ALBERT

Description: Potential changes in glacier area, mass balance and runoff in the Yarkant River Basin (YRB) and Beida River Basin (BRB) are projected for the period from 2011 to 2050 employing the modified monthly degree-day model forced by climate change projection. Future monthly air temperature and precipitation were derived from the simple average of 17, 16 and 17 GCM projections following the A1B, A2 and B1 scenarios, respectively. These data were downscaled to each station employing the Delta method, which computes differences between current and future GCM simulations and adds these changes to observed time-series. Model parameters calibrated with observations or results published in the literature between 1961 and 2006 were kept unchanged. Annual glacier runoff in YRB is projected to increase until 2050, and the total runoff over glacier area in 1970 is projected to increase by about 13–35% during 2011–2050 relative to the average during 1961–2006. Annual glacier runoff and the total runoff over glacier area in 1970 in BRB is projected to increase initially and then to reach a tipping point during 2011–2030. There are prominent increases in summer, but only small increase in May and October of glacier runoff in YRB, and significantly increases during late spring and early summer and significant decreases in July and late summer of glacier runoff in BRB. This study highlights the great differences among basins in their response to future climate warming. The specific runoff from areas exposed after glacier retreat relative to 1970 is projected to general increasing, which must be considered when evaluating the potential change of glacier runoff. Copyright © 2011 John Wiley & Sons, Ltd.

Description: The retreat of mountain glaciers and ice caps has dominated the rise in global sea level and are likely to remain an import component of eustatic sea-level rise in the 21st century. Mountain glaciers are critical in supplying freshwater to populations inhabiting the valleys downstream who heavily rely on glacier runoff, such as arid and semi-arid regions of western China. Owing to recent climate warming and the consequent rapid retreat of many glaciers, it is essential to evaluate the long-term change in glacier melt water production, especially when considering the glacier area change. This paper describes the structure, principles and parameters of a modified monthly degree-day model considering glacier area variation. Water balances in different elevation bands are calculated with full consideration of the monthly precipitation gradient and air temperature lapse rate. The degree-day factors for ice and snow are tuned by comparing simulated variables to observation data for the same period, such as mass balance, equilibrium line altitude and glacier runoff depth. The glacier area-volume scaling factor is calibrated with the observed glacier area change monitored by remote sensing data of seven sub-basins of the Tarim interior basin. Based on meteorological data, the glacier area, mass balance and runoff are estimated. The model can be used to evaluate the long term changes of melt water in all glacierized basins of western China, especially for those with limited observation data. Copyright © 2011 John Wiley & Sons, Ltd.

Description: The glacier mass balance, area change, and glacier runoff in the Yarkant River Basin (YRB) and the Beida River Basin (BRB) are estimated for the period from 1961 to 2006 by employing a modified monthly degree-day model. Comparisons between the simulated and observed mass balance, equilibrium line altitude, and glacier runoff suggest that the model can be used to analyze the long-term changes of glacier mass balance and runoff in the YRB and the BRB. The glacier mass balances of the YRB and the BYB both have a significantly decreasing trend with −4.39 mm a -1 and −8.15 mm a -1 from 1961 to 2006 owing to significantly increased ablation caused by increasing summer air temperatures, especially since 1996. The total runoff in glacier areas has a significant increasing trend with 0.23 × 10 8  m 3 a -1 and 0.02 × 10 8  m 3 a -1 in the YRB and the BRB, respectively. By comparing the mean mass balance during 1961 to 1986 and that during 1987 to 2006, the sensitivity of the glacier mass balance to temperature of the BRB is 0.33 m a -1  °C, nearly twice as much as that of the YRB 0.16 m a -1  °C. The primary cause of this difference of glacier temperature sensitivity in the YRB and the BRB is that the glacier elevation band area weighted altitude of the YRB is about 700 m higher than that of BRB. The glacier elevation band area weighted summer air temperature in the YRB is around 2 °C lower than that of the BRB. Therefore, the annual positive degree day of the YRB and the BRB increase by about 21.0 °C and 77.3 °C respectively when the summer air temperature increases by 1 °C , resulting into more glacier ablation and runoff in the BRB than in the YRB. Copyright © 2011 John Wiley & Sons, Ltd.

Description: The forthcoming Surface Water and Ocean Topography (SWOT) NASA satellite mission will measure water surface width, height, and slope of major rivers worldwide. The resulting data could provide an unprecedented account of river discharge at continental scales, but reliable methods need to be identified prior to launch. Here, we present a novel algorithm for discharge estimation from only remotely sensed stream width, slope, and height at multiple locations along a mass-conserved river segment. The algorithm, termed the Bayesian AMHG-Manning (BAM) algorithm, implements a Bayesian formulation of streamflow uncertainty using a combination of Manning's equation and at-many-stations hydraulic geometry (AMHG). Bayesian methods provide a statistically defensible approach to generating discharge estimates in a physically underconstrained system, but rely on prior distributions that quantify the a priori uncertainty of unknown quantities including discharge and hydraulic equation parameters. These were obtained from literature-reported values and from a USGS dataset of acoustic Doppler current profiler (ADCP) measurements at USGS stream gauges. A dataset of simulated widths, slopes, and heights from 19 rivers was used to evaluate the algorithms using a set of performance metrics. Results across the 19 rivers indicate an improvement in performance of BAM over previously tested methods, and highlight a path forward in solving discharge estimation using solely satellite remote sensing.

