Illuminating Sea-Level Fall around AD 1220–1510 (730-440 cal yr BP) in the Pacific Islands: Implications for Environmental Change and Cultural Transformation

This paper focuses on the climatic transition between the Little Climatic Optimum (approximately AD 750–1300 or 1200‐650 cal yr BP) and the Little Ice Age (approximately AD 1300–1800 or 650‐150 cal yr BP) in the Pacific Islands. This transition was marked by rapid temperature and sea‐level fall, and perhaps by sharply‐increased precipitation associated with an increase in El Nino frequency. Examples from throughout the Pacific Islands demonstrate the possible and/or likely effects of sea‐level fall at this time on inland horticulture through water‐table fall; on coral reefs and lagoons through the emergence of reef surfaces and the consequent reduction of nearshore water circulation; on the emergence of reef islets and the conversion of tidal inlets to brackish lakes. The effects of such changes on human lifestyles are explored.     

The end of the Pacific? Effects of sea level rise on Pacific Island livelihoods

As in the past, most Pacific Island people live today along island coasts and subsist largely on foods available both onshore and offshore. On at least two occasions in the 3500 years that Pacific Islands have been settled, sea level changes affected coastal bioproductivity to the extent that island societies were transformed in consequence. Over the past 200 years, sea level has been rising along most Pacific Island coasts causing loss of productive land through direct inundation (flooding), shoreline erosion and groundwater salinization. Responses have been largely uninformed, many unsuccessful. By the year 2100, sea level may be 1.2 m higher than today. Together with other climate‐linked changes and unsustainable human pressures on coastal zones, this will pose huge challenges for livelihoods. There is an urgent need for effective and sustainable adaptation of livelihoods to prepare for future sea level rise in the Pacific Islands region. There are also lessons to be learned from past failures, including the need for adaptive solutions that are environmentally and culturally appropriate, and those which appropriate decision makers are empowered to design and implement. Around the middle of the twenty‐first century, traditional coastal livelihoods are likely to be difficult to sustain, so people in the region will need alternative food production systems. Within the next 20–30 years, it is likely that many coastal settlements will need to be relocated, partly or wholly. There are advantages in anticipating these needs and planning for them sooner rather than later. In many ways, the historical and modern Pacific will end within the next few decades. There will be fundamental irreversible changes in island geography, settlement patterns, subsistence systems, societies and economic development, forced by sea level rise and other factors.     

100 Myr record of sequences, sedimentary facies and sea level change from Ocean Drilling Program onshore coreholes, US Mid-Atlantic coastal plain

We analyzed the latest Early Cretaceous to Miocene sections (～110–7 Ma) in 11 New Jersey and Delaware onshore coreholes (Ocean Drilling Program Legs 150X and 174AX). Fifteen to seventeen Late Cretaceous and 39–40 Cenozoic sequence boundaries were identified on the basis of physical and temporal breaks. Within‐sequence changes follow predictable patterns with thin transgressive and thick regressive highstand systems tracts. The few lowstands encountered provide critical constraints on the range of sea‐level fall. We estimated paleowater depths by integrating lithofacies and biofacies analyses and determined ages using integrated biostratigraphy and strontium isotopic stratigraphy. These datasets were backstripped to provide a sea‐level estimate for the past ～100 Myr. Large river systems affected New Jersey during the Cretaceous and latest Oligocene–Miocene. Facies evolved through eight depositional phases controlled by changes in accommodation, long‐term sea level, and sediment supply: (1) the Barremian–earliest Cenomanian consisted of anastomosing riverine environments associated with warm climates, high sediment supply, and high accommodation; (2) the Cenomanian–early Turonian was dominated by marine sediments with minor deltaic influence associated with long‐term (10⁷ year) sea‐level rise; (3) the late Turonian through Coniacian was dominated by alluvial and delta plain systems associated with long‐term sea‐level fall; (4) the Santonian–Campanian consisted of marine deposition under the influence of a wave‐dominated delta associated with a long‐term sea‐level rise and increased sediment supply; (5) Maastrichtian–Eocene deposition consisted primarily of starved siliciclastic, carbonate ramp shelf environments associated with very high long‐term sea level and low sediment supply; (6) the late Eocene–Oligocene was a starved siliciclastic shelf associated with moderately high sea‐level and low sediment supply; (7) late early–middle Miocene consisted of a prograding shelf under a strong wave‐dominated deltaic influence associated with major increase in sediment supply and accommodation due to local sediment loading; and (8) over the past 10 Myr, low accommodation and eroded coastal systems were associated with low long‐term sea level and low rates of sediment supply due to bypassing.     

