Natal homing and connectivity in Atlantic bluefin tuna populations

Atlantic bluefin tuna populations are in steep decline, and an improved understanding of connectivity between individuals from eastern (Mediterranean Sea) and western (Gulf of Mexico) spawning areas is needed to manage remaining fisheries. Chemical signatures in the otoliths of yearlings from regional nurseries were distinct and served as natural tags to assess natal homing and mixing. Adults showed high rates of natal homing to both eastern and western spawning areas. Trans-Atlantic movement (east to west) was significant and size-dependent, with individuals of Mediterranean origin mixing with the western population in the U.S. Atlantic. The largest (oldest) bluefin tuna collected near the northern extent of their range in North American waters were almost exclusively of western origin, indicating that this region represents critical habitat for the western population.     

Influence of the Atlantic subpolar gyre on the thermohaline circulation

During the past decade, record-high salinities have been observed in the Atlantic Inflow to the Nordic Seas and the Arctic Ocean, which feeds the North Atlantic thermohaline circulation (THC). This may counteract the observed long-term increase in freshwater supply to the area and tend to stabilize the North Atlantic THC. Here we show that the salinity of the Atlantic Inflow is tightly linked to the dynamics of the North Atlantic subpolar gyre circulation. Therefore, when assessing the future of the North Atlantic THC, it is essential that the dynamics of the subpolar gyre and its influence on the salinity are taken into account.     

Geographic origin of benthic foraminiferal species

Museum collections were used to document the worldwide Pliocene and Pleistocene fossil record of 59 species that now occur on the Atlantic continental margin of North America. Tabulation of these data indicates that benthic foraminifera evolve at all latitudes and in all parts of the world ocean rather than from some center or centers of origin. Dispersal in geologic time is very rapid.     

Equatorial pacific seismic reflectors as indicators of global oceanographic events

The origin of a series of regionally correlatable seismic horizons in the Neogene sediments of the central equatorial Pacific is examined through seismic modeling and the detailed analyses of stratigraphic and physical property relationships in Deep Sea Drilling Project cores. These regionally traceable reflectors are synchronous; the younger reflectors are the direct result of carbonate dissolution events, the older ones of stratigraphically selective diagenetic processes. The changes in ocean chemistry associated with these events appear to be linked to global reorganizations of surface and bottom-water circulation patterns, the most dramatic of which are associated with reorganizations of North Atlantic bottom waters. These deepwater seismic horizons appear to correlate with the major events on the "relative sea-level" curve of Vail et al. for the Neogene.     

An eocene hystricognathous rodent from Texas: its significance in interpretations of continental drift

The earliest known representative of the fundamentally South American and African hystricognathous rodents has recently been found in the middle or late Eocene of southwestern Texas; this discovery supports the postulate of a northern and independent origin for the two southern groups and increases the evidence against mid-Tertiary trans-Atlantic migration of these rodents at a time when the South Atlantic was narrower than it is at present. The fossil seems to be related to the North American Eocene family Sciuravidae.     

Dating of pore waters with (129)I: relevance for the origin of marine gas hydrates

Pore waters associated with gas hydrates at Blake Ridge in the Atlantic Ocean were dated by measuring their iodine-129/iodine ratios. Samples collected from sediments with ages between 1.8 and 6 million years ago consistently yield ages around 55 million years ago. These ages, together with the strong iodine enrichment observed in the pore waters, suggest that the origin of iodine is related to organic material of early Tertiary age, which probably is also the source of the methane in the gas hydrates at this location.     

Soot carbon and excess fine potassium: long-range transport of combustion-derived aerosols

During a cruise from Hamburg to Montevideo, aerosol samples representing air masses from Europe, the Sahara, tropical Africa, South America, and open oceanic regions were collected. They showed significant amounts of soot carbon over large areas of the remote Atlantic, often similar to concentrations in rural continental areas. Back-trajectories and the ratios of soot carbon to total fine (less than 1.7 micrometers in diameter) carbon and of excess fine potassium (the portion not attributable to soil dust or sea salt) to soot carbon indicate that biomass burning in tropical regions is an important source of soot carbon to the world atmosphere. The ratio of excess potassium to soot carbon in the fine fraction of aerosols is proposed as an indicator of the relative contributions of biomass and fossil-fuel burning to soot carbon aerosols. The ratio of soot carbon to fine carbon suggests that most of the particulate organic carbon over the Atlantic is of continental origin.     

