Organic carbon flow in the Ob, Yenisey Rivers and Kara Sea of the Arctic region     

Krishnamurthy RV  Machavaram M  Baskaran M  Brooks JM  Champs MA 《Marine pollution bulletin》2001,42(9):726-732

Stable carbon isotope and elemental C/N ratios of the organic fraction of a set of samples along a transect in the Ob and Yenisey Rivers into the Kara Sea in the Arctic were measured. Previously, the concentrations of 239,240Pu and 137Cs in these same samples had been determined. The coupled measurements were carried out to assess possible connectivity between organic carbon flow into the Kara Sea and transport of radioactive nuclides in this marine environment. Organic carbon flow into the Kara Sea is influenced significantly by terrigenous sources carried by the Ob and Yenisey Rivers. The carbon isotope-organic carbon relationship provides evidence that a rich source of terrigenous carbon exists in the riverine system. A weak, but significant relationship between stable carbon isotope ratio and 137Cs suggests that most of the 137Cs is derived from riverine particles, as compared to Pu which is also derived from in situ scavenging within the water column.  相似文献   

Late Glacial and Holocene Paleolimnology of two temperate lakes inferred from sediment organic δ13C chronology     

N. A. Lovan  R. V. Krishnamurthy 《Journal of Earth System Science》2000,109(1):129-140

The stable carbon isotope (δ¹³C) and elemental C/N ratios in Total Organic Carbon (TOC) extracted from radiometrically dated cores from two Midwestern USA lakes were determined to investigate the factors that control these values in temperate lakes. The range of δ¹³C values (-26 to -32%) and C/N ratios (mean value ∼10.8) are typical of values reported for other temperate lake organic matter in this region. In the core from Lake Winnebago, Wisconsin, a negative correlation was seen between the TOC and δ¹³C, which can be interpreted in terms of a re-mixing and consumption of sedimented organic carbon along with rapid equilibration throughout the water column. No correlation was seen between the TOC and δ¹³C in the record from Ladd Lake, Ohio, implying that in this latter lake productivity alone was not a singular process controlling the isotope ratio. Here, it is suggested that equilibrium conditions are maintained such that the DIC of the water is never depleted of aqueous CO₂ during high organic production and the resulting δ¹³C of the organic carbon lacks correlation with the TOC. Further, in this lake a fine resolution analysis was carried out which indicated a possible anthropogenic influence on the isotope ratio around times when human settlement (∼300 yrs ago) and enhanced agricultural practices (∼80 yrs ago) were significant. The study shows that carbon isotope studies are useful in paleolimnologic investigations.  相似文献   

Daily modes of South Asian summer monsoon variability in the NCEP climate forecast system   总被引：1，自引：0，他引：1  

Deepthi Achuthavarier  V. Krishnamurthy 《Climate Dynamics》2011,36(9-10):1941-1958

The leading modes of daily variability of the Indian summer monsoon in the climate forecast system (CFS), a coupled general circulation model, of the National Centers for Environmental Predictions (NCEP) are examined. The space?Ctime structures of the daily modes are obtained by applying multi-channel singular spectrum analysis (MSSA) on the daily anomalies of rainfall. Relations of the daily modes to intraseasonal and interannual variability of the monsoon are investigated. The CFS has three intraseasonal oscillations with periods around 106, 57 and 30?days with a combined variance of 7%. The 106-day mode has spatial structure and propagation features similar to the northeastward propagating 45-day mode in the observations except for its longer period. The 57-day mode, despite being in the same time scale as of the observations has poor eastward propagation. The 30-day mode is northwestward propagating and is similar to its observational counterpart. The 106-day mode is specific to the model and should not be mistaken for a new scale of variability in observations. The dominant interannual signal is related to El Ni?o-Southern Oscillation (ENSO), and, unlike in the observations, has maximum variance in the eastern equatorial Indian Ocean. Although the Indian Ocean Dipole (IOD) mode was not obtained as a separate mode in the rainfall, the ENSO signal has good correlations with the dipole variability, which, therefore, indicates the dominance of ENSO in the model. The interannual variability is largely determined by the ENSO signal over the regions where it has maximum variance. The interannual variability of the intraseasonal oscillations is smaller in comparison.  相似文献   

Mainstreaming local perceptions of hurricane risk into policymaking: A case study of community GIS in Mexico   总被引：1，自引：0，他引：1  

P. Krishna Krishnamurthy  Joshua B. Fisher  Craig Johnson 《Global Environmental Change》2011,21(1):143-153

This article suggests a framework for incorporating and communicating local perceptions of hurricane risk into policymaking through a case study conducted at El Zapotito commune in the State of Veracruz, Mexico. The authors constructed a geographical information system (GIS)-based model to quantify and spatially assess specific household-level vulnerabilities from information generated through interviews. This research developed a household vulnerability index applied to a participatory GIS to map vulnerability to hurricane hazard. The results indicate that infrastructural weaknesses are the most important factor contributing to vulnerability, explaining on their own 72.2% of the variation in the vulnerability patterns. These findings are corroborated by a vulnerability and capacity assessment (VCA), which shows that the community lacks strategies to cope with unsafe housing. It is suggested that linking community participation with modern techniques to analyse risk can empower communities and mobilise their capacities to address very specific vulnerabilities.  相似文献   

