Clipperton Island

Clipperton Island, also known historically as Clipperton Atoll or Clipperton’s Rock, is an uninhabited French coral atoll situated in the eastern Pacific Ocean. It is the only French possession in the North Pacific and is frequently visited for scientific and environmental research. Although geographically closer to Mexico and Central America, the island is politically administered as an overseas territory of France.

Historical Background

Clipperton Island was first recorded by French merchant explorers in 1711 and formally incorporated into the French protectorate of the Kingdom of Tahiti in 1858. Despite this, American companies began extracting guano from the atoll in the late nineteenth century, prompting Mexican interest in the island. Based on Spanish navigational accounts from the 1520s, Mexico asserted that the island had been previously sighted and subsequently claimed.
In 1905 Mexico established a small military colony, but disruption during the Mexican Revolution resulted in reduced communication with the mainland. Most of the colonists died from starvation or disease, and the island descended into lawlessness under lighthouse keeper Victoriano Álvarez, who declared himself ruler. In 1917 the remaining eleven survivors, mostly women and children, were rescued and the outpost was abandoned.
The competing claims of France and Mexico were submitted to arbitration in 1909. Victor Emmanuel III of Italy was appointed as arbitrator, and the decision upheld France’s sovereignty. The island remained uninhabited until 1944 when the United States Navy set up a temporary weather station during the Second World War. France lodged official protests, and the station was dismantled in 1945 as military activities in the eastern Pacific declined. Since then, Clipperton has seldom been occupied permanently, though it has been periodically used for scientific study, environmental monitoring and amateur radio expeditions.

Physical Geography

Clipperton Island lies in the eastern Pacific Ocean southwest of Mexico, west of Central America and northwest of the Galápagos Islands. Its nearest landmass is Socorro Island in the Revillagigedo archipelago to the northwest. Although close to the American continent, Clipperton is often counted among the easternmost islands of Oceania due to its administrative links to the French Indo-Pacific and biogeographical similarities with the central Pacific islands.
The island is the only part of the East Pacific Rise to break the ocean’s surface and the only above-water feature of the Clipperton Fracture Zone. The exposed land consists of a circular ring of coral surrounding a central lagoon, with a small volcanic outcrop, Clipperton Rock, rising above the otherwise low-lying terrain. Sparse vegetation, mainly grasses and scattered coconut palms, covers parts of the land ring. Coral reefs fringe the island, forming a barrier that is difficult for ships to navigate and making landing hazardous, especially during unfavourable weather.
In 2001 a geodetic marker was installed to monitor potential subsidence or uplift of the island’s surface, reflecting ongoing interest in the region’s geological behaviour.

Environment and Scientific Research

Clipperton is valued for its largely undisturbed ecosystems. The island supports large seabird colonies, particularly masked and brown boobies, and serves as a research site for marine biologists, climatologists and ecologists.
Scientific expeditions began in the nineteenth century and have continued intermittently. Notable missions include:

• The SURPACLIP expedition (1997), organised by the National Autonomous University of Mexico and the University of New Caledonia, which gathered extensive oceanographic and ecological data.
• The Passion 2001 mission, led by French geographer Christian Jost, which examined environmental change on the atoll.
• A National Geographic venture in 2003, during which a cinematographer lived on the island for over a month to document conditions and produce a detailed GPS survey.
• A 2005 French scientific mission led by Jean-Louis Étienne, which catalogued the island’s species, examined marine pollution and studied deep-water algae.
• A 2008 research expedition from the University of Washington that sampled sediment from the lagoon to investigate long-term climate variability.

Clipperton’s isolation and limited human impact make it an important natural laboratory for studying migratory wildlife patterns in the Eastern Tropical Pacific, including species whose ranges overlap with Hawaii and the Line Islands.

Lagoon and Marine System

The atoll completely encloses a lagoon that measures several kilometres in circumference. As the only coral lagoon of its kind in the eastern Pacific, it provides a unique hydrographic environment. The lagoon is shallow across much of its extent but contains deeper basins, including one referred to as the “bottomless hole,” which contains highly acidic water.
The lagoon became cut off from the sea roughly 170 years ago, forming a meromictic lake. Its upper layer is brackish and oxygenated, while deeper layers are saline, anoxic and rich in hydrogen sulfide. These conditions inhibit coral growth and create sharp stratification in the water column. Fossilised coral and clams indicate that marine fauna once thrived when the lagoon was still connected to the ocean.
Phytoplankton blooms occur seasonally, and the island’s deeper waters contain diverse microbial communities, including bacteria and archaea adapted to the chemically distinct layers. In 2005 scientists identified three species of dinoflagellates within the lagoon, one of which is unique to Clipperton. Millions of isopods inhabit the lagoon, and their stings are noted by visitors.
Although often classified as unsuitable for consumption, testimonies from shipwreck survivors and stranded fishing crews indicate that the lagoon water, while unpleasant in taste, has been used in emergencies for drinking. American personnel stationed on the island during the Second World War relied on desalination systems, and rainwater collection remains the only reliable source of fresh water.

Climate and Weather Patterns

Clipperton Island experiences a tropical oceanic climate with consistently warm temperatures and very high humidity. Average temperatures remain in the mid-20s Celsius, with peaks reaching above 30°C. Annual rainfall is substantial, with a wetter season extending from May to October and a drier period between December and March. Southeast trade winds dominate, contributing to the island’s relatively stable weather patterns.
The region is subject to tropical cyclones from April to September. While many storms pass to the northeast, the island has occasionally been impacted by significant systems, including Hurricane Felicia in 1997 and Hurricane Sandra in 2015. Several tropical storms have also grazed the atoll, shaping its coastal features and contributing to erosion.