Climate change and warm‐water species at the north‐western boundary of the Mediterranean Sea

The effects of global change are particularly serious in areas where range shifts of species are physically constrained such as the Ligurian Sea, which is one of the coldest sectors of the Mediterranean. In this basin, historical information on water temperature (from the sea surface down to 75 m depth) dates back to the 1950s. Early studies also recorded warm‐water species occurrence. Thanks to these data we provide the first detailed characterization of water temperature variation from 1958 up to 2010 in the layer 0–75 m depth. We coupled this analysis with the available information on rocky reef epibenthic communities (literature review from 1955 to 1964 and field data from 1980 to 2010). The analysis of water temperature revealed several patterns of variation: a cooling phase from 1958 to 1980, a phase of rapid warming from 1980 to 1990 and a phase of slower warming from 1990 to 2010. Inter‐annual variation in temperature increased over the entire period for the water layer down to 20 m. Warm‐water native and alien species richness increased during the warming phases. Literature estimates suggest a decrease in warm‐water native species richness during the cooling phase. The analysis of quantitative data collected in the early 1990s and late 2000s indicated a decrease in the cover of warm‐water native species on shallow rocky reefs and an increase in deeper waters. We argue that increased inter‐annual variation in water temperature may disadvantage native warm‐water species in shallow waters. Our results indicate that the effect of temperature rises in cold, constrained basins may be more complex than the simple prediction of species changing their geographical range according to their thermal limits.     

盐度对变化2014年东北太平洋“暖泡”的作用

A significant strong, warm "Blob"(a large circular water body with a positive ocean temperature anomaly)appeared in the Northeast Pacific(NEP) in the boreal winter of 2013–2014, which induced many extreme climate events in the US and Canada. In this study, analyses of the temperature and salinity anomaly variations from the Array for Real-time Geostrophic Oceanography(Argo) data provided insights into the formation of the warm"Blob" over the NEP. The early negative salinity anomaly dominantly contributed to the shallower mixed layer depth(MLD) in the NEP during the period of 2012–2013. Then, the shallower mixed layer trapped more heat in the upper water column and resulted in a warmer sea surface temperature(SST), which enhanced the warm"Blob". The salinity variability contributed to approximately 60% of the shallowing MLD related to the warm"Blob". The salinity anomaly in the warm "Blob" region resulted from a combination of both local and nonlocal effects. The freshened water at the surface played a local role in the MLD anomaly. Interestingly, the MLD anomaly was more dependent on the local subsurface salinity anomaly in the 100–150 m depth range in the NEP.The salinity anomaly in the 50–100 m depth range may be linked to the anomaly in the 100–150 m depth range by vertical advection or mixing. The salinity anomaly in the 100–150 m depth range resulted from the eastward transportation of a subducted water mass that was freshened west of the dateline, which played a nonlocal role.The results suggest that the early salinity anomaly in the NEP related to the warm "Blob" may be a precursor signal of interannual and interdecadal variabilities.     

An overview of the Oyashio ecosystem

The Oyashio shelf region and the seasonally ice-covered areas north of Hokkaido are highly productive, supporting a wide range of species including marine mammals, seabirds and commercially important species in the western subarctic Pacific. The fishes include gadids, such as walleye pollock and Pacific cod, and subarctic migratory pelagic fishes such as chum salmon and pink salmon. It is also an important summer feeding ground for subtropical migrants such as the Japanese sardine, Japanese anchovy, Pacific saury, mackerels, Japanese common squid, whales and seabirds. In recent decades, some components of the Oyashio ecosystem (i.e., phytoplankton, mesozooplankton, gadid fish, and subtropical migrants) have shown changes in species abundance or distribution that are correlated with environmental changes such as the 1976/1977 and 1988/1989 regime shifts. The First Oyashio Intrusion moved northward from the mid-1960s until the late 1970s, when it moved southward until the 1980s, after which it returned to the north again after the mid-1990s. The sea-surface temperature in spring decreased after the late 1970s, increased after the late 1980s, and remained high during the 1990s. The extent of ice cover in the Sea of Okhostk also decreased during the latest warming in the 1980–1990s but has increased again since the late 1990s. This and other variabilities affect the Oyashio ecosystem and the surrounding region.     

