Recent contributions of glaciers and ice caps to sea level rise

Glaciers and ice caps (GICs) are important contributors to present-day global mean sea level rise. Most previous global mass balance estimates for GICs rely on extrapolation of sparse mass balance measurements representing only a small fraction of the GIC area, leaving their overall contribution to sea level rise unclear. Here we show that GICs, excluding the Greenland and Antarctic peripheral GICs, lost mass at a rate of 148?±?30?Gt?yr(-1) from January 2003 to December 2010, contributing 0.41?±?0.08?mm?yr(-1) to sea level rise. Our results are based on a global, simultaneous inversion of monthly GRACE-derived satellite gravity fields, from which we calculate the mass change over all ice-covered regions greater in area than 100?km(2). The GIC rate for 2003-2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches our study period. The high mountains of Asia, in particular, show a mass loss of only 4?±?20?Gt?yr(-1) for 2003-2010, compared with 47-55?Gt?yr(-1) in previously published estimates. For completeness, we also estimate that the Greenland and Antarctic ice sheets, including their peripheral GICs, contributed 1.06?±?0.19?mm?yr(-1) to sea level rise over the same time period. The total contribution to sea level rise from all ice-covered regions is thus 1.48?±?0.26?mm?(-1), which agrees well with independent estimates of sea level rise originating from land ice loss and other terrestrial sources.     

Low sea level rise projections from mountain glaciers and icecaps under global warming

The mean sea level has been projected to rise in the 21st century as a result of global warming. Such projections of sea level change depend on estimated future greenhouse emissions and on differing models, but model-average results from a mid-range scenario (A1B) suggests a 0.387-m rise by 2100 (refs 1, 2). The largest contributions to sea level rise are estimated to come from thermal expansion (0.288 m) and the melting of mountain glaciers and icecaps (0.106 m), with smaller inputs from Greenland (0.024 m) and Antarctica (- 0.074 m). Here we apply a melt model and a geometric volume model to our lower estimate of ice volume and assess the contribution of glaciers to sea level rise, excluding those in Greenland and Antarctica. We provide the first separate assessment of melt contributions from mountain glaciers and icecaps, as well as an improved treatment of volume shrinkage. We find that icecaps melt more slowly than mountain glaciers, whose area declines rapidly in the 21st century, making glaciers a limiting source for ice melt. Using two climate models, we project sea level rise due to melting of mountain glaciers and icecaps to be 0.046 and 0.051 m by 2100, about half that of previous projections.     

海平面上升对福建的影响及对策

目的通过研究福建海平面上升的成因及其影响,提出相关应对措施确保社会经济安全可持续发展。方法根据中国海平面公报和相关资料进行分析。结果海平面上升不但会淹没滨海土地,而且会不同程度地加大风暴潮、咸潮入侵、海水入侵与土壤盐渍化、海岸侵蚀等灾害的致灾程度。结论福建省可通过以下措施来应对海平面上升:积累碳汇;稳定人口低生育水平;加强海洋环境的监测和预警能力;开展海平面变化影响评价和脆弱性区划;强化应对海平面上升的适应性对策等。     

Similar meltwater contributions to glacial sea level changes from Antarctic and northern ice sheets

The period between 75,000 and 20,000 years ago was characterized by high variability in climate and sea level. Southern Ocean records of ice-rafted debris suggest a significant contribution to the sea level changes from melt water of Antarctic origin, in addition to likely contributions from northern ice sheets, but the relative volumes of melt water from northern and southern sources have yet to be established. Here we simulate the first-order impact of a range of relative meltwater releases from the two polar regions on the distribution of marine oxygen isotopes, using an intermediate complexity model. By comparing our simulations with oxygen isotope data from sediment cores, we infer that the contributions from Antarctica and the northern ice sheets to the documented sea level rises between 65,000 and 35,000 years ago were approximately equal, each accounting for a rise of about 15 m. The reductions in Antarctic ice volume implied by our analysis are comparable to that inferred previously for the Antarctic contribution to meltwater pulse 1A (refs 16, 17), which occurred about 14,200 years ago, during the last deglaciation.     

Initial estimate of the contribution of cryospheric change in China to sea level rise

Recent studies have shown that cryospheric melting is becoming the dominant factor responsible for sea level rise,and that the melt-water from mountain glaciers and ice caps has comprised the majority of the cryospheric contribution since 2003.Analysis of the estimations of cryospheric melt-water and precipitation in glacier regions indicated that the potential contribution of the cryosphere in China is 0.14 to 0.16 mm a–1,of which approximately 0.12 mm a–1 is from glaciers.The contribution of glaciers in the outflow river basins is about 0.07 mm a–1,accounting for 6.4%of the total from global glaciers and ice caps.     