Middle Miocene–Pliocene siliciclastic influx across a carbonate shelf and influence of deltaic sedimentation on shelf construction,Northern Carnarvon Basin,Northwest Shelf of Australia

Middle Miocene to Pliocene siliciclastics of the Bare Formation represent a long‐lived (ca. 11 Myr) break in the otherwise carbonate‐dominated shelf of the Northern Carnarvon Basin, Northwest Shelf of Australia. The quartz‐sandstone interval is correlated with the appearance of spectacular clinoform sets mapped on 3D and dense 2D seismic data. Twenty‐seven clinoform sets are interpreted as delta lobes primarily based on their plan‐view morphology (strike‐elongate to lobate features) and their 40–100‐m‐high clinoform amplitudes. The delta lobes were deposited on outer‐shelf to shelf‐edge positions, and the older deltas show evidence of a higher degree wave reworking than the younger deltas. Measurements of the along‐strike (migration) and down‐dip (progradation) movement of these deltas are compared with relative sea‐level behaviour inferred from shelf‐edge trajectory analysis. Delta lobes exhibit greater lateral shifting during relative sea‐level rise, whereas delta lobes are more restricted to dip‐oriented fairways during sea‐level fall, although no major incised valleys have been identified. Long‐term (cumulative) progradation of this delta system and subsequent backstepping correlates with long‐term sea‐level fall and rise during the late middle and late Miocene. In addition, a long‐term northeastward migration trend for these delta lobes was likely a result of localized uplift of an inversion anticline in the Rosemary–Legendre Trend; the growth of this anticline probably steered the fluvial source for the delta system towards the northeast. The Bare Formation siliciclastic influx correlates with other middle Miocene increases in siliciclastic sediment supply worldwide. Global cooling and a shift to more arid conditions, negatively influencing vegetation cover, may have combined with more seasonally variable rainfall to generate the high sediment supply that built the deltas. Retreat of the siliciclastics could correlate with ice‐sheet growth in the Northern Hemisphere and/or increase in the Indonesian Throughflow and Leeuwin Current (ca. 1.6 Ma), which might have modified climate regionally.     

The role of climate variation in delta architecture: lessons from analogue modelling

Sequence‐stratigraphic models for fourth to sixth order, glacio‐eustatic sequences based only on relative sea‐level variations result in simplified and potentially false interpretations. Glacio‐eustatic sea‐level variations form only one aspect of cyclic climate variation; other aspects, such as variations in fluvial water discharge, vegetation cover, weathering and sediment supply can lead to variable sediment yield, thus adding complexity to sequence‐stratigraphic patterns normally attributed to sea‐level variations. Analogue flume models show a significant impact of water discharge on the timing and character of sequence boundaries, and on changes in the relative importance of systems tracts, as expressed in sediment volumes. Four deltas, generated under the influence of an identical sea‐level curve, and affected by different water‐discharge cycles were generated in the Eurotank facility: (1) constant discharge; (2) high‐frequency discharge variations (HFD); (3) discharge leading sea level by a quarter phase; (4) discharge lagging sea level by a quarter phase. HFD shift the parasequence stacking pattern consistently but do not alter large‐scale delta architecture. Water‐discharge changes that lead sea‐level changes result in high sediment yield during sea‐level rise and in the poor development of maximum flooding surfaces. Delta‐front erosion during sea‐level fall is expressed by multiple, small channels related to upstream avulsions, and does not result in an incised valley that efficiently routs sediment to the shelf edge. When water‐discharge changes lag sea‐level changes, sediment yield is high during falling sea level and results in rapid progradation during forced regression. Erosion from incised valleys is strong on the proximal delta top and dissipates towards the delta front. The combination of high discharge and sea‐level fall provides the most efficient mode of valley incision and sediment transport to the shelf edge. During sea‐level rise, low water discharge results in sediment starvation and well‐developed maximum flooding surfaces. Water‐discharge variations thus alter sequence‐stratigraphic patterns and provide an alternative explanation to the amplitude of sea‐level fall for generating either type 1 or 2 erosional unconformities.     