Secular variation of iron isotopes in north atlantic deep water

A high-precision iron isotope time series for a ferromanganese crust demonstrates that the iron isotope composition in North Atlantic Deep Water has changed substantially over the past 6 million years and that iron isotope variations in the crust are closely correlated to those of lead isotopes. The close correlation between the two isotope series indicates that the observed iron isotope variations predominantly reflect those of iron input from terrigenous sources and provides no evidence for biologically induced mass fractionation within North Atlantic Deep Water.     

Identification of widespread pollution in the southern hemisphere deduced from satellite analyses

Vertical profiles of ozone obtained from ozonesondes in Brazzaville, Congo (4 degrees S, 15 degrees E), and Ascension Island (8 degrees S, 15 degrees W) show that large quantities of tropospheric ozone are present over southern Africa and the adjacent eastern tropical South Atlantic Ocean. The origin of this pollution is widespread biomass burning in Africa. These measurements support satellite-derived tropospheric ozone data that demonstrate that ozone originating from this region is transported throughout most of the Southern Hemisphere. Seasonally high levels of carbon monoxide and methane observed at middle- and high-latitude stations in Africa, Australia, and Antarctica likely reflect the effects of this distant biomass burning. These data suggest that even the most remote regions on this planet may be significantly more polluted than previously believed.     

Eight centuries of north atlantic ocean atmosphere variability

Climate in the tropical North Atlantic is controlled largely by variations in the strength of the trade winds, the position of the Intertropical Convergence Zone, and sea surface temperatures. A high-resolution study of Caribbean sediments provides a subdecadally resolved record of tropical upwelling and trade wind variability spanning the past 825 years. These results confirm the importance of a decadal (12- to 13-year) mode of Atlantic variability believed to be driven by coupled tropical ocean-atmosphere dynamics. Although a well-defined interdecadal mode of variability does not appear to be characteristic of the tropical Atlantic, there is evidence that century-scale variability is substantial. The tropical Atlantic may also have been involved in a major shift in Northern Hemisphere climate variability that took place about 700 years ago.     

基于灰色理论系统的西非海域捕捞渔获量预测

西非海域包括中东大西洋和东南大西洋两个渔区，是全球重要的渔业生产区域，科学预测其未来渔获量变化趋势，有利于该海域渔业资源的科学管理和开发。根据2000—2020年联合国粮农组织（FAO）提供的渔获量数据，采用灰色关联分析法和灰色预测理论，分别分析了影响中东大西洋和东南大西洋总渔获量的主要渔获类别，建立多种 GM (1,N)模型并进行比较分析，同时利用2018—2020年渔获量数据进行验证，获得最优GM（1,N）模型预测2021—2025年中东大西洋和东南大西洋总渔获量。本研究分析发现两海域最优预测模型均为GM（1,6），模型预测值与原始值的灰色关联系数均最大，分别为0.825和0.867，平均相对误差均为最小，分别为2.705%和1.734%；2018—2020年渔获量预测平均相对误差分别为4.63%和8.24%；2021—2025年中东大西洋和东南大西洋总渔获量预测值分别为497.67～588.79万t和138.20～147.41万t。研究认为，中东大西洋总渔获量在十四五期间最多增长约为48万t，增长幅度较小，建议加强资源养护、管控捕捞规模，制定和实施禁渔期等有效管理养护措施，建立科学合理渔业合作机制；东南大西洋总渔获量呈平稳波动状态，建议加强重点鱼种的养护管理，深化区域渔业合作，适当扩大捕捞海域范围，实现渔业可持续利用。     

Mid-depth circulation of the subpolar north atlantic during the last glacial maximum

