South Pacific Gyre
Encyclopedia
The “South Pacific Gyre
” is the Earth’s biggest system of rotating ocean currents, bounded by equator
to the north, Australia
to the west, the Antarctic Circumpolar Current
to the south, and South America
to the east. The center of the South Pacific Gyre is the site on Earth farthest from any continents and productive ocean regions and is regarded as Earth’s largest oceanic desert
and few nutrients are transported there by the wind (eolian processes
) because there is relatively little land in the Southern Hemisphere to supply dust to the prevailing winds
. The low levels of nutrients in the region result in extremely low primary productivity in the ocean surface and subsequently very low flux of organic material settling to the ocean floor as marine snow
. The low levels of biogenic and eolian deposition cause sediments to accumulate on the ocean floor very slowly. In the center of the South Pacific Gyre, the sedimentation rate is 0.1 to 1 m (0.328083989501312 to 3.3 ft) per million years. The sediment thickness (from basement basalts to the seafloor) ranges from 1 to 70m, with thinner sediments occurring closer to the center of the Gyre. The low flux of particles to the South Pacific Gyre cause the water there to be the clearest seawater in the world.
. Despite extremely low amounts of buried organic material, microbes live throughout the entire sediment column. Average cell abundances and net rates of respiration
are a few orders of magnitude lower than any other subseafloor biosphere previously studied.
The South Pacific Gyre subseafloor community is also unusual because it contains oxygen
throughout the entire sediment column. In other subseafloor biospheres, microbial respiration will break down organic material and consume all the oxygen near the seafloor leaving the deeper portions of the sediment column anoxic. However, in the South Pacific Gyre the low levels of organic material, the low rates of respiration, and the thin sediments allow the porewater to be oxygenated throughout the entire sediment column.
data images show that some areas in the gyre are greener than the surrounding clear blue water, which is frequently interpreted as areas with higher concentrations of living phytoplankton
. However, the assumption that greener the ocean water always contains more phytoplankton is not always true. Even though the South Pacific Gyre contains these patches of green water, it has very little organism growth. Instead, some studies hypothesize that these green patches are a result of the accumulated waste of marine life. The optical properties of the South Pacific Gyre remain largely unexplored.
Gyre
A gyre in oceanography is any large system of rotating ocean currents, particularly those involved with large wind movements. Gyres are caused by the Coriolis Effect; planetary vorticity along with horizontal and vertical friction, which determine the circulation patterns from the wind curl...
” is the Earth’s biggest system of rotating ocean currents, bounded by equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
to the north, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
to the west, the Antarctic Circumpolar Current
Antarctic Circumpolar Current
The Antarctic Circumpolar Current is an ocean current that flows from west to east around Antarctica. An alternative name for the ACC is the West Wind Drift. The ACC is the dominant circulation feature of the Southern Ocean and, at approximately 125 Sverdrups, the largest ocean current...
to the south, and South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
to the east. The center of the South Pacific Gyre is the site on Earth farthest from any continents and productive ocean regions and is regarded as Earth’s largest oceanic desert
Sediment Flux and Accumulation
Earth’s trade winds and Coriolis force cause the ocean currents in the South Pacific Ocean to circulate counter clockwise. The currents act to isolate the center of the gyre from nutrient upwellingUpwelling
Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water. The increased availability in upwelling regions results in high levels of primary...
and few nutrients are transported there by the wind (eolian processes
Eolian processes
Aeolian processes pertain to the activity of the winds and more specifically, to the winds' ability to shape the surface of the Earth and other planets. Winds may erode, transport, and deposit materials, and are effective agents in regions with sparse vegetation and a large supply of...
) because there is relatively little land in the Southern Hemisphere to supply dust to the prevailing winds
Prevailing winds
Prevailing winds are winds that blow predominantly from a single general direction over a particular point on Earth's surface. The dominant winds are the trends in direction of wind with the highest speed over a particular point on the Earth's surface. A region's prevailing and dominant winds...
. The low levels of nutrients in the region result in extremely low primary productivity in the ocean surface and subsequently very low flux of organic material settling to the ocean floor as marine snow
Marine snow
In the deep ocean, marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the water column. It is a significant means of exporting energy from the light-rich photic zone to the aphotic zone below. The term was first coined by the explorer William Beebe as he...
. The low levels of biogenic and eolian deposition cause sediments to accumulate on the ocean floor very slowly. In the center of the South Pacific Gyre, the sedimentation rate is 0.1 to 1 m (0.328083989501312 to 3.3 ft) per million years. The sediment thickness (from basement basalts to the seafloor) ranges from 1 to 70m, with thinner sediments occurring closer to the center of the Gyre. The low flux of particles to the South Pacific Gyre cause the water there to be the clearest seawater in the world.
Subseafloor Biosphere
Beneath the seafloor, the marine sediments and surrounding porewaters contain an unusual subseafloor biosphereBiosphere
The biosphere is the global sum of all ecosystems. It can also be called the zone of life on Earth, a closed and self-regulating system...
. Despite extremely low amounts of buried organic material, microbes live throughout the entire sediment column. Average cell abundances and net rates of respiration
Respiration
Respiration may refer to:Biology* Respiratory system, the anatomical system of an organism used for respiration* Cellular respiration, the process in which nutrients are converted into useful energy in a cell...
are a few orders of magnitude lower than any other subseafloor biosphere previously studied.
The South Pacific Gyre subseafloor community is also unusual because it contains oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
throughout the entire sediment column. In other subseafloor biospheres, microbial respiration will break down organic material and consume all the oxygen near the seafloor leaving the deeper portions of the sediment column anoxic. However, in the South Pacific Gyre the low levels of organic material, the low rates of respiration, and the thin sediments allow the porewater to be oxygenated throughout the entire sediment column.
Water Color
SatelliteSatellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
data images show that some areas in the gyre are greener than the surrounding clear blue water, which is frequently interpreted as areas with higher concentrations of living phytoplankton
Phytoplankton
Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...
. However, the assumption that greener the ocean water always contains more phytoplankton is not always true. Even though the South Pacific Gyre contains these patches of green water, it has very little organism growth. Instead, some studies hypothesize that these green patches are a result of the accumulated waste of marine life. The optical properties of the South Pacific Gyre remain largely unexplored.