全球海水热含量变化规律及其对海平面变化的影响

利用Ishii温盐资料及T/P高度计资料,分析上层700m全球及区域海水热含量变化特征,并探讨海平面变化与上层海水热含量的关系.研究结果表明,1945-2006年全球大部分海域上层700m海水热含量均存处于上升趋势,全球平均上升速率为2.1×107 J/(m2·a),并表现出显著的年际和年代际变化,尤其在湾流附近海域上...     

长江河口径流量与海平面上升对气候变化及人类活动的响应（英文）

气候变化和人类活动所导致的径流量变化和海平面上升都是数值模式中重要的边界条件。因此,为了得到合适的边界条件,本文给出2030、2050和2100年气候变化和人类活动影响下长江径流量和海平面上升的变化情况.考虑到三峡工程于2003年坝体合拢,利用大通站1865至2002年的历史径流量资料,发现利用资料外推获得的径流量变化率与气候模型所得结果近似,得到在2030、2050和2100年1、2月平均径流量在气候变化影响下分别为12348、12683和13 522 m~3·s~(-1).在过去20年,长江河口绝对海平面上升率约为2.5 mm·a~(-1).根据海平面变化资料分析预报模型,2012年至2030、2050和2100年绝对海平面分别上升49.1、148.1和395.6mm.长江河口的盐水入侵数值模拟需考虑三峡水库和南水北调对入海径流量的影响.同时,相对海平面变化需要考虑地壳下沉和地基沉降.本文给出各个预估时期上述内容的量值.     

Trends of sea level rise in the South China Sea during the 1990s: An altimetry result

Using 7 years of TOPEX/POSEIDON satellite altimetry data, we have identified a general trend of sea level rising in the South China Sea between January 1993 and December 1999. The estimated bulk rising rate of the entire basin is -1 cm/a. The rise of sea level appears to be spatially non-homogeneous, which shows a highest rate of 2.7 cm/a in the deep basin west of Luzon and generally low (even negative) rates over the shallow continental shelves. It is believed that the observed rapid rising of sea level is a regional phenomenon and is mainly caused by warming of the upper layer of the South China Sea, which showed a bulk warming rate of 0.15℃/a in the same period. It is also suggested that the observed rising trend is mainly a decadal signal, which is possibly associated with decadal variation of the Pacific warm pool region.     

Response of rice cultivation to fluctuating sea level during the Mid-Holocene

Archaeological analysis of a section of ancient rice fields at Tianluoshan for diatoms, seeds and phytoliths has shown that the highest local sea level in eastern China during the Holocene appeared before 7.0 ka BP. Entering the Mid-Holocene, as seawater regressed, a vast wetland plain appeared in the coastal area, where farmers of the Neolithic Hemudu culture cultivated rice. However, there were still several sea-level fluctuations in the Mid-Holocene, of which the biggest were from 6.4 to 6.3 ka BP and from 4.6 to 2.1 ka BP. In addition, in the period dominated by wetland grass vegetation, 6.3 to 4.6 ka BP, smaller fluctuations appar- ently pushed the coastline back on to the land. Even though the sea-level rises associated with these shoreline transgressions did not have the intensity of the highest sea level period, there still would have been profound impacts on the lives and production activities of people living in the region. Archaeological evidence from ancient rice fields at Tianluoshan shows that larger sea-level rise events pushed seawater onto the land and inundated large areas of rice fields, whereas weaker sea-level rise events resulted in the intrusion of seawater along rivers, causing an increase in soil salinity and a decrease in rice yields. The impact of sea-level rise on rice cultivation caused changes in local diet. In regions where rice production fell, the prevalence of gathering and hunting rose. High sea levels in the early Holocene imply that the origin of rice cultivation in the eastern coastal plain is likely to have been in small nearby mountain basins.     

