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  • 1
    Publication Date: 2017-01-04
    Description: Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 112 (2007): G04S54, doi:10.1029/2006JG000353.
    Description: Dramatic changes have been observed in the Arctic over the last century. Many of these involve the storage and cycling of fresh water. On land, precipitation and river discharge, lake abundance and size, glacier area and volume, soil moisture, and a variety of permafrost characteristics have changed. In the ocean, sea ice thickness and areal coverage have decreased and water mass circulation patterns have shifted, changing freshwater pathways and sea ice cover dynamics. Precipitation onto the ocean surface has also changed. Such changes are expected to continue, and perhaps accelerate, in the coming century, enhanced by complex feedbacks between the oceanic, atmospheric, and terrestrial freshwater systems. Change to the arctic freshwater system heralds changes for our global physical and ecological environment as well as human activities in the Arctic. In this paper we review observed changes in the arctic freshwater system over the last century in terrestrial, atmospheric, and oceanic systems.
    Description: The authors gratefully acknowledge the National Science Foundation (NSF) for funding this synthesis work. This paper is principally the work of authors funded under the NSF-funded Freshwater Integration (FWI) study.
    Keywords: Arctic ; Freshwater ; System ; Changes ; Impacts
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    Elsevier
    In:  Global and Planetary Change, 48 (1-3). pp. 84-95.
    Publication Date: 2015-01-26
    Description: Historical data analyses show that the Lena River and its major tributaries experienced an extended low water period over 1936–1957 and high water periods over 1974–1983 and 1988–2001. Higher than normal river discharge and annual precipitation is particularly pronounced since the late 1960s due to large-scale changes in atmospheric circulation patterns. The trend in runoff observed in the Lena River basin increased by 10% from 1936 to 2001 due to extended wet periods during the second part of last century. The trend is weakened for the Vilui River basin since it experiences reservoir regulation, which causes additional water losses through reservoir filling and increased evaporation. Runoff regulation strongly affects the winter runoff regime of both the Vilui River and the lower reaches of the Lena River causing an increased winter discharge at the Lena river outlet station of approximately 33%.
    Type: Article , PeerReviewed
    Format: text
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  • 3
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    AGU (American Geological Union)
    In:  Geophysical Research Letters, 31 (21). L21502.
    Publication Date: 2015-01-26
    Description: The consistency of long-term yearly precipitation and runoff trends over the largest Arctic watersheds (Ob, Yenisei and Lena Rivers) is examined. Three gridded precipitation datasets (Climatic Research Unit, University of Delaware, NCEP) are used for comparative analyses with runoff data collected at basin outlets. The results generally demonstrate inconsistency in long-term changes of basin precipitation and runoff. The Yenisei River runoff increases significantly, while precipitation data show mostly negative trends. The Ob River does not show any significant trend either in precipitation or runoff. Positive trend in the Lena River runoff is accompanied by a weak precipitation increase; however, the precipitation increase is not strong enough to support the observed runoff change. The inconsistency identified in basin precipitation and runoff trends suggests uncertainty in both the quality of basin precipitation and runoff datasets, as well as the perceived hydrologic factors impacting runoff change.
    Type: Article , PeerReviewed
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  • 4
    Publication Date: 2015-03-03
    Description: This study systematically analyzes long-term (1950-1992) stream temperature records for the major sub-basins within the Lena River watershed in order to describe water temperature regimes over the various parts of the Lena watershed and document significant stream temperature changes induced by reservoir regulation, and by natural variations/changes. The results show that the open water season can be divided into three consecutive stages---"increasing temperature stage" in the early open water season, "stable temperature stage" in the mid-warm season, and "decreasing temperature stage" in the late open water season. Temperature conditions are similar over the Aldan and Upper Lena regions. However, stream temperatures at the Lena basin outlet are up to 8 °C lower than those over the southern sub-basins. This suggests that the latitudinal difference in climatic variables, such as air temperature, might be the major control on stream temperature regime. Results also demonstrate that the reservoir regulation has a strong influence on the regional water temperature regime and change in the regulated sub-basin. Reservoir regulation has increased (decreased) the downstream water temperatures in the Vilui valley during the early (mid) open water season. Trend analyses show consistent warming trends across the entire Lena River basin in the early open water season. This may indicate a response to earlier snowmelt over the Lena River watershed. Trend results also demonstrate that the Aldan tributary, without much human impact, experiences warming (cooling) trends in the first (second) half of the open water season, leading to a stream temperature regime shift toward early open water season. The upper Lena River has warming (cooling) trends in the early (mid-late) open water season. Over the regulated Vilui tributary, however, stream temperatures have significantly increased in the early and late parts of the warm season due to combined effects of natural changes and reservoir regulation. Over the Lena basin as a whole, strong positive correlations have been found between the basin mean monthly air and water temperatures during the warm season. Increasing water temperatures were observed during the early and mid-June. Because of stream temperature increase in this peak flow period, the Lena River heat flux has gone up by 23% in June. This may have considerable impact on the thermal conditions of the Laptev Sea in the early summer season.