Distribution of and predation on saury Scomberesox saurus scombroides in continental shelf waters off the Cape Province,South Africa

Although the size distribution of larvae and early juveniles of the saury Scomberesox saurus scombroides in continental shelf waters off the Cape Province, South Africa, is consistent with a south-north passive dispersal by known currents, the size of late juveniles and adults increases from north-west to south-east. Occurrence of these stages is highly seasonal: they are found in summer off the Western Cape and mainly from late summer to winter in Algoa Bay in the Eastern Cape, possibly reflecting longitudinal migration. Large numbers of late juveniles and adults are often found downstream of upwelling plumes off the Western Cape when warmer waters lie close inshore. They are sometimes taken in purse-seines in association with adult round herring Etrumeus whiteheadi and pilchard Sardinops ocellatus. Important predators of late juvenile and adult saury are fast-moving, surface-feeding species: yellowfin tuna Thunnus albacares, Cape gannet Morus capensis and Cory's shearwater Calonectris diomedea. Cape gannets consume an estimated 2 277–6 044 tons of saury annually in South African waters. Predator diets provide important time-series of occurrence, abundance and length-frequency distributions of late juvenile and adult saury.     

Cooling in the western Bering Sea in 1999: quick propagation of La Niña signal or compensatory processes effect?

In 1999, synoptic and hydrological conditions in the western Bering Sea were characterized by negative SST and air temperature anomalies, extensive ice coverage and late melting. Biological processes were also delayed. In 1999, the average zooplankton biomass was 1.76 g/m³, approximately half the average 3.07 g/m³ in 1998. Pacific salmon migrated to the northeastern Kamchatka streams two weeks later. This contrasts with 1997 (spring and summer) and 1998 (summer) when positive SST anomalies were widely distributed throughout the northwestern Bering Sea shelf. Since the second half of the 1990s, seasonal atmospheric processes developed over the western Bering Sea that were similar to those of the cold decades of the 1960–1970s. A meridional atmospheric circulation pattern began to replace zonal transport. Colder Arctic air masses have shifted over the Bering Sea region and shelf water temperatures have cooled considerably with the weakening of zonal atmospheric circulation. Temperature decreased in the cold intermediate layer during its renewal in winter. Besides, oceanic water inflow intensified into the Bering Sea in intermediate layers. Water temperature warmed to 4°C and a double temperature maximum existed in the warm intermediate layer in late summer in both 1997 and 1998. Opposing trends of cold water temperature and a warm intermediate layer led to an increase of vertical gradients in the main thermocline and progressing frontogenesis. It accelerates frontal transport and can be regarded as a chief cause of increased water exchange with the Pacific Ocean.     

Atmospheric forcing of the southeast Bering Sea Shelf during 1995–99 in the context of a 40-year historical record

The atmospheric forcing of the Bering Sea over its eastern shelf is estimated using the 40-year record of daily data from the NCEP/NCAR Reanalysis. This data set includes estimates of the processes responsible for the atmospheric forcing, namely the surface fluxes of momentum, sensible and latent heat, and longwave and shortwave radiation, and therefore permits quantifying effects that previously could be inferred only from the large-scale nature of the flow. The forcing in 1995–1999 is described in detail using daily time series; historical context for these results is provided with seasonal averages for the years 1959–1999.The analysis for winter concentrates on aspects related to the formation and advection of sea ice. Results indicate that the presence of sea ice is strongly related to the net surface-heat fluxes as well as the cross-shelf component of the wind. The 40-year record lacks any discernible long-term trend in the winter forcing and response. There was a notably cold period in the early to middle 1970s, and a warm period from the late 1970s into the early 1980s, but conditions during the 1990s are similar to those in the late 1950s and 1960s.The analysis for the warm season focuses on the mechanisms responsible for the variability in SST warming. Much of the intraseasonal and interannual variability in this warming can be attributed to variations in the downward shortwave radiation (solar heating). The 40-year record does indicate a long-term trend toward increased solar heating, and reduced surface latent-heat fluxes (evaporative cooling). These changes have led to August SSTs in the 1990s that are roughly 1°C warmer than in the 1960s.     

