The Role of the Irminger Current in the Irminger Sea Northward Transport Variability. Issue 3 (23rd February 2022)

• Record Type: Journal Article
• Authors: Fried, Nora; de Jong, M. Femke
• Is Part Of: Journal of geophysical research. Volume 127:Issue 3(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-23
• Subjects: AMOC -- Irminger Current -- Irminger Sea -- convection -- OSNAP; Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2021JC018188
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: The Irminger Current (IC) on the western flank of the Reykjanes Ridge is an important contributor to the northward transport in the Atlantic Meridional Overturning Circulation. Here, we combine 28 years of Copernicus Marine Environment Monitoring Service (CMEMS) ocean reanalysis data with 6 years of mooring data to investigate variability in volume transport of the IC. We found a mean volume transport for the IC of 11.6 Sv between 1993 and 2020 revealing the dominance of the IC in the total Irminger Sea northward volume transport (20.3 Sv). We found a significant decrease (−3.7 Sv) in volume transport of the IC until 2011 followed by a steeper (but shorter, leading to +2.7 Sv) increase until 2020. These changes across the Irminger Sea section are dominated by the IC, which in turn are driven by changes in the density gradient across the Irminger Sea related to convection. On decadal and interannual time scales the IC volume transport is well correlated with the decrease in the sea surface height difference over the basin. In 2019, a temporary intensification of the western IC core led to an exceptionally strong volume transport of the IC with 20 Sv. This was caused by density changes within the IC boundaries due to the presence of mesoscale eddies. Thus, IC transport variability is a superposition of basin‐wide to local processes that influence the velocity field on different time scales. Plain Language Summary: The Irminger Current (IC) transports relatively warm and saline water northwards along the Mid Atlantic Ridge toward Iceland, where one part continues further north and the rest turns around to flow south along Greenland. We investigate changes in the IC's northward transport using a combination of direct observations from moorings and a longer reanalysis time series. We found that the IC is dominating the northward volume transport in the eastern Irminger Sea. The IC is also driving the long‐term decrease in the total northward volume transport. Its intensity depends on changes in the basin‐wide density gradient between sea surface height (SSH) minimum in the convection area of the central Irminger Sea and the SSH maximum on top of the Mid Atlantic Ridge. This study shows that the high variability in transport can be explained by a combination of processes acting on different time scales. Changes in the IC and the central Irminger Sea are crucial to help us monitor changes in the overturning of the eastern subpolar North Atlantic. Key Points: The Irminger Current (IC) is a major contributor to the northward volume transport in the Irminger Sea The IC's volume transport decreased from 1993 to 2011 followed by an increase from 2012 to 2020 Basin‐wide to local changes in the density field contribute to transport variability at different time scales