Three decades of deep water mass investigation in the Weddell Sea (1984–2014): Temporal variability and changes

• Published in: Deep Sea Research Part II: Topical Studies in Oceanography
• Main Authors: Kerr, Rodrigo, Dotto, Tiago S., Mata, Mauricio M., Hellmer, Hartmut H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2018
• Subjects: Antarctic; Indian; Southern Ocean; Weddell; Weddell Sea; Antarc*; Ice Shelf
• Online Access: https://oceanrep.geomar.de/id/eprint/44892/; https://oceanrep.geomar.de/id/eprint/44892/1/Kerr.pdf; https://doi.org/10.1016/j.dsr2.2017.12.002

Highlights • Shifts in WSBW properties to less dense varieties likely equate to less formation of WSBW. • The decline of WSBW volume ceased around 2005 and likely recovering after that. • Dense Shelf Waters drive and modulate the recent WSBW variability. • WSBW is composed by 71% of mWDW and 29% of Dense Shelf Waters. Abstract The role of Antarctic Bottom Water (AABW) in changing the ocean circulation and controlling climate variability is widely known. However, a comprehensive understanding of the relative contribution and variability of Antarctic regional deep water mass varieties that form AABW is still lacking. Using a high-quality dataset comprising three decades of observational shipboard surveys in the Weddell Sea (1984–2014), we updated the structure, composition and hydrographic properties variability of the Weddell Sea deep-layer, and quantified the contribution of the source waters composing Weddell Sea Bottom Water (WSBW) in its main formation zone. Shifts in WSBW hydrographic properties towards less dense varieties likely equate to less WSBW being produced over time. WSBW is primarily composed of 71 ± 4% of modified-Warm Deep Water (mWDW) and 29 ± 4% of Dense Shelf Waters, with the latter composed by ~ two-thirds (19 ± 2%) of High Salinity Shelf Water and ~ one-third (10 ± 6%) of Ice Shelf Water. Further, we show evidence that WSBW variability in the eastern Weddell Sea is driven by changes in the inflow of Dense Shelf Waters and bottom water from the Indian Sector of the Southern Ocean. This was observed through the rise of the WSBW contribution to the total mixture after 2005, following a twenty-year period (1984–2004) of decreasing contribution.