Description: High-latitude regions are a hot spot of global warming, but the scarce availability of observations often limits the investigation of climate change impacts over these regions. However, the utilization of satellite-based remote sensing data offers new possibilities for such investigations. In the present study, vegetation greening, vegetation moisture and lake distribution derived from medium-resolution satellite imagery were analyzed over the Pechora catchment for the last 35 years. Here, we considered the entire Pechora catchment and the Pechora Delta region, located in the northern part of European Russia, and we investigated the vegetation and lake dynamics over different permafrost zones and across the two major biomes, taiga, and tundra. We also evaluated climate data records from meteorological stations and re-analysis data to find relations between these dynamics and climatic behavior. Considering the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Moisture Index (NDMI) in the summer, we found a general greening and moistening of the vegetation. While vegetation greenness follows the evolution of summer air temperature with a delay of one year, the vegetation moisture dynamics seems to better concur with annual total precipitation rather than summer precipitation, and also with annual snow water equivalent without lag. Both NDVI and NDMI show a much higher variability across discontinuous permafrost terrain compared to other types. Moreover, the analyses yielded an overall decrease in the area of permanent lakes and a noticeable increase in the area of seasonal lakes. While the first might be related to permafrost thawing, the latter seems to be connected to an increase of annual snow water equivalent. The general consistency between the indices of vegetation greenness and moisture based on satellite imagery and the climate data highlights the efficacy and reliability of combining Landsat satellite data, ERA-Interim reanalysis and meteorological data to monitor temporal dynamics of the land surface in Arctic areas.

Description: Potential changes in glacier area, mass balance and runoff in the Yarkant River Basin (YRB) and Beida River Basin (BRB) are projected for the period from 2011 to 2050 employing the modified monthly degree-day model forced by climate change projection. Future monthly air temperature and precipitation were derived from the simple average of 17, 16 and 17 General Circulation Model (GCM) projections following the A1B, A2 and B1 scenarios, respectively. These data were downscaled to each station employing the Delta method, which computes differences between current and future GCM simulations and adds these changes to observed time series. Model parameters calibrated with observations or results published in the literature between 1961 and 2006 were kept unchanged. Annual glacier runoff in YRB is projected to increase until 2050, and the total runoff over glacier area in 1970 is projected to increase by about 13%-35% during 2011-2050 relative to the average during 1961-2006. Annual glacier runoff and the total runoff over glacier area in 1970 in BRB is projected to increase initially and then to reach a tipping point during 2011-2030. There are prominent increases in summer, but only small increase in May and October of glacier runoff in YRB, and significant increases during late spring and early summer and significant decreases in July and late summer of glacier runoff in BRB. This study highlights the great differences among basins in their response to future climate warming. The specific runoff from areas exposed after glacier retreat relative to 1970 is projected to general increasing, which must be considered when evaluating the potential change of glacier runoff. © 2011 John Wiley & Sons, Ltd.

Description: The glacier mass balance, area change, and glacier runoff in the Yarkant River Basin (YRB) and the Beida River Basin (BRB) were estimated from 1961 to 2006 by employing a modified monthly degree-day model. Comparisons between the simulated and observed mass balance, equilibrium line altitude, and glacier runoff suggest that the model can be used to analyze the long-term changes of glacier mass balance and runoff in the YRB and the BRB. The glacier mass balances of the YRB and the BYB both have a significantly decreasing trend with -4.39mm a -1 and -8.15mm a -1 from 1961 to 2006 because of a significant increase in ablation caused by increasing summer air temperatures, especially since 1996. The total runoff in glacier areas has a significant increasing trend with 0.23×10 8m 3 a -1 and 0.02×10 8m 3 a -1 in the YRB and the BRB, respectively. By comparing the mean mass balance during the period 1961 to 1986 with that of the 1987 to 2006, the BRB glacier mass balance's sensitivity to temperature is at 0.33m a -1°C, nearly twice as much as that of the YRB at 0.16m a -1°C. The difference between the glacier temperature sensitivity in the YRB and the BRB is primarily because the glacier elevation band area weighted altitude of the YRB is about 700m higher than that of BRB. The glacier elevation band area weighted summer air temperature in the YRB is around 2°C lower than that of the BRB. Therefore, the annual positive degree-day of the YRB and the BRB increases by about 21.0°C and 77.3°C respectively when the summer air temperature increases by 1°C, resulting into more glacier ablation and runoff in the BRB than in the YRB. © 2011 John Wiley & Sons, Ltd.

Description: The retreat of mountain glaciers and ice caps has dominated the rise in global sea level and is likely to remain an import component of eustatic sea-level rise in the 21st century. Mountain glaciers are critical in supplying freshwater to populations inhabiting the valleys downstream who heavily rely on glacier runoff, such as arid and semi-arid regions of western China. Owing to recent climate warming and the consequent rapid retreat of many glaciers, it is essential to evaluate the long-term change in glacier melt water production, especially when considering the glacier area change. This paper describes the structure, principles and parameters of a modified monthly degree-day model considering glacier area variation. Water balances in different elevation bands are calculated with full consideration of the monthly precipitation gradient and air temperature lapse rate. The degree-day factors for ice and snow are tuned by comparing simulated variables to observation data for the same period, such as mass balance, equilibrium line altitude and glacier runoff depth. The glacier area-volume scaling factor is calibrated with the observed glacier area change monitored by remote sensing data of seven sub-basins of the Tarim interior basin. Based on meteorological data, the glacier area, mass balance and runoff are estimated. The model can be used to evaluate the long-term changes of melt water in all glacierized basins of western China, especially for those with limited observation data. © 2011 John Wiley & Sons, Ltd.