Reconstruction of late Quaternary sea-level change in southwestern British Columbia from sediments in isolation basins     

IAN HUTCHINSON  THOMAS S. JAMES  JOHN J. CLAGUE  J. VAUGHN BARRIE  KIM W. CONWAY 《Boreas: An International Journal of Quaternary Research》2004,33(3):183-194

Bracketing ages on marine—freshwater transitions in isolation basins extending from sea level to 100 m elevation on Lasqueti Island, and data from shallow marine cores and outcrops on eastern Vancouver Island, constrain late Pleistocene and Holocene sea-level change in the central Strait of Georgia. Relative sea level fell from 150 m elevation to about —15 m from 14000 cal. yr BP to 11 500 cal. yr BP. Basins at higher elevations exhibit abrupt changes in diatom assemblages at the marine-freshwater transition. At lower elevations an intervening brackish phase suggests slower rates of uplift. Relative sea level rose to about +1 m about 9000 cal. yr BP to 8500 cal. yr BP, and then slowly fell to the modern datum. The mean rate of glacio-isostatic rebound in the first millennium after deglaciation was about 0.11 in a ^-1, similar to the peak rate at the centres of the former Laurentide and Fennoscandian ice complexes. The latter feature smooth, exponential-style declines in sea level up to the present day, whereas in the study area the uplift rate dropped to less than one-tenth of its initial value in only about 2500 years. Slower, more deeply seated isostatic recovery generated residual uplift rates of <0.01 m a^-1 in the early Holocene after the late-Pleistocene wasting of the Cordilleran ice sheet.  相似文献   

Simulation of Storm Surge and Wave Due to Typhoon Isewan (5915)     

Jin-Hee YUK  Kyeong Ok KIM  Han Soo LEE  Byung Ho CHOI 《海洋工程》2015,29(4):473-488

An integrally coupled wave-tide-surge model was developed and then applied to the simulation of the wave-typhoon surge for the typhoon Isewan (typhoon Vera (5915)), which is the strongest typhoon that has struck Japan and caused incalculable damage. An integrally coupled tide-surge-wave model using identical and homogeneous meshes in an unstructured grid system was used to correctly resolve the physics of wave-circulation interaction in both models. All model components were validated independently. The storm surge and wave properties such as the surge height, the significant wave height, wave period and direction were reproduced reasonably under the meteorological forcing, which was reprocessed to be close to the observations. The resulting modeling system can be used extensively for the prediction of the storm surge and waves and the usual barotropic forecast.  相似文献   

Response of the Rhine–Meuse fluvial system to Saalian ice-sheet dynamics     

FREEK S. BUSSCHERS  RONALD T. VAN BALEN  KIM M. COHEN  CEES KASSE  HENK J. T. WEERTS  JAKOB WALLINGA  FRANS P. M. BUNNIK 《Boreas: An International Journal of Quaternary Research》2008,37(3):377-398

A new reconstruction of the interaction between the Saalian Drente glaciation ice margin and the Rhine–Meuse fluvial system is presented based on a sedimentary analysis of continuous core material, archived data and a section in an ice-pushed ridge. Optically Stimulated Luminescence (OSL) was applied to obtain independent age control on these sediments and to establish a first absolute chronology for palaeogeographical events prior to and during the glaciation. We identified several Rhine and Meuse river courses that were active before the Drente glaciation (MIS 11-7). The Drente glaciation ice advance into The Netherlands (OSL-dated to fall within MIS 6) led to major re-arrangement of this drainage network. The invading ice sheet overrode existing fluvial morphology and forced the Rhine–Meuse system into a proglacial position. During deglaciation, the Rhine shifted into a basin in the formerly glaciated area, while the Meuse remained south of the former ice limit, a configuration that persisted throughout most of the Eemian and Weichselian periods. An enigmatic high position of proglacial fluvial units and their subsequent dissection during deglaciation by the Meuse may partially be explained by glacio-isostatic rebound of the area, but primarily reflects a phase of high base level related to a temporary proglacial lake in the southern North Sea area, with lake levels approximating modern sea levels. Our reconstruction indicates that full 'opening' of the Dover Strait and lowering of the Southern Bight, enabling interglacial marine exchange between the English Channel and the North Sea, is to be attributed to events during the end of MIS 6.  相似文献   

Rate of late Quaternary ice-cap thinning on King George Island, South Shetland Islands, West Antarctica defined by cosmogenic ³⁶Cl surface exposure dating     

YEONG BAE SEONG  LEWIS A. OWEN  HYOUN SOO LIM  HO IL YOON  YEADONG KIM  YONG IL LEE  MARC W. CAFFEE 《Boreas: An International Journal of Quaternary Research》2009,38(2):207-213

