利用ICESat数据解算南极冰盖冰雪质量变化

南极冰盖冰雪质量变化反映了全球气候变化,并且直接影响着全球海平面变化.ICESat测高卫星的主要任务之一就是要确定南北两极冰盖的质量变化情况并评估其对全球海平面变化的影响.本文利用2003年10月至2008年12月的ICESat测高数据,针对南极DEM分辨率有限的特殊性,通过求解坡度改正值,解决重复轨道地面脚点不重合的问题,计算了南极大陆(86°S以北区域,后文所述南极冰盖均不包括86°S以南区域)在这5年里的冰雪质量变化情况,得到东南极冰盖的质量变化为-18±20Gt/a,西南极-26±6Gt/a,南极冰盖的冰雪质量变化为-44±21Gt/a,对全球海平面上升的影响约为0.12mm·a~(-1).解算结果表明,南极冰盖质量亏损主要集中在西南极阿蒙森海岸附近冰川以及东南极波因塞特角区域.     

近500 年南极涛动指数重建及其变率分析

南极涛动是南半球大气环流的主要模态, 在多种尺度上对南半球及北半球部分地区的气候系统产生重要影响。在对树轮、珊瑚、冰芯等多种代用资料进行挑选与主成分分析的基础上,重建了公元1500 年以来南半球夏季(当年12 月-次年2 月) 的南极涛动指数。重建序列的解释方差(r2)、误差减少量(RE) 平均值分别为59.9%、0.47,较高的r2、RE表明重建具有了较高的可信度;而整体呈减少趋势的标准误差(SE) 表明代用资料的增多可以减少重建序列的不确定性。重建结果与其它研究给出的南极涛动指数有着较好的一致性。重建序列的功率谱分析表明,过去500 多年南极涛动年际变率突出的周期有2.4a、2.6a、6.3a,年代际变率突出的周期有24.1a、37.6a,均达到95%显著性水平。进一步的小波分析表明南极涛动在不同时间尺度上的变率及其周期有着随时间而演变的特征。     

Temperature variation and its driving forces over the Antarctic coastal regions in the past 250 years

By comparing the oxygen isotopic temperatures recorded by many shallow ice cores from the coastal regions of Antarctica, this paper presents the special characteristics of the temperature variations over the Antarctic coastal regions in the past 50 years, 150 years and 250 years. In the past 50 years, the isotopic temperatures recorded in the ice cores over different sites on the Antarctic coastal regions differ greatly. For instance, although increasing isotopic temperatures have been reported for many sites studied, many sites show decreasing trends, the regional regularity in temperature variations is still insignificant. In the past 150 years, the isotopic temperature trends in the coastal regions of Antarctica show an alternate-distributing pattern. In the past 250 years, all the ice cores from the coastal regions of Antarctica have recorded the so-called Little Ice Age (LIA). The above-mentioned spatial characteristics of the temperature variations over the Antarctic coastal regions are likely to reflect the impacts of the unique Southern Hemisphere atmospheric circulation, the Antarctic Circumpolar Wave (ACW) and the special terrain (such as the large drainage basins) on the coastal regions of Antarctica. Furthermore, the impacting intensity of the unique Southern Hemisphere atmospheric circulation, the Antarctic Circumpolar Wave and the special terrain differs in terms of the temporal scale of the temperature change.     

南极长城站地区环境演变的生物地球化学研究——古降水的复原与末次冰盖消退时间的推断

作者在南极地区近代环境的研究中提出了一种新的研究方法——利用生物地球化学指示元素来研究古环境的变迁。通过研究南极长城站地区西湖底沉积物丛其所含的植物残体、复原了约4000年来的年平均降水量的变化,推断了末次冰盖从本区消退的时间为3500年前。研究南极地区近代环境的演变对解决全球性环境演变是不可缺少的内容。     

LENGTH FREQUENCY ANALYSIS OF PLEURAGRAMMA ANTARCTICUM,ELECTRONA ANTARCTICA,PROTOMYCTOPHUM BOLINI

British Antarctic Survey(BAS)data collected near the Antarctic Peninsula area were used in this1988/1989 study on the length frequency of three Antarctic fish species(Pleuragramma antarcticum,Electrona antarctica and Protomyctophum bolini)showing that the standard length(SL)of P.Antarcticumranged from 26.0 mm to 161.0 mm,that the 26.0 mm to 54.0 mm SL juveniles could be considered tobe the age group 1 fish,and that the SL of E.antarctica ranged from 39.4 mm to 89.7 mm for themales and 48.0 mm to 118.0 mm for the females,which may contain at least 6 age groups.This ismore than previously thought.P.Bolini had 29.2 mm to 60.2 mm SL and complicated age com-position.     

The role of diatoms, dissolved silicate and Antarctic glaciation in glacial/interglacial climatic change: a hypothesis

A new theory is proposed to explain global cooling at the onset of Pleistocene glacial periods. Atmospheric CO₂ drawdown is considered to be the driving force behind global cooling, brought about by heightened productivity at the equatorial divergences and along continental margins, particularly in upwelling regions. Eutrophication appears to be triggered when global warming during late interglacial periods causes accelerated melting of the West Antarctic Ice Sheet. This would release large reserves of silicate-enriched subglacial meltwaters into the surrounding oceans where entrainment would take place into deep and intermediate currents forming in Antarctic and subantarctic waters. Subsequent advection, mixing and upwelling of silicate-enriched deep and intermediate waters into the coastal zones and open-ocean divergences results in the proliferation of large, rapidly-sinking diatom species with a high affinity for dissolved silicate. These blooms enhance rates of recycling of N and P in upwelling regions and accelerate rates of organic carbon production, export and sequestration in shelf and slope sediments and in the deep sea. The resultant atm. CO₂ drawdown initiates global cooling. Consequent expansion of Northern Hemisphere glaciers lowers sea level, while increased temperature and pressure gradients between equatorial and polar regions intensify meridional winds. The former process exposes nutrient-enriched coastal sediments to wave erosion, thereby releasing new nutrient supplies, while the latter process enhances upwelling. The combined effect is to greatly increase rates of org. C production and export from continental margins and further accelerate atm. CO₂ drawdown. Glacial-period cooling is also enhanced by a number of other positive feedbacks, including changes in albedo, water vapour and cloud cover. Episodic warming intervals during glacial periods may be related to insolation changes associated with orbital precession and tilt cycles, but processes involved in deglaciation and reversion to the interglacial climatic regime are complex and not yet fully understood.     

南极半岛西北海域表层沉积物中硅藻的初步研究

本文对南极半岛西北海域22个表层沉积物中的硅藻进行了初步研究,鉴定出硅藻82种.根据硅藻的数量分布和生态特征,将本区硅藻分为三个组合;1.Yhalassiosiraantarctica—Charcatia actionchilus—Eucampia balautium组合.2.Th.antarctica——Nitzschiakerguelensis—Coscinodiscus lentignosus组合.3.Coscinodiscus lentiginosus——Eucampiabalaustium—Nitzschia kerguelesis—Schimperiella antarctica组合.文章还通过沉积物中和水体中硅藻的对比,水动力状况,以及海水对硅藻壳体的溶解作用等特征.讨论了区内硅藻壳体的沉积作用.     

BOOK REVIEWS

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