induced processes. This acts on the cycling of matter and on biogenic elements in the Arctic Ocean having feedback mechanisms with the global climate, for example by interacting with atmospheric trace gas concentration. A contemporary budget for biogenic elements as well as suspended matter for the Arctic Ocean as a baseline for comparison with effects of further global change is, thus, needed. Available budgets are based on the late Holocene sedimentary record and are therefore quiet different from the present which has already been affected by the intense anthropogenic activity of the last centuries.
We calculated a contemporary suspended matter and organic carbon budget for the Kara Sea utilizing the numerous available data from the recent literature as well as our own data from Russian-German SIRRO (Siberian River Run-off) expeditions. For calculation of the budgets we used a multi-box model to simplify the Kara Sea shelf and estuary system: input was assumed to comprise riverine and eolian input as well as coastal erosion, output was assumed to consist of sedimentation and export to the Arctic Ocean. Exchange with the adjacent seas was considered in our budget, and primary production as well as recycling of organic material was taken into account. According to our calculations, about 18.5 × 106 t yr− 1 of sediments and 0.37 × 106 t yr− 1 of organic carbon are buried in the estuaries, whereas 20.9 × 106 t yr− 1 sediment and 0.31 × 106 t yr− 1 organic carbon are buried on the shelf. Most sources and sinks of our organic carbon budget of the Kara Sea are in the same order of magnitude, making it a region very sensitive to further changes. 相似文献