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- Title
Deep Argo Reveals Bottom Water Properties and Pathways in the Australian‐Antarctic Basin.
- Authors
Foppert, Annie; Rintoul, Stephen R.; Purkey, Sarah G.; Zilberman, Nathalie; Kobayashi, Taiyo; Sallèe, Jean‐Baptiste; van Wijk, Esmee M.; Wallace, Luke O.
- Abstract
Changes in properties and quantity of Antarctic Bottom Water (AABW) have major implications for the climate system, through sequestration of heat and carbon into, and ventilation of, the abyssal ocean. Yet, it remains one of the most difficult water masses to observe. An array of 12 Deep Argo floats, capable of profiling