نتایج جستجو برای: median of northern atlantic
تعداد نتایج: 21183427 فیلتر نتایج به سال:
Anthropogenic emissions have dominated marine Pb sources during the past century. Here we present Pb concentrations and isotope compositions for ocean depth profiles collected in the eastern Tropical Atlantic Ocean (GEOTRACES section GA06), to trace the transfer of anthropogenic Pb into the ocean interior. Variations in Pb concentration and isotope composition were associated with changes in hy...
Morphologically similar Boroecia borealis and B. maxima are redescribed from the Central Arctic. Their morphological differences are minor but well defined. Their geographic and vertical distribution is studied based on an extensive body of materials collected by many expeditions in the Arctic Ocean during the period from 1929 to 1993 at the depth range of 0-4000 m. The comparison of the distri...
Sequence analysis of the mtDNA control region of four samples (n=195) of Atlantic bonito (Sarda sarda) collected along the northern Mediterranean reveals two clades about 8.1% divergent distributed in an east-west cline that fits an isolation by distance (IBD) model. The vicariant origin of this genetic discontinuity is proposed, supported in addition to the cline, by evidence of distinct histo...
Proxy records of temperature from the Atlantic clearly show that the Younger Dryas was an abrupt climate change event during the last deglaciation, but records of hydroclimate are underutilized in defining the event. Here we combine a new hydroclimate record from Palawan, Philippines, in the tropical Pacific, with previously published records to highlight a difference between hydroclimate and t...
The influence of ocean circulation changes on atmospheric CO2 hinges primarily on the ability to alter the ocean interior's respired nutrient inventory. Here we investigate the Atlantic overturning circulation at the Last Glacial Maximum and its impact on respired carbon storage using radiocarbon and stable carbon isotope data from the Brazil and Iberian Margins. The data demonstrate the existe...
Overlooked possibility of a collapsed Atlantic Meridional Overturning Circulation in warming climate
Changes in the Atlantic Meridional Overturning Circulation (AMOC) are moderate in most climate model projections under increasing greenhouse gas forcing. This intermodel consensus may be an artifact of common model biases that favor a stable AMOC. Observationally based freshwater budget analyses suggest that the AMOC is in an unstable regime susceptible for large changes in response to perturba...
Climatic variabilities on millennial and longer time scales with a bipolar seesaw pattern have been documented in paleoclimatic records, but their frequencies, relationships with mean climatic state, and mechanisms remain unclear. Understanding the processes and sensitivities that underlie these changes will underpin better understanding of the climate system and projections of its future chang...
Tectonically induced changes in oceanic seaways had profound effects on global and regional climate during the Late Neogene. The constriction of the Central American Seaway reached a critical threshold during the early Pliocene ~4.8-4 million years (Ma) ago. Model simulations indicate the strengthening of the Atlantic Meridional Overturning Circulation (AMOC) with a signature warming response i...
Meteorologically-driven circulation and flushing times of the Bay of Algeciras, Strait of Gibraltar.
A primitive-equation model has been used to investigate the meteorologically-driven circulation of the Bay of Algeciras. It is shown that the mean circulation of Atlantic Water (AW) is characterized by an anticyclonic cell, while Mediterranean Water (MW) follows a preferred cyclonic pathway. Meteorological forcing distorts substantially the AW mean circulation pattern, and only modulates that o...
Owing to the lack of absolutely dated oceanographic information before the modern instrumental period, there is currently significant debate as to the role played by North Atlantic Ocean dynamics in previous climate transitions (for example, Medieval Climate Anomaly-Little Ice Age, MCA-LIA). Here we present analyses of a millennial-length, annually resolved and absolutely dated marine δ18O arch...
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