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  • 1
    Publication Date: 2018-06-22
    Description: Publication date: Available online 19 June 2018 Source: Polar Science Author(s): Abdul Shakoor, Alice Burri, Mathias Bavay, Naeem Ejaz, Abdul Razzaq Ghumman, Francesco Comola, Michael Lehning Comparison of energy Balance (EB) and temperature Index (TI) snow/ice melt methods for glacio-hydrological modeling in the Alps has been the subject of numerous studies; however, the debate on which method is preferable under which conditions and for which application is still ongoing. In this study, both melting routines were tested within the common numerical framework of the fully distributed model (Alpine3D) to analyze the differences. We included two high-altitude Swiss alpine glaciered catchments, which represent two distinct types of glaciers, namely cirque and valley glaciers, with different weather conditions, topography, and data type. In this experiment, hydrological discharge in the Damma catchment was overestimated by the model with EB approach, which demonstrated Nash-Sutcliffe efficiency (NSE) of 0.61 mainly due to the overestimation of wind speed and longwave radiation. On the other hand, the TI approach obtained a high NSE of 0.93, as this simple conceptual model does not rely on the abovementioned variables. For the Arolla catchment, better results were observed for both EB and TI approaches, with slight underestimation in modeled runoff as shown by NSEs of 0.89 and 0.77, respectively. The very satisfactory performance of EB model at the Arolla catchment is due to the use of input data sets from local weather stations that are more representative of the real catchment conditions. It was observed that the EB melt scheme performs better if driven with correct meteorological data sets from catchment-representative stations and that the calibration procedure of TI-based model significantly affects its accuracy.
    Print ISSN: 1873-9652
    Topics: Geosciences
    Published by Elsevier
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  • 2
    Publication Date: 2018-06-21
    Description: Publication date: Available online 18 June 2018 Source: Polar Science Author(s): Amit Dharwadkar, S.P. Shukla, Abhishek Verma, Deepak Gajbhiye Schirmacher Oasis is an emergent isolated landmass, surrounded on all sides by ice, occurring along the Princess Astrid Coast in central Dronning Maud Land, East Antarctica. Geomorphological mapping on the oasis revealed different stages of glaciation/deglaciation during the current interglacial period. The scrutiny of various geomorphic signatures, both erosional and depositional, indicate that the deglaciation in this area, spanning a temporal range from 171 Ka to present, was episodic in nature. The recessional regime in Schirmacher Oasis was set in at ∼22 Ka and subsequently the area remained ice free. The warming trend, as evidenced by the continuous recession of ice front since eighties, points towards increase in the area of the oasis in future.
    Print ISSN: 1873-9652
    Topics: Geosciences
    Published by Elsevier
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  • 3
    Publication Date: 2018-06-17
    Description: Publication date: Available online 15 June 2018 Source: Polar Science Author(s): Yushiro Tsukada, Hiromichi Ueno, Naoki Ohta, Motoyo Itoh, Eiji Watanabe, Takashi Kikuchi, Shigeto Nishino, Kohei Mizobata Solar heating in summer in the Chukchi Sea was estimated using satellite-derived sea-ice concentration data and reanalysis shortwave radiation data. The shortwave radiation was validated by in-situ data obtained by the R/V Mirai and NCEP-CFSR/CFSv2 was found to reproduce in-situ data accurately compared with NCEP/NCAR Reanalysis 1 and ERA-Interim. Solar heating integrated over the Chukchi Sea in summer varied interannually from 3.6 × 10 20  J in 2000 to 6.7 × 10 20  J in 2015, and was up to twice the northward heat flux through the Bering Strait. The total heating in the Chukchi Sea implies that the heat in the Chukchi Sea provided by northward heat flux through the Bering Strait is amplified by solar heating in the Chukchi Sea. We further compared these heat fluxes into the Chukchi Sea with the summertime northward heat flux through Barrow Canyon, an indicator of heat flux from the Chukchi Sea to the Arctic basin. The northward heat flux through Barrow Canyon was affected by the interannual variation of solar heating in the eastern Chukchi Sea. These results imply that modification of Pacific water in the Chukchi Sea by solar heating plays an important role in the interannual variation in heat transport from the Chukchi Sea to the western Arctic basin.
