Lagrangian perspective on the origins of Denmark Strait Overflow

• Published in: Journal of Physical Oceanography
• Main Authors: Saberi, Atousa, Haine, Thomas W. N., Gelderloos, Renske, de Jong, Marieke Femke, Furey, Heather H., Bower, Amy S.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Meteorological Society 2020
• Subjects: Abyssal circulation; Bottom currents; Lagrangian circulation/transport; Meridional overturning circulation; Greenland; Denmark Strait; East Greenland; east greenland current; Iceland; NADW; North Atlantic Deep Water; North Atlantic
• Online Access: https://hdl.handle.net/1912/26690

Author Posting. © American Meteorological Society, 2020. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 50(8), (2020): 2393-2414, doi:10.1175/JPO-D-19-0210.1. The Denmark Strait Overflow (DSO) is an important contributor to the lower limb of the Atlantic meridional overturning circulation (AMOC). Determining DSO formation and its pathways is not only important for local oceanography but also critical to estimating the state and variability of the AMOC. Despite prior attempts to understand the DSO sources, its upstream pathways and circulation remain uncertain due to short-term (3–5 days) variability. This makes it challenging to study the DSO from observations. Given this complexity, this study maps the upstream pathways and along-pathway changes in its water properties, using Lagrangian backtracking of the DSO sources in a realistic numerical ocean simulation. The Lagrangian pathways confirm that several branches contribute to the DSO from the north such as the East Greenland Current (EGC), the separated EGC (sEGC), and the North Icelandic Jet (NIJ). Moreover, the model results reveal additional pathways from south of Iceland, which supplied over 16% of the DSO annually and over 25% of the DSO during winter of 2008, when the NAO index was positive. The southern contribution is about 34% by the end of March. The southern pathways mark a more direct route from the near-surface subpolar North Atlantic to the North Atlantic Deep Water (NADW), and needs to be explored further, with in situ observations. This work was financially supported by the U.S. National Science Foundation under Grant Numbers OAC-1835640, OCE-1633124, OCE-1433448, and OCE-1259210.