    Type: Article , PeerReviewed
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  • 5
    Publication Date: 2019-11-15
    Description: Ten years of terrestrial water storage anomalies from the Gravity Recovery and Climate Experiment (GRACE) were used to estimate high latitude snowfall accumulation using a mass balance approach. The estimates were used to assess two common gauge-undercatch correction factors (CFs): Legates climatology (CF-L) utilized in the Global Precipitation Climatology Project (GPCP), and Fuchs dynamic correction model (CF-F) used in the Global Precipitation Climatology Centre (GPCC) Monitoring product. The two CFs can be different by more than 50%. CF-L tended to exceed CF-F over northern Asia and Eurasia, while the opposite was observed over North America. Estimates of snowfall from GPCP, GPCC-L (GPCC corrected by CF-L), and GPCC-F (GPCC corrected by CF-F) were 62%, 64%, and 46% more than GPCC over northern Asia and Eurasia. GRACE-based estimate (49% more than GPCC) was the closest to GPCC-F. We found that as near surface air temperature decreases, the products increasingly underestimated the GRACE-based snowfall accumulation. Overall, GRACE showed that CFs are effective in improving GPCC estimates. Furthermore, our case studies and overall statistics suggest that CF-F is likely more effective than CF-L in most of the high latitude regions studied here. GPCP showed generally better skill than GPCC-L, which might be related to the use of satellite data or additional quality controls on gauge inputs to GPCP. This study suggests that GPCP can be improved if it employs CF-L instead of CF-F to correct for gauge undercatch. However, this implementation requires further studies, region-specific analysis, and operational considerations.
    Keywords: Meteorology and Climatology
    Type: GSFC-E-DAA-TN60737 , Journal of Climate (ISSN 0894-8755) (e-ISSN 1520-0442); 31; 21; 8689-8704
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  • 6
    Publication Date: 2019-09-28
    Description: Dam building and reservoir operations alter the downstream hydrological regime, and as a result, affect the health of the river aquatic ecosystem, particularly for large-scale cascade reservoirs. This study investigated the impact of the Gezhouba Reservoir (GR) and the Three Gorges Reservoir (TGR) on the spawning conditions of two critical taxa, i.e., the endemic four major carps and the endangered Chinese sturgeon in the Yangtze River. We analyzed the flow, sediment, and thermal regime in these two taxa spawning seasons and compared their features between the predam and postdam periods. Our results revealed that the GR and the TGR had altered the frequency distributions of flow, sediment, and water temperature to different degrees, with the impact by the GR on the carps and Chinese sturgeon ranked as water temperature 〉 flow, sediment 〉 water temperature 〉 flow, and the effect of the TGR on these two taxa were ordered as flow 〉 water temperature, sediment 〉 flow 〉 water temperature. For the GR, the satisfying degree of the suitable flow and water temperature of the carps increased, whilst the suitable flow, sediment, and water temperature for the Chinese sturgeon decreased. These changes in TGR showed a significant ascending (descending) trend in the suitable flow (water temperature) for the carps, and a clear decreasing trend in the flow, sediment, and temperature for Chinese sturgeon. Both the TGR and the GR had negative impacts on the spawning of these two taxa in terms of the rising/falling flow characteristics.
    Electronic ISSN: 2073-4441
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 7
  • 8
    Publication Date: 2012-06-05
    Description: In this study, long-term discharge data and climate records, such as temperature and precipitation during 1977-2006, have been used to define basin climatic and hydrologic regimes and changes. Discharge analyses at four key gauging stations (Eagle, Stevens Village, Nenana, and Pilot Station) in the Yukon River Basin show that the runoff in the cold season (November to April) is low with small variations, whereas it is high (28500-177000ft3/s; 810-5000m3/s) with high fluctuations in the warm season (May to October). The Stevens Village Station is in the upper basin and has similar changes with the flow near basin outlet. Flow increases in May (61074ft3/s; 1729m3/s) and September (23325ft3/s; 660m3/s); and decreases in July (35174ft3/s; 996m3/s) and August (6809ft3/s; 193m3/s). Discharge in May at the Pilot Station (near the basin outlet) shows a positive trend (177000ft3/s; 5010m3/s). Daily flow analyses show high fluctuation during the warm season and very low flow during the cold season; the 10-year average analyses of daily flow at Pilot Station show a small increase in the peak and its timing shifted to a little earlier date. The annual flow, average of 227900ft3/s (6450m3/s) with high inter-annual fluctuations, has increased by 18200ft3/s (or 8%; 520m3/s) during 1977-2006. From 1977 to 2006, basin air temperature in June has increased by 3.9°F (2.2°C) and decreased by 10.5°F (5.8°C) in January. A strong and positive correlation exists between air temperature in April and discharge in May, whereas a strong and negative correlation relates August temperature and September discharge. Negative trend during 1977-2006 is observed for precipitation in June (0.6 in.; 15mm) with a confidence over 93%. Precipitation in August and September has strong and positive correlations with discharge in September and October at basin outlet; the precipitation in other months has weak correlation with the discharge. The mean annual precipitation during 1977-2006 increased by 1.1 in. (or 8%; 28mm), which contributes to the annual flow increase during the study period. © 2012 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 9
    Publication Date: 2014-10-14
    Description: This study assessed the long-term (1979-2008) water budget closures for 19 large cold region drainage basins in Canada using recently developed datasets for precipitation (P), land surface evapotranspiration and water surface evaporation, and observed streamflow. Total water storage (TWS) trends from the GRACE satellite observations were also used to assist the assessment. The objectives are to quantify the magnitudes and spatial patterns of the water budget imbalance (ε) and its source of errors for these cold region basins. Results showed that the water budget was closed within 10% of the P on average for all the basins. The ε showed a general pattern of positive values in the south and negative values in the north and mountainous regions over the country. Basins with large ε values were mostly found in the north. Uncertainties in the water budget variables, particularly P, were found to play a major role in the ε. Significant trends in TWS were found over 11 basins, which accounted for 31% of their ε on average. Improvements in the observation network, data quality assurance, and spatial models for P are critical for further improving the water budget closure for the cold region drainage basins. © John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 10
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