近十年我国海平面变化研究进展

系统地回顾了2006—2015年我国在海平面变化规律、机制及影响领域的最新研究进展。分析了全球及区域海平面以及比容海平面在不同时间尺度上的变化规律;探讨了海平面的变化机制,海表热通量、淡水通量、环流、风应力以及Rossby波对不同区域海平面变化的动力及热力影响;采用统计方法和数值模拟等手段,对21世纪海平面变化进行了预测;同时海平面变化会影响海洋的动力过程(如潮波系统的变化),并进而对近海和海岸带环境产生重要影响(如海岸侵蚀、海水入侵和土地盐渍化、河口咸潮入侵、近岸低地淹没、红树林衰退等)。     

Modelled atmospheric temperatures and global sea levels over the past million years

Marine records of sediment oxygen isotope compositions show that the Earth's climate has gone through a succession of glacial and interglacial periods during the past million years. But the interpretation of the oxygen isotope records is complicated because both isotope storage in ice sheets and deep-water temperature affect the recorded isotopic composition. Separating these two effects would require long records of either sea level or deep-ocean temperature, which are currently not available. Here we use a coupled model of the Northern Hemisphere ice sheets and ocean temperatures, forced to match an oxygen isotope record for the past million years compiled from 57 globally distributed sediment cores, to quantify both contributions simultaneously. We find that the ice-sheet contribution to the variability in oxygen isotope composition varied from ten per cent in the beginning of glacial periods to sixty per cent at glacial maxima, suggesting that strong ocean cooling preceded slow ice-sheet build-up. The model yields mutually consistent time series of continental mean surface temperatures between 40 and 80 degrees N, ice volume and global sea level. We find that during extreme glacial stages, air temperatures were 17 +/- 1.8 degrees C lower than present, with a 120 +/- 10 m sea level equivalent of continental ice present.     

长江河口水位上升对流场和盐水入侵的影响

基于长江河口水动力和盐水入侵三维数值模式ECOM-si,通过数值模拟分析长江河口水位上升对径流、潮流和风生流的影响,以及在多种动力因子综合作用下对流场和盐水入侵的影响.数值实验结果表明,在长江河口水位上升30 cm的情况下,各河道横截面面积增大,向海的径流流速减小;潮流随水深增深略微增大;枯季北风作用产生的北港进、南港出的水平风生环流加强,在北支向陆的风生流有所加强.水位上升后,北支盐水入侵增强;南支中段盐度变化不明显;北港、北槽盐水入侵随水位增加变化最为显著,小潮期间盐度增大值大于1,大潮期间增幅有所降低,北港北汊受水深增加盐水入侵变化最为强烈;南槽口门处滩地由于水位增加,非线性效应减弱,盐度不同程度的降低.水位上升后南支水源地三个水库取水口盐度均有所上升,减少了可取水时间,不利于供水安全.     

Biodiversity of Early-Middle Ordovician acritarchs and sea level changes in South China

Acritarchs are organic-walled cysts of unicellular pro- tists that cannot be assigned to any known group of or- ganisms. Most acritarchs are probably the resting cysts of marine eukaryotic phytoplankton. Because of their small size, abundance and diversity, as well as widespread distri- bution, acritarchs are very useful in biostratigraphic cor- relation, as well as paleobiogeographic and paleoenviron- mental studies. Furthermore, they represent the fossil re- cord of the base of the marine fo…     

水位升降引起的砂土孔隙压力变化特性

孔隙压力对土的力学性能和变形特性都有影响.利用自研设备对无载和加载工况升降水位过程砂性土中的孔隙压力变化进行了监测,获得了砂性土孔隙压力变化的一些规律.水位上升和下降引起的孔隙压力路径不重合;水位上升时孔隙压力零点在测点或测点以上,水位下降时孔隙压力零点在测点以下;加载试验中,与同条件不加载情况相比,孔隙正负压力均增加,增加值与附加应力在趋势上一致.     

Low-frequency sea level variation and its correlation with climate events in the Pacific

Global mean sea level(GMSL) has not only significant secular trend and seasonal variations,but also inter-annual and decadal variations.This paper reconstructs the time series of GMSL variations between 1948 and 2007 by combining satellite altimeter measurements and tide gauge observations.Based on the time series,the acceleration of GMSL rise in the second half of 20th century is estimated to be 0.010±0.009 mm/a 2,and multi-scale low frequency sea level oscillations including decadal variations are detected,and the high-rate of GMSL rise during 1993-2003 is locate in the ascending phase of low frequency oscillation.Then,using the reconstructed GMSL time series after removing the secular trend from satellite altimetry and tide gauges measurements,it shows that low frequency signal of sea level variation has strong correlations with the index of El Ni o/Southern Oscillation(ENSO) and Pacific Decadal Oscillation(PDO).But in several time periods,they have large difference due to effects of both high frequency occurrence of El Ni o and La Ni a phenomenon and short term switch of PDO events.