Earthquakes as a potential contributing factor to climate change at multi-decadal scale

Climate changes at the multi-decadal scale are often associated with multi-decadal phase shifts of the dominant sea surface temperature （SST） pattern, such as the Pacific Decadal Oscillation （PDO）. The PDO may be associated with the North Pacific branch of the Thermohaline Circulation （THC）. Great earthquakes （M 〉8）, particularly along the route of the THC, might modulate the vertical mixing and bring deep, cold water to surface, contributing to multi-decadal changes in surface currents and the PDO. This may eventually lead to multi-decadal climate changes. We tested this hypothesis for the Pacific Ocean where great earthquakes have been frequently recorded. We found associations between the PDO and recurrent earthquakes along the route of the deep currents of the THC in the modern period since 1900, and relationships between hydroclimate change in Monsoonal Asia and historical earthquakes since 1300. However, it should be noted that this hypothesis is very preliminary and has many gaps that needs further evidences from more observational records and modeling studies.     

Long-term Callovian–Oxfordian sea-level changes and sedimentation in the Iberian carbonate platform (Jurassic, Spain): possible eustatic implications

Facies analysis across the carbonate platform developed during the Callovian–Oxfordian in the northern Iberian basin (Jurassic, Northeast Spain) is used to characterize successive stages of sedimentary evolution, including palaeoenvironmental reconstructions showing the distribution of a wide spectrum of facies, from ferruginous oolitic, peloidal, spongiolithic to intraclastic. The studied successions consist of two long‐term transgressive–regressive cycles bounded by a major unconformity with a major gap, comprising at least the upper Lamberti (Callovian) and Mariae (Oxfordian) Zones. Major transgressive peaks of these two cycles occurred at the end of the Early Callovian (late Gracilis Zone) and at the end of the Middle Oxfordian. The Callovian and Oxfordian successions were further divided into three and seven higher frequency cycles, respectively. The modelling of two sections (i.e. Ricla and Tosos) located 40 km apart in the more subsident open platform areas, allows the reconstruction of two curves showing a similar evolution of long‐term sea‐level changes that are in theory eustatic, though subject to uncertainties derived form the assumptions required for their construction. The changes affecting the northern Iberian basin seem to reflect nearly homogeneous subsidence (rates around 2 cm kyr^?1) combined with possible eustatic changes including an Early Callovian rise, a fall at the middle Callovian–earliest Oxfordian (i.e. the Anceps–Mariae Zones), with average long‐term rates around 2 cm kyr^?1 (total fall of 40–60 m), a period of lowstand at the Early–Middle Oxfordian transition and a long‐term rise at the Middle–Late Oxfordian transition (Transversarium and Bifurcatus Zones). Facies distribution across the Iberian platform indicates a progressive Middle–Late Callovian relative sea‐level fall rather than a rapid relative sea‐level fall at the end of the Callovian. After this falling episode, the progressive onlap over the swell areas during the Early Oxfordian and at the beginning of the Middle Oxfordian indicates a period of accommodation gain, which is explained by the combined effects of continuous subsidence across the platform and reduced sedimentation rates in spite of the possible eustatic lowstand. Eustatic lowstand, combined with other factors (ocean water circulation, volcanism) could help to explain the loss of carbonate production during the latest Callovian–Early Oxfordian, previous to the widespread eustatic rise and warning recorded at the onset of the Transversarium Zone (Middle Oxfordian).     

