Third mate Amy Biddle (right) and bosun Peter Liarikos prepare to tie up to a surface mooring to ready it for ship recovery on the R/V Neil Armstrong. The mooring is part of the Global Irminger Sea Array in the NSF-funded Ocean Observatories Initiative (OOI). The OOI's global arrays provide researchers with year-round, long-term access to under-sampled waters in critical areas of the Atlantic and Pacific Oceans. (Sheri White, WHOI) [ Hide caption ]
The Global Array component of the Ocean Observatories Initiative initially included four remote, high-latitude locations, selected for scientifically strategic reasons:
WHOI physical oceanographer Bob Pickart has called the Irminger Sea “the windiest spot on the global ocean.” That makes it not only a difficult place to observe for any length of time, but also an important place to study how the air and ocean interact. The Irminger is where warm surface waters flowing north lose their heat to the atmosphere, become colder and denser, and sink to the seafloor to form the so-called North Atlantic deep water that helps drive Earth’s “global ocean conveyor” circulation system. The region is also where the Atlantic and Arctic Oceans connect. As the Arctic warms and more sea ice and glaciers thaw, the influx of more buoyant fresh water threatens to reduce deep-water formation. The Irminger Array was specifically designed to integrate with another large monitoring effort recently undertaken by institutions in the U.S., U.K., and Europe: the Overturning in the Subpolar North Atlantic Program (OSNAP).
The Argentine Basin is home to a strong, deep current that was discovered by chance only in the 1990s, but that is far from any coastline to help steer the flow. “That tells you how little we know about this part of the ocean and how much is actually going on,” said WHOI physical oceanographer Sebastien Bigorre. It is also a place where water masses meet—cold, deep water flowing south from the North Atlantic; warm, fresh water from the Southern Ocean; and extremely cold, extremely deep water from Antarctica. It is unlike almost any other ocean, but very few observations from the region exist, other than from a ship- and mooring-based program by the National Oceanic and Atmospheric Administration known as the Southern Ocean Meridional Overturning Circulation (SAMOC) Initiative and occasional releases of free-floating Argo floats. Data from the OOI Global Array augment these efforts and bolster the Southern Ocean Observing System (SOOS) made up of nearly 50 universities and institutions worldwide. (Deployments were suspended in 2017.)
Sailors don’t like to frequent the Southern Ocean, a place where they can encounter 60-knot winds and 33-foot (10-meter) waves—even in the summer. But the region is experiencing unprecedented changes with far-reaching consequences. The site for this Global Array at the edge of the Southern Ocean, chosen based partly on findings by the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES), is another key part of the Earth’s “global ocean conveyor” circulation. The region is also critical to understanding how the ocean can take up and sequester large amounts of the greenhouse gas carbon dioxide from the atmosphere. The first OOI mooring deployments in 2015 provided the first time-series data of heat and water mass movement from the region ever recorded—something of particular interest to the people of Chile as the country struggles with a persistent drought caused by changing wind and atmospheric pressure patterns over the ocean. (Deployments were suspended in 2017.)
Station P or Papa in the Northeast Pacific is a Global Array with a history. The site has been occupied continuously since 1949, first by a meteorological ship keeping station at the site and, beginning in the early 1980s, by a surface mooring operated by the NOAA Pacific Marine Environmental Lab. In addition, the Canadian government has sponsored cruises to collect data and samples three times per year along Line P, which stretches from Station Papa to Victoria, British Columbia, since 1981. The long history and thorough understanding of Station Papa make it a popular location for process studies, where multiple platforms are engaged in intensive multidisciplinary studies for a period of weeks to months to improve understanding of critical phenomena such as ocean acidification. “It’s a widely studied area with a long data set,” said OOI Program Manager Greg Ulses. “It was an easy one to pick.”