North Atlantic Ocean

The impact of future emissions from aviation and shipping on the atmospheric chemical composition has been estimated using an ensemble of six different atmospheric chemistry models. This study considers an optimistic emission scenario (B1) taking into account e.g. rapid introduction of clean and resource-efficient technologies, and a mitigation option for the aircraft sector (B1 ACARE), assuming further technological improvements. Results from sensitivity simulations, where emissions from each of the transport sectors were reduced by 5 %, show that emissions from both aircraft and shipping will have a larger impact on atmospheric ozone and OH in near future (2025; B1) and for longer time horizons (2050; B1) compared to recent time (2000). However, the ozone and OH impact from aircraft can be reduced substantially in 2050 if the technological improvements considered in the B1 ACARE will be achieved. Shipping emissions have the largest impact in the marine boundary layer and their ozone contribution may exceed 4 ppbv (when scaling the response of the 5 % emission perturbation to 100 % by applying a factor 20) over

This article discusses the rôle of the THC in climate, based upon the results of several numerical experiments which use a coupled ocean-atmosphere model developed at the Geophysical Fluid Dynamics Laboratory of NOAA, USA. The first part of the article explores the mechanism which is responsible for the abrupt climate change such as the Younger Dryas event using the coupled model. In response to the freshwater discharge into high north Atlantic latitudes over a period of 500 years, the THC in the Atlantic Ocean weakens, reducing surface air temperature over the northern north Atlantic Ocean, the Scandinavian Peninsula, and the circumpolar ocean and Antarctic Continent of the southern hemisphere. Upon the termination of the water discharge at the 500th year, the THC begins to intensify, regaining its original intensity in a few hundred years. In addition, the sudden onset and the termination of the discharge of freshwater induces the multidecadal fluctuation in the intensity of the THC, which generates the almost abrupt change of climate. It is noted that similar but much weaker oscillation of the THC is also evident in the control integration of the coupled model without freshwater forcing. The irregular oscillation of the THC mentioned above appears to be related to the fluctuation of the Subarctic Gyre and associated east Greenland current, yielding the evolution of the surface salinity anomaly which resembles that of ''great salinity anomaly''. The second part of this article describes the response of a coupled ocean-atmosphere model to the doubling and quadrupling of atmospheric carbon dioxide over centuries timescale. In one integration, the CO 2 concentration increases by 1%/year (compounded) until it reaches 4× the initial value at the 140th year and remains unchanged thereafter. In another integration, the CO 2 concentration also incleases at the rate of 1%/year until it reaches 2× the initial value at the 70th year and remains unchanged thereafter. One of the most notable features of the CO 2-quadrupling integration is the gradual disappearance of thermohaline circulation in most of the model oceans during the first 250-year period, leaving behind wind-driven cells. For example, thermohaline circulation nearly vanishes in the north Atlantic by the 250 years of the integration and remains very weak until the 900th year. However, it begins to restore the original intensity by the 1600th year. In the CO 2-doubling integration, the thermohaline circulation weakens by a factor of more than 2 in the North Atlantic during the first 150 years, but almost recovers its original intensity by the 500th year. The weakening of the THC moderates temporarily the greenhouse warming over the north Atlantic Ocean and its vicinity. In both numerical experiments described above, the initial weakening of the THC results from the capping of oceanic surface by relatively fresh, low-density water, which surpresses the convective cooling of water in the sinking region of the THC.

Historical and modern migrations and dispersal of most marine organisms (intertidal, benthic, meiofaunal, planktonic, nektonic, or neustonic) are classically interpreted in terms of their natural dispersal potential. Exceptions are introduced species, largely recognized since the 19th century, known to have been transported by human activities. However, humans were transporting species along coastlines and across oceans for millennia and centuries prior to the advent of the first biological surveys. Thus, the presumptive natural distributions of many species may be questioned. Reviewed here are some basic concepts about invasions of non-native species. Human activities move species isolated in time and space from other oceans or continents, and thus human-mediated transport does not simply speed up natural dispersal processes. Both past and modern-day invasions are often overlooked, leading to an underestimation of the scale of invasion diversity and impact. Because vectors, donor regions, and recipient regions change over time, invasions will continue along long-standing but un-managed corridors. The impact of most invasions has never been studied and, therefore, it is not possible to conclude that most invasions have no impact, nor is it generally possible to say that invasions have become 'integrated' into a community or ecosystem in ecological time. Finally, invasions in the ocean are not limited to harbours and ports, but are found in a wide variety of marine habitats, ranging from the open ocean continental shelf to exposed rocky shores. The existence of human-mediated vectors has created extraordinary challenges to our understanding and interpretation of the ecology, biogeography, evolutionary biology, and conservation biology of marine communities.