A NEW RECONSTRUCTION OF TEMPERATURE VARIABILITY IN THE EXTRA‐TROPICAL NORTHERN HEMISPHERE DURING THE LAST TWO MILLENNIA

A new temperature reconstruction with decadal resolution, covering the last two millennia, is presented for the extratropical Northern Hemisphere (90–30°N), utilizing many palaeo‐temperature proxy records never previously included in any large‐scale temperature reconstruction. The amplitude of the reconstructed temperature variability on centennial time‐scales exceeds 0.6°C. This reconstruction is the first to show a distinct Roman Warm Period c. ad 1–300, reaching up to the 1961–1990 mean temperature level, followed by the Dark Age Cold Period c. ad 300–800. The Medieval Warm Period is seen c. ad 800–1300 and the Little Ice Age is clearly visible c. ad 1300–1900, followed by a rapid temperature increase in the twentieth century. The highest average temperatures in the reconstruction are encountered in the mid to late tenth century and the lowest in the late seventeenth century. Decadal mean temperatures seem to have reached or exceeded the 1961–1990 mean temperature level during substantial parts of the Roman Warm Period and the Medieval Warm Period. The temperature of the last two decades, however, is possibly higher than during any previous time in the past two millennia, although this is only seen in the instrumental temperature data and not in the multi‐proxy reconstruction itself. Our temperature reconstruction agrees well with the reconstructions by Moberg et al. (2005) and Mann et al. (2008) with regard to the amplitude of the variability as well as the timing of warm and cold periods, except for the period c. ad 300–800, despite significant differences in both data coverage and methodology.     

Quantitative analogue flume-model study of river–shelf systems: principles and verification exemplified by the Late Quaternary Colorado river–delta evolution

ABSTRACT Physical modelling of clastic sedimentary systems over geological time spans has to resort to analogue modelling since full scaling cannot be achieved within the spatial and temporal restrictions that are imposed by a laboratory set‐up. Such analogue models are suitable for systematic investigation of a sedimentary system's sensitivity to allocyclic changes by isolating governing parameters. Until now, analogue models of landscape evolution were mainly qualitative in nature. In this paper, we present a quantitative approach. The quantitative experimental results are verified and discussed by comparison with high‐resolution data from the Colorado river–shelf system of the Texas shelf that we used as a prototype. The model's dimensions are proportionally scaled to the prototype, except for a vertical exaggeration. Time is scaled using a Basin Response factor to maintain a similar ratio between the period of change and the system's equilibrium time for model and prototype. A Basin Fill factor was used to compare the ratio between the time‐averaged sedimentation rate and the rate of change in accommodation space of model and prototype. The flume‐model results are in the form of sediment budgets that are related to shelf cannibalism and fluvial supply, which are compared with the ancestral Colorado river–delta evolution of the last 40 kyr. Model and prototype have similarities in delta evolution in response to one cycle of sea‐level change. With sea‐level change as the isolated variable, the flume model generates a significant supply pulse caused by headward erosion of the shelf in response to the sea‐level fall. This pulse adds to the yield of the hinterland. The supply induced by sea‐level change persists during the early rise, although its rate declines. A similar trend is observed on the east Texas shelf. We argue that shelfal and fluvial degradation cycles induced by sea‐level changes can significantly influence the timing and amount of sediment supply to basins and must therefore be taken into consideration.     

Settlement distribution and its relationship with environmental changes from the Neolithic to Shang-Zhou dynasties in northern Shandong, China

In this paper, the spatial and temporal distribution of the settlement sites of six periods from the Neolithic Age to the Shang and Zhou dynasties in northern Shandong was investigated using the ArcGIS program, and the relationship between settlement distribution and environmental changes was discussed, based on the proxy records of climatic and environmental change contained in the sediments from three sections at the Shuangwangcheng site and the previous work. The results show that the climate was warm and humid and the sea level was relatively high during the period of 8000-5000 a BP in the study area, and the ancient people lived in the relatively flat （slope of 〈2°） areas at high elevation （20-300 m above sea level）, such as diluvial tableland and alluvial plain. On the other hand, few archaeological sites in the low-lying plain in the west of the study area indicate that few people lived there during that period. This might be attributed to frequent flooding in the area. After 5000 years ago, the scope of human activity extended to the area close to the sea because the relatively colder and drier climate results in sea-level fall, meanwhile the low-lying plain in the west was occupied by the ancient people. The study area of this period was characterized by the rapid development of prehistoric culture, the intensified social stratification and the emergence of early city-states. However, around 4000 a BP, the abrupt change in climate and the increase in frequency and intensity of floods severely disrupted human activities, and eventually led to the decline of the Yueshi culture. During the Shang and Zhou dynasties, the climatic conditions gradually stabilized in a mild-dry state, which promoted the redevelopment and flourish of the Bronze Culture. The previous situation, which was characteristic of sparse human settlements due to freshwater shortage and unfitted conditions for sedentary agriculture, changed during the Shang and Zhou dynasties in northern coastal wetlands.Local residents effectively adapted themselves to the tough environmental conditions by producing sea-salt, which led to the rapid growth of human activities.     

