Reactive mercury in the eastern North Atlantic and southeast Atlantic

The vertical distribution of reactive mercury has been measured at two stations in the eastern North Atlantic and one station in the southeast Atlantic in conjunction with the IOC Open Ocean Baseline Survey. The average concentrations of reactive Hg in vertical profiles ranged from 0.70 to 1.07 pM with the highest values found at the northeast Atlantic stations and the lowest at the southeast station. No significant concentration gradients were found below the surface mixed layer at the two stations in the eastern North Atlantic. At station 7, in the southeast Atlantic, an increase in reactive Hg was noted in the water adjacent to the mixed layer (35–200 m) which was coincident with an oxygen depletion, down to 20% saturation at 200 m. The concentration of reactive Hg in the North Atlantic Deep Water (0.48–1.34 pM), the Antarctic Intermediate Water (0.47 pM), the Antarctic Bottom Water (0.67–1.25 pM), and the Mediterranean Outflow Water (0.83–1.06 pM) were noted. The trends in Hg concentration in the water masses between stations showed the concentration decreasing with distance from the water mass source except for Hg in the Antarctic Bottom Water. The increase noted in this water mass was attributed to mixing with North Atlantic Deep Water and or release from bottom sediments.     

Silver in the far North Atlantic Ocean

Total (unfiltered) silver concentrations in higher latitudes of the North Atlantic (52–68°N) are reported for the second Intergovernmental Oceanographic Commission (IOC) Global Investigation of Pollutants in the Marine Environment (GIPME) baseline survey of 1993. These silver concentrations (0.69–7.2 pM) are oceanographically consistent with those (0.24–9.6 pM) previously reported for lower latitudes in the eastern North and South Atlantic (Flegal et al., 1995). However, surface (⩽200 m) water concentrations of silver (0.69–4.6 pM) in the northern North Atlantic waters are, on average, ten-fold larger than those (0.25 pM) considered natural background concentrations in surface waters of the central Atlantic. In contrast, variations in deep far North Atlantic silver concentrations are associated with discrete water masses. Consequently, the cycling of silver in the far North Atlantic appears to be predominantly controlled by external inputs and the advection of distinct water masses, in contrast to the nutrient-like biogeochemical cycling of silver observed in the central Atlantic and Pacific oceans.     

热带大西洋对全球变暖的响应

与太平洋和印度洋不同，全球变暖下热带大西洋变化的研究较少。本文使用地球系统模型CESM（Community Earth System Model），发现全球变暖后热带大西洋在秋季的升温类似大西洋尼诺（Atlantic Niño）的正位相，即大西洋西部增暖幅度小于东部；在夏季类似大西洋尼诺的负位相，即大西洋西部增暖幅度大于东部。利用覆盖（overriding）技术，分离了风应力、风速和CO₂的直接热效应对海洋升温的作用，探讨了大西洋尼诺本身和全球变暖作用下类似大西洋尼诺正位相（下文简称“类大西洋尼诺升温”）的形成机制。结果表明，这两种情况下的形成机制基本相同，风应力的变化是导致大西洋东部暖异常的主要机制。但两者之间也存在区别：1）全球变暖下海表温度的季节变化振幅减小，而大西洋尼诺时变化不大；2）全球变暖下西风异常主要集中在大西洋东部，而大西洋尼诺时主要集中在大西洋中部；3）除风应力外，CO₂的热效应对类尼诺升温的变化也有一定影响。     

Atlantic meridional overturning circulation and phosphate-classified bottom-up control of Atlantic pelagic ecosystems through the 20th century

