Arctic Mediterranean exchanges: a consistent volume budget and trends in transports from two decades of observations

• Published in: Ocean Science
• Main Authors: S. Østerhus, R. Woodgate, H. Valdimarsson, B. Turrell, L. de Steur, D. Quadfasel, S. M. Olsen, M. Moritz, C. M. Lee, K. M. H. Larsen, S. Jónsson, C. Johnson, K. Jochumsen, B. Hansen, B. Curry, S. Cunningham, B. Berx
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2019
• Subjects: geo; envir; Arctic; Arctic Ocean; Bering Strait; Faroe Bank; Greenland; Pacific; Denmark Strait; Greenland-Scotland Ridge; Nordic Seas
• Online Access: https://doi.org/10.5194/os-15-379-2019; https://www.ocean-sci.net/15/379/2019/os-15-379-2019.pdf; https://doaj.org/article/69cd8ba8071d4d8aa4796fb19a849ab7

The Arctic Mediterranean (AM) is the collective name for the Arctic Ocean, the Nordic Seas, and their adjacent shelf seas. Water enters into this region through the Bering Strait (Pacific inflow) and through the passages across the Greenland–Scotland Ridge (Atlantic inflow) and is modified within the AM. The modified waters leave the AM in several flow branches which are grouped into two different categories: (1) overflow of dense water through the deep passages across the Greenland–Scotland Ridge, and (2) outflow of light water – here termed surface outflow – on both sides of Greenland. These exchanges transport heat and salt into and out of the AM and are important for conditions in the AM. They are also part of the global ocean circulation and climate system. Attempts to quantify the transports by various methods have been made for many years, but only recently the observational coverage has become sufficiently complete to allow an integrated assessment of the AM exchanges based solely on observations. In this study, we focus on the transport of water and have collected data on volume transport for as many AM-exchange branches as possible between 1993 and 2015. The total AM import (oceanic inflows plus freshwater) is found to be 9.1 Sv (sverdrup, 1 Sv =106 m3 s−1) with an estimated uncertainty of 0.7 Sv and has the amplitude of the seasonal variation close to 1 Sv and maximum import in October. Roughly one-third of the imported water leaves the AM as surface outflow with the remaining two-thirds leaving as overflow. The overflow water is mainly produced from modified Atlantic inflow and around 70 % of the total Atlantic inflow is converted into overflow, indicating a strong coupling between these two exchanges. The surface outflow is fed from the Pacific inflow and freshwater (runoff and precipitation), but is still approximately two-thirds of modified Atlantic water. For the inflow branches and the two main overflow branches (Denmark Strait and Faroe Bank Channel), systematic monitoring of volume transport ...