We present a new digital crustal model for Moho depth and crustal structure in Europe, Greenland, Iceland, Svalbard, European Arctic shelf, and the North Atlantic Ocean (72W-62E, 30N-84N). Our compilation is based on digitization of original seismic profiles and Receiver Functions from ca. 650 publications which provides a dense regional data coverage. Exclusion of non-seismic data allows application of the database to potential field modeling. EUNAseis model includes Vp velocity and thickness of five crustal layers, including the sedimentary cover, and Pn velocity. For each parameter we discuss uncertainties associated with theoretical limitations, regional data quality, and interpolation. By analyzing regional trends in crustal structure and links to tectonic evolution illustrated by a new tectonic map, we conclude that: (1) Each tectonic setting shows significant variation in depth to Moho and crustal structure, essentially controlled by the age of latest tectono-thermal processes; (2) Published global averages of crustal parameters are outside of observed ranges for any tectonic setting in Europe; (3) Variation of Vp with depth in the sedimentary cover does not follow commonly accepted trends; (4) The thickness ratio between upper-middle (Vp b 6.8 km/s) and lower (Vp N 6.8 km/s) crystalline crust is indicative of crustal origin: oceanic, transitional, platform, or extended crust; (5) Continental rifting generally thins the upper-middle crust significantly without changing Vp. Lower crust experiences less thinning, also without changing Vp, suggesting a complex interplay of magmatic underplating, gabbro-eclogite phase transition and delamination; (6) Crustal structure of the Barents Sea shelf differs from rifted continental crust; and (7) Most of the North Atlantic Ocean north of 55°N has anomalously shallow bathymetry and anomalously thick oceanic crust. A belt of exceptionally thick crust (ca. 30 km) of probable oceanic origin on both sides of southern Greenland includes the Greenland-Iceland-Faeroe Ridge in the east and a similar "Baffin Ridge" feature in the west.

Infrared satellite images and two ensembles of satellite-tracked buoys have been used to analyze eddy scales in the central and eastern North Atlantic between 35øN and 60øN. Both data sets yield eddy scales which decrease northward from the subtropical Atlantic and can be closely related to the Rossby radius of the first baroclinic mode.

The broadcast spawner, Centropages typicus, is a very successful copepod species in many coastal areas of the Mediterranean Sea and North Atlantic Ocean. This review assembles the large amount of information on the reproduction and early life history of C. typicus that has emerged since the 1970s and has made this species one of the best-studied copepods, similar in that regard to species of Acartia and Calanus. Observations on mating behavior and the female gametogenic and oogenic cycles are presented, together with information on seasonal cycles of egg production rates in Mediterranean and Atlantic populations from various regions. These studies indicate a strong latitudinal gradient, with continuous reproduction and the main spawning season occurring earlier (late winter/spring) in warmer waters such as the Mediterranean Sea, compared to northern areas such as the North Sea and in the Kattegat, where C. typicus actively reproduces mainly in late summer and fall with reproduction ceasing altogether in winter in the German Bight. These observations strongly suggest that temperature is the controlling factor for reproductive activity in this species. Egg development times are also temperature dependent but do not vary with latitude, and there is as yet no conclusive evidence that diapause egg production occurs in C. typicus. Laboratory experiments have shown that food quantity and quality both affect fecundity and offspring fitness, but most of these studies have focused on diatom and dinoflagellate diets and non-algal prey have been strongly underrepresented, despite their importance for this omnivorous copepod. Large fluctuations in hatching success and naupliar survival have been reported in field surveys and have subsequently been related to maternal feeding history and food quality or toxicity in laboratory experiments. We identify future lines of research that will help to explain the interannual variability in breeding intensity and recruitment of C. typicus in the field based on better understanding of the species' reproductive biology.

Depois de um ano em que todos os dias tentamos levar aos nossos seguidores o que de mais relevante ocorre no mundo, chegamos agora, com esta edição da PACTA, ao fim do terceiro ano deste projeto, que não pára de crescer e nos faz trabalhar com tanto gosto e afinco. Em Setembro a equipa da PACTA volta com novas ideias para continuar a desenvolver este apaixonante trabalho, de forma a tratar o que de melhor e pior se passa no mundo das Relações Internacionais, e para trabalhar de forma ainda mais intensa no sentido de vos surprender, pois a PACTA não é nossa, é de todos! Para a última edição deste ano lectivo, e seguindo sempre o nosso lema, procurámos oferecer-vos informação com qualidade, pertinência e actualidade. Uma vez mais, temos o orgulho de vos apresentar uma edição recheada de artigos de opinião e uma entrevista, que incidem sobre os principais temas da realidade internacional que nos rodeia.