Both the Atlantic Meridional Overturning Circulation (AMOC) and the North Atlantic Ocean (NA) biosphere have recognized associations with the North Atlantic Oscillation (NAO). These multidecadal physical–biological affinities inspired a closer look at AMOC influences on bottom-up control of NA and South Atlantic Ocean (SA) pelagic ecosystem variability. Various ocean models associate changes in the AMOC with sea surface temperature (SST) differences in the western subpolar NA and SA represented as the Atlantic Dipole SST Anomaly (ADSA) index. The Extended Reconstructed SST version 2 (ERSSTv2) dataset for 2° quadrangles from 1890 to 2007 was used here to represent Atlantic Ocean SST patterns and to gauge 20th century AMOC variability using an Atlantic Dipole SST (ADS) index, an un-normalized version of ADSA index. Temperature–phosphate (T–PO₄) linear regressions were used to convert temperature to phosphate concentration ([PO₄]). The interannual stability of T–PO₄ linear regressions first was examined using 26 Bermuda area T–PO₄ datasets between 1958 and 2001. Within the constraints provided by the Bermuda analysis, climatological T–PO₄ linear regressions based on GEOSECS-derived slopes and NODC-derived X-intercepts supported the conversion of monthly Atlantic Ocean ERSSTv2 temperatures for each 2° quadrangle to monthly surface [PO₄]. A representative annual surface phosphate utilization (SPU) was calculated for each 2° quadrangle by subtracting monthly minimum surface [PO₄] from monthly maximum surface [PO₄] to determine the annual surface [PO₄] ranges from 1890 to 2007. Annual average SST tended to increase and overall annual average SPU tended to decrease through the 20th century in both the NA and SA, but the NA exhibited more temporal variability. An Atlantic Dipole Phosphate Utilization (ADPU) index related to the ADS index was calculated for each year from 1890 to 2007. The ADS and ADPU indices were inversely correlated with about 57% of the variability in the ADPU index explained by the ADS index. The ADPU index exhibited three distinct cycles through the 20th century. Cross-correlation analysis showed that the NAO led the ADS and ADPU indices by about 14 years. Differences in annual average SPU for each Atlantic Ocean 2° quadrangle between the three high and four low years of the ADPU cycles yielded six maps that, when averaged, clearly exhibited reversed east–west patterns distributed in alternating latitudinal bands in both the NA and SA. The east–west patterns spatially corresponded to the NA and SA surface circulation and temporally resembled NA patterns previously associated with the NAO. AMOC variability, mediated by Kelvin and Rossby waves associated with changes in both deep and surface arm circulation, likely contributed to meridional continuity of phosphate-classified, NA, and SA pelagic ecosystem variability, including fisheries, through the 20th century. Based on the results, future global warming influences on the AMOC, well short of shutdown, likely will have complex pelagic ecosystem impacts throughout the Atlantic Ocean.     

The Continuous Plankton Recorder survey and the North Atlantic Oscillation: Interannual- to Multidecadal-scale patterns of phytoplankton variability in the North Atlantic Ocean

At interannual to multidecadal time scales, much of the oceanographic and climatic variability in the North Atlantic Ocean can be associated with the North Atlantic Oscillation (NAO). While evidence suggests that there is a relationship between the NAO and zooplankton dynamics in the North Atlantic Ocean, the phytoplankton response to NAO-induced changes in the environment is less clear. Time series of monthly mean phytoplankton colour values, as compiled by the Continuous Plankton Recorder (CPR) survey, are analysed to infer relationships between the NAO and phytoplankton dynamics throughout the North Atlantic Ocean. While a few areas display highly significant (p < 0.05) trends in the CPR colour time series during the period 1948–2000, nominally significant (p < 0.20) positive trends are widespread across the basin, particularly on the continental shelves and in a transition zone stretching across the Central North Atlantic. When long-term trends are removed from both the NAO index and CPR colour time series, the correlation between them ceases to be significant. Several hypotheses are proposed to explain the observed variability in the CPR colour and its relationship with climate in the North Atlantic.     

Evaporite deposition in the Aptian South Atlantic Ocean

The Aptian salt deposits of the South Atlantic Ocean extend for 250 km offshore and underlie the continental rise off Brazil and Angola in 4000 m water depth. These salt deposits do not occur south of the Walvis Ridge and Rio Grande Rise, and apparently lie on oceanic and continental crust. Geological evidence and an Aptian-Middle Barremian reconstruction of the South Atlantic suggests the pre-Aptian South Atlantic was closed at both ends, thus favouring widespread salt deposition on oceanic and continental crust. Three models of halite deposition are discussed briefly.     

