Inter-comparisons of thermodynamic sea-ice modeling results using various parameterizations of radiative flux

Radiative fluxes are of primary importance in the energy and mass balance of the sea-ice cover. Various parameterizations of the radiative fluxes are studied in a thermodynamic sea-ice model. Model outputs of the surface radiative and heat fluxes and mass balance are compared with observations. The contribution of short-wave radiation is limited to a long part of winter. Therefore, simple schemes are often sufficient. Errors in estimations of the short-wave radiation are due mainly to cloud effects and occasionally to multi-reflection between surface and ice crystals in the air. The long-wave radiation plays an important role in the ice surface heat and mass balance during most part of a winter. The effect of clouds on the accuracy of the simple radiative schemes is critical, which needs further attention. In general, the accuracy of an ice model depends on that of the radiative fluxes.

Stability of the Hailuogou glacier during the“9.5”Luding Earthquake:a preliminary assessment based on multi-source observations

On 5th September 2022,a magnitude Ms-6.8 earthquake occurred nearby Mt.Gongga,western Sichuan.The stability of the glaciers in east Mt.Gongga close to the epicenter was widely concerned due to the strong shake triggered by the earthquake.Using multi-source observations(including in-situ photographs,remote sensing datasets before and after the event),we carried out a preliminary assessment of the stability and hazard risks of the Hailuogou(HLG)glacier.Triggered by the earthquake,a small block of fractured ice at the lowest part of icefall collapsed.The magnitude of the coseismic ice avalanche was relatively small,which is comparable in size to most ice avalanches over the past seven years,but much less than the previous mapped largest one(03 April 2018,runout~699 m).One most recent large(runout~608 m)ice avalanche occurred between 01 and 04 September,just before the earthquake,likely unloaded large amount of ice mass and made a larger ice avalanche avoided during the earthquake shake.Nevertheless,the momentum of collapsed snow-icerock mass could be safely unloaded over a wide and gentler-slope ice tongue area,limiting its mobility and the risk of a cascading hazard.Glacier-wide surface flow dynamics monitored by Sentinel-1 satellite SAR time series(12 September 2021–19 September 2022)show that HLG glacier velocity was generally consistent before and after the earthquake.The entire HLG glacier exhibited more stable than expected,with almost no abnormal features detected in its upper accumulation part,the lower ice tongue,and its lateral paraglacial slopes.Since the glacier valley has experienced remarkable downwasting and the paraglacial environment has been strongly disturbed and destabilized,we suggested that,to efficiently evaluate glacier-related cascading hazard risks,it is also necessary to systematically combine multi-source observations(e.g.,high-resolution UAV survey,radar/Lidar scan,ground investigation,monitoring and warning systems)to continuously monitor the regional glacier anomalies in the post-earthquake seismic active areas.

Spatial variation of stable isotopes in different waters during melt season in the Laohugou Glacial Catchment, Shule River basin

To evaluate isotopic tracers at natural abundances by providing basic isotope data of the hydrological investigations and assessing the impacts of different factors on the water cycle, a total of 197 water samples were collected from the Laohugou Glacial catchment in the Shule River basin northwestern China during the 2013 ablation seasons and analyzed their H- and O-isotope composition. The results showed that the isotopic composition of precipitation in the Qilianshan Station in the Laohugou Glacial catchment was remarkable variability. Correspondingly, a higher slope of δ180-δD diagram, with an average of 8.74, is obtained based on the precipitation samples collected on the Glacier No.la, mainly attributed to the lower temperature on the glacier surface. Because of percolation and elution, the bottom of the firn the isotopic composition at is nearly steady. The 6180 /altitude gradients for precipitation and melt water were -o.37%o/100 m and -o.34%o/100 m, respectively Exposed to the air and influenced by strong ablation and evaporation, the isotopic values and the 6180 vs 6D diagram of the glacial surface ice show no altitudinal effect, indicating that glacier ice has the similar origins with the firn. The variation of isotopic composition in the melt water, varying from -l0.7‰ to -16.9‰ （8180） and from -61.1%o to -122.1%o （6D） indicates the recharging of snowmelt and glacial ice melt water produced at different altitudes. With a mean value of -13.3‰ for 8180 and -89.7‰ for 8D, the isotopic composition of the stream water is much closer to the melt water, indicating that stream water is mainly recharged by the ablation water. Our results of the stable isotopic compositions in natural water in the Laohugou Glacial catchment indicate the fractionations and the smoothing fluctuations of the stable isotopes during evaporation, infiltration and mixture.