Coastal boulder accumulations are often mentioned in the literature, even though their interpretation remains difficult, especially along rock coasts affected both by storms and tsunamis. Studies on the geomorphic impact of such high-energy events are actually of great interest, since their intensity and frequency are key issues for the future evolution of coasts in the framework of the global change. The southwest coast of Iceland faces the powerful storms of the North Atlantic Ocean, with wave heights of more than 15 m. The probability for past and present tsunamis to hit this coast is very low. In this paper, we describe boulder accumulations along the volcanic rock coast of Reykjanes (southwest Iceland). They consist of cliff-top boulders, clusters and ridges, beaches, and boulder fields. Large boulders, up to 70 t in weight, have been transported and deposited up to 65 m inland (6 masl). The maximum limit of boulder deposition and driftwood was found respectively 210 m and 550 m inland. Storms appear to be a predominant factor in the geomorphic evolution of Reykjanes coasts. Our observations also give new insight for the interpretation of coastal boulder accumulations. Processes of erosion and deposition by tsunamis are a rising topic in the literature, and the effects of recurrent and powerful storms are neglected.

In the mid-latitudes of the North Atlantic Ocean, six large iceberg surges, called Heinrich events, have been recognised between 60 and 10 kyr BP. They are characterised by meltwater events associated with iceberg discharges from both the Laurentide and the Fennoscandian-Greenland ice sheets. The hydrological conditions associated with these surges show changes in sea surface temperature (2}63C drop) and in sea surface salinity (1}3 decrease). Carbon isotopic analyses tend to show that the thermohaline circulation is a!ected by such discharges with a signi"cant decrease in the ventilation of deep waters. During the same period, ice cores record large climatic #uctuations, called Dansgaard-Oeschger events, which have been recognised in the North Atlantic Ocean and in the Norwegian Sea, and more recently, in various sedimentary environments world wide.

At the turn of the sixteenth century, John Cabot and his successors discovered abundant fish stocks in the northwest Atlantic waters near
Newfoundland. This article accounts for how sixteenth- and seventeenth-century mapping provide another strand of evidence that supplement our
knowledge of the subsequent Iberian, French, and British fisheries. Such
cartography exhibited significant mutations and innovations in rendering
fishing locations, and illustrating fishing practices and fish species.
Fishermen’s knowledge must have informed such mapping. The innovation of hydrographical indicators in aesthetically appealing maps recognized from an early stage the status of the Grand Banks as a globally important feature of submarine topography. More refined and accurate delineations of its submarine plateaus and other adjacent continental shelves closely followed the development of fishing activities, encompassing both Newfoundland’s nearshore and the Grand Banks themselves. Furthermore, such cartography reflected transformative and reciprocal relationships with commerce and
inter-state politics across the North Atlantic.

Scholarship discussing european expansion into the north atlantic and territorial claims over newfoundland rarely examines the impact of Danonorwegian claims in greenland. This article integrates the history of the greenland norse into the narrative of european expansion to better understand the multinational nature of the early modern north atlantic fishery. It discusses the rise of island-Iberia in response to the influence of island-Scandinavia, particularly in matters of trade and imperial claims. John cabot's reports of "new found land" allowed the other europeans to fish in waters beyond the Dano-norwegian atlantic claims, creating a multinational fishery over which no european power recognized sovereignty until the peace of Utrecht in 1713. once Dano-norwegian control over the north atlantic and europe's cod fishery was broken, norse occupation of greenland on the far western edge of europe became a forgotten though still important part of the history of european expansion.

En la Antigüedad, las representaciones de amazonas fueron numerosas y relativamente variadas, gracias a los diversos mitos que de ellas existían A lo largo de este trabajo intentaré elaborar una relación de los motivos y los paralelismos, tanto temáticos como artísticos, que aparecen en el mundo griego a lo largo de los periodos Arcaico y Clásico. En este sentido, destaca el análisis de las escenas recogidas en numerosos vasos, ya que se trata del soporte mayoritario en que este mito fue utilizado como elemento decorativo; no obstante, su aparición en otro tipo de obras, como esculturas, pinturas o relieves, será igualmente tratada con el fin de intentar establecer pautas y "modas" tanto en los elementos como en las temáticas, buscando desentrañar la finalidad que este tipo de obras suscitó en el ámbito griego y en aquellos pueblos con los que éste tuvo contacto a través del comercio.

"In the northern North Atlantic, the 4.2 ka BP event is evident in lake, bog, marine, glacial, speleothem and tree ring cores with extensive, coherent, and high resolution proxy data for abrupt century-scale alterations of temperature and precipitation. These records extend across the northern North Atlantic, 1900 kms northeast to southwest, from Spitzbergen, Svalbard to Agassiz Ice Cap, Ellesmere Island, including Sweden, Norway, Denmark, Faroe Islands, Iceland and adjacent seas, and Greenland. Adjacent region, high resolution proxy data in Europe and North America provide synchronous and similar records. The proposed article by Bradley and Bakke (cp-2018-162, in review), however, ignores the relevant data from Svalbard, Sweden, Norway, Denmark, Faroe Islands, Iceland, Nordic Seas, Greenland and Ellesmere Island. 