Atlantic multidecadal oscillation and its manifestations in the Atlantic-European region

We present a brief survey of the works devoted to the investigation of the Atlantic Multidecadal Oscillation, i.e., of the quasiperiodic variations of sea-surface temperature in the North Atlantic with typical time scales of 50–100 yr. This oscillation is a manifestation of the natural variability in the ocean-atmosphere system. The characteristic scale of the Atlantic Multidecadal Oscillation is determined by the speed of the meridional oceanic circulation in the North Atlantic. The analyzed oscillation affects various climatic characteristics: air temperature, river discharge in the European and North-American regions, the number and intensity of tropical cyclones in the Atlantic Ocean, and the parameters of mid-latitude cyclones and anticyclones in the Atlantic-European region. The main mechanism by which the Atlantic Multidecadal Oscillation affects the climatic characteristics of the regions neighboring with the North Atlantic is the atmospheric response to the thermal anomalies in the ocean leading to a shift of the centers of atmospheric action and to the changes in the intensity and predominant directions of propagation of atmospheric cyclones and anticyclones. By using the results of long-term instrumental observations carried out in Eastern Europe and the data array of reconstructed temperature in the Alpine region, it is shown that the Atlantic Multidecadal Oscillation is responsible for a significant part of low-frequency variations of temperature in Europe. This fact confirms the potential predictability of the regional atmospheric manifestations of the Atlantic Multidecadal Oscillation on the decadal-scale. Translated from Morskoi Gidrofizicheskii Zhurnal, No. 4, pp. 69–79, July–August, 2008.     

On the mechanisms behind salinity anomaly signals of the northern North Atlantic

Hydrographic time series from the northern North Atlantic throughout the 20th century show oscillations in temperature and salinity at more or less regular intervals. The Great Salinity Anomalies described during the 1970s [Dickson, R.R., Meincke, J., Malmberg, S.-A., Lee, A.J., 1988. The “Great Salinity Anomaly” in the North Atlantic, 1968-1982. Progress in Oceanography 20, 103-151.], during the 1980s [Belkin, I.M., Levitus, S., Antonov, J., Malmberg, S.-A., 1998. “Great Salinity Anomalies” in the North Atlantic. Progress in Oceanography 41, 1-68.], and during the 1990s [Belkin, I.M., 2004. Propagation of the “Great Salinity Anomaly” of the 1990s around the northern North Atlantic. Geophysical Research Letters 31(8), L08306, doi:10.1029/2003GL019334.] have distinct amplitudes, and all three of them were interpreted as low salinity anomalies propagating downstream through the anti-clockwise circulation system of the northern North Atlantic Ocean. Further inspection of time series from the Northeast Atlantic and the Northwest Atlantic over the past century shows, however, several other distinct negative anomalies of lesser amplitudes. Additionally, a number of high salinity anomalies can be identified. The present paper analyses further the propagation of the negative and positive anomalies and links them together. It is shown that they have varying speeds of propagation, and that the varying speeds are correlated across the North Atlantic. We propose that varying volume fluxes in and out of the Arctic Basin is the causal mechanism behind the anomaly signals, and that the North Atlantic Oscillation (NAO) partly has influence on the flux variations described. Periods of large decadal-scale amplitudes of the NAO coincide with periods of large decadal-scale oscillation in the marine climate.     

Thermohaline Structure of Waters in the North Atlantic in Different Phases of the Atlantic Multidecadal Oscillation

Izvestiya, Atmospheric and Oceanic Physics - The meridional structure of climatic trends and anomalies of potential temperature and salinity in the North Atlantic waters in different periods of the...     

Tsunami Travel Time Atlas for the Atlantic Ocean

Compared to the Pacific Ocean, tsunamis are rare both in the Atlantic and Indian Oceans. However, the December 26, 2004, tsunami demonstrated that, no matter how rare they may be, when a major tsunami occurs, it could be very disastrous. The most basic information in tsunami warning center requires are charts showing tsunami travel times to various locations around the rim of the ocean. With this in mind, a tsunami travel time atlas for the Atlantic Ocean is in preparation. The Caribbean Sea is also included in this Atlas, as it is more or less a part of the Atlantic Basin.     

Nannoplankton of the Atlantic Ocean from sediment trap samples

Calcareous nannoplankton from sediment trap samples collected at six sites in the Atlantic Ocean from 23° S to 73° N (cruise 20 of R/V Vityaz’ and cruise 33 and 34 of R/V Akademik Mstislav Keldysh). Those samples were studied with a scanning electron microscope. In the coastal and open-sea regions of the North and South Atlantic and in the subarctic region of the Norwegian Sea, the conditions are significantly different. In the shelf area of the Benguela upwelling, 11 species were recognized; some of them were agglutinated by diatoms and tintinnides or covered the surface of pellets. The Broken Spur and TAG pelagic areas of the North Atlantic contained up to 43 coccolith species. They included holococcoliths, large pelagic, and delicate easily soluble species distributed over the entire water column. The presence of coccoliths in the high-latitude area of the Norwegian Sea is related to their supply with the warmer North Atlantic waters. These assemblages are distinguished by a low species diversity and an enhancement of the coccolith solubility with the depth increase.     

