Featured
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Letter |
Central Pacific El Niño and decadal climate change in the North Pacific Ocean
Decadal fluctuations in the North Pacific Ocean and overlying atmosphere significantly affect the weather and climate of North America and Eurasia. An ensemble of simulations with a coupled ocean–atmosphere model reveals a link between these decadal oscillations and central Pacific El Niño events.
- E. Di Lorenzo
- , K. M. Cobb
- & D. J. Vimont
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Editorial |
Trouble at depth
The deep ocean is largely uncharted territory. The aftermath of the BP oil spill has been a poignant reminder that its relative inaccessibility hinders exploration, but does not extend much protection from human interference.
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Review Article |
The biogeochemical cycle of iron in the ocean
Iron controls phytoplankton growth in large tracts of the global ocean, and thereby influences carbon dioxide drawdown. Recent advances reveal the importance of iron-binding ligands and organic matter remineralization in regulating ocean iron levels.
- P. W. Boyd
- & M. J. Ellwood
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News & Views |
Sea change
The Atlantic meridional overturning circulation delivers warmth to high latitudes and carbon to depth. Historical temperature and salinity records call into question the traditional view that these waters form a single coherent conveyer system of currents.
- Agatha M. de Boer
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Letter |
External forcing as a metronome for Atlantic multidecadal variability
Instrumental records, proxy data and climate modelling show that multidecadal variability is a dominant feature of North Atlantic sea-surface temperature variations. Simulations with a coupled climate model suggest that the timing of this variability is determined mainly by external forcing, for example from volcanic eruption or solar forcing.
- Odd Helge Otterå
- , Mats Bentsen
- & Lingling Suo
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Article |
Opposing decadal changes for the North Atlantic meridional overturning circulation
Hydrographic properties of the North Atlantic Ocean have changed significantly over the past decades. A combination of changes in seawater density, calculated from observed properties of sea water and a numerical ocean model, reveals that the strength of the meridional overturning circulation has changed in different directions in the subpolar and subtropical basins, respectively.
- M. Susan Lozier
- , Vassil Roussenov
- & Richard G. Williams
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Letter |
Significant sink of ocean-eddy energy near western boundaries
Ocean eddies generated through instability of the mean flow are a vital component of the energy budget of the global ocean. Modelling combined with satellite altimetry data suggests that the energy from westward-propagating eddies is scattered and eventually dispersed when they reach the western boundary of an ocean basin.
- Xiaoming Zhai
- , Helen L. Johnson
- & David P. Marshall
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Letter |
A seasonal cycle in the export of bottom water from the Weddell Sea
Dense water that formed over the Antarctic continental shelf spreads throughout the global ocean as Antarctic Bottom Water. Observations over eight years reveal a strong seasonal cycle in the flow of Weddell Sea bottom water northwards that is linked to winds over the western margin of the Weddell Sea.
- Arnold L. Gordon
- , Bruce Huber
- & Martin Visbeck
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Letter |
Patterns of Indian Ocean sea-level change in a warming climate
Sea-level rise is not globally uniform. A combination of observations and climate-model simulations reveals a pattern of sea-level changes in the Indian Ocean, with a decrease in the southern tropical Indian Ocean and a rise elsewhere, that can be attributed to changes in the atmospheric overturning circulation.
- Weiqing Han
- , Gerald A. Meehl
- & Stephen Yeager
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Backstory |
Into the deep
In an attempt to assess the factors controlling the rates of glacial melt in West Antarctica, Adrian Jenkins and colleagues found themselves waiting anxiously for their submersible, Autosub3, to return from under an ice shelf.
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Letter |
Observations beneath Pine Island Glacier in West Antarctica and implications for its retreat
Thinning ice in West Antarctica is currently contributing about 10% of the observed rise in global sea level. Observations obtained from an autonomous underwater vehicle operating beneath Pine Island Glacier, West Antarctica, reveal that the glacier was recently grounded on a transverse ridge in the sea floor, but now warm sea water flows through the widening gap above the ridge.
- Adrian Jenkins
- , Pierre Dutrieux
- & David White
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Letter |
Spatial variability in oceanic redox structure 1.8 billion years ago
The deposition of iron formations ceased about 1.84 billion years ago. Reconstructions of ocean chemistry suggest that the advent of euxinic conditions along ocean margins preferentially removed dissolved iron from the water column in the form of the mineral pyrite, inhibiting widespread iron-oxide mineral deposition.
- Simon W. Poulton
- , Philip W. Fralick
- & Donald E. Canfield
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Letter |
The structure of oceanic core complexes controlled by the depth distribution of magma emplacement
Extension at mid-ocean ridges can be accommodated by detachment faults, forming oceanic core complexes that develop under low rates of magma intrusion. Modelling reveals that oceanic core complexes can also form under high rates of magma intrusion, if the magma is injected into the lower ductile layer of the crust.
- Jean-Arthur Olive
- , Mark D. Behn
- & Brian E. Tucholke
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News & Views |
Atmosphere and ocean chemistry
Low atmospheric carbon dioxide concentrations during glacial periods must have been accompanied by changes in surface-ocean carbonate chemistry. But it is unclear whether concurrent changes in the deep sea contributed to the glacial carbon dioxide decline.
- Richard E. Zeebe
- & Thomas M. Marchitto Jr
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News & Views |
Promoting marine origination
The rate at which new marine animals evolve has varied through time, but the factors that ultimately drive these fluctuations are unclear. A statistical analysis shows that global changes in abiotic factors play an important role.
