Subantarctic
Subantarctic region: islands and waters north of the Antarctic Convergence.
The subantarctic region is a physiographic zone in the Southern Hemisphere, located immediately north of the Antarctic region, roughly between 46° and 60° south latitude. It comprises two geographic zones—the Subantarctic Zone (SAZ) and the Polar Frontal Zone (PFZ)—and is bounded to the north by the Subtropical Front and to the south by the Antarctic Convergence. The region includes numerous islands in the southern Atlantic, Indian, and Pacific oceans, and its glaciers are defined as those on islands within this zone, distinct from Antarctic glaciers on the continent. The northern boundary, the Subtropical Front, is ill-defined, while the southern border is marked by the Antarctic Convergence, which lies about 200 kilometers south of the Antarctic Polar Front. The Subantarctic Front, which defines the northern limit of the Antarctic Circumpolar Current (ACC), is found between 48°S and 58°S in the Indian and Pacific Oceans and between 42°S and 48°S in the Atlantic. The ACC is the only current to flow completely around the Earth, linking the southern Atlantic, Indian, and Pacific basins, and transports up to 150 Sverdrups—150 times the flow of all the world’s rivers. This current, along with global thermohaline circulation, strongly influences regional and global climate and underwater biodiversity. A lesser factor is the formation of Antarctic Bottom Water through halothermal dynamics, driven by density gradients from surface heat and evaporation. Politically, the Antarctic Treaty defines Antarctica as all land and ice shelves south of 60°S latitude, but scientifically, the Antarctic Convergence marks the boundary due to the convergence of water masses like Subantarctic Mode Water and Antarctic Surface Water, creating a zone of high marine productivity, particularly for Antarctic krill. Subantarctic islands include the Crozet, Prince Edward, Kerguelen, and Auckland Islands in the Roaring Forties, characterized by tundra and some trees. Further south, in the Furious Fifties, lie the Falkland Islands, Tierra del Fuego-associated islands, and the South Georgia Group, with the former featuring trees and arable land, while the latter exhibit tundra, permafrost, and volcanoes.
- Location
- Southern Hemisphere, 46°–60° south latitude
- Northern boundary
- Subtropical Front (STF)
- Southern boundary
- Antarctic Convergence
- Key ocean current
- Antarctic Circumpolar Current (ACC)
- Major water masses
- Subantarctic Mode Water (SAMW), Antarctic Intermediate Water (AAIW)
- Political limit
- 60° south latitude (Antarctic Treaty)
Lore & Background
The subantarctic region is a physiographic zone in the Southern Hemisphere, located immediately north of the Antarctic region, roughly between 46° and 60° south latitude. It includes numerous islands in the southern Atlantic, Indian, and Pacific oceans, particularly those north of the Antarctic Convergence. The region comprises two geographic zones and three distinct fronts. Its northern boundary is the ill-defined Subtropical Front, south of which lies the Subantarctic Zone. Further south is the Subantarctic Front, followed by the Polar Frontal Zone; together, the Subantarctic Zone and Polar Frontal Zone form the subantarctic region. The southern border is the Antarctic Convergence, located about 200 kilometers south of the Antarctic Polar Front. The Subantarctic Front, found between 48°S and 58°S in the Indian and Pacific oceans and between 42°S and 48°S in the Atlantic, defines the northern boundary of the Antarctic Circumpolar Current. This current flows eastward, linking the southern Atlantic, Indian, and Pacific basins, and extends from the sea surface to depths of 2000–4000 meters, with a width up to 2000 kilometers. Subantarctic glaciers are defined as those on islands within the region, distinct from Antarctic glaciers on the continent.
Reader's Guide
The subantarctic region holds significance for its role in global climate and ocean circulation. The ACC and thermohaline circulation strongly influence regional and global climate and underwater biodiversity. The Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) act as a carbon sink, absorbing atmospheric carbon dioxide. The region also hosts unique flora and fauna, with many endemic genera and species, and its islands feature tundra, permafrost, volcanoes, and retreating glaciers. The political definition of Antarctica under the Antarctic Treaty (south of 60°S) differs from the biological and hydrological definition (south of the Antarctic Convergence), creating a zone of subantarctic islands that are north of 60°S but may lie south of the Convergence.
Did You Know?
- The subantarctic region includes islands such as the Crozet Islands, Kerguelen Islands, and South Georgia Group, all north of 60°S latitude.
- The Subantarctic Mode Water and Antarctic Intermediate Water together act as a carbon sink, absorbing atmospheric carbon dioxide.
Frequently Asked Questions
What is the Subantarctic?
The Subantarctic is a physiographic zone in the Southern Hemisphere that sits just north of the Antarctic region, spanning roughly between 46° and 60° south latitude. It is divided into two sub-zones—the Subantarctic Zone and the Polar Frontal Zone—and encompasses a scattered archipelago of islands across the southern Atlantic, Indian, and Pacific oceans.
What are the exact boundaries of the Subantarctic?
To the north, the region is delimited by the Subtropical Front, while the Antarctic Convergence marks its southern edge. The Antarctic Circumpolar Current is the dominant ocean current threading through the zone, and the key water masses found here are Subantarctic Mode Water and Antarctic Intermediate Water.
How is the Subantarctic different from Antarctica itself?
The Subantarctic consists of island groups and surrounding ocean waters north of the Antarctic Convergence, whereas Antarctica refers to the continental landmass and its associated ice. Glaciers on Subantarctic islands are classified separately from the continent's glaciers, even though both sit at high southern latitudes.
Why does the 60° south latitude line matter politically?
The 60° south parallel serves as the outer boundary recognized under the Antarctic Treaty, which governs claims and activity on the Antarctic continent. The Subantarctic islands, falling north of that line, are therefore subject to the sovereignty and jurisdiction of individual nations rather than the treaty's special regime.
What makes the Subantarctic's climate and ecology distinct?
Sitting in a transitional band between subtropical and polar waters, the region experiences cool, wet, and highly variable conditions shaped by the constant passage of the Antarctic Circumpolar Current. This creates a unique island ecosystem that is neither truly tropical nor fully polar, supporting specialized flora and fauna found nowhere else.
More in Physical Geography & Elevation 1-24
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record