Tsunami Travel Time Atlas for the Atlantic Ocean

Compared to the Pacific Ocean, tsunamis are rare both in the Atlantic and Indian Oceans. However, the December 26, 2004, tsunami demonstrated that, no matter how rare they may be, when a major tsunami occurs, it could be very disastrous. The most basic information in tsunami warning center requires are charts showing tsunami travel times to various locations around the rim of the ocean. With this in mind, a tsunami travel time atlas for the Atlantic Ocean is in preparation. The Caribbean Sea is also included in this Atlas, as it is more or less a part of the Atlantic Basin.     

Optimum multiparameter analysis of the water mass structure in the Atlantic Ocean thermocline

An analysis of the water mass structure of the Atlantic Ocean central layer is conducted by applying optimum multiparameter (OMP) analysis to an expansive historical data set. This inverse method utilises hydrographic property fields to determine the spreading and mixing of water masses in the permanent thermocline. An expanded form of OMP analysis is used, incorporating Redfield ratios and pseudo-age to correct for the non-conservative behaviour of oxygen and nutrients over large oceanic areas.Three water masses are considered to contribute to the central layer of the Atlantic Ocean. One of these is formed in each hemisphere of the Atlantic Ocean and the other advects around the southern tip of Africa from its formation region in the Indian Ocean. The Atlantic Ocean is analysed on a fine three-dimensional grid so that at every grid point the relative contributions of each water mass and the pseudo-age are determined.The model is remarkably successful in verifying many accepted circulation features in the Atlantic Ocean, including the large-scale circulations of the subtropical gyres, the zonal flows of equatorial currents at the equator, and a cross-equatorial flow of the water masses formed in the southern hemisphere near the western boundary. The inter-hemisphere flow is so important that almost half of the thermocline waters in the Caribbean Sea and the Gulf of Mexico are supplied by the two water masses formed in the South Atlantic and Indian Oceans. This provides support for an upper-layer replacement path for the formation of North Atlantic Deep Water. Further east, the sharp front at about 15°N between North and South Atlantic Central Waters is clearly discriminated throughout the thermocline. The central waters of the South Atlantic thermocline are found to be highly stratified, with central water formed in the Indian Ocean underlying the South Atlantic Central Water. At around 5°N a strong upwelling zone is identified in which the central water formed in the Indian Ocean penetrates towards the surface. The pseudo-age results allow pathways for the flow of water masses to be inferred, and clearly identify circulation features such as the subtropical gyres, the Equatorial Undercurrent, and the shadow zones in the eastern equatorial regions of the Atlantic Ocean. Water mass renewal in these shadow zones occurs on considerably longer time scales than for the well-ventilated subtropical gyres.     

On the correlation between oscillations of the Caspian Sea level and the North Atlantic climate

Correlations between the changes in the climate of the Caspian Sea region and in its level and the variations in the North Atlantic climate are studied. The indices of North Atlantic oscillation (NAO), Atlantic multidecadal oscillation (AMO), the intensity of Atlantic thermohaline circulation (ATHC), and the air humidity above the North Atlantic are used as basic indicators of climatic variations that influence the Caspian Sea. Results of an experiment for reproducing the World Ocean circulation and the parameterization of cyclic climate peculiarities made it possible to reveal their impact on the formation of Eurasian climatic variability and on the level regime of the Caspian Sea. This impact is studied through the variability of ATHC, the NAO index, and a composite index of moisture transport (CIMT) that is proposed as a result of the studies.     

大西洋波高熵的分布变化规律研究

使用1992年10月-1998年12月连续75个月、230个重复周期的Topex／Poseidon卫星高度计有效波高资料，对南北大西洋波高熵的空间分布特征和时间变化规律进行了研究，统计分析了大西洋波高熵的多年的空间分布特征和多年各月的时间变化规律。结果表明，大西洋波高熵呈现出中间低、南北高的马鞍形空间分布特征和明显季节变化的规律，与大西洋的平均有效波高、气候的地理分布以及大气活动分布特征和变化规律相一致。     

The irony and the exclusivity of Atlantic bluefin tuna management

The eastern stock of Atlantic bluefin tuna (thunnus thynnus) was recently nominated for protection under the Convention on International Trade in Endangered Species of Flora and Fauna (CITES). That nomination failed, which leaves management of the heavily overfished stock in the hands of the International Commission for the Conservation of Atlantic Tunas (ICCAT). This paper reviews the history of ICCAT management of Atlantic bluefin tuna to show that (1) early elimination of competitive forces prevented agreement on management in keeping with scientific advice, resulting in the steep decline of the stock, (2) even just the threat of a CITES listing can provide temporary impetus for marked improvement in ICCAT management, and (3) long-term sustainable management by ICCAT will require continued economic and political pressure.     