In Figure 1,  a) - b) are Greenland Ice Sheet Total mass balance and ice volume experiments 5 and 6 from Nielsen et al., 2017 that present an abrupt ca 200 year warming event beginning at ca 4.3 ka BP. This melt spike is synchronous with c), the modeled 4 degree SST cooling spike in the Northwest Atlantic, ca. 4.3-4.1 ka BP (Klus et al., 2017) and with the abrupt NGRIP ca. 5 degree K warm spike ca. 4.5-3.9 ka BP (Gkinis et al, 2014).  In d), the Agassiz, Ellesmere Island and Renland, Greenland ice core temperature spike is 3-stage, beginning at 4290 BP, reaching its apogee at 4150 BP, returning to  baseline at 3990 BP, and descending to pre-event levels at 3790 BP (Vinther et al., 2009).  The sudden GISP2, Greenland temperature spike (Kobashi et al, 2017), although less well-defined, conforms to this event. These six key North Atlantic high resolution and modeled data are summarized in e), which presents the remarkable congruence of the Lake Hajeren, Svalbard, sediment core and the Agassiz, Ellesmere Island ice core. The Lake Hajeren neo-glaciation spike, recognized in minerogenic / glacigenic indicators TDBD (dry bulk density) and Ti/Loss on Ignition z-scores from core HAP0212, extends from ca. 4250 BP to ca. 4100/4050 BP, a calibrated radiocarbon interpolation across two hundred years (van der Bilt et al., 2015). The synchronous Agassiz ice core melt spike extends from ca. 4250 – 3950 BP, with an error of ca. 20 years (Fisher et al., 2012; Lecavalier et al., 2017).   

In summary, the Lake Hajeren, Spitsbergen, Svalbard cold glaciation event was synchronous with the Ellesmere Island Agassiz ice core warm melt event 1900 kms distant across the span of Iceland and adjacent seas and Greenland. The same relationship obtains with the NGRIP warm event (Gkinis et al., 2014) and the modeled Northwest Atlantic Sea Surface Temperature event (Klus et al., 2018): in the northern North Atlantic, cold lake and sea events were synchronous with warm, elevation-corrected, glacier events that extend as far west as Mount Logan, Yukon (Fisher et al., 2012). This curious, highly resolved, 4.2 ka BP event situation has not been discussed previously and there exist neither proximate nor ultimate explanations for it."

Laminaria is a kelp that finds its place in the brown algae family. It has been an area of study for past many years, and its wonderful biological properties have always attracted medical professionals and researchers to explore more and more from this wonder kelp. The constituents of Laminaria include iodine, potassium, magnesium, calcium and iron. Iodine compounds, TEA-hydroiodide in particular, are great lipolytic agents as they stimulate lipase activity. Laminarins on the other hand are used as a tumor angiogenic blocker. This genus of the kelps is also rich in algin, a high molecular weight polysaccharide that forms viscous colloidal solutions or gels in water leading to the use of kelp derivatives as bulk laxatives. It has great applications in cosmeceutical science, as well as some antibacterial properties have also been assigned to Laminaria. A deeper insight into the physical, biological, and chemical properties of this wonder kelp would lead to further exploitation of Laminaria for medicinal and cosmeceutical purpose.

Two piston cores, DS97-2P from the Reykjanes Ridge in the central North Atlantic Ocean (1685 m water depth) and ENAM33 from southwest of the Faeroe Islands in the NE Atlantic (1217 m water depth), have been investigated for their planktic and benthic foraminiferal content. DS97-2P is situated near the Subarctic Front and productivity measured by accumulation rates of benthic and planktic foraminifera has been generally high during the Holocene. The productivity shows a clear decrease from an early Holocene maximum to a late Holocene minimum. Coeval changes in the benthic faunas indicate that the food supply changed from large, irregular pulses during the early Holocene to a more sustained flux during the late Holocene. Presumably in concert with decreasing bottom current activity oxygen conditions in the bottom water became poorer. Another feature of the late Holocene is an increasing instability of the North Atlantic thermohaline circulation regime. Nevertheless, the changes in faunal composition and productivity during the Holocene were gradual as compared to the discontinuous distribution patterns and abrupt productivity shifts during the glacial. The glacial shifts were on a millennial time scale and correlate with the interstadial^stadial phases of the Dansgaard^Oeschger cycles in the Greenland ice cores. The faunas of the warm interstadial phases resembled the Holocene faunas, and both surface and bottom productivity was high. The faunas suggest that the interstadial circulation pattern was very similar to the modern system with convection in the Nordic seas and generation of North Atlantic Deep Water. The planktic faunas during the cold stadials and Heinrich events were completely dominated by the polar species Neogloboquadrina pachyderma s, and surface conditions were cold and the productivity low. The benthic faunas were dominated by species that presently thrive in areas with a low amount of food and reduced oxygen content. The water column was probably stratified with low saline, cold surface water overlying poorly aerated, intermediate water masses. 0377-8398 / 02 / $^see front matter ß 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 7 -8 3 9 8 ( 0 2 ) 0 0 1 1 5 -9

