Oceanography

All waters in nature, whether rain water or ocean water, contain dissolved
mineral salts. Salinity is the term used to define the total content of dissolved salts in sea
water. Factors affecting ocean salinity are mentioned below:
•The salinity of water in the surface layer of oceans depends mainly on evaporation
and precipitation.
•Surface salinity is greatly influenced in coastal regions by the fresh water flow from
rivers, and in Polar Regions by the processes of freezing and thawing of ice.
•Wind, also influences salinity of an area by transferring water to other areas.
•The ocean currents contribute to the salinity variations. Salinity, temperature and
density of water are interrelated. Hence, any change in the temperature or density
influences the salinity of water in an area.

Oceanic and atmospheric Rossby waves — also known as planetary waves —
naturally occur largely due to the Earth’s rotation. These waves affect the planet’s weather
and climate.
•Waves in the ocean come in many different shapes and sizes.
•Slow-moving oceanic Rossby waves are fundamentally different from ocean
surface waves.
•Unlike waves that break along the shore, Rossby waves are huge, undulating
movements of the ocean that stretch horizontally across the planet for
hundreds of kilometers in a westward direction.
•They are so large and massive that they can change Earth’s climate conditions.
•Along with rising sea levels, King Tides, and the effects of El Niño, oceanic Rossby
waves contribute to high tides and coastal flooding in some regions of the world

In 1865, the Danish geologist and mineralogist Johan Georg Forchhammer,
with the help of naval and civilian collaborators, collected numerous samples of seawater from the Northern Atlantic and the Arctic Ocean. He wanted to determine why the
salinity (or “saltiness”) of seawater varies in different areas of the ocean.
•Forchhammer put the samples through a detailed series of chemical analyses and
found that the proportions of the major salts in seawater stay about the same
everywhere.
•This constant ratio is known as Forchhammer’s Principle, or the Principle of
Constant Proportions.
•In addition to this principle, Forchhammer is credited with defining the
term salinity to mean the concentration of major salts in seawater.
•Forchhammer’s discovery helped scientists understand that salinity levels in
seawater vary due to the addition or removal of fresh water, rather than differing
amounts of salt minerals in the water.
•The principle is still applied today in marine research, and provides a simple way to
estimate salinity and trace the mixing of water masses in the global ocean.

On December 11, 2019, the South Pacific Archipelago of Bougainville voted
to become independent of Papua New Guinea.
•Around 98% of 1,81,067 voters voted to get independent from Papua New Guinea. It
is the largest island of the Solomon Islands Archipelago.
•The island has the world’s largest copper deposits. The most widely spoken language
in the country is Halia.
•The country is yet to prove its recognition in the United Nations.

The Great Lakes are, from west to east: Superior, Michigan, Huron, Erie and
Ontario.
•They are a dominant part of the physical and cultural heritage of North America.
•Shared with Canada and spanning more than 750 miles (1,200 kilometers) from
west to east, these vast inland freshwater seas provide water for consumption,
transportation, power, recreation and a host of other uses.
•The Great Lakes are one of the world’s largest surface freshwater ecosystems.

There are four main types of estuaries, based on how they were formed.
•Bar-built estuaries form when a shallow lagoon or bay is protected from the ocean
by a sand bar, delta or island.
•Coastal plains estuaries are formed when the rising sea fills existing river
valleys.
•Tectonic estuaries are caused by the folding of land surfaces due to volcanic
activity.
•Fjord and Ria estuaries are drowned river valleys where the river valley was
originally formed by glacial action.

According to the scientists, including those from NASA’s Jet Propulsion Laboratory in the US, a sea-water current called the Beaufort Gyre keeps the polar environment in balance by storing fresh water near the surface of the Arctic Ocean.
• Wind blows the gyre in a clockwise direction around the western Arctic Ocean, north of Canada, where it naturally collects fresh water from the melting of glaciers, and river runoff.
• The researchers said this fresh water is important in the Arctic since it floats above the warmer, salty water, and helps protect the sea ice from melting – in turn regulating the Earth’s climate.
• As the fresh water is slowly released by the gyre into the Atlantic Ocean over a period of decades, it allows the Atlantic Ocean currents to carry it away in small amounts.
• However, since the 1990s, the researchers said, the gyre has accumulated a large amount of fresh water – 8,000 cubic kilometres – or almost twice the volume of Lake Michigan in the US.
• According to the new study, the cause of this gain in freshwater concentration is the loss of sea ice in summer and autumn.
• Due to this decades-long decline of the Arctic’s summertime ice cover, the Beaufort Gyre is more exposed to the wind, which has spun the gyre faster, trapping the fresh water in its current.