Glacial landforms on the Barton and Weaver peninsulas of King George Island in the South Shetland Islands, West Antarctica were mapped and dated using terrestrial cosmogenic ³⁶Cl methods to provide the first quantitative terrestrial record for late Quaternary deglaciation in the South Shetland Islands. ³⁶Cl ages on glacially eroded and striated bedrock surfaces range from 15.5±2.5 kyr to 1.0±0.7 kyr. The ³⁶Cl ages are younger with decreasing altitude, indicating progressive downwasting of the southwestern part of the Collins Ice Cap at a rate of ∼12 mm yr⁻¹ since 15.5±2.5 kyr ago, supporting the previously published marine records for the timing and estimate of the rate of deglaciation in this region.  相似文献   

Two-stage growth of porphyroblastic biotite and garnet in the Barrovian metapelites of the Imjingang belt, central Korea     

Y. KIM  M. CHO 《Journal of Metamorphic Geology》2008,26(3):385-399

Porphyroblastic biotite and garnet in the Barrovian metapelites of the Imjingang belt, Korea, were investigated to unravel the sequence and mechanism of mineral growth. Poikiloblastic biotite contains straight inclusion trails (S_i) discontinuous to the major foliation, and develops clear zones at the grain margin. These microstructures suggest an initial growth of biotite between two contractional deformations (D_n−1 and D_n) followed by an overgrowth during D_n. Although garnet poikiloblasts contain variable S_i patterns, their major growth is likely to have occurred during D_n on the basis of compositional relationships among variable garnet types. Early poikiloblasts of both minerals were formed by chemical replacement of the matrix that consisted mainly of chlorite, muscovite and quartz. Subsequent growth of biotite was governed by a crack-filling mechanism, and was accompanied by the production of extensional cracks inside or around biotite, providing fluid pathways. The overgrowth of garnet was favoured at the biotite–garnet interface, and the consequence was a partial replacement of inclusion-poor garnet after biotite subsequent to D_n. In addition, clear zones and pressure shadows as well as the matrix around biotite porphyroblasts were replaced by garnet, suggesting an inheritance of various pre-existing microstructures in the S_i pattern of garnet. Further attention is thus required for any attempt to delineate the microstructural interaction between deformation and metamorphism, particularly in a sample containing early-grown porphyroblasts. Microstructural evidence for the two-stage growth of biotite and garnet is present up to the kyanite zone, indicating that this growth mechanism is prevalent during progressive metamorphism of Barrovian metapelites.  相似文献   

A New Video and Digital Camera System for Studies of the Dynamics of Microtopographic Features on Tidal Flats     

LARS CHRESTEN LUND-HANSEN  EINER LARSEN  KURT THOMAS JENSEN  KIM N. MOURITSEN  CHRISTIAN CHRISTIANSEN  THORBJØRN JOEST ANDERSEN 《Marine Georesources & Geotechnology》2013,31(1-2):115-122

A newly developed video and camera system for tidal flat microtopographic studies is presented. It consists of a SONY handy cam placed in an underwater housing mounted on a frame about 70?cm above the sediment surface. A rectangular surface area of 30?×40?cm is imaged by the camera. The camera records video sequences and/or digital images at predetermined time lapses. The total number of images is about 540, and a similar number of 10-second long video sequences can be recorded. The camera is programmed with a PC before deployment, and the total deployment time depends on the time lapse between recordings. The camera is connected to an external power supply (12?volt), and a halogen projector pointing towards the sediment surface ensures that the system is operable on a 24-hours scale. The system has been tested in the Danish Wadden Sea. It has proved to be a very useful tool in studies of topographic effects of erosion and deposition sequences, and for studies of benthic organisms-sediment interactions. The test site was further equipped with sensors for water and seabed measurements, which proved to be indispensable regarding the interpretation of recorded image time-series.  相似文献   

The diel vertical migration of the sound-scattering layer in the Yellow Sea Bottom Cold Water of the southeastern Yellow Sea：focus on its relationship with a temperature structure     

LEE Hyungbeen  CHO Sungho  KIM Woongseo  KANG Donhyug 《海洋学报(英文版)》2013,32(9):44-49

Using the hydroacoustic method with a 200 kHz scientific echo sounding system,the diel vertical migration(DVM) of the sound-scattering layer(SSL) in the Yellow Sea Bottom Cold Water(YSBCW) of the southeastern Yellow Sea was studied in April(spring) and August(summer) of 2010 and 2011.For each survey,13–27 hours of acoustic data were continuously collected at a stationary station.The acoustic volume scattering strength(Sv) data were analyzed with temperature profile data.In the spring of both 2010 and 2011,the SSL clearly showed the vertical migration throughout the entire water column,moving from the surface layer at night to near the bottom during the day.Conductivity,temperature,and depth data indicated that the entire water column was well mixed with low temperature of about 8 C.However,the SSL showed different patterns in the summers of 2010 and 2011.In the summer of 2010(28 C at the surface),the SSL migrated to near the bottom during the day,but there were two SSLs above and below the thermocline at depth of 10–30 m at night.In the summer of 2011(20 C at the surface),the SSL extended throughout the entire water column at night,possibly owing to an abrupt change in sea weather conditions caused by the passage of a Typhoon Muifa over the study area.It was concluded that the DVM patterns in summer in the YSBCW area may be greatly influenced by a strengthened or weakened thermocline.  相似文献   