Testing long-term patterns of basin sedimentation by detrital zircon geochronology, Centralian Superbasin, Australia

Detrital zircon geochronology of Neoproterozoic to Devonian sedimentary rocks from the Georgina and Amadeus basins has been used to track changes in provenance that reflect the development and inversion of the former Australian Superbasin. Through much of the Neoproterozoic, sediments appear to have been predominantly derived from local sources in the Arunta and Musgrave inliers. Close similarities between the detrital age signatures of late Neoproterozoic sedimentary rocks in the two basins suggests that they were contiguous at this time. A dominant population of 1.2–1.0 Ga zircon in Early Cambrian sediments of the Amadeus Basin reflects the uplift of the Musgrave Inlier during the Petermann Orogeny between 560 and 520 Ma, which shed a large volume of detritus northwards into the Amadeus Basin. Early Cambrian sedimentary rocks in the Georgina Basin have a much smaller proportion of 1.2–1.0 Ga detritus, possibly due to the formation of sub‐basins along the northern margin of the Amadeus Basin which might have acted as a barrier to sediment transfer. An influx of 0.6–0.5 Ga zircon towards the end of the Cambrian coincides with the transgression of the Larapintine Sea across central Australia, possibly as a result of intracratonic rifting. Detrital zircon age spectra of sedimentary rocks deposited within this epicontinental sea are very similar to those of coeval sedimentary rocks from the Pacific Gondwana margin, implying that sediment was transported into central Australia from the eastern continental margin. The remarkably consistent ‘Pacific Gondwana’ signature of Cambro‐Ordovician sediments in central and eastern Australia reflects a distal source, possibly from east Antarctica or the East African Orogen. The peak of the marine incursion into central Australia in the early to mid Ordovician coincides with granulite‐facies metamorphism at mid‐crustal depths between the Amadeus and Georgina basins (the Larapinta Event). The presence of the epicontinental sea, the relative lack of a local basement zircon component in Cambro‐Ordovician sedimentary rocks and their maturity suggest that metamorphism was not accompanied by mountain building, consistent with an extensional or transtensional setting for this tectonism. Sediments deposited at ～435–405 and ～365 Ma during the Alice Springs Orogeny have detrital age signatures similar to those of Cambro‐Ordovician sedimentary rocks, reflecting uplift and reworking of the older succession into narrow foreland basins adjacent to the orogen.     

Climate change and community resilience in Samoa

Being resilient in the face of climate change seems especially important for island societies, which face the effects of rising temperatures, unpredictable rainfall, changing wind patterns and sea level rise. To date, most studies of adaptation and resilience among Pacific island communities have used indicators and methods rooted in Western science and neo-classical economics. These have been criticized as being locally irrelevant and inadequate to appreciate the dynamic nature and social structures of island communities and their capacity to adapt. This paper challenges the paradigm that defines resilience as a return to equilibrium, by using a non-equilibrium, cultural ecological lens. The non-equilibrium view of resilience sees the social systems of island nations as highly dynamic and undergoing persistent adaptation in the face of changing environmental factors. Field-based research undertaken in eight villages in Samoa found that, through constant exposure to environmental change over extended periods of time, communities have become resilient and are in a position to adapt to future changes. In developing future policy in relation to climate change, Pacific island governments need to develop a more nuanced understanding of islanders’ perceptions and historical actions in the context of both their physical locations and their dynamic socio-cultural systems.     

南极长城站潮汐特征分析

本文使用南极长城站 1 987年 3月至 1 988年 2月连续观测资料 (每小时观测一次 ) ,对这里的潮波系统、潮汐类型、潮时、潮差和水位等潮汐特征进行了分析描述     

Interaction of tectonics, eustasy, climate and carbonate production on the sedimentary evolution of an early/middle Jurassic extensional basin (Southern Provence Sub-basin, SE France)