1] Close to 1800 surface drifters are used to investigate the 15 m circulation of the North Atlantic Ocean. The data are used to describe structures of the average Eulerian circulation and of the associated eddy variability. The data resolve scales on the order of 50 km, which have hitherto not been systematically described, in particular, near shelf breaks and near the most intense currents, the Gulf Stream, the North Atlantic Current (NAC), and the frontal currents of the subpolar gyre. This reveals a complex series of quasi-permanent eddies, meanders, and recirculation patterns. Gulf Stream intensity is portrayed as changing abruptly near 54°W, east of which, it is identified as two current branches centered near 39°and 41.5°N, the northern one connecting more directly with the NAC, and the southern one with the recirculation gyre and the Azores Current (AC). Many features of the currents are controlled by topography, in particular, currents are often intensified near shelf breaks or parallel to ridges in the subpolar gyre. However, the largest northward branch of the NAC in the Icelandic basin is located near the deepest bathymetry, not near steep bathymetry. Other currents, in particular, in the subtropical gyre, are less clearly related to topography: for instance, the AC is featured as a zonal eastward current extending far west of the Mid-Atlantic Ridge (MAR) to at least 55°W and possibly 63°W. In the interior and away from topographic features the eddy kinetic energy (EKE) is the largest where the mean currents are the largest. In the subpolar gyre, there are striking differences in EKE between southward flowing currents (the Labrador and east Greenland Current) and the northward flowing currents (west Greenland Current and branches of the NAC), which have higher EKE. The areas of weakest variability are located in the southwest part of the subpolar gyre, northeast of Iceland, and in the eastern Atlantic south of 45°N. The AC eddies and the mesoscales south of the Canary Islands transect this eastern eddy desert. Drifter trajectories are used as realizations of Lagrangian particles in the vicinity of current cores. These illustrate the variety of paths or connections between different current systems and demonstrate cross-stream dispersions.

This study reports the first inventory of physical properties of individual plastic debris in the North Atlantic. We analyzed 748 samples for size, mass, and material composition collected from surface net tows on 11 expeditions from Cape Cod, Massachusetts to the Caribbean Sea between 1991 and 2007. Particles were mostly fragments less than 10 mm in size with nearly all lighter than 0.05 g. Material densities ranged from 0.808 to 1.24 g ml À1 , with about half between 0.97 and 1.04 g ml À1 , a range not typically found in virgin plastics. Elemental analysis suggests that samples in this density range are consistent with polypropylene and polyethylene whose densities have increased, likely due to biofouling. Pelagic densities varied considerably from that of beach plastic debris, suggesting that plastic particles are modified during their residence at sea. These analyses provide clues in understanding particle fate and potential debris sources, and address ecological implications of pelagic plastic debris.

We have used the modern analogue technique to derive sea surface temperature (SST) records of the last 18,000 years from two well-dated deep-sea cores recovered in the Tyrrhenian Sea. Results show two major cooling events synchronous with the European and North Atlantic Oldest and Younger Dryas events. A later cooling of lower amplitude is observed between about 8000 and 4500 yr BP. Tyrrhenian

The planktonic foraminiferal record of core MD99-2346 (Gulf of Lion) shows a decrease of sea surface temperature (SST) at the time of Heinrich event H2 (24-23.5 cal kyr BP), Younger Dryas and during the early to middle Holocene. These events were associated with a decrease of surface water salinity. The salinity lowering events were similar and synchronous to those recorded in the North Atlantic Ocean during H1, H2 and the Younger Dryas. They can be explained by a decrease in the salinity of the Atlantic surface water entering the Mediterranean through the Strait of Gibraltar. This result indicates that the Mediterranean Sea remained a concentration basin and that its freshwater budget was not significantly different from the modern conditions at the time of these low salinity events. Higher abundances of the benthic foraminifer Cibicidoides pachydermus at the time of Heinrich events (H2 and H1) may result from a seasonal, and more pulsed supply of labile organic matter. A high abundance of intermediate and deep infaunal taxa (Globobulimina spp.) during the warm Bölling/Alleröd period is interpreted as a result of an increased lateral advection of organic matter to the deeper environments of the Gulf of Lion. Surface water productivity, as reflected by the organic flux to the benthic ecosystem, reaches a maximum during the cold Younger Dryas period. It is possible that cold conditions at the time of the Younger Dryas have allowed an enhanced vertical mixing and deep-water cascading in the Gulf of Lion. This may have resulted in an increase of primary and export production. This putative intensification of deep-water cascading would have occurred after the sustained rise of the global sea-level from 16 to 12.5 cal kyr BP. The deglacial sea-level rise may also have played an important role in favouring the downslope movement of dense shelf water enriched in organic matter originating from the early Rhône delta complex. The conditions during the Holocene were characterized by a low surface productivity and oligotrophic environment similar to the modern situation.

