Wind-driven upwelling of iron sustains dense blooms and food webs in the eastern Weddell Gyre
Sébastien Moreau, Tore Hattermann, Laura de Steur, Hanna M. Kauko, Heidi Ahonen, Murat V. Ardelan, Philipp Assmy, Melissa Chierici, Sébastien Descamps, Tilman Dinter, Tone Falkenhaug, Agneta Fransson, Eirik Grønningsæter, Elvar H. Hallfredsson, Oliver Huhn, Anaïs Lebrun, Andrew Lowther, Nico Lübcker, Pedro M. S. Monteiro, Ilka Peeken, Alakendra N. Roychoudhury, Magdalena Różańska, Thomas Ryan‐Keogh, Nicolás Sánchez, Asmita Singh, Jan Henrik Simonsen, Nadine Steiger, Sandy Thomalla, André van Tonder, Józef Wiktor, Harald Steen
Abstract
Abstract The Southern Ocean is a major sink of anthropogenic CO 2 and an important foraging area for top trophic level consumers. However, iron limitation sets an upper limit to primary productivity. Here we report on a considerably dense late summer phytoplankton bloom spanning 9000 km 2 in the open ocean of the eastern Weddell Gyre. Over its 2.5 months duration, the bloom accumulated up to 20 g C m −2 of organic matter, which is unusually high for Southern Ocean open waters. We show that, over 1997–2019, this open ocean bloom was likely driven by anomalies in easterly winds that push sea ice southwards and favor the upwelling of Warm Deep Water enriched in hydrothermal iron and, possibly, other iron sources. This recurring open ocean bloom likely facilitates enhanced carbon export and sustains high standing stocks of Antarctic krill, supporting feeding hot spots for marine birds and baleen whales.