This paper describes the evolution of an extensional basin in regard to the nature and sequence stratigraphic arrangement of its carbonate deposits. The purpose of this study is to evaluate the respective effects of tectonism, eustasy, climate and oceanography on a carbonate sedimentary record. The case study is the early to mid‐Jurassic age carbonate succession of the Southern Provence Sub‐basin (SE France), located within the southern part of the extensional Western European Tethyan Margin. This work is based on sedimentologic, biostratigraphic (using ammonites and brachiopods) and sequence stratigraphic analysis of the carbonate facies of the Cherty Reddish Limestone Formation (late Sinemurian to earliest Bajocian). These strata were deposited in shoreface to lower offshore depositional environments. The succession of the various environments together with the recognition of key stratigraphic surfaces allow us to define four second‐order depositional sequences; of late Sinemurian to earliest Pliensbachian, early Pliensbachian to late Pliensbachian, earliest Toarcian to middle Aalenian and late Aalenian to early Bathonian ages. The architecture of the depositional sequences (thickness and facies variations within the systems tracts, wedge‐shaped geometries) reflects a strong tectonic control. The sub‐basin was structured by extensional faults (oriented approximately 070–090/250–270). Sea‐level variations, fluctuations in carbonate production and preservation, and environmental changes were also significant controlling factors of the carbonate deposition. The interplay of the tectonic control with the other factors resulted in five main phases in the sedimentary evolution of the sub‐basin: (1) dominant tectonic control during the initial rifting stage (late Sinemurian to early Pliensbachian); (2) increasing extensional tectonics (mid‐Pliensbachian); (3) global climato‐eustatic sea‐level fall (latest Pliensbachian) and global climato‐eustatic sea‐level rise plus hypoxia/anoxia (early Toarcian); (4) relative sea‐level fall linked to tectonic uplift related to the ‘Mid‐Cimmerian phase’ (mid‐Aalenian) and (5) oceanographic events (upwelling) and reduction in carbonate production (hypoxia/anoxia) plus tectonic downwarping (late Aalenian/earliest Bajocian).     

Climate‐induced migration: Exploring local perspectives in Kiribati

A number of studies have indicated that the long term habitability of Kiribati, a low‐lying country in the central tropical Pacific Ocean, is tenuous given the impacts of climate change, particularly sea level rise. In an effort to plan for the resultant challenges ahead, a number of national policies and programs have surfaced to reduce the impact of localized changes on people's livelihoods. This study explores how local community members (n = 60) have taken it upon themselves to respond to the impacts of climate change by utilizing a number of different strategies. The results highlight that: first, respondents consider climate change to be the most concerning issue for sustaining their livelihoods; second, respondents have built physical defences, relocated temporarily or permanently, and sought government assistance to adapt to localized climate‐related impacts; and third, the majority of respondents indicated that they would migrate as a long term strategy to respond to the future impacts of climate change.     

Interdecadal change in Western Pacific Subtropical High and climatic effects

Western North Pacific Subtropical High is a very important atmospheric circulation system influencing the summer climate over eastern China. Its interdecadal change is analyzed in this study. There is a significant decadal shift in about 1979/1980. Since 1980, the Western North Pacific Subtropical High has enlarged, intensified, and shifted southwestward. This change gives rise to an anti-cyclonic circulation anomaly over the region from the South China Sea to western Pacific and thus causes wet anomalies over the Yangtze River valley. During the summers of 1980–1999, the precipitation is 63.9 mm above normal, while during 1958–1979 it is 27.3 mm below normal. The difference is significant at the 99% confidence level as at-test shown. The southwestward expanding of the Western North Pacific Subtropical High also leads to a significant warming in southern China, during 1980–1999 the summer mean temperature is 0.37°C warmer than that of the period 1958–1979. The strong warming is primarily due to the clearer skies associated with the stronger downward air motion as the Western North Pacific Subtropical High expanding to the west and controlling southern China. It is also found that the relative percentage of tropical cyclones in the regions south of 20°N is decreasing since the 1980s, but in the regions north of 20°N that is increasing at the same time. The Western North Pacific Subtropical High responds significantly to sea surface temperature of the tropical eastern Pacific with a lag of one-two seasons and simultaneously to sea surface temperature of the tropical Indian Ocean. The changes in the sea surface temperatures are mainly responsible for the interdecadal variability of the Western North Pacific Subtropical High.     

