A competition for the North Pole heated up last month, as Canada became the third country to claim—based on extensive scientific data—that it should have sovereignty over a large swath of the Arctic Ocean, including the pole. Canada's bid, submitted to the United Nations's Commission on the Limits of the Continental Shelf (CLCS) on 23 May, joins competing claims from Russia and Denmark. Like theirs, it is motivated by the prospect of mineral riches: the large oil reserves believed to lie under the Arctic Ocean, which will become more accessible as the polar ice retreats. And all three claims, along with dozens of similar claims in other oceans, rest on extensive seafloor mapping, which has proved to be a boon to science, whatever the outcome for individual countries. The race to obtain control over parts of the sea floor has "dramatically changed our understanding of the oceans," says marine geophysicist Larry Mayer of the University of New Hampshire in Durham.
Coastal nations have sovereign rights over an exclusive economic zone (EEZ), extending by definition 200 nautical miles (370 kilometers) out from their coastline. But the 1982 United Nations Convention on the Law of the Sea opened up the possibility of expanding that zone if a country can convince CLCS that its continental shelf extends beyond the EEZ's limits.
Most of the 84 submissions so far were driven by the prospect of oil and gas, although advances in deep-sea mining technology have added new reasons to apply. Brazil, for example, filed an application in December 2018 that included the Rio Grande Rise, a deep-ocean mountain range 1500 kilometers southeast of Rio De Janeiro that's covered in cobalt-rich ferromanganese crusts.
To make a claim, a country has to submit detailed data on the shape of the sea floor and on its sediment, which is thicker on the shelf than in the deep ocean. The data come from sonar, which reveals seafloor topography, and seismic profiling, which uses low-frequency booms to probe the sediment. Canada's bid also enlisted ships to conduct high-resolution gravimetry—measurements of gravity anomalies that reveal seafloor structure. Elevated gravity readings are found over higher-density mantle rocks found in oceanic crust, and lower readings over lighter, continental structures. And the bid used analyses of 800 kilograms of rock samples dredged up from the sea floor, whose composition can distinguish continental from ocean crust.
The studies don't come cheap; Canada's 17 Arctic expeditions alone cost more than CA$117 million. But the work by the three countries vying for the Arctic—and that of dozens of others elsewhere in the world—has been a bonanza for oceanography. In the Arctic alone, the mapping has revealed several sunken mountains, previously missed or undetected by older sonar methods. Hundreds of pockmarks found on the Chukchi Cap, a submarine plateau extending out from Alaska, suggest that bursts of previously frozen methane have erupted from the seabed, a phenomenon that could accelerate climate change. And gaps discovered across submarine ridges allow currents to flow from basin to basin, with "important ramifications on the distribution of heat in the Arctic and on overall modeling of climate and ice melting," Mayer says.