Glider Observations of the Northwestern Iberian Margin During an Exceptional Summer Upwelling Season. Issue 8 (5th August 2020)

• Record Type: Journal Article
• Authors: Rollo, Callum; Heywood, Karen J.; Hall, Rob A.; Barton, Eric Desmond; Kaiser, Jan
• Is Part Of: Journal of geophysical research. Volume 125:Issue 8(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-08-05
• Subjects: Glider -- Upwelling -- EBUS; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2019JC015804
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: Glider observations from the Northwestern Iberian Margin during the exceptionally strong 2010 summer upwelling season resolved the evolution of physical and biogeochemical variables during two upwelling events. Upwelling brought low‐oxygen Eastern North Atlantic Central Water from 190 m depth onto the shelf up to a depth of 50 m. During the two observed periods of upwelling, a poleward jet developed over the shelf break. The persistent upwelling favorable winds maintained equatorward flow on the outer shelf for 2 months with no reversals during relaxation periods, a phenomenon not previously observed. During upwelling, near‐surface chlorophyll a concentration increased by more than 6 mg m −3 . Oxygen supersaturation in the near surface increased by more than 20%, 6 days after the chlorophyll a maximum. Plain Language Summary: In summer 2010, an autonomous underwater vehicle was used to measure changing water properties in the ocean offshore of Vigo, NW Spain. During summer, winds blowing southward along the Iberian coast push surface waters offshore, causing deep, cold, nutrient‐rich water to rise to the surface. The nutrients brought up with this cold water enable growth of phytoplankton, impacting higher trophic levels and local fisheries. During June and July 2010 we observed two episodes of deep water rising and the subsequent increases in phytoplankton. Increases in dissolved oxygen concentration and ocean current speed were also observed. Using a robotic underwater glider allowed us to obtain high‐resolution observations over a longer time period at a fraction of the cost of a research vessel cruise. Key Points: A glider observed two upwelling events during a 70 day deployment over the Northwestern Iberian Margin in summer 2010 During upwelling decreasing temperature and increasing chlorophyll a concentration lead increasing dissolved oxygen concentration by 6 days Equatorward flow persisted over the shelf and upper slope throughout the deployment