The North Atlantic Ocean receives the largest allochthonous supplies of nitrogen of any ocean basin because of the close proximity of industrialized nations. In this paper, we describe the major standing stocks, fluxes and transformations of nitrogen (N) and phosphorus (P) in the pelagic regions of the North Atlantic, as one part of a larger effort to understand the entire N and P budgets in the North Atlantic Ocean, its watersheds and overlying atmosphere. The primary focus is on nitrogen, however, we consider both nitrogen and phosphorus because of the close inter-relationship between the N and P cycles in the ocean. The oceanic standing stocks of N and P are orders of magnitude larger than the annual amount transported off continents or deposited from the atmosphere. Atmospheric deposition can have an impact on oceanic nitrogen cycling at locations near the coasts where atmospheric sources are large, or in

Marine localities on the west European shelf have been studied to reconstruct the nearshore palaeoceanography of the last two millennia. The sites form a transect from the Iberian margin northeastward via Scotland to western Norway and Iceland. Proxies used for palaeoclimatic reconstructions include stable isotopes, benthic and planktonic foraminfera, diatoms, dinoflagellates, as well as geochemical and sedimentological parameters. Major changes

Previous optimum multiparameter analyses have investigated spatial distribution of water masses and reported successful results. This study tests the method further with application to a time series to examine temporal variability in water mass distribution. Observations collected from the Sargasso Sea are utilised, mainly to detect well-documented property changes that have occurred in Labrador Sea Water, but also possible fluctuations in water mass contributions as a whole.

The results show much structure and variability in the contributions of Central Water and upper deep waters in the depth range 900–2000 m. It is proposed that the passage of warm and cold core eddies is indicated by these changes in relative contributions of water masses, although quantitative comparison of satellite altimetry data with the model results is not conclusive.

Significant irregularities in the distribution of Labrador Sea Water are also revealed by the model. Through-flow of modified (since the early 1990s) Labrador Sea Water is denoted in the results by an apparent absence from mid-1995 to early 1998. This suggests a transit time of 5–6 years between the Labrador Sea and Bermuda, which is consistent with observational findings described in the literature.

The Aptian/Albian oceanic anoxic event 1b contains the record of several perturbations in the global carbon cycle and multiple black shale levels, particularly in the Western Tethys. The local lithological expression of an oceanic anoxic event depends on palaeogeographical and depositional setting as well as on regional palaeoclimate. Marine sediments at a particular location may therefore be more or less organic-rich (or not at all) and they may consist of different lithologies. In most studies, however, much of the lithological variability associated with oceanic anoxic events is left unaccounted for and, thus, the exact processes leading to the enrichment of organic matter in these marine sediments and their subsequent preservation in the geological record are unknown. This study focuses on the local sedimentary processes behind the deposition of organic-rich sediments at Deep Sea Drilling Project Site 545 and Ocean Drilling Program Sites 1049 and 1276 in the North Atlantic during oceanic anoxic event 1b. Although specifically dealing with the sediments deposited during this particular event at these localities, it is expected that the same processes were responsible for determining the exact sedimentary products at localities in similar settings, as well as during other similar events in the Mesozoic. Here, it is shown that the deposition of organic-rich sediments during oceanic anoxic event 1b was a consequence of the enhanced productivity favoured by upwelling and by riverine nutrient input, or aeolian fertilization of the euphotic zone depending on geographical location. Slope instability processes resulted in the transfer of part of these organic-rich sediments from the shelf to deep sea depocentres as mud-laden organic-rich turbidites, especially in the northern North Atlantic. The so-called ‘black shales’ are much more varied than their name implies. The end product of sedimentation during an oceanic anoxic event at a particular location is commonly the result of several equifinal processes acting on a local scale rather than the direct result of basinal or even global mechanisms.

Well-preserved arthropods are reported from Miocene sedimentary rocks of the Skarðsströnd-Mókollsdalur (9-8 Ma) and Hreðavatn-Stafholt (7-6 Ma) Formations in Iceland. Fossil remains of terrestrial and/or freshwater animals have rarely been reported from the island before. Here we provide the first overview of the surprisingly rich Tortonian fauna from the Hrútagil locality and additional Messinian-aged trichopteran larval cases from the Stafholt locality. The Hrútagil fauna includes representatives of Cladocera (Crustacea: Branchiopoda) and seven insect orders, including several morphotypes of the orders Plecoptera, Dermaptera, Hemiptera (Cercopoidea, Aphididae), Coleoptera, Hymenoptera, Trichoptera (Drusinae), and Diptera (Bibionidae). Previous studies on the Miocene of Iceland have been based principally on pollen analysis and the macrobotanical record with little attention paid to other aspects of the island's palaeontology. This study provides the first comprehensive systematic description of Miocene arthropods from the northern North Atlantic region and offers the opportunity for a rare glimpse into the late Cenozoic arthropod fauna of Iceland in the context of transatlantic migration and palaeobiogeography and the onset of major global cooling events.