Long-term changes in the fish community structure from the Tsushima warm current region of the Japan/East Sea with an emphasis on the impacts of fishing and climate regime shift over the last four decades

Japanese fisheries production in the Japan/East Sea between 1958 and 2003 increased to their peak (1.76 million tons) in the late 1980s and decreased abruptly with the collapse of Japanese sardine. Catch results for 58 fisheries and various environmental time-series data sets and community indices, including mean trophic level (MTL) and Simpson’s diversity index (DI), were used to investigate the impacts of fishing and climate changes on the structure of the fish community in the Tsushima warm current (TWC) region of the Japan/East Sea. The long-term trend in fisheries production was largely dependent on the Japanese sardine that, as a single species, contributed up to 60% of the total production in the Japanese waters of the Japan/East Sea during the late 1980s. Excluding Japanese sardine, production of the small pelagic species was higher during 1960s and 1990s but lower during 1970s and 1980s. This variation pattern generally corresponds with the trend in water temperature, warmer before early 1960s and after 1990s but colder during 1970s and 1980s. The warm-water, large predatory fishes and cold water demersal species show opposite responses to the water temperature in the TWC region, indicating the significant impact of oceanic conditions on fisheries production of the Japan/East Sea. Declines in demersal fishes and invertebrates during 1970s and 1980s suggested some impact of fishing. MTL and DI show a similar variation pattern: higher during 1960s and 1990s but lower during 1970s and 1980s. In particular, the sharp decline during the 1980s resulted from the abundant sardine catches, suggesting that dominant species have a large effect on the structure of the fish community in the Japan/East Sea. Principal component analysis for 58 time-series data sets of fisheries catches suggested that the fish community varied on inter-annual to inter-decadal scales; the abrupt changes that occurred in the mid-1970s and late 1980s seemed to correspond closely with the climatic regime shifts in the North Pacific. These results strongly suggest that the structure of the fish community in the Japan/East Sea was largely affected by climatic and oceanic regime shifts rather than by fishing. There is no evidence showing “fishing down food webs” in the Japan/East Sea. However, in addition to the impacts of abrupt shifts that occurred in the late 1980s, the large predatory and demersal fishes seem to be facing stronger fishing pressure with the collapse of the Japanese sardine.     

Hydrographic changes in the Labrador Sea, 1960–2005

The Labrador Sea has exhibited significant temperature and salinity variations over the past five decades. The whole basin was extremely warm and salty between the mid-1960s and early 1970s, and fresh and cold between the late 1980s and mid-1990s. The full column salinity change observed between these periods is equivalent to mixing a 6 m thick freshwater layer into the water column of the early 1970s. The freshening and cooling trends reversed in 1994 starting a new phase of heat and salt accumulation in the Labrador Sea sustained throughout the subsequent years. It took only a decade for the whole water column to lose most of its excessive freshwater, reinstate stratification and accumulate enough salt and heat to approach its record high salt and heat contents observed between the late 1960s and the early 1970s. If the recent tendencies persist, the basin’s storages of salt and heat will fairly soon, likely by 2008, exceed their historic highs.The main process responsible for the net cooling and freshening of the Labrador Sea between 1987 and 1994 was deep winter convection, which during this period progressively developed to its record depths. It was caused by the recurrence of severe winters during these years and in its turn produced the deepest, densest and most voluminous Labrador Sea Water (LSW_1987–1994) ever observed. The estimated annual production of this water during the period of 1987–1994 is equivalent to the average volume flux of about 4.5 Sv with some individual annual rates exceeding 7.0 Sv. Once winter convection had lost its strength in the winter of 1994–1995, the deep LSW_1987–1994 layer lost “communication” with the mixed layer above, consequently losing its volume, while gaining heat and salt from the intermediate waters outside the Labrador Sea.While the 1000–2000 m layer was steadily becoming warmer and saltier between 1994 and 2005, the upper 1000 m layer experienced another episode of cooling caused by an abrupt increase in the air-sea heat fluxes in the winter of 1999–2000. This change in the atmospheric forcing resulted in fairly intense convective mixing sufficient to produce a new prominent LSW class (LSW₂₀₀₀) penetrating deeper than 1300 m. This layer was steadily sinking or deepening over the years following its production and is presently overlain by even warmer and apparently less dense water mass, implying that LSW₂₀₀₀ is likely to follow the fate of its deeper precursor, LSW_1987–1994. The increasing stratification of the intermediate layer implies intensification in the baroclinic component of the boundary currents around the mid-depth perimeter of the Labrador Sea.The near-bottom waters, originating from the Denmark Strait overflow, exhibit strong interannual variability featuring distinct short-term basin-scale events or pulses of anomalously cold and fresh water, separated by warm and salty overflow modifications. Regardless of their sign these anomalies pass through the abyss of the Labrador Sea, first appearing at the Greenland side and then, about a year later, at the Labrador side and in the central Labrador Basin.The Northeast Atlantic Deep Water (2500–3200 m), originating from the Iceland–Scotland Overflow Water, reached its historically freshest state in the 2000–2001 period and has been steadily becoming saltier since then. It is argued that LSW_1987–1994 significantly contributed to the freshening, density decrease and volume loss experienced by this water mass between the late 1960s and the mid 1990s via the increased entrainment of freshening LSW, the hydrostatic adjustment to expanding LSW, or both.     