Holocene and glacial carbon isotope data of benthic foraminifera from shallow to mid-depth cores from the northeastern subpolar Atlantic show that this region was strongly stratified, with carbon-13-enriched glacial North Atlantic intermediate water (GNAIW) overlying carbon-13-depleted Southern Ocean water (SOW). The data suggest that GNAIW originated north of the polar front and define GNAIW end-member carbon isotope values for studies of water-mass mixing in the open Atlantic. Identical carbon isotope values in the core of GNAIW and below the subtropical thermocline are consistent with rapid cycling of GNAIW through the northern Atlantic. The high carbon isotope values below the thermocline indicate that enhanced nutrient leakage in response to increased ventilation may have extended into intermediate waters. Geochemical box models show that the atmospheric carbon dioxide response to nutrient leakage that results from an increase in ventilation rate may be greater than the response to nutrient redistribution by conversion of North Atlantic deep water into GNAIW. These results underscore the potential rule of Atlantic Ocean circulation changes in influencing past atmospheric carbon dioxide values.     

Trajectory shifts in the Arctic and subarctic freshwater cycle

Manifold changes in the freshwater cycle of high-latitude lands and oceans have been reported in the past few years. A synthesis of these changes in freshwater sources and in ocean freshwater storage illustrates the complementary and synoptic temporal pattern and magnitude of these changes over the past 50 years. Increasing river discharge anomalies and excess net precipitation on the ocean contributed approximately 20,000 cubic kilometers of fresh water to the Arctic and high-latitude North Atlantic oceans from lows in the 1960s to highs in the 1990s. Sea ice attrition provided another approximately 15,000 cubic kilometers, and glacial melt added approximately 2000 cubic kilometers. The sum of anomalous inputs from these freshwater sources matched the amount and rate at which fresh water accumulated in the North Atlantic during much of the period from 1965 through 1995. The changes in freshwater inputs and ocean storage occurred in conjunction with the amplifying North Atlantic Oscillation and rising air temperatures. Fresh water may now be accumulating in the Arctic Ocean and will likely be exported southward if and when the North Atlantic Oscillation enters into a new high phase.     

气候变化对西南大西洋渔业生态系统的影响研究进展

西南大西洋是世界重要的渔区之一，捕捞国家包括阿根廷等西南大西洋沿海国以及中国、日本等众多非沿海国家，其中阿根廷滑柔鱼（Illex argentinus）、阿根廷无须鳕（Merluccius hubbsi）、巴西小沙丁鱼（Sardinella brasiliensis）与弗氏绒须石首鱼（Micropogonias furnieri）是西南大西洋年均产量最高的4种主要经济渔获物。探究气候变化对西南大西洋生态系统的影响有利于建立基于生态系统的渔业资源保护与利用格局。本文从渔业资源与生态系统两个角度出发，分别归纳了生态系统的生物因子（主要经济渔获物）、非生物因子（环境因素）与营养结构（食物链和食物网）对气候变化的响应情况。分析认为，在今后探究西南大西洋生态系统对气候变化的响应的研究中，选取代表物种表征生态系统的变化并结合人类活动与气候变化的影响可以丰富生态系统的相关结论，为西南大西洋海域提供基于生态系统的科学管理策略。     

Phytoplankton blooming off the u.s. East coast: a satellite description

A "bloom" of near-surface phytoplankton occurs in the Atlantic Slope region of the western Atlantic Ocean off the U.S. East Coast in the spring. Satellite time series of sea-surface temperature and phytoplankton pigment concentration, derived from measurements of the National Oceanic and Atmospheric Administration NOAA-7 Advanced Very-High-Resolution Radiometer and the National Aeronautics and Space Administration Nimbus-7 Coastal Zone Color Scanner, respectively, give information on the spatial extent and temporal development of such a bloom for a 28-day period in April through May 1982. The phytoplankton concentration of the slope area is comparable to that of the Atlantic Shelf. Total primary productivity of the slope during this period is equivalent to that of the shelf. The primary productivity within a warm-core ring and in the Gulf Stream system is less by a factor of 2.     