At the end of the last century, steam power came into use in British
trawlers. Steam trawlers were extraordinarily effective and much
admired abroad, also in Denmark, where they were seen as the fishing
vessels of the future. At the same time, however, the ships were
expensive to run, and called for massive financial backing. This article
is the story of how a number of Danish shipowners and naval officers
attempted to emulate the British model. Their aim was indeed to make
money, but at the same time they maintained that they were serving
the nation by training seamen for the navy, and by showing the Danish
flag at sea, especially off the then Danish territory of Iceland.
At their disposal they had large amounts of private and state
capital, and the fiasco which resulted left its mark not only on the
future of Danish fisheries, but also on the attitude adopted by the
financial world towards investments in fishing, and indeed laid the
basis for official Danish fishery policies of this century.
The 1890s was a decade of technological breakthrough in the
fisheries, marked by innovations such as otter trawling, adaptation of
steam and kerosene engine propulsion, mechanical winches, etc. The
major investments in Danish Icelandic fisheries initiated a period of
remarkable technological progress, which was to be of momentous
importance for the development of the fishing fleets of the twentieth
century. Paradoxically, the experiment in large-scale fishing was to
stimulate a growth in artisanal fishing methods.

The vegetation on the northeastern margin of the Tibetan Plateau is highly sensitive to climatic changes and thus represents a potentially interesting environmental archive. Pollen samples from the Fanjiaping Loess section in Lanzhou on the western Chinese Loess Plateau (CLP) were analyzed in conjunction with OSL dating. The results indicate that pollen zone B (60.6e46.0 ka, correlative to the early MIS 3) had the greatest abundances of Cupressaceae, Tsuga, Gramineae and Cyperaceae of the entire section, suggesting a warm phase during the last glacial period. These pollen taxa decreased significantly in abundance in the zones C (46.0e39.0 ka) and D (39.0e27.0 ka), reflecting a substantial climate cooling from the middle MIS 3 to MIS 2. These results correlate with climate records from the South China Sea, the CLP, Baikal Lake, North America, North Atlantic Ocean and other regions, and probably correspond with the decline of northern high-latitude insolation and the increase of global ice volume from 50 to 20 ka. In particular, arboreal pollen, fern spore and algae abundances declined sharply since w40 ka, while shrub and herb pollen reached the highest abundances. Conifer pollen Picea and Abies abundance also rose markedly and increased up the section. This implies significant climate deterioration and likely corresponded with substantial growth of the polar ice sheets since w40 ka. The decreasing temperature caused by an insolation decline during the last glacial period probably reinforced the cooling effect in a 'snow/ice/ albedo' feedback, which would result in less climate sensitivity to radiative forcing. Meanwhile, vegetation decline in the Northern Hemisphere during the last glacial period and tundra development at high latitudes possibly caused additional cooling, enhancing the growth of polar ice sheets since 40 ka. The development of polar ice sheets increased the polar-to-equator temperature and pressure gradients, strengthening the westerlies and supplying plenty of moisture to Northwest China during 40e30 ka. Lake sediments developed widely on the Tibetan Plateau during 40e30 ka, probably related to an increase in the seasonality of middle-to-low latitude insolation which caused an enhancement of glacier melting on the Plateau.

During the 1920s and 1930s, there was a dramatic warming of the northern North Atlantic Ocean. Warmer-thannormal sea temperatures, reduced sea ice conditions and enhanced Atlantic inflow in northern regions continued through to the 1950s and 1960s, with the timing of the decline to colder temperatures varying with location. Ecosystem changes associated with the warm period included a general northward movement of fish. Boreal species of fish such as cod, haddock and herring expanded farther north while colder-water species such as capelin and polar cod retreated northward. The maximum recorded movement involved cod, which spread approximately 1200 km northward along West Greenland. Migration patterns of ''warmer water'' species also changed with earlier arrivals and later departures. New spawning sites were observed farther north for several species or stocks while for others the relative contribution from northern spawning sites increased. Some southern species of fish that were unknown in northern areas prior to the warming event became occasional, and in some cases, frequent visitors. Higher recruitment and growth led to increased biomass of important commercial species such as cod and herring in many regions of the northern North Atlantic. Benthos associated with Atlantic waters spread northward off Western Svalbard and eastward into the eastern Barents Sea. Based on increased phytoplankton and zooplankton production in several areas, it is argued that bottom-up processes were the primary cause of these changes. The warming in the 1920s and 1930s is considered to constitute the most significant regime shift experienced in the North Atlantic in the 20th century.

