Impact of ocean model resolution on CCSM climate simulations   总被引：1，自引：1，他引：0  

Ben P. Kirtman  Cecilia Bitz  Frank Bryan  William Collins  John Dennis  Nathan Hearn  James L. Kinter III  Richard Loft  Clement Rousset  Leo Siqueira  Cristiana Stan  Robert Tomas  Mariana Vertenstein 《Climate Dynamics》2012,39(6):1303-1328

The current literature provides compelling evidence suggesting that an eddy-resolving (as opposed to eddy-permitting or eddy-parameterized) ocean component model will significantly impact the simulation of the large-scale climate, although this has not been fully tested to date in multi-decadal global coupled climate simulations. The purpose of this paper is to examine how resolved ocean fronts and eddies impact the simulation of large-scale climate. The model used for this study is the NCAR Community Climate System Model version 3.5 (CCSM3.5)—the forerunner to CCSM4. Two experiments are reported here. The control experiment is a 155-year present-day climate simulation using a 0.5° atmosphere component (zonal resolution 0.625 meridional resolution 0.5°; land surface component at the same resolution) coupled to ocean and sea-ice components with zonal resolution of 1.2° and meridional resolution varying from 0.27° at the equator to 0.54° in the mid-latitudes. The second simulation uses the same atmospheric and land-surface models coupled to eddy-resolving 0.1° ocean and sea-ice component models. The simulations are compared in terms of how the representation of smaller scale features in the time mean ocean circulation and ocean eddies impact the mean and variable climate. In terms of the global mean surface temperature, the enhanced ocean resolution leads to a ubiquitous surface warming with a global mean surface temperature increase of about 0.2?°C relative to the control. The warming is largest in the Arctic and regions of strong ocean fronts and ocean eddy activity (i.e., Southern Ocean, western boundary currents). The Arctic warming is associated with significant losses of sea-ice in the high-resolution simulation. The sea surface temperature gradients in the North Atlantic, in particular, are better resolved in the high-resolution model leading to significantly sharper temperature gradients and associated large-scale shifts in the rainfall. In the extra-tropics, the interannual temperature variability is increased with the resolved eddies, and a notable increases in the amplitude of the El Ni?o and the Southern Oscillation is also detected. Changes in global temperature anomaly teleconnections and local air-sea feedbacks are also documented and show large changes in ocean–atmosphere coupling. In particular, local air-sea feedbacks are significantly modified by the increased ocean resolution. In the high-resolution simulation in the extra-tropics there is compelling evidence of stronger forcing of the atmosphere by SST variability arising from ocean dynamics. This coupling is very weak or absent in the low-resolution model.  相似文献   

Determination of potential mine water discharge zones in crystalline rocks at Rozna,Czech Republic   总被引：3，自引：2，他引：1  

Adam Ricka  Tomas Kuchovsky  Ondra Sracek  Josef Zeman 《Environmental Earth Sciences》2010,60(6):1201-1213

The Rozna Mine is one of the last active uranium mines in Europe. When the mine is closed and flooded, the natural groundwater flow pattern will be partly restored. Re-established groundwater flow system will be associated with an increase of groundwater discharge into draining rivers and streams. Since the groundwater inflows to streams can be contaminated by the mine water, the groundwater drainage characteristic of fractured aquifer should be carefully identified. Several methods of groundwater discharge zones identification were used including morphological analysis, thermometry, and electrical conductivity (EC) measurements. Stream temperatures and EC at more than 700 points in the area covering about 85 km² were measured. The measurements were performed during winter period, when stream discharges were low and there was a maximum temperature contrast. There was a frequent presence of preferential discharge zones with resulting anomalous temperatures and electric conductivity values of stream water. The results show evident correlation of discharge zones with surface morphology and geological settings. Just like the aquifer discharge characteristics, the aquifer is strongly heterogeneous. The thermometry supported by measurement of EC proved to be a useful tool for large-scale investigation of groundwater flow and drainage in fractured aquifers.  相似文献   

