Heat flow measurements on the Lomonosov Ridge, Arctic Ocean

Heat flow was measured on the Lomonosov Ridge during the 5th Chinese National Arctic Expedition in 2012. To derive the time-temperature curve, resistivity data were transformed to temperature by the resistivity- temperature program. Direct reading and linear regression methods were used to calculate the equilibrium temperature, which were regressed against the depth of the probes in sediment to derive the geothermal gradient. Then, heat flow was calculated as the product of geothermal gradient and thermal conductivity of sediments. The heat flow values on the basis of the two methods were similar （i.e., 67.27 mW/m2 and 63.99 mW/m2, respectively）. The results are consistent with the measurements carried out at adjacent sites. The age of the Lomonosov Ridge predicted by the heat flow-age model was 62 Ma, which is in accordance with the inference that the ridge was separated from Eurasia at about 60 Ma.     

Hydrochemical characteristics of typical rivers in a temperate glacier basin, China

This study focused on the chemical compositions of the rivers around Yulong Mountain, one of the typical monsoonal temperate glacier regions in China. Water samples were collected from Baishui, Sanshu and Geji hydrological stations around Mt. Yulong during rainy season. The chemical analyses indicated that the river water around Mt. Yulong was characterized by high pH values (>8.0) and EC values varied from 36.4 to 71.7 μS/cm with an average of 52.6 μS/cm. Ca²⁺ and Mg²⁺ were the dominant cations, together accounting for about 90 % of the total cations. HCO₃ ^?, followed by SO₄ ^2?, was the dominant anion. Obvious variations had been perceived during the rainy season. River water chemistry in rainy season was mainly influenced by precipitation and rock weathering. The proportions of Na⁺, K⁺, Ca²⁺, Mg²⁺ and SO₄ ^2? from precipitation in river water were 23.44, 9.66, 3.10, 17.81 and 10.48 %, respectively. In addition, the ion characteristics of river water were mainly influenced by carbonate weathering. The human activities should not be ignored though its influence was little.     

Geochemical characteristics and environmental significance of Talede loess–paleosol sequences of Ili Basin in Central Asia

The loess–paleosol deposit in Central Asia is a sensitive indicator of the evolution of the quaternary paleoclimate in the Westerlies, providing insight into the quaternary climate history and its relationship with global climatic changes. Based on the geochemical analysis of elemental composition of densely sampled strata from Talede loess–paleosol sequence in the Ili Basin, the results showed that SiO₂ had the highest major elements content, followed by Al₂O₃. The order of compositional abundance of major elements was generally as follows: SiO₂ > Al₂O₃ > CaO > Fe₂O₃ > MgO > Na₂O > K₂O. Trace elements (i.e. Rb, Sr, Sc, Ni, Cu, Ga, Mo, Y, Pb, Th) in the paleosol layers (i.e. S ₀, S _m, S ₁) and the loess layer of L ₁ were enriched relative to underlain loess (L ₂) horizons, except for the contents of Zr, Cs, Nd, and La in paleosol layers. All of geochemical proxies, such as enrichment factor, Rb/Sr ratio, eluvial coefficient (K _i ) and chemical weathering index, display no obvious differentiation in the Talede loess–paleosol deposit. The results indicate that the weak chemical weathering, greater evaporation and low effective moisture in Ili Basin, are to a degree weaker than those in the China Loess Plateau and the climate was warm–dry during the interglacial period. In addition, the loess of Ili area is rich in schistose minerals and implies that the loess may come from the deserts of Central Asia and it may be closely related to the widespread aridification of Central Asia.     

The Features of Climate Variation and Glacier Response in Mt.Yulong,Southeastern Tibetan Plateau

The Features of climate change in Mt.Yulong, southeasten Tibetan Plateau were analyzed using linear regression, Mann Kendall abrupt test and Morlet wavelet analyses. In addition, the relationship between glacier retreating (Baishui Glacier No.1) and climate warming wasalso analyzed in this study. The main results are showedas follow: ① The annual mean temperature, precipitation have an increasing trend, withinclination rates being 0.15℃/10a and 9.0 mm/10a;annual temperaturedramatically ascend in 1998 with the change values 0.7 ℃; Morlet waveletsin annual temperature andtemperature in dry season mainly have a 10 to 15 year periods,while annual precipitation amount and the precipitation in rainy season presented a quasi 10 year periods. ②Prior to 1998, the important meteorological factor influencing the change of Baishui Glacier No.1 are temperature and precipitation, while in the following years, temperature plays a more important role in affecting its retreat and advance; The main characteristic ofvertical climate change in Mt. Yulong (1982/2009) is that the cold season shortens and temperature rises with elevation, and the maximal value of increased temperature in glacier zone is 2.2~2.5 ℃, resulting in greatly accelerated glacier ablation.     

