Drake Passage
The Drake Passage (
The Drake Passage is considered one of the most treacherous voyages for ships to make. Currents at its latitude meet no resistance from any landmass, and waves top 40 feet (12 m), giving it a reputation for being "the most powerful convergence of seas".[1]
As the Drake Passage is the narrowest passage (choke point) around Antarctica, its existence and shape strongly influence the circulation of water around Antarctica and the global oceanic circulation, as well as the global climate. The bathymetry of the Drake Passage plays an important role in the global mixing of oceanic water.
History
In 1525, Spanish navigator Francisco de Hoces discovered the Drake Passage while sailing south from the entrance of the Strait of Magellan.[2] Because of this, the Drake Passage is referred to as the "Mar de Hoces (Sea of Hoces)" in Spanish maps and sources, while almost always in the rest of the Spanish-speaking countries it is mostly known as “Pasaje de Drake” (Argentina, mainly), “Paso Drake” or “Mar de Drake” (Chile, mainly).
The passage received its English name from
In 1616, Dutch navigator Willem Schouten became the first to sail around Cape Horn and through the Drake Passage.[5]
On December 25, 2019, a crew of six explorers successfully rowed across the passage, becoming the first in history to do so.[6] This accomplishment became the subject of a 2020 documentary, The Impossible Row.[7]
Geography
The Drake Passage opened when Antarctica separated from South America due to plate tectonics, however, there is much debate about when this occurred, with estimates ranging from 49 to 17 million years ago (Ma).[8][9]
The opening had a major effect on the global oceans due to deep currents like the Antarctic Circumpolar Current (ACC). This opening could have been a primary cause of changes in global circulation and climate, as well as the rapid expansion of Antarctic ice sheets, because, as Antarctica was encircled by ocean currents, it was cut off from receiving heat from warmer regions.[10]
The 800-kilometre-wide (500 mi) passage between Cape Horn and Livingston Island is the shortest crossing from Antarctica to another landmass. The boundary between the Atlantic and Pacific Oceans is sometimes taken to be a line drawn from Cape Horn to Snow Island (130 kilometres (81 mi) north of mainland Antarctica), though the International Hydrographic Organization defines it as the meridian that passes through Cape Horn: 67° 16′ W.[11] Both lines lie within the Drake Passage.
The other two passages around the southern extremity of South America — the Strait of Magellan and the Beagle Channel — have frequent narrows, leaving little maneuvering room for a ship, as well as unpredictable winds and tidal currents. Most sailing ships thus prefer the Drake Passage, which is open water for hundreds of miles.
No significant land sits at the latitudes of the Drake Passage. This is important to the unimpeded eastward flow of the Antarctic Circumpolar Current, which carries a huge volume of water through the passage and around Antarctica.
The passage hosts whales, dolphins, and seabirds including giant petrels, other petrels, albatrosses, and penguins.
Importance in physical oceanography
The presence of the Drake Passageway allows the three main ocean basins (Atlantic, Pacific and Indian) to be connected via the Antarctic Circumpolar current (ACC), the strongest oceanic current, with an estimated transport of 100–150 Sv (Sverdrups, million m3/s). This flow is the only large-scale exchange occurring between the global oceans, and the Drake passage is the narrowest passage on its flow around Antarctica. As such, a significant amount of research has been done in understanding how the shape of the Drake passage (bathymetry and width) affects the global climate.
Oceanic and climate interactions
Major features of the modern ocean’s temperature and salinity fields, including the overall thermal asymmetry between the hemispheres, the relative saltiness of deep water formed in the northern hemisphere, and the existence of a transequatorial conveyor circulation, develop after Drake Passage is opened.[12]
The importance of an open Drake Passage extends farther than the Southern Ocean latitudes. The Roaring Forties and the Furious Fifties blow around Antarctica and drive the Antarctic Circumpolar Current (ACC). As a result of Ekman Transport, water gets transported northward from the ACC (on the left-hand side while facing the stream direction). Using a Lagrangian approach, water parcels passing through the Drake Passage can be followed in their journey in the oceans. Around 23 Sv of water is transported from the Drake Passage to the equator, mainly in the Atlantic and Pacific Oceans.[13] This value is not far from the Gulf Stream transport in the Florida Strait (33 Sv[14]), but is an order of magnitude lower than the transport of the ACC (100–150 Sv). Water transported from the Southern Ocean to the Northern Hemisphere contributes to the global mass balance and permits the meridional circulation across the oceans.
