Oceanus Online Archive
Access to the Sea
Oceanographic fieldwork has traditionally meant going to sea on a ship. In recent years, it has expanded to include activities that may require a ship for a short period but then continue independently. Floats that drift with ocean currents, periodically reporting their positions via satellite, for example, are generally launched from ships but do most of their work independently. Long-term seafloor observatories may need ships to set them up and service them occasionally, but, again, they are designed to collect data for long periods without needing a ship. We have come to think of the body of ways oceanographers glean information from the ocean as “access to the sea,” and so that is the topic for this issue of Oceanus.
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The Magnetic Thickness of a Recent Submarine Lava Flow
Submarine lava flows and their associated narrow feeder conduits known as dikes constitute the basic building blocks of the upper part of the ocean crust. We are only beginning to understand how lava erupts and forms on the seafloor by flooding topographic lows, flowing through channels or tubes, centralizing into volcanoes, or some combination of all of these.
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New Data on Deep Sea Turbulence Shed Light on Vertical Mixing
The global thermohaline circulation is basically a wholesale vertical overturning of the sea, driven by heating and cooling, precipitation and evaporation.
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Labrador Sea Water Carries Northern Climate Signal South
Changes in wind strength, humidity, and temperature over the ocean affect rates of evaporation, precipitation, and heat transfer between ocean and air. Long-term atmospheric climate change signals are imprinted onto the sea surface layer, a thin skin atop an enormous reservoirA? and subsequently communicated to the deeper water masses. Labrador Sea Water is a subpolar water mass shaped by air-sea exchanges in the North Atlantic. It is a major contributor to the deep water of the Atlantic, and changes of conditions in its formation area can be read several years later at mid-depths in the subtropics. Mapping these changes through time is helping us to understand the causes of significant warming and cooling patterns we have observed at these depths in the North Atlantic and links the subtropical deep signals back to the subpolar sea surface conditions.
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North Atlantic’s Transformation Pipeline Chills and Redistributes Subtropical Water
Warm and salty waters from the upper part of the South Atlantic flow northward across the equator and then progress through the tropical and subtropical North Atlantic to reach high latitudes. Beginning with the intense northward flow of the Gulf Stream off the East Coast of the United States, these waters are exposed to vigorous cooling, liberating considerable oceanic heat to the atmosphere. This is the first stage of “warm water transformation within the North Atlantic, a process that culminates in the high latitude production of cold and fresh waters that return to the South Atlantic in deep reaching currents beneath the warm waters of the subtropics and tropics.
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If Rain Falls on the OceanDoes It Make a Sound?
As with similar questions about a tree in the forest or a grain of sand on the beach, it may be hard to imagine that a few inches of rain matters to the deep ocean.
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Alpha, Bravo, Charlie…
The ocean weather station idea originated in the early days of radio communications and trans-oceanic aviation. As early as 1921, the Director of the French Meteorological Service proposed establishing a stationary weather observing ship in the North Atlantic to benefit merchant shipping and the anticipated inauguration of trans-Atlantic air service. Up to then, temporary stations had been set up for special purposes such as the US Navy NC-4 trans-Atlantic flight in 1919 and the ill-fated Amelia Earhart Pacific flight in 1937.
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Computer Modelers Stimulate Real and Potential Climate, Work Toward Prediction
Although weather forecasting is accepted by the public as part of daily life, oceanic forecasting is not yet so advanced. There are, however, successful examples of oceanic forecasting—one is the newly developed skill to predict El Nino/Southern Oscillation (ENSO) events, largely due to improvements in ocean modeling.
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A Century of North Atlantic Data Indicates Interdecadal Change
For hundreds of years mariners have recorded the weather over the world ocean. Some 100 million marine weather reports have accumulated worldwide since 1854, when an international system for the collection of meteorogical data over the oceans was established. These reports include measurements of sea surface temperature, air temperature, wind, cloudiness, and barometric pressure. In the 1980s, the National Oceanic and Atmospheric Administration (NOAA) compiled these weather observations into a single, easily accessible digital archive called the Comprehensive Ocean-Atmosphere Data Set. This important data set forms the basis for our empirical knowledge of the surface climate and its variability over the world’s oceans: One example of a variable system is the phenomenon known as El Nino in the tropical Pacific. A major challenge in climate research is to use these data to document and understand the role of the oceans in long-term—decadal and centennial—climate change.
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Oceans & Climate
The past decade has brought rapid scientific progress in understanding the role of the ocean in climate and climate change. The ocean is involved in the climate system primarily because it stores heat, water, and carbon dioxide, moves them around on the earth, and exchanges these and other elements with the atmosphere.
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Sedimentary Record Yields Several Centuries of Data
Natural climate changes like the Little Ice Age and the Medieval Warm Period are of interest for a few reasons. First, they occur on decade to century time scales, a gray zone in the spectrum of climate change. Accurate instrumental data do not extend back far enough to document the beginning of these events, and historical data are often of questionable accuracy and are not widespread geographically.
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Transient Tracers Track Ocean Cimate Signals
Transient tracers provide us with a unique opportunity to visualize the effects of the changing climate on the ocean. They trace the pathways climate anomalies follow as they enter and move through the ocean and give us valuable information about rates of movement and amounts of dilution. This knowledge is important for developing ocean-climate models to predict long term climate changes.
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The El Niño/Southern Oscillation Phenomenon
The El Niño/Southern Oscillation (ENSO) phenomenon, an eastward shift of warm water in the tropical Pacific and associated effects on the atmosphere, is at the heart of global interannual climate variability.
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The Bermuda Station SA Long-Running Oceanographic Show
A time series of hydrographic measurements was initiated at Bermuda in 1954 and continues to the present. It began under the banner of the International Geophysical Year (1957-1958) with the scientific support of Henry Stommel of the Woods Hole Oceanographic Institution and William Sutcliffe, director of the Bermuda Biological Station (BBS). The scientists and personnel of the originating institutions have been the most active participants over the years, but the data have been widely used by the international oceanographic community. While other long time series of measurements in the North Atlantic began in association with weather ships, only the Bermuda measurements have a strong oceanographic focus.
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