Sea‐level rise,depth‐dependent carbonate sedimentation and the paradox of drowned platforms     

WONSUCK KIM  BRUCE W. FOUKE  ANDREW L. PETTER  TERRENCE M. QUINN  CHARLES KERANS  FRED TAYLOR 《Sedimentology》2012,59(6):1677-1694

A mathematical model of carbonate platform evolution is presented in which depth‐dependent carbonate growth rates determine platform‐top accumulation patterns in response to rising relative sea‐level. This model predicts that carbonate platform evolution is controlled primarily by the water depth and sediment accumulation rate conditions at the onset of relative sea‐level rise. The long‐standing ‘paradox of a drowned platform’ arose from the observation that maximum growth rate potentials of healthy platforms are faster than those of relative sea‐level rise. The model presented here demonstrates that a carbonate platform could be drowned during a constant relative sea‐level rise whose rate remains less than the maximum carbonate production potential. This scenario does not require environmental changes, such as increases in nutrient supply or siliciclastic sedimentation, to have taken place. A rate of relative sea‐level rise that is higher than the carbonate accumulation rate at the initial water depth is the only necessary condition to cause continuous negative feedbacks to the sediment accumulation rates. Under these conditions, the top of the carbonate platform gradually deepens until it is below the active photic zone and drowns despite the strong maximum growth potential of the carbonate production factory. This result effectively resolves the paradox of a drowned carbonate platform. Test modelling runs conducted with 2·5 m and 15 m initial sea water depths at bracketed rates of relative sea‐level rise have determined how fast the system catches up and maintains the ‘keep‐up’ phase. This is the measure of time necessary for the basin to respond fully to external forcing mechanisms. The duration of the ‘catch‐up’ phase of platform response (termed ‘carbonate response time’) scales with the initial sea water depth and the platform‐top aggradation rate. The catch‐up duration can be significantly elongated with an increase in the rate of relative sea‐level rise. The transition from the catch‐up to the keep‐up phases can also be delayed by a time interval associated with ecological re‐establishment after platform flooding. The carbonate model here employs a logistical equation to model the colonization of carbonate‐producing marine organisms and captures the initial time interval for full ecological re‐establishment. This mechanism prevents the full extent of carbonate production to be achieved at the incipient stage of relative sea‐level rise. The increase in delay time due to the carbonate response time and self‐organized processes associated with biological colonization increase the chances for platform drowning due to deepening of water depth (> ca 10 m). Furthermore this implies a greater likelihood for an autogenic origin for high‐frequency cyclic strata than has been estimated previously.  相似文献   

Depth distribution of Calanus finmarchicus and C. glacialis in relation to environmental conditions in the Barents Sea     

KIM H. UNSTAD  KURT S. TANDE 《Polar research》1991,10(2):409-420

Stage composition and vertical distribution of copepodids of Calanus finmarchicus and C. glacialis are described during spring and summer in Atlantic and Arctic waters, respectively. The two species co-occurred in the region of the Polar Front, both in moderate to high population densities. Ontogenetic migration, meaning that the migration range becomes progressively wider with advancing stage, was found in both species. The present study also revealed that C. finmarchicus had modifications in its ontogenetic vertical distribution. The standing crop of phytoplankton, predominantly Phaeocystis pouchetii , appeared to influence the degree of stage-specific segregation. Both low and high food concentrations tended to increase the vertical distribution of the instars. On the other hand, a narrow subsurface stratum of abundant phytoplankton led to an aggregation of copepodids at this depth. In the region of the Polar Front, where the two species co-occur, C. glacialis had a deeper distribution than C. finmarchicus , thus creating a bimodal vertical distribution pattern within the uppermost 200 m.  相似文献   

2002年3月21-22日影响韩国的沙尘天气分析   总被引：1，自引：0，他引：1  

金正润  牛生杰  河惠卿 《南京气象学院学报》2007,30(5):643-647

利用气象卫星、天气形势场和NCEP/NCAR再分析资料,分析了2002年3月21-22日影响韩国沙尘天气的原因. 结果表明:影响韩国沙尘天气的沙尘主要源地是蒙古国和中国内蒙古地区.沙尘天气发生在地面冷锋后部,高压伸展的前面;19日和20日沙尘暴发生后,沙尘沿着西北风输送,21日早晨影响韩国;PM10最高值达到 2 778.2 μg/m3,由于西北风较强,沙尘暴发生后很快影响到韩国,但在韩国持续的时间较短.  相似文献