Industrial-Era Decline in Subarctic Atlantic Productivity

• Published in: Nature (London) 2019-05, Vol.569 (7757), p.551-555
• Main Authors: Osman, Matthew B, Das, Sarah B, Trusel, Luke D, Evans, Matthew J, Fischer, Hubertus, Grieman, Mackenzie M, Kipfstuhl, Sepp, McConnell, Joseph R, Saltzman, Eric S
• Format: Article
• Language: English
• Subjects: 21st century; 704/106/125; 704/106/413; 704/106/694; 704/158/2446/2447; Aerosols; Animals; Aquatic Organisms - metabolism; Arctic Regions; Atlantic Meridional Overturning Circulation (AMOC); Atlantic Ocean; Atmosphere - chemistry; Atmospheric carbon dioxide; Carbon; Carbon dioxide; Carbon dioxide atmospheric concentrations; Collapse; Cores; Drawdown; Environmental aspects; Fisheries; Food Chain; Food chains; Food webs; Global Warming; Greenland; History, 18th Century; History, 19th Century; History, 20th Century; History, 21st Century; Humanities and Social Sciences; Ice cores; Letter; Methanesulfonic acid; multidisciplinary; Net Primary Productivity; Observations; Ocean basins; Oceanography; Oceans; Phytoplankton; Phytoplankton - metabolism; Plankton; Principal components analysis; Production management; Productivity; Proxy; Satellite monitoring; Satellite observation; Science; Science (multidisciplinary); Sea surface temperature; Seawater - analysis; Surface temperature; Thermohaline circulation; Water Movements
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-019-1181-8

Marine phytoplankton play a critical role in modulating marine-based food webs, fishery yields, and the global drawdown of atmospheric CO2. Due to sparse measurements prior to 21st century satellite monitoring, however, little is known of the long-term response of planktonic stocks to climate forcing. Here we produce the first continuous, multi-century record of subarctic Atlantic marine productivity, showing a marked 10 ± 7% decline has occurred across this highly-productive ocean basin over the last two centuries. We support this conclusion through the application of a novel marine-productivity proxy, established using a unique signal of planktonic-derived aerosol commonly identified across an array of Greenlandic ice cores. Utilizing contemporaneous satellite-era observations, we demonstrate this signal’s use as a robust and high-resolution proxy for spatially-integrated marine productivity variations. We show that the initiation of declining subarctic Atlantic productivity broadly coincides with the onset of Arctic surface warming, and that productivity strongly covaries with regional sea-surface temperatures and basin-wide gyre circulation strength over recent decades. Taken together, our results suggest the industrial era productivity decline may be evidence of the predicted5 collapse of northern Atlantic planktonic stocks in response to a weakened Atlantic Meridional Overturning Circulation (AMOC). Continued AMOC weakening, as projected for the 21st century, may therefore result in further productivity declines across this globally-relevant region.