Characteristics of Habitats Used by Enteroctopus dofleini in Prince William Sound and Cook Inlet,Alaska

Abstract. Habitat characteristics associated with the giant Pacific octopus, Enteroctopus dofleini (Wülker 1910), were studied in Prince William Sound and Port Graham, Alaska, from beach walk, SCUBA and submersible surveys at depths of 0 to 197 m. Octopus counts on beach walk transects were positively correlated with soft substrates (sand, gravel or broken rubble), the presence of boulders, and dense kelp cover immediately offshore of the transect; and negatively correlated with depth on SCUBA transects. No significant habitat correlations were found with counts on submersible transects. On beach walks, octopus counts were reduced on hard substrates to 38 % of the counts on soft substrates. Counts increased five‐fold in the presence of boulders over counts in their absence, and increased fifteen‐fold adjacent to dense (> 75 %) kelp cover over counts adjacent to sparse (< 25 %) kelp cover. On SCUBA transects, the average density at less than 5 m depth was over five times that below 5 m. No trends in octopus size or sex ratio were detected with depth. Den use was inversely correlated with depth although there was no indication that den availability declined with depth. Octopuses were found at densities from 0 to 2.5 per 1000 m². These densities were only 1 to 50 % of densities of the same species recorded in British Columbia in the late 1970s and early 1980s. Few data are available to test recruitment, mortality, and habitat selection hypotheses that would account for differences between habitats. However, the presence of the highest octopus densities in intertidal and very shallow subtidal areas indicates the likely importance of near‐shore, shallow‐water habitats, and highlights the vulnerability of octopus populations to changes in these habitats.     

连续深度基准面构建及通航水深服务模式研究

通航水深是船舶在某时段沿着一定航线通过特定区域的最浅水深,对船舶的安全航行具有重要意义。海图测绘时将水深归算至深度基准面,由验潮资料求得,而潮汐值是通过临近区域发布的潮汐表来进行推算,由此获得的通航水深精度不 高,且不同港区之间采用深度基准不统一,所以无法为船舶提供精确、连续的通航水深。本文提出了一种基于高精度 GNSS的通航水深测量方法,直接测量海底高程,通过精密数值模型模拟海面高程,由此获得通航水深,并提出了实时通航水深的应用模式。为了建立与陆地地形相衔接的海底地形模型,以 CGCS2000 参考椭球面为垂直参考基准面,深度基准面采用 POM（Princeton Ocean Model） 模式进行潮波数值模拟的方法构建。实验结果显示：数值模型精度较高,构建的深度基准面误差在5 cm 以内。本文提出的方法改变了传统的通航水深测量及服务模式,提供高效率、高精度通航水深、海图水深数据,可为船舶用户提供实时动态水深服务。     

ADCP测量数据深度值的正确解析

介绍了声学多普勒流速剖面仪(ADCP)测流和测深的基本原理,着重论述了汇整ADCP测量的层深、水深数据的误差来源、判读和校正方法,并给出了实用的计算公式。本文研究的方法对于船载、向下观测的走航、定点ADCP测量深度数据的处理,精确定位海流测量结果、保证海流测量结果反映真实海洋环境状况,具有实际的应用价值,同时能够为锚系ADCP测量层深与水深数据的处理提供可参考的技术依据。     