    Print ISSN: 1873-9652
    Topics: Geosciences
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  • 4
    Publication Date: 2018-06-17
    Description: Publication date: Available online 15 June 2018 Source: Polar Science Author(s): Pinlu Cao, Miaomiao Liu, Zhuo Chen, Baoyi Chen, Qi Zhao Drilling with air reverse circulation is considered one of the most promising technologies in ice core drilling, especially in firn-ice drilling, as it has many advantages in preventing air circulation loss, improving stability of the borehole, and promoting penetration rate. The effectiveness of this technology depends on whether or not the ice chips and cores can be conveyed to the surface through the central channel of the drill tool. In order to determine the adequate volume flow rate of the gas needed to satisfy the demand for continuous return of the ice cores and chips, a mathematical model to evaluate the injection pressure was studied. A series of experiments were carried out to test the actual air velocity required to move ice cores and ice chips with different sizes and clearances between the ice cores and the inner wall of the pipe. Based on the calculation and testing results, the minimum air volume requirements with different borehole depths in ice core drilling with air reverse circulation were confirmed. For a borehole with depth of 1000 m and diameter of 134 mm, the volume flow rate and pressure of air under standard atmosphere condition are at least 6.27 m 3 /min and 0.70 MPa to transport ice chips and ice cores with diameter of 60 mm and length of 250 mm.
    Print ISSN: 1873-9652
    Topics: Geosciences
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  • 5
    Publication Date: 2018-06-14
    Description: Publication date: Available online 12 June 2018 Source: Polar Science Author(s): Sanja Knezevic Antonijevic, Jonathan M. Lees Ambient noise tomography is used to image Greenland's lithosphere, which passed over the Iceland plume between ∼70 and ∼40 Ma. Cross-correlations from 21 stations from GLISN seismic network were used to invert for 2-D Rayleigh wave phase velocity maps for 14 periods between 8 and 40 s. We find that Rayleigh wave phase velocities substantially vary across Greenland, with slow velocities coinciding with NW-SE trending Iceland plume track. In east Greenland the detected velocity reduction at longer periods (33–40s) reflects substantially thinned lithosphere, thermally ablated by the plume. From the east, the reduced velocities shift NW at shorter periods (12–20s), indicating shallowing of the plume-related slow anomaly. In north-central Greenland, the reduced velocities appear in the proximity of the plume ∼60 Ma, reflecting lithospheric weakening in the presence of residual heat that still persists within the lithosphere. Our results provide important new constraints on variations in the seismic velocity structure of Greenland's crust and uppermost mantle, revealing prolonged effects of the mantle plume on the overpassing craton.
    Print ISSN: 1873-9652
    Topics: Geosciences
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  • 6
    Publication Date: 2018-06-14
    Description: Publication date: Available online 12 June 2018 Source: Polar Science Author(s): Shabnam Choudhary, G.N. Nayak, Anoop Kumar Tiwari, N. Khare Source of sediments and depositional processes of surface sediments along the Prydz Bay were investigated through grain size, organic carbon, nitrogen, phosphorus, calcium carbonate and metal concentration. High content of sand and higher values of Al 2 O 3 and TiO 2 at shallow water depth indicate their terrigenous source and relatively higher hydrodynamic conditions near the coast. Al 2 O 3 /TiO 2 ratio ranging from 3.77- 12.73 suggests a mafic source for the sediments. C/N ratio ranging from 5.76 to 9.13 indicates autochthonous (in-situ) source for organic matter, for which phytoplanktons and algae may be the major contributors. However, N/P ratio lower than the Redfield ratio indicated a limitation of either N or P in the study area. Calcium carbonate concentration is low possibly due to increased loads of clay which must have caused the dilution of carbonates. Metals like Fe, Mn and Mg exhibit strong correlation with lithogenic elements while, the trace metals such as Cd, Co, Cu, Ni and Zn show significant correlation with organic elements indicating that lithogenic and biogenic inputs are their main sources. Trace elements namely, Cd and Zn show nutrient like behavior suggest the role of trace metal in addition to nutrients in the regulation of productivity. Thus, the present study provides an understanding of recent sedimentary environments and processes, which are used as a tool to interpret palaeoenvironmental records.
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    Topics: Geosciences
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  • 7
    Publication Date: 2018-06-14
    Description: Publication date: Available online 12 June 2018 Source: Polar Science Author(s): Pankaj Kumar, J.K. Pattanaik, N. Khare, S. Balakrishnan Major, trace and rare earth element (REE) concentrations in combination with textural and mineralogical analysis of sediments has been used to understand geochemical fractionation in the sediment due to weathering and subsequent transport in the Svalbard region. Surface sediments from different water depths and a short sediment core have been collected from two Fjord system Krossfjorden and Kongfjorden, located between Lat: 78° 50′ to 79° 30’ N and Long: 11°–13° E in the west coast of Svalbard (Arctic Ocean). Bimodal distributions of grain size suggest that the finer size sediments were possibly deposited from the suspended load and coarser size from melting of sea ice and iceberg. Geochemical study reflects that the variation of chemical composition of the sediments is due to first order fractionations of elements during the grain size reduction and subsequent transport. The chemical weathering in the catchment area is incipient and the grain size reduction is dominated by mechanical weathering. REEs are mainly controlled by the presence of less weathered aluminosilicate minerals in these sediments. The source rock composition of the sediments is intermediate between granitic and granodioritic, with negligible contribution from the mafic rocks.