Recent research suggests a link between drought occurrence in the conterminous United States (US) and sea surface temperature (SST) variability in both the tropical Pacific and North Atlantic Oceans on decadal to multidecadal (D2M) time scales. Results show that the Atlantic Multidecadal Oscillation (AMO) is the most consistent indicator of D2M drought variability in the conterminous US during the 20th century, but during the 19th century the tropical Pacific is a more consistent indicator of D2 M drought. The interaction between El Nin˜o-Southern Oscillation (ENSO) and the AMO explain a large part of the D2M drought variability in the conterminous US. More modeling studies are needed to reveal possible mechanisms linking low-frequency ENSO variability and the AMO with drought in the conterminous US. r

1] We present results from an intercomparison of 11 different climate models of intermediate complexity, in which the North Atlantic Ocean was subjected to slowly varying changes in freshwater input. All models show a characteristic hysteresis response of the thermohaline circulation to the freshwater forcing; which can be explained by Stommel's salt advection feedback. The width of the hysteresis curves varies between 0.2 and 0.5 Sv in the models. Major differences are found in the location of present-day climate on the hysteresis diagram. In seven of the models, present-day climate for standard parameter choices is found in the bi-stable regime, in four models this climate is in the mono-stable regime. The proximity of the present-day climate to the Stommel bifurcation point, beyond which North Atlantic Deep Water formation cannot be sustained, varies from less than 0.1 Sv to over 0.5 Sv. Citation: Rahmstorf, S., et al. (2005), Thermohaline circulation hysteresis: A model intercomparison, Geophys. Res. Lett., 32, L23605,

Quaternary organic-and calcitic-walled dinoflagellate cysts have received considerable attention within the last two decades due to their potential as tracers of sea surface parameters (temperature, salinity, sea ice cover, productivity). Despite uncertainties about taxonomical identity and limitations due to taphonomical processes, dinoflagellate cysts provide extremely useful and unique information on marine environments of the past. This is illustrated in the present special issue, which contains a selection of papers dealing with various approaches for reconstructing oceanographic parameters such as productivity, sea-ice cover, salinity, temperature, seasonality, and stratification in the upper water mass. All papers use organic-walled dinoflagellate cysts as their main proxy, but most combine the dinocyst information with results from complementary proxies, including benthic foraminifers, coccoliths, pollen, and stable isotopes in carbonates or organic matter. In all contributions, the approaches are based upon rigorous statistical treatment.

The key objective of investigation of hemipelagic sediments from the Gresten Klippenbelt (Blassenstein Formation, Ultrahelvetic paleogeographic realm) was to shed light on environmental changes around the Jurassic-Cretaceous (J/K) boundary on the northern margin of the Penninic Ocean. This boundary is well exposed in a newly discovered site at Nutzhof. Around the critical interval including the boundary, this new outcrop bears a rich microplanktonic assemblage characterized by typical J/K (Tithonian/Berriasian) boundary faunas. The Nutzhof section is located in the Gresten Klippenbelt (Lower Austria) tectonically wedged into the deep-water sediments of the Rhenodanubian Flysch Zone. In Late Jurassic-Early Cretaceous time the Penninic Ocean was a side tract of the proto-North Atlantic Oceanic System, intercalated between the European and the Austroalpine plates. Its opening started during the Early Jurassic, induced by sea floor spreading, followed by Jurassic-Early Cretaceous deepening of the depositional area of the Gresten Klippenbelt. These tectonically induced paleogeographic changes are mirrored in the lithology and microfauna that record a deepening of the depositional environment from Tithonian to Berriasian sediments of the Blassenstein Formation at Nutzhof. The main lithological change is observed in the Upper Tithonian <italic>Crassicollaria</italic> Zone, in Chron M20N, whereas the J/K boundary can be precisely fixed at the <italic>Crassicollaria-Calpionella</italic> boundary, within Chron M19n.2n. The lithological turnover of the deposition from more siliciclastic pelagic marl-limestone cycles into deep-water pelagic limestones is correlated with the deepening of the southern edge of the European continent at this time. Within the Gresten Klippenbelt Unit, this transition is reflected by the lithostratigraphic boundary between siliciclastic-bearing marl-limestone sedimentation in the uppermost Jurassic and lowermost Cretaceous limestone formation, both within the Blassenstein Formation. The cephalopod fauna (ammonites, belemnites, aptychi) and crinoids from the Blassenstein Formation, correlated with calcareous microfossil and nannofossil data combined with isotope and paleomagnetic data, indicate the Tithonian to middle Berriasian (<italic>Hybonoticeras hybonotum</italic> Zone up to the <italic>Subthurmannia occitanica</italic> Zone; M17r-M21r). The succession of the Nutzhof section thus represents deposition of a duration of approximately 7 Myr (ca. 150-143 Ma). The deposition of the limestone, marly limestone and marls in this interval occurred during tectonically unstable conditions reflected by common allodapic material. Along with the integrated biostratigraphic, geochemical and isotopic analysis, the susceptibility and gamma-ray measurements were powerful stratigraphic tools and important for the interpretation of the paleogeographic setting. Two reverse magneto-subzones, Kysuca and Brodno, were detected within magnetozones M20n and M19n, respectively.