穿透性太阳短波辐射对混合层深度的影响

用数值方法研宄穿透性太阳短波辐射对混合层深度的影响时,有些学者人为地设定了风速和热通量。这种做法可能会出现风速和热通量数值不匹配的问题。为了弥补这一缺陷,本文采用国内外常用的块体公式计算热通量的方法来代替人为设置,并以北太平洋为例,研究了穿透性太阳短波辐射对海洋混合层深度的影响。结果表明:低风速(U10<10m／s),且海表短波净辐射处于40～200 W／m2时,穿透性太阳短波辐射对混合层深度影响很显著;高风速(U10>10m／s)和短波净辐射高值区(S*(0)>200 W／m2),穿透性太阳短波辐射对混合层深度的影响较小。     

Interannual variability of mixed layer depth and heat storage of upper layer in the tropical Pacific Ocean

By using the upper layer data(downloaded from the web of the Scripps Institution of Oceanography ),the interannual variability of the heat storage of upper layer(from surface to 400 m depth) and the mixed layer depth in the tropical Pacific Ocean are investigated. The abnormal signal of the warm event comes from the central and west Pacific Ocean, whereas it is regarded that the abnormal signal of the warm event comes from the east Pacific Ocean in the popular viewpoint. From the viewpoint on the evolution of the interannual variability of the mixed layer depth and the heat storage of the whole upper layer, the difference between the two types of E1Nino is so small that it can be neglected. During these two E1Nino/La Nina events( 1972/1973 and 1997/1998), other than the case of the heat storage or for the mixed layer depth, the abnormal signal propagates from the central and west Pacific Ocean to the east usually by the path along the equator whereas the abnormal signal propagates from the east to the west by the path northern to the equator. For the interannual variability, the evolution of the mixed layer depth corresponds to that of the heat storage in the upper layer very well. This is quite different from the evolution of seasonality.     

顾及特征水深点距离重分配的反距离加权插值算法

水深是反映海底地形地貌的最基础要素,对缺失的水深点进行准确的插值能帮助有效地表达海底地形地貌起伏形态。针对海底地形变化复杂的区域,传统的反距离加权插值法存在只考虑样本水深点与待插值水深点之间的距离,而忽略了样本水深点之间的空间相关性的问题。本文提出了一种顾及特征水深点距离重分配的反距离加权插值算法。该算法首先对离散的水深点构建特征水深线,在特征水深线的基础上,提取特征水深线上的特征点作为特征水深点;然后在所有样本水深点到待插值水深点距离之和不变的约束下,提出距离重分配的量化指标;最后构造出一个顾及特征水深点距离重分配的IDW插值算法模型。实验结果表明,在海底地形变化复杂的区域,顾及特征水深点距离重分配的反距离加权插值算法与传统的IDW、自然邻域插值、样条函数插值算法等相比,能有效提高水深点的插值精准度。     

Warped temperature profiles observed in the sediment of geothermally active areas in the Japan Sea— A hypothesis of double diffusive sinking

Some temperature profiles observed in sea floor sediments of the Japan Sea, west of the northern part of Honshu, show distinct gradients changing with depth, for which we use the term warping. Using a simplified model, this warping can be attributed to an abrupt temperature change in the bottom water just above the sediment. The bottom water temperature change might be explained by the hypothesis that warm and salt surface water in the region sank to the sea bottom, through colder and less saline water, maintaining a relatively warmer temperature than the bottom water which originates from ordinary lateral intrusion.     

印度洋-太平洋暖池的变异研究

为了研究在何种时间尺度上定义研究印度洋-太平洋暖池（简称印-太暖池）更有意义, 本文中应用功率谱等统计学方法, 对印-太暖池的季节、年际及年代际变化特征进行了分析.结果表明, 印-太暖池、东印度洋暖池（简称东印暖池）在季节变化上表现为单峰结构, 而西太平洋暖池（简称西太暖池）则为双峰结构; 在年际变化上印-太暖池和西太暖池表现出很强的3-6年变化周期, 东印暖池则存在准两年的振荡周期; 印-太暖池还存在10年以上的年代际周期振荡, 特别是70年代中后期的年代际突变明显, 而东印暖池的这种变化更为明显.由此可知印-太暖池的年代际变化与东印暖池、西太暖池年代际变化较为相似, 季节和年际变化颇为不同, 所以, 在研究年代际尺度的问题上, 定义并研究印-太暖池的意义更大, 而在研究年际、季节尺度上的问题时东印暖池、西太暖池应分而视之.     