- Wolfgang Kiessling
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Letter |
Effect of nutrient availability on marine origination rates throughout the Phanerozoic eon
The diversity of marine life has varied throughout the past 500 million years. Statistical analyses suggest that fluctuations in the availability of marine nutrients has been one important regulator of rates of origination during this time.
- Andrés L. Cárdenas
- & Peter J. Harries
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Letter |
Magnitude of oceanic nitrogen fixation influenced by the nutrient uptake ratio of phytoplankton
The ratio of nitrogen to phosphorus in phytoplankton varies greatly with taxa and growth conditions. An ecosystem model suggests that the relative abundance of fast- and slow-growing phytoplankton controls the amount of new nitrogen added to the ocean.
- Matthew M. Mills
- & Kevin R. Arrigo
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News & Views |
Recycling bottom waters
The formation and flow of deep water around Antarctica contributes to the global ocean circulation. New measurements report the strongest flow speeds recorded so far in a current below 3,000 m depth, and help to document a pathway for Antarctic Bottom Water.
- Alejandro H. Orsi
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Letter |
Strong export of Antarctic Bottom Water east of the Kerguelen plateau
Deep western boundary currents east of the Antarctic Peninsula and the Kerguelen plateau are important pathways for transporting deep Antarctic water masses to the global ocean. An array of moored current meters, used to quantify the water transport in this system, reveals a flow that is stronger than any measured in a deep western boundary current at similar depths so far.
- Y. Fukamachi
- , S. R. Rintoul
- & M. Wakatsuchi
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Backstory |
Bagging basalt
After dodging icebergs and flying fish, Jeff Standish and colleagues collected a suite of basalts from the Southwest Indian Ridge, to try and determine the mechanisms of mid-ocean-ridge formation.
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News & Views |
Widening the goal-posts
Oceanic crust forms through the addition of volcanic rock to mid-ocean ridges. Widely dispersed, young lavas observed at an ultraslow-spreading ridge provide impetus for the redevelopment of models of oceanic magmatism.
- John Maclennan
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News & Views |
Asymmetric response
The surface layer of the Southern Ocean connects the atmosphere with the deep subtropical ocean. Ocean observations reveal that the thickness of this layer — important for biological productivity — is controlled by the strength and position of the southern circumpolar winds.
- Sarah Gille
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Article |
Zonally asymmetric response of the Southern Ocean mixed-layer depth to the Southern Annular Mode
Interactions between the atmosphere and ocean are mediated by the mixed layer at the ocean surface. Analyses of ocean temperature and salinity data from Argo floats show that changes in the Southern Annular Mode, including recent and projected trends attributed to human activity, drive variations in mixed-layer depth in the Southern Ocean.
- J. B. Sallée
- , K. G. Speer
- & S. R. Rintoul
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News & Views |
Sulphate-sensitive seas
About 94.5 million years ago, oxygen levels in the deep ocean dropped while carbon burial rapidly increased. Geochemical analyses suggest that the release of sulphate from extensive volcanism set off a sequence of biogeochemical reactions that led to ocean anoxia.
- Haydon P. Mort
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News & Views |
Beyond the spring barrier?
Predicting an El Niño or La Niña event before the preceding spring has proved to be difficult. Taking into account coupled ocean–atmosphere modes in the Indian Ocean region that have a two-year periodicity may provide the basis for longer forecasting lead times.
- Peter J. Webster
- & Carlos D. Hoyos
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Letter |
Influence of the state of the Indian Ocean Dipole on the following year’s El Niño
Anomalies of the El Niño/Southern Oscillation in the Pacific Ocean and the Indian Ocean Dipole often occur simultaneously. An analysis of observations and models suggests that, in addition, the negative phase of the Indian Ocean Dipole tends to occur 14 months before an El Niño event, with implications for El Niño predictability.
- Takeshi Izumo
- , Jérôme Vialard
- & Toshio Yamagata
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Letter |
Past constraints on the vulnerability of marine calcifiers to massive carbon dioxide release
Increasing concentrations of carbon dioxide in sea water are driving a progressive acidification of the ocean, with as yet unclear impacts on marine calcifying organisms. Simulations with an Earth system model suggest that future changes in the marine environment could be more severe than those experienced during the Palaeocene–Eocene thermal maximum, both in the deep ocean and near the surface.
- Andy Ridgwell
- & Daniela N. Schmidt
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Letter |
Rapid submarine melting of the calving faces of West Greenland glaciers
Widespread glacier acceleration has been observed in Greenland in the past few years. Oceanographic observations taken in summer 2008 show that ocean waters melted a substantial fraction of ice along the calving fronts of three West Greenland glaciers, indicating that submarine melting has a profound influence on grounding-line stability.
- Eric Rignot
- , Michele Koppes
- & Isabella Velicogna
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Letter |
Rapid circulation of warm subtropical waters in a major glacial fjord in East Greenland
The recent rapid increase in mass loss from the Greenland ice sheet is primarily attributed to an acceleration of outlet glaciers. Oceanographic data obtained in summer 2008 show that subtropical waters that reside year-round in the shelf ocean off Greenland continuously enter a large glacial fjord in East Greenland and contribute to melting at the glacier terminus.
- Fiammetta Straneo
- , Gordon S. Hamilton
- & Aqqalu Rosing-Asvid
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Letter |
Influence of Bering Strait flow and North Atlantic circulation on glacial sea-level changes
Throughout the most recent glacial period sea level fluctuated by 20–30 m. Climate model simulations indicate that the barrier to water exchange between the Atlantic and Pacific oceans posed by the Bering Strait during low sea levels could have been instrumental in generating these fluctuations.
- Aixue Hu
- , Gerald A. Meehl
- & Nan Rosenbloom