1998年冬季台湾海峡的暖水入侵及其生态响应

就 1998年 2— 3月台湾海峡AVHRR表层水温和SeaWiFS叶绿素数据以及当年 2月 2 0日至 3月 8日在台湾海峡北部海区所实施的多学科现场调查资料进行综合分析 ,着重探讨暖水入侵的过程及其生态响应。结果表明 ,1998年冬季由澎湖水道北上进入台湾海峡的高温高盐黑潮入侵水强度大于往年 ,在 2月 8日— 3月 13日期间不断增强 ,直至侵占整个海峡东侧海域 ,迫使低温低盐且富含营养盐的闽浙沿岸水主流顺大陆沿岸南下。这一过程向海峡西侧海域输入营养盐并使之达到适宜的水温 ,极可能是西侧海域出现叶绿素高值区、呈现出与往年相反的叶绿素分布态势的主控机制。分析这一现象与 1997— 1998年的E1Nino事件可能存在着某种关联。

Seasonal variation of the Taiwan Warm Current Water and its underlying mechanism

Based on the historical observed data and the modeling results,this paper investigated the seasonal variations in the Taiwan Warm Current Water(TWCW)using a cluster analysis method and examined the contributions of the Kuroshio onshore intrusion and the Taiwan Strait Warm Current(TSWC)to the TWCW on seasonal time scales.The TWCW has obviously seasonal variation in its horizontal distribution,T-S characteristics and volume.The volume of TWCW is maximum(13746 km^3)in winter and minimum(11397 km^3)in autumn.As to the contributions to the TWCW,the TSWC is greatest in summer and smallest in winter,while the Kuroshio onshore intrusion northeast of Taiwan Island is strongest in winter and weakest in summer.By comparison,the Kuroshio onshore intrusion make greater contributions to the Taiwan Warm Current Surface Water(TWCSW)than the TSWC for most of the year,except for in the summertime(from June to August),while the Kuroshio Subsurface Water(KSSW)dominate the Taiwan Warm Current Deep Water(TWCDW).The analysis results demonstrate that the local monsoon winds is the dominant factor controlling the seasonal variation in the TWCW volume via Ekman dynamics,while the surface heat fl ux can play a secondary role via the joint ef fect of baroclinicity and relief.

Intrusions of Kuroshio and Shelf Waters on Northern Slope of South China Sea in Summer 2015

The northern slope region of the South China Sea(SCS) is a biological hot spot characterized by high primary productivity and biomasses transported by cross-shelf currents, which support the spawning and growth of commercially and ecologically important fish species. To understand the physical and biogeochemical processes that promote the high primary production of this region, we conducted a cruise from June 10 and July 2, 2015. In this study, we used fuzzy cluster analysis and optimum multiparameter analysis methods to analyze the hydrographic data collected during the cruise to determine the compositions of the upper 55-m water masses on the SCS northern slope and thereby elucidate the cross-slope transport of shelf water(SHW) and the intrusions of Kuroshio water(KW). We also analyzed the geostrophic currents derived from acoustic Doppler current profiler measurements and satellite data. The results reveal the surface waters on the northern slope of the SCS to be primarily composed of waters originating from South China Sea water(SCSW), KW, and SHW. The SCSW dominated a majority of the study region at percentages ranging between 60% and 100%. We found a strong cross-slope current with speeds greater than 50 cms^(-1) to have carried SHW into and through the surveyed slope area, and KW to have intruded onto the slope via mesoscale eddies, thereby dominating the southwestern section of the study area.

Native woody legumes respond more negatively to extreme drought than invasive ones

Plant invasion potentially will be affected by increased extreme drought events and deposition of atmospheric N.However,results from previous research indicate that it is not clear as to how extreme drought,N deposition and their interaction affect alien plant invasion,in particular for the invasive woody legumes.We conducted a greenhouse experiment with three invasive and three native woody species of legumes(Fabaceae).We grew plants in extreme drought and in well-watered conditions combined with low and high levels of N and compared plant height,number of leaves and biomass production and allocation.Growth of native woody legumes was suppressed more by extreme drought than that of invasive woody legumes.Although an increase in soil N availability decreased the root mass fraction of plants of all species,it did not affect their overall performance.We found that invasive woody legumes can tolerate the adverse effects of the prolonged extreme drought better than native woody legumes.These results enhance our understanding of the effects of drought due to climate change on the invasion of alien woody legumes.