西太平洋副热带高压的年代际变化 及其气候影响

西北太平洋副热带高压是影响我国夏季气候的一个非常重要的环流系统，本文主要分析了其年代际尺度的变化。发现在１９７９／１９８０年前后，其强度和范围发生了一次明显的年代际尺度的变化。１９８０年代以来，副高明显偏强，范围向西向南显著扩展。副高的年代际变化也对我国东部地区的气候产生了显著的影响。主要表现在近２０多年来长江中下游地区夏季降水显著增加，华南地区夏季气温显著偏高，以及西太平洋２０°Ｎ以南台风活动相对偏弱而２０°Ｎ以北洋面台风活动相对增强。副高的年代际变化与冬、春季赤道太平洋海表温度及同期热带印度洋海温有密切联系。     

IPCC-AR4以来华南沿海海平面变化研究若干进展

综述自IPCC-AR4(联合国政府间气候变化委员会第四次评估报告)以来,华南沿海海平面变化研究的新进展,结果显示:1)7 100-3 500 cal a BP时期华南沿海的海平面较今高1.5～2.5 m;2)1970-2010年的海平面上升率为2.5 mm/a,高于同时期全球平均上升率2.1 mm/a,原因与西太平洋暖池直接影响有关;3)采用新的全球冰川均衡调整(GIA)模型分析得出,华南沿海各验潮站的GIA效应值为-0.18～-0.30 mm/a;4)实施“海平面观测与影响评价标准”(HY/T134-2     

Can sediment supply variations create sequences? Insights from stratigraphic forward modelling

Classic sequence stratigraphy suggests depositional sequences can form due to changes in accommodation and due to changes in sediment supply. Accommodation‐dominated sequences are problematic to define rigorously, but are commonly interpreted from outcrop and subsurface data. In contrast, supply‐dominated sequences are much less commonly identified. We employ numerical stratigraphic forward modelling to compare stratal geometries forced by cyclic changes in relative sea level with stratal geometries forced by sediment discharge and water discharge changes. Our quantitative results suggest that both relative sea‐level oscillations and variations in sediment/water discharge ratio are able to form sequence‐bounding unconformities independently, confirming previous qualitative sequences definitions. In some of the experiments, the two types of sequence share several characteristics, such as an absence of coastal‐plain topset deposits and stratal offlap, something typically interpreted as the result of falling relative sea level. However, the stratal geometries differ when variations in amplitude and frequency of relative sea‐level change, sediment/water discharge ratio, transport diffusion coefficient and initial bathymetry are applied. We propose that the supply‐dominated sequences could be recognised in outcrop or in the subsurface if the observations of stratal offlap and the absence of coastal‐plain topset can be made without any strong evidence of relative sea‐level fall (e.g. descending shoreline trajectory). These quantitative results suggest that both supply‐dominated and accommodation‐dominated sequences are likely to occur in the ancient record, as a consequence of multiple, possibly complex, controls.     

ENSO循环过程对南极海冰的影响

应用 1 951- 2 0 0 2年NINO特征指数 (NINO1 +2 ,NINO3 ,NINO4 ,NINO3 .4)和 1 973-1 998年南极海冰北界范围以及 1 950- 2 0 0 1年SODA海洋温度资料。首先分析探讨了在ElNi no期间 ,堆积于赤道东太平洋的异常暖水在南半球的传播途径 ,进而研究了ENSO以及东南太平洋异常海温场与南极海冰之间的关系。结果表明 ,在ElNino期间 ,堆积于赤道东太平洋的异常暖水 ,是沿秘鲁和智利沿岸向极传播。其传播过程持续大约 1年的时间 ,但未发现沿南赤道流的西传现象。ENSO循环过程与南极海冰变化存在一定联系 ,特别是Amundsen Belling shausen海和南极半岛海冰的变化与ENSO暖事件 (ElNino)较为密切。当ElNino事件发生后 ,时滞 2年左右的时间 ,Amundsen Bellingshausen海和南极半岛的海冰将出现明显的减少现象 ,特别是南极半岛的海冰减少最为明显。ElNino事件对南极海冰的影响过程是 ,堆积于赤道东太平洋的大量异常暖水 ,沿南美 (秘鲁和智利 )沿岸近海向极地传播 ,异常暖水的这种向极传播过程将引起近极的海温场出现异常升高 ,最终导致Amundsen Bellingshausen海和南极半岛地区的海冰减少。自 2 0世纪 80年代以来 ,Amundsen Bellingshausen海和南极半岛的海冰出现明显减少的趋势 ,与这一时期的ElNino事件的频繁发生