Human response to the Holocene environmental changes in the Biržulis Lake region, NW Lithuania     

Migl&#x; Stan ikait&#x;  Valentinas Baltrnas  Petras &#x;inknas  Dalia Kisielien&#x;  Tomas Ostrauskas 《Quaternary International》2006,150(1):113

Palaeoenvironmental studies combining ¹⁴C dating, palaeobotanical and archaeological data provide information about the human reaction to Holocene environmental changes registered in the surroundings of Biržulis Lake in northwest Lithuania.Responding to water regression, early Mesolithic communities were established on the lower lake terraces, which were overgrown by predominantly birch and pine forest. The formation of a mixed forest with Ulmus (immigrated at 8100–7500 cal yr BC), Corylus (7600–7200 cal yr BC) and Alnus (7300–6900 cal yr BC) provided plenty of natural resources, which led to the increase in population during the late Mesolithic. The expansion of Tilia (6400–5900 cal yr BC) and Quercus (5900–5700 cal yr BC), as well as the subsequent flourishing of broad-leaved forest, provided inhabitants with suitable living conditions.The reduction of broad-leaved woodland and the expansion of Picea (4400–3700 cal yr BC), which suggest changing temperature and moisture conditions as well as increasing erosion activity, could have negatively influenced the early-middle Neolithic population, as evidenced by the partial abandoning of the land. The lowering of the water level and thinning of the forest structure possibly related to some dry episode, positively influenced late Neolithic groups, as intensive exploitation of the area, including the earliest attempts at agriculture, has been registered. Since 1770–1490 cal yr BC, when intensive bogging began, evidence of periodic inhabitation around the lake has been registered.  相似文献   

Steady-State Soil Vapor Extraction from a Pressure-Controlled or Flow-Controlled Well     

Tomas Perina  Tien-Chang Lee 《Ground Water Monitoring & Remediation》2005,25(3):63-72

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Natural attenuation of chlorinated solvents: a comparative study     

Tomas Kuchovsky  Ondra Sracek 《Environmental Geology》2007,53(1):147-157

Sites contaminated by chlorinated solvents have been investigated. Sites Dolni Tresnovec and Zetor located in Czech Republic exhibit relatively reducing conditions. Primary chlorinated solvents are attenuated by reductive dechlorination processes, and plumes have probably reached steady-state at Zetor site. Terminal electron accepting processes (TEAP) are ferric iron reduction and sulfate reduction at respective Dolni Tresnovec and Zetor sites. Source of organic matter at Dolni Tresnovec site is the waste deposited at local landfill. At Zetor site reducing conditions are linked to the petroleum hydrocarbons spill from broken pipeline. In contrast, site Dubnica in Slovak Republic exhibits oxidizing conditions, and natural attenuation of chlorinated solvents occurs mostly by dispersion. Modeling by the program BIOCHLOR indicated formation of steady-state plumes close to source at Zetor site, much longer steady-state plumes at Dolni Tresnovec site, and extremely long plumes at Dubnica site. Results demonstrate an important role of redox conditions in natural attenuation of chlorinated solvents.  相似文献   

A decameter type II burst associated with a behind-the-limb flare     

Tomas E. Gergely  Mukul R. Kundu 《Solar physics》1976,48(2):357-360

The characteristics of a decameter type II burst associated with a possible behind-the-limb flare are discussed. The burst source had an unusually high velocity. Assuming that the disturbance propagated as an MHD wave, the magnetic field strength at the 40 MHz plasma level is estimated to be 5.6 gauss.  相似文献   

Further studies on the Fennoscandian gravity field versus the Moho depth and land uplift     