The 2010 Zhouqu mudflow disaster: possible causes, human contributions, and lessons learned

On August 7, 2010, a giant mudflow occurred in Zhouqu County, in China’s Gansu Province. It killed at least 1,467 people and destroyed many buildings. The extensive damage resulted partially from the impact of the swift mudflow, and partially from subsequent flooding caused by damming of the Bailong River, creating a lake. The mudflow had both internal and external causes. We discuss these in detail from the perspective of their relationship to human activities, with the goal of helping to provide advance warning of such disasters in the future.     

Pyropia yezoensis can utilize CO2 in the air during moderate dehydration

Pyropia yezoensis,an intertidal seaweed,experiences regular dehydration and rehydration with the tides.In this study,the responses of P.yezoensis to dehydration and rehydration under high and low CO 2 concentrations((600–700)×10-6 and(40–80)×10-6,named Group I and Group II respectively)were investigated.The thalli of Group I had a signifi cantly higher effective photosystem II quantum yield than the thalli of Group II at 71% absolute water content(AWC).There was little difference between thalli morphology,total Rubisco activity and total protein content at 100% and 71% AWC,which might be the basis for the normal performance of photosynthesis during moderate dehydration.A higher effective photosystem I quantum yield was observed in the thalli subjected to a low CO 2 concentration during moderate dehydration,which might be caused by the enhancement of cyclic electron fl ow.These results suggested that P.yezoensis can directly utilize CO 2 in ambient air during moderate dehydration.     

Using Allan variance to analyze the error characteristics of GNSS positioning

Currently, we evaluate the positioning accuracy of GNSS mainly by providing statistical values that can represent the overall error level, such as CEP, RMS, 2DRMS, and maximum error. These are solid indicators of the general performance of the GNSS positioning. But some applications like GNSS/INS integrated system require a detailed analysis of the error characteristics and knowledge of the precise error model. This requirement necessitates the modeling of the error components of the GNSS positioning solutions. In our research, the Allan variance method is proposed to analyze the GNSS positioning errors, describe the error characteristics, and build the corresponding error models. Based on our research, four dominant noise terms are identified in the GNSS positioning solutions, that is, 1st order Gauss-Markov process, Gaussian white noise, random walk noise, and flicker noise, which indicates that white noise is not always enough and appropriate to model GNSS positioning errors for some applications. The results show that the Allan variance is a feasible and effective way to analyze the error characteristics of the GNSS positioning solutions.     

白令海Navarinsky海底峡谷地震剖面解译

第五次北极科学考察在北极区的白令海首次进行了高分辨率单道地震作业。Navarinsky峡谷头部测线BL11-12剖面中部识别出不对称沙波,陡的一面朝向陆架,波高约为9m、波长约为882m。结合站位U1345的沉积速率及站位U1344表层纵波速率推测沙波沉积可以追溯到中更新世(距今约0.258Ma),同时近陆架的洼地逐渐填平。将地层分为3个沉积层,分析沉积物变化情况,结合0.25Ma以来白令海海平面变化历史,推测最大海退事件对应的界面。结合沙波的地理位置及海平面变化情况,认为内波对沙波的形成起主要作用。     

Simulation of export production and biological pump structure in the South China Sea

The export flux of particulate organic carbon (POC) consumes upwelled dissolved inorganic carbon (DIC), which hinders surplus CO₂ being released to the atmosphere. The export flux of POC is therefore crucial to the carbon and biogeochemical cycles. This study aims to model the long-term (1958–2009) variation of export flux and structure of the biological pump in the South China Sea (SCS) using a three-dimensional physical-biogeochemical coupled (ROMS-CoSiNE) model. The modeled POC export flux in the northeastern and north central SCS is high in winter and low in summer, whereas the flux in the central, southwestern and southern SCS varies following a “W” shape: two maxima in winter and summer, and two minima in spring and autumn. The pattern follows the variation of the East Asian monsoon and is consistent with observations. On the interannual scale, export flux is anti-phased with the El Niño-Southern Oscillation such that El Niño (La Niña) conditions correspond to low (high) export flux. Modeled annual mean POC export flux reaches up to 1.95 mmol m^–2 day^–1, which is underestimated comparing with field observations. The f-ratio is estimated to be ~0.4. The b value of the Martin equation for POC is 1.18±0.03. Remineralization rate of POC is greater than the classical Martin equation but is consistent with its subtropical counterparts. The modeled results indicate that the SCS is a weak source of atmospheric CO₂ with a flux estimated at 1.0 mmol m^–2 day^–1. The modeled results provide an insight of the temporal and spatial variability of the carbon cycle in this monsoon-driven, semi-enclosed basin.