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    Topics: Geosciences
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  • 8
    Publication Date: 2018-05-31
    Description: Publication date: Available online 29 May 2018 Source: Polar Science Author(s): Xiaodan Jiang, Houming Fan, Ying Zhan, Zhongkai Yuan This paper aims to present a novel and useful analytical technique to identify risk factors and calculate risk share proportions in the prospective Arctic shipping strategic alliance, an alliance formed by shipping companies, using the combination of interpretive structural modeling (ISM) and fuzzy analytic network process (F-ANP). Based on in-depth review of relevant literature and interviews with experts, thirty-three risk factors are identified and categorized into five clusters: environment, service and infrastructure, policy, economy, and relation. The ISM technique is applied to identify inherent interactions among risk factors and construct a structural graph. Based on the results of ISM, F-ANP is then used to quantify risk allocation proportion. The results reveal that establishing an alliance can effectively balance the risk sharing proportion among shipping enterprises and the alliance should focus on monitoring the environment, service and communication risks. The proposed modeling approach can be extremely valuable for Arctic shipping alliances to focus on the most prominent risks and effectively allocate risks among partners.
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    Topics: Geosciences
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  • 9
    Publication Date: 2018-05-24
    Description: Publication date: Available online 22 May 2018 Source: Polar Science Author(s): Anurag Kumar, Suneet Dwivedi, D.Ram Rajak, A.C. Pandey A coupled ocean sea ice model is used to carry out sensitivity experiments to decipher the respective roles of wind, heat and freshwater flux forcings in changing the sea ice variability (concentration, volume, salinity, and drift speed) of the Antarctic region with special emphasis near the Indian Stations, Maitri [11.7°E; 70.7°S] and Bharati [76.1°E; 69.4°S]. The simulations are carried out in the Southern Ocean region [9°E−78°E; 58°S-71°S] during 1997–2012 at a resolution of 6–10 km. It is found that the air-sea forcings greatly impact the spatio-temporal variability of the sea ice variables. In the absence of wind and heat/freshwater flux forcing, the sea ice concentration (SIC) and sea ice volume (SIV) of the region decreases, except at higher latitudes. The effect of absence of heat and freshwater flux forcing on the seasonal variability of the SIC and SIV is more as compared to the wind forcing. Interestingly, the absence of wind and heat flux forcing exhibit opposite nature in influencing the temporal variability of SIV around the Maitri and Bharati regions. On using the climatological wind and heat/freshwater flux forcing, the SIC and SIV of the region increases. The climatological wind forcing have a greater effect in increasing the SIC and SIV of the region as compared to corresponding heat and freshwater flux forcings. The highest contribution in the SIV comes from the thick ice. The SIV of thick ice is found to be significantly increasing (4% per year). However, the interannual increase in medium thick ice and thin ice is very small (0.1% per year). The changes in the sea ice drift speed and vertical stability of ocean is studied vis-à-vis changes in air-sea forcing. The mixed layer heat budget of the region is also estimated and the effect of wind and heat flux forcing on it is investigated.
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    Topics: Geosciences
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  • 10
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    Elsevier
    Publication Date: 2018-05-21
    Description: Publication date: Available online 19 May 2018 Source: Polar Science Author(s): Jaswant Singh, Rudra P. Singh, Rajni Khare Biodiversity of Antarctica includes climatically adapted microflora. Antarctic flora mainly contains cryptogams and are dominated by lichens, followed by mosses and algae. Among three bio-geographic zones of Antarctica, Sub-Antarctic zone is the most diverse and followed by Maritime and Continental zone. The Antarctic plant growth is largely limited to the coastal areas of Sub- and Maritime Antarctic regions. Two vascular plants; Deschampsia antarctica and Colobanthus quitensis are restricted along with other cryptogams at Antarctic Peninsula region. The average increase in temperature is the most prominent change in Antarctic Peninsula. Due to favorable conditions, cryptogams (lichens and mosses) are widely distributed in several localities of Antarctica. The algal growth is restricted to the semi permanent to permanent snow or melt ice and in floating water bodies of Antarctica. About 700 non-marine algal taxa were recorded from the different region of the Antarctica. Beside this, 200 additional taxa have been recorded from the continental Antarctica. The changes in temperature, pattern of cyclonic activity, availability of nutrients, water, high UV-B radiation along with other stresses posses obstacles for survival and distribution of Antarctic flora.
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    Topics: Geosciences
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