ENSO related modulation of coastal upwelling in the eastern Atlantic

An index of ENSO in the Pacific during early boreal winter is shown to account for a significant part of the variability of coastal SST anomalies measured a few months later within the wind driven West African coastal upwelling region from 10°N to 26°N. This teleconnection is thought to result from an atmospheric bridge between the Pacific and Atlantic oceans, leading to warm (cold) ENSO events being associated with a relaxation (intensification) of the Atlantic trade winds and of the wind-induced coastal upwelling. This ENSO related modulation of the wind-driven coastal upwelling appears to contribute to the connection observed at the basin-scale between ENSO and SST in the north Atlantic. The ability to use this teleconnection to give warnings of large changes in the West African upwelling several months in advance is successfully tested using data from the 1998 and 1999 ENSO events.     

On the Statistical Structure of Hydrometeorological Fields in the North Atlantic

We study the possibility of detection of statistically significant trends as a characteristic of low-frequency variability of hydrometeorological fields in the North Atlantic on the basis of relatively short time series. We use the monthly data of the Russian Hydrometeorological Center for 1957–1990 and analyze their statistical structure. It is shown that significant linear and quadratic trends can be detected in the fields of most hydrometeorological characteristics of the North Atlantic. The residual signal is approximated by using the first-order autoregressive model. Typical values of the coefficient of autoregression vary within the range 0.3–0.6 (for different hydrometeorological characteristics of the North Atlantic). The maximum correlation is observed for the fields of sea-surface temperature and humidity, whereas the minimum correlation is typical of the fields of wind velocity and the difference between the temperatures of water and air.     

Deep-sea pycnogonids from the North Atlantic and their distribution in the World Ocean

The information on the composition and distribution of present-day pycnogonids in different regions of the World Ocean and, especially, in the northern part of the Atlantic Ocean acquired during the past decades allowed us to perform a biogeographical analysis of these animals, which represent a permanent component of bottom communities. For 34 species of sea spiders (Pycnogonida) found in the North Atlantic deeper than 2 km, ten types of geographical distribution were recognized. Half of the species identified represent Atlantic forms, and 41% of them are endemic forms with West-Atlantic, East-Atlantic, amphi-Atlantic, and central-Atlantic distributions. The other half of the deep-sea Atlantic species have broad geographical ranges. Among them, 11.7% are Atlantic-Pacific species, 14.7% dwell in the Atlantic and West Pacific, 8.9% are low-latitudinal panocaanic species, and 14.7% are panoceanic species able to penetrate to higher latitudes. The zoogeographical species composition shows a significant independence of this fauna in the northern Atlantic Ocean and its relation to the Pacific and Indian oceans. At present, these relations are probably maintained via the temperate latitudes of the Southern Hemisphere and via the Drake Passage; meanwhile, it seems that, previously, they were realized possibly via the ancient Tethys Ocean.     

Measuring the maritime economy: Spain in the European Atlantic Arc

Despite the importance of the socio-economic dimension of the use of marine waters, there has been little research in the field until recently, when interest has grown in the concept of ‘blue growth'. This paper aims to contribute to filling this gap with a socio-economic assessment of the main maritime sectors, focused on the Spanish part of the European Atlantic Arc. To this end, it first proposes a theoretical structure for the maritime economy and then collects and classifies comparable and reliable maritime socio-economic indicators. The data obtained allows us to assess the size of the Spanish maritime sector and the position of the Spanish Maritime Cluster in the wider context of the maritime economy of the European Atlantic, as well as discuss the appropriateness of a strategy of forming clusters at the national level vs. a transnational approach. The results indicate differences between regions in the European Atlantic Arc that complicate the development of integrated policies to stimulate blue growth. Extending our knowledge of the maritime economy of the European Atlantic Arc will make it possible to design strategies that address the real issues, increasing the likelihood of these being effective.