Several studies have linked the current shape of the Drake Passage to an effective Atlantic meridional overturning circulation (AMOC). Models have been run with different widths and depths of the Drake Passage, and consequent changes in the global oceanic circulation and temperature distribution have been analyzed:[12][15] It appears that the "conveyor belt" of the global thermohaline circulation appears only in presence of an open Drake Passage, subject to wind forcing.[12] With a closed Drake Passage, there is no North Atlantic Deep Water (NADW) cell, and no ACC. With a shallower Drake Passage, a weak ACC appears, but still no NADW cell.[15]
It has also been shown that present-day distribution of dissolved inorganic carbon can be obtained only with an open Drake Passage.[16]
Regarding the global surface temperature, an open (and sufficiently deep) Drake Passage cools the Southern Ocean and warms the high latitudes of the Northern Hemisphere. The isolation of Antarctica by the ACC (that can flow only with an open Drake Passage) is credited by many researchers with causing the glaciation of the continent and global cooling in the Eocene epoch.
Turbulence and mixing
In short, without the coarse topography in the depths of the Drake Passage, oceanic internal mixing would be weaker, and the global circulation would be affected.
Historical importance in oceanographic observations
Worldwide satellite measurements of oceanic properties have been available since the 1980s. Before then, data could be only gathered through oceanic ships taking direct measurements. The Antarctic Circumpolar Current (ACC) has been (and is) surveyed making repeated transects. South America and the Antarctic Peninsula constrain the ACC in the Drake Passage; the convenience of measuring the ACC across the passage lays in the clear boundaries of the current in that stripe. Even after the advent of satellite altimetry data, direct observations in the Drake Passage have not lost their exceptionality. The relative shallowness and narrowness of the passage makes it particularly suitable to assess the validity of horizontally and vertically changing quantities (such as velocity in Ekman's theory[22]).
In addition, the strength of the ACC makes meanders and pinching cold-core cyclonic rings easier to observe.[23]
Fauna
Wildlife in the Drake Passage includes the following species:
Birds
- Sooty shearwater
- White-chinned petrel
- Southern giant petrel
- Northern giant-petrel
- Black-browed albatross
- Campbell albatross
- Grey-headed albatross
- Atlantic yellow-nosed albatross
- Indian yellow-nosed albatross
- Buller's albatross
- Salvin's albatross
- Shy albatross
- Southern royal albatross
- Northern royal albatross
- Wandering albatross
- Light-mantled albatross
- Sooty albatross
- Great shearwater
- Great-winged petrel
- Kerguelen petrel
- Southern fulmar
- Cape petrel
- Soft-plumaged petrel
- White-headed petrel
- Atlantic petrel
- Grey petrel
- Antarctic prion
- Slender-billed prion
- Blue petrel
- Black-bellied storm petrel
- Wilson's storm-petrel
Cetaceans
Gallery
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Rough seas are common in the Drake Passage
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Tourists watch whales in the Drake Passage
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Seabird (light-mantled sooty albatross) flying over the Drake Passage
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Humpback whales are a common sight in the Drake Passage
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Hourglass dolphins leaping in the Passage
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Drake Passage or Mar de Hoces between South America and Antarctica
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Drake Passage
See also
- Elizabeth Island (Cape Horn)
- Garcia de Nodal expedition
- Bransfield Strait
- Sars Bank
- Timeline of Francis Drake's circumnavigation
References
- ^ "6 men become 1st to cross perilous Drake Passage unassisted". AP NEWS. Associated Press. 2019-12-28. Retrieved 2020-10-30.
- ISBN 978-84-7232-130-4
- ISBN 978-1-844-13762-6.
- .
- ISBN 0810853957.
- ^ "Impossible Row team achieve first ever row across the Drake Passage". Guinness World Records. 2019-12-27. Retrieved 2020-03-10.
- ^ "'The Impossible Row'. Historic first row of the Southern Ocean". World Rowing. 17 January 2020.
- S2CID 19604128.
- S2CID 233576410.
- ISSN 1525-2027.
- ^ International Hydrographic Organization, Limits of Oceans and Seas, Special Publication No. 28, 3rd edition, 1953 [1] Archived 2011-10-08 at the Wayback Machine, p.4
- ^ ISSN 1099-1417.
- ISSN 1520-0485.
- S2CID 219927256.
- ^ ISSN 0022-3670.
- OSTI 1193435.
- .
- ^ S2CID 1624477.
- S2CID 4235009.
- S2CID 1681960.
- S2CID 16754887.
- S2CID 129749697.
- .
- ISBN 978-0-691-15033-8.