Lars E. Sjöberg  Huaan Fan  Tomas Nord 《Journal of Geodesy》1994,69(1):32-42

Whether post-glacial rebound or/and crustal variation contributes to the pattern of the Fennoscandian gravity field has been of great interest to geoscientists. Previous numerical studies are based on different Moho maps, different global Earth gravity models and different isostatic models of Pratt type, resulting in quite different conclusions.In this study, we use the improved Moho depth map of Korja et al. (1993), the OSU91A Earth gravity model and a refined modeling of the Moho depth contribution. We conclude that not more than about 40% and 30% of the Fennoscandian geoid and gravity depressions of the orders of -12m and -40 mGal might be caused by crustal thickening, leaving at least -6 m and -28 mGal to be adjusted in accordance with post-glacial rebound.  相似文献   

Heterogeneous processes of geochemical migration: V. S. Golubev and A. A. Garibyants,Consultant Bureau, 1971, 150 pp. Translated by J. P. Fitzsimmons. $22.50     

Tomas Paces 《Geochimica et cosmochimica acta》1973,37(3):711-712

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Phosphorus Cycling in a Freshwater Estuary Impacted by Cyanobacterial Blooms     

Jolita Petkuviene  Mindaugas Zilius  Irma Lubiene  Tomas Ruginis  Gianmarco Giordani  Arturas Razinkovas-Baziukas  Marco Bartoli 《Estuaries and Coasts》2016,39(5):1386-1402

The availability of reactive phosphorus (P) may promote cyanobacterial blooms, a worldwide increasing phenomenon. Cyanobacteria may also regulate benthic P cycling through labile organic input to sediments, favouring reduced conditions and P release, ultimately acting as self-sustainment mechanism for the phytoplankton blooms. To analyse P–cyanobacteria feedbacks and compare external versus internal loads, we investigated P cycling in the Curonian Lagoon, a freshwater estuary with recurrent summer blooms. At two sites representing the dominant sediment types, we characterised P pools and mobility, via combined pore water analysis, calculation of diffusive exchanges and flux measurements via sediment core incubations. Annual P budgets were also calculated, to analyse the whole lagoon role as net sink or source. Muddy sediments, representing nearly 50 % of the lagoon surface, displayed higher P content if compared with sandy sediments, and most of this pool was reactive. The muddy site had consequently higher pore water dissolved inorganic phosphorus (DIP) concentrations maintaining high diffusive gradients. However, measured fluxes suggested that both sediment types were mostly P sinks except for a large DIP regeneration (nearly 30 μmol m^?2 h^?1) recorded at the muddy site during an intense cyanobacteria bloom. Such internal regeneration had the same order of magnitude as the annual external P load and may offset the net annual DIP sink role of the estuary. It may also prolong the duration of the bloom. Our results suggest that positive feedbacks can regulate N-fixing cyanobacteria blooms and internal P recycling, through either diffusive fluxes or sediment settling and resuspension.  相似文献   

Meteoric phreatic speleothems and the development of cave stratigraphy: An example from Tounj Cave, Dinarides, Croatia     

Ljubomir Babi?  Damir Lackovi?  Nada Horvatin?I? 《Quaternary Science Reviews》1996,15(10):1013-1022

Speleothems occurring in some caves of the carbonate Dinarides line all channel surfaces, and have been deposited from meteoric waters under phreatic conditions. Such phreatic speleothemic deposition modifies common experience (l) that meteoric phreatic conditions cause dissolutional widening of cave voids, and (2) that speleothems imply vadose conditions. The phreatic speleothems described here postdate an early polygenetic evolution of the cave voids, and predate the last, vadose stage. They were likely produced during the late/postglacial warming period, when dissolved carbonate was amply supplied, and when there was much water available for saturation of underground voids. Phreatic speleothems may be used as a tool for time correlation of internal deposits, both within one cave and within a karst region. They indicate an important stage in the history of the ground-water regime of an area. In general, phreatic speleothems help in better understanding of the development of subterranean voids and related karst/palaeokarst.  相似文献