Monsoon variability and chemical weathering during the late Pleistocene in the Goriganga basin, higher central Himalaya, India     

Steven P. Beukema  R.V. Krishnamurthy  N. Juyal  N. Basavaiah  A.K. Singhvi 《Quaternary Research》2011,75(3):597-604

Stable isotope analysis along with radiocarbon and luminescence dating of late Pleistocene lacustrine deposits at Burfu in the higher central Himalaya are used to interpret hydrologic changes in the lake basin. From 15.5 ka to ~ 14.5 ka the Burfu lake was largely fed by melting glaciers. A warming event at 14.5 ka suggests an enhanced monsoon and increased carbonate weathering. From ~ 13.5 ka to ~ 12.5 ka the isotopic data suggest large-amplitude climate variability. Following this, the isotope data suggest a short-lived, abrupt cooling event, comprising a ~ 300-yr intense cool period followed by a ~ 500-yr interval of moderate climate. A shift in isotope values at ~ 11.3 ka may signify a strengthening monsoon in this region. The inferred climatic excursions appear to be correlative, at least qualitatively, with global climatic events, and perhaps the Burfu lake sequence provides regional evidence of globally recorded excursions. This study also suggests a potential use of radiocarbon ages in specific environments as a paleoenvironmental proxy.  相似文献   

A Photographic Atlas of Flood Basalt Volcanism by Hetu Sheth,Springer International Publishing AG 2018, 363p. Rs.18,910.     

P. Krishnamurthy 《Journal of the Geological Society of India》2018,91(1):120-124

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Report on the International Seminar on Carbonatites-Alkaline Rocks and Associated Economic Mineral Deposits and Field Visit to Amba Dongar Carbonatite Complex     

P. Krishnamurthy  Raymond A. Duraiswami  S. G. Viladkar 《Journal of the Geological Society of India》2018,91(2):259-260

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Large-Scale Synoptic Systems and Fog During the C-FOG Field Experiment     

Dorman  Clive E.  Hoch  Sebastian W.  Gultepe  Ismail  Wang  Qing  Yamaguchi  Ryan T.  Fernando  H. J. S.  Krishnamurthy  Raghavendra 《Boundary-Layer Meteorology》2021,181(2-3):171-202

Boundary-Layer Meteorology - The goal of this work is to summarize synoptic meteorological conditions during the Coastal Fog (C-FOG) field project that took place onshore and offshore of the Avalon...  相似文献   

A Review of Coastal Fog Microphysics During C-FOG     

Gultepe  I.  Heymsfield  A. J.  Fernando  H. J. S.  Pardyjak  E.  Dorman  C. E.  Wang  Q.  Creegan  E.  Hoch  S. W.  Flagg  D. D.  Yamaguchi  R.  Krishnamurthy  R.  Gaberšek  S.  Perrie  W.  Perelet  A.  Singh  D. K.  Chang  R.  Nagare  B.  Wagh  S.  Wang  S. 《Boundary-Layer Meteorology》2021,181(2-3):227-265

Boundary-Layer Meteorology - Our goal is to provide an overview of the microphysical measurements made during the C-FOG (Toward Improving Coastal Fog Prediction) field project. In addition, we...  相似文献   

Cartosat-1 derived DEM (CartoDEM) towards Parameter Estimation of Microwatersheds and Comparison with ALTM DEM     

Rajashree Vinod Bothale  A. K. Joshi  Y. V. N. Krishnamurthy 《Journal of the Indian Society of Remote Sensing》2013,41(3):487-495

Hydrologic analysis of microwatersheds is essential for water resources planning at large scale. Space based input for decentralized planning at panchayat level use high resolution DEM. Drainage and slope play important role in planning and Digital Elevations Models (DEM) are widely being used for estimation of hydrologic parameters which are useful as input for hydrologic models. The estimates vary as per resolution and type of DEM. This paper evaluates the suitability of DEM derived through Cartosat-1 satellite stereo data(CartoDEM) for hydrologic parameter estimation of microwatersheds and compares the results with Airborne Laser Terrain Mapper (ALTM) based DEM data. Comparison is based on the hydrologic parameters delineated in Geographical Information System. Microwatersheds are delineated and drainage length extracted using two different cell sizes for both DEMs. Correctness Index, Figure of Merit, visual comparison, Percent within buffer and Junction comparison method, compared extracted river network. Average watershed slope is calculated using three different methods. CartoDEM derived drainage is comparable with ALTM derived drainage. There is high correlation between Carto5 and Caro10 DEMs in terms of drainage delineation and slope calculation. Average watershed slope vary as per calculation methods but average channel slope value (S3) although less, is comparable across DEMs.  相似文献