大西洋蓝鳍金枪鱼资源开发与养护问题分析

长达数十年的持续不断的高强度捕捞使得大西洋蓝鳍金枪鱼资源处于严重衰退状态。通过渔获数据分析大西洋蓝鳍金枪鱼资源开发状况,结合区域渔业管理制度和养护措施,探讨大西洋蓝鳍金枪鱼管理存在的问题与不足。分析认为:各个国家出于本国利益考虑忽视总可捕量的科学建议,使得大西洋金枪鱼养护国际委员会最终确定的总可捕量高于科学家们的建议量;现有分配机制有失公平,偏离国际法公平原则,因而其不能有效引导各国采取积极养护措施;大西洋金枪鱼养护国际委员会对大西洋蓝鳍金枪鱼捕捞活动监管是整个管理过程中脆弱的环节,且因缺乏有效执行机制而未能有效限制非法捕捞。提出改善总可捕量设定过高现状,使总可捕量设定符合使资源达到最大可持续产量的目标;改进配额分配机制,保障大西洋蓝鳍金枪鱼资源利用的公平合理;加强大西洋蓝鳍金枪鱼捕捞活动监管,完善入渔管理机制,推动成员履约。     

Atmospheric trace metals at remote northern and southern hemisphere sites: pollution or natural?

The chemical composition of atmospheric particles collected near sea level over the North Atlantic indicates that Al, Sc, Mn, Fe, Co, Cr, Na, Mg, Ca, K, and Sr are derived from either crustal weathering or the ocean. The elements V, Zn, Cu, Cd, Pb, Sb, and Se are present in concentrations higher than expected from these sources. Although the V is probably derived from pollution sources on the North American continent, a comparison of enrichment factors relative to average crustal material for the remainder of these elements over the North Atlantic with enrichment factors for similar samples collected at the geographic South Pole suggests that the anomalously high enrichment factors may be due to natural rather than anthropogenic sources. A vapor phase for these metals may be involved at their source.     

The deglacial evolution of North Atlantic deep convection

Deepwater formation in the North Atlantic by open-ocean convection is an essential component of the overturning circulation of the Atlantic Ocean, which helps regulate global climate. We use water-column radiocarbon reconstructions to examine changes in northeast Atlantic convection since the Last Glacial Maximum. During cold intervals, we infer a reduction in open-ocean convection and an associated incursion of an extremely radiocarbon ((14)C)-depleted water mass, interpreted to be Antarctic Intermediate Water. Comparing the timing of deep convection changes in the northeast and northwest Atlantic, we suggest that, despite a strong control on Greenland temperature by northeast Atlantic convection, reduced open-ocean convection in both the northwest and northeast Atlantic is necessary to account for contemporaneous perturbations in atmospheric circulation.     

Florida current: seasonal and interannual variability

Annual and interannual variations in the Florida Current, Caribbean, and subtropical Atlantic are investigated with the use of historical sea level differences and wind field data. Observational and model evidence suggests that the seasonal transport cycle of the Florida Current is locally forced, either upstream in the Caribbean or downstream over topography. Although at seasonal and shorter periods sea level or bottom pressure fluctuations on the left side of the Florida Current contribute almost all of the variance of sea level difference across the Florida Straits and hence transport, this relation does not seem to apply at interannual time scales. Using results from the Subtropical Atlantic Climate Studies, it is estimated from historical sea level data that interannual transport fluctuations of the Florida Current are only of order 1 x 10(6) cubic meters per second. Interannual fluctuations in the 2- to 3-year period range in the Florida Straits seem to be correlated with sea level differences across the Caribbean and the subtropical Atlantic but not with Sverdrup transport fluctuations in the subtropical Atlantic.     

Deep, zonal subequatorial currents

Large-scale, westward-extending tongues of warm (Pacific) and cold (Atlantic) water are found between 2000 and 3000 meters both north and south of the equator in the Pacific and Atlantic oceans. They are centered at 5 degrees to 8 degrees north and 10 degrees to 15 degrees south (Pacific) and 5 degrees to 8 degrees north and 15 degrees to 20 degrees south (Atlantic). They are separated in both oceans by a contrasting eastward-extending tongue, centered at about 1 degrees to 2 degrees south, in agreement with previous helium isotope observations (Pacific). Thus, the indicated deep tropical westward flows north and south of the equator and eastward flow near the equator may result from more general forcing than the hydrothermal forcing previously hypothesized.