Study of attenuation depths for MODIS bands in the Bohai Sea in China

An attenuation depth is defined for remote sensing purposes as a depth above which 90% of the arising light leaving the water surface is originated.The deeper the attenuation depth,the more information of water is detectable by remote sensing,then the more precise information of water is extracted.Meanwhile,the attenuation depth is helpful to know water layer (by its thickness) from which remote sensing will be able to extract information.A number of investigators are using the moderate resolution imaging spectroradiometer (or MODIS) for remote sensing of ocean color.It is necessary to have a rough idea of the effective attenuation depth of imagery in each of the spectral bands employed by the MODIS.The attenuation depth is directly determined from MODIS data.Though analyzing the spectral distribution of the attenuation depth on 7 August 2003 and the seasonal variation of the attenuation depth (551 nm) in the Bohai Sea indicated that:the spectral distribution of the attenuation depth for the spectral range between 400 to 700 nm is single-peak curve,and it''s similar and difference in different regions is consistent with other scholars'' results of zoning,moreover,it supports the Bohai Sea is Case 2 water; the maximum attenuation depth shifts toward longer wavelengths,liking the red shift,with increase of turbidity of water,just like the maximum attenuation depth in the outside of the northwest coast of the Bohai Sea and the Bohai Strait is at 531nm,in the central of the Bohai Sea is at 551nm,in the region controlled by the Huanghe (Yellow) River,the region impacted by the old Huanghe River,the western side of the Liaodong Bay and the eastern side of the Liaodong Bay is at 555 nm; the seasonal change of the attenuation depth is the largest in the summer,followed by the fall,and the ranking of winter and spring in different regions is distinct.The attenuation depth in different regions is dissimilar:the order of the attenuation depth in different regions from small to big is the region controlled by the Huanghe River or the eastern side of the Liaodong Bay,the western side of the Liaodong Bay,the region impacted by the old Huanghe River,the central of the Bohai Sea or the outside of the northwest coast of the Bohai Sea,the Bohai Strait (except at 412 nm and 645 nm),in which between the region controlled by the Huanghe River and the eastern side of the Liaodong Bay (and between the central of the Bohai Sea and the outside of the northwest coast of the Bohai Sea) it varies in different seasons and different bands.     

Benthic community structure and water column characteristics at two sites in the Kermadec Islands Marine Reserve,New Zealand

The Kermadec Islands Marine Reserve (KIMR), which is located at 30°S, is New Zealand's largest marine reserve at 748 000 ha, and its biota is composed of a mix of warm temperate, subtropical, and tropical species. A depth‐stratified ecological survey was conducted of the abundance and percentage cover of macrobenthic species and of the water column at two sites (Meyer Island and West Chanter Island), 2km apart. Significant differences in benthic community structure and in water column turbidity and chlorophyll concentrations were observed between the two sites despite their proximity and physical similarity. Compared with other “snapshot” surveys of benthic community structure at sites within the KIMR there was a high degree of similarity among the species observed, but often a low degree of similarity in species abundance or percentage cover as a function of depth. We suggest that despite its isolation and the degree of difficulty of working at this location, a full‐scale ecological survey of the coastal marine biota of the KIMR is warranted to better understand New Zealand's subtropical marine biota and its affinities with other marine biotas of the South Pacific.     

基于分段自适应算法的浅海水深遥感反演融合模型研究

对于水深光学遥感反演研究，虽然已经建立了大量的模型方法，然而对于不同水深段，同一模型的反演精度各异，且采用单一模型进行水深反演得到的整体反演精度未必最佳。为了提高水深光学遥感反演的整体精度，本文提出一种分段自适应水深反演融合模型，模型在误差估计的基础上，结合了对数线性模型、对数转换比值模型、改进的对数转换比值模型与多调节因子模型的优势。利用模型在西沙群岛东岛开展了水深遥感反演实验，从整体反演精度、不同水深段反演精度及逐米水深精度等角度进行分析，结果表明，分段自适应融合模型的整体精度最高，平均绝对误差为1.09 m，平均相对误差达到16.06%；分水深段来看，分段自适应融合模型在多数不同水深段内的反演效果均最好；从逐米精度来看，分段自适应融合模型在大部分逐米水深段的反演能力均优于其他模型。