A Lagrangian mixed layer model of Atlantic 18 C water formation

• Published in: Nature
• Main Authors: Woods, J. D., Barkmann, Wolfgang
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group 1986
• Subjects: North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/14793/; https://oceanrep.geomar.de/id/eprint/14793/1/Woods.pdf; https://doi.org/10.1038/319574a0

One of the most striking features of the upper North Atlantic Ocean is an extensive layer of water with temperature close to 18°C and salinity close to 36.5‰, (ref. 1). This 18°C water is formed by winter convection in the Sargasso sea2,3, but aspects of the annual rate of 18°C water formation remain obscure4. We have simulated this water mass formation by integrating a one-dimensional model along a 4-yr trajectory of a water column circulating around the Sargasso Sea. Winter convection is deep (≥200 m) in regions where the ocean suffers a net annual heat loss to the atmosphere, and shallow (≤lOOm) where the ocean gains heat each year. The origin of the thermostad (nearly isothermal layer) is a thick layer of nearly homogeneous water subducted beneath the seasonal boundary layer in the year that the water column passes through the line dividing annual cooling from annual heating. We estimate the annual production of 18°C water to be 446,000 km3 yr−1. Downstream, more stratified central water is formed each year at a rate that depends more on Ekman pumping (wind-forced convergence) than on the decreasing depth of winter convection