The Atlantic Meridional Overturning Circulation (AMOC) is a large system of ocean currents that carry warm water from the tropics northwards into the North Atlantic.
• The AMOC is a large system of ocean currents, like a conveyor belt, driven by differences in temperature and salt content – the water’s density.
• As warm water flows northwards it cools and some evaporation occurs, which increases the amount of salt.
• Low temperature and a high salt content make the water denser, and this dense water sinks deep into the ocean.
• The cold, dense water slowly spreads southwards, several kilometres below the surface (As that water cools and sinks it drives a slow circulation of the oceans that is critical to global climate, affecting the location of droughts and frequency of hurricanes).
• Eventually, it gets pulled back to the surface and warms in a process called “upwelling” and the circulation is complete.
• This global process makes sure that the world’s oceans are continually mixed, and that heat and energy are distributed around the earth. This, in turn, contributes to the climate we experience today.
• As that water cools and sinks it drives a slow circulation of the oceans that is critical to global climate, affecting the location of droughts and frequency of hurricanes.
• It also stores heat-trapping carbon dioxide deep in the ocean.

THE KUROSHIO IS a warm northeasterly ocean current off the coast of Japan. This current is also called the gulf stream of the Pacific or Japan Current.
• Kuroshio means “the black stream” in Japanese, named after the deep ultramarine color of the high salinity water, which is found flowing north of the current’s axis.
• The system includes the following branches: Kuroshio, up to 35 degrees N; Kuroshio extension, extending eastward into two branches up to 160 degrees E longitude;
• North Pacific current, a further eastward continuation, which throws branches to the south as far as 150 degrees W;
• Tsushima current, branches of the main current that run into the Japan Sea, along the west coast of JAPAN;
• And Kuroshio counter-current, the large swirl or eddy on the east and south east of the Kuroshio.

About 71 per cent of the planetary water is found in the oceans. The remaining is held as freshwater in glaciers and icecaps, groundwater sources, lakes, soil moisture, atmosphere, streams and within life. Nearly 59 per cent of the water that falls on land returns to the atmosphere through evaporation from over the oceans as well as from other places. The remainder runs-off on the surface, infiltrates into the ground or a part of it becomes glacier.

The ocean floors can be divided into four major divisions:

 The Continental Shelf;

 The Continental Slope;

• The Deep Sea Plain;

 The Oceanic Deeps.

Besides, these divisions there are also major and minor relief features in the ocean floors like ridges, hills, sea mounts, guyots, trenches, canyons, etc.

Scientists estimate that 50-80% of the oxygen production on Earth comes from the ocean.

 The majority of this production is from oceanic plankton — drifting plants, algae, and some bacteria that can photosynthesize.

 One particular species, Prochlorococcus, is the smallest photosynthetic organism on Earth.

 But this little bacteria produces up to 20% of the oxygen in our entire biosphere.

 That’s a higher percentage than all of the tropical rainforests on land combined.

 It’s important to remember that although the ocean produces at least 50% of the oxygen on Earth, roughly the same amount is consumed by marine life.

 Like animals on land, marine animals use oxygen to breathe, and both plants and animals use oxygen for cellular respiration.

 Oxygen is also consumed when dead plants and animals decay in the ocean.

A massive “dead zone” in the Arabian Sea is the largest in the world, a new study reveals.

 Dead zones are oxygen-starved ocean regions where few organisms can survive.

 They emerge in ocean depths ranging from 650 to 2,600 feet (200 to 800 meters), when influxes of chemical nutrients — typically from human pollution — spur algae growth, which sucks up oxygen.

 A significant oxygen-deprived region has bloomed in the Gulf of Oman for decades, but it was last surveyed in the 1990s.

 The Gulf of Oman, which spans 70,000 square miles (181,000 square kilometers), connects the Arabian Sea to the Persian Gulf.

 It has long been off-limits to researchers because of the region’s political instability and the threat of ocean piracy.

 For eight months, these AUVs gathered data on oxygen levels, and then transmitted their readings to the scientists via satellite.

• Researchers then used computer models to visualize the ocean currents that circulated oxygen around the gulf from the Arabian Sea.

 They found that the oxygen-poor region had grown dramatically, and the scant oxygen formerly held in the depleted zone — based on data from the 1990s — had drained significantly, leaving bigger areas with no oxygen at all.

Namib Desert: the Namib Desert is a direct result of the Benguela Current.

 Seamounts near to the coastline beneath the Atlantic’s surface cause the icy Benguela River to flow very close to the Namibian coast.

 This causes a harsh coastal climate with very little rainfall.

Atacama Desert: Cold ocean currents contribute to the formation of coastal deserts.

 Air blowing toward shore, chilled by contact with cold water, produces a layer of fog. This heavy fog drifts onto land.

 The Atacama Desert, on the Pacific shores of Chile, is a coastal desert.

 Some areas of the Atacama are often covered by fog. But the region can go decades without rainfall. In fact, the Atacama Desert is the driest place on Earth.

Gobi Desert: Interior deserts, which are found in the heart of continents, exist because no moisture-laden winds reach them.

 By the time air masses from coastal areas reach the interior, they have lost all their moisture. Interior deserts are sometimes called inland deserts.

 The Gobi Desert, in China and Mongolia, lays hundreds of kilometers from the ocean. Winds that reach the Gobi have long since lost their moisture.

 The Gobi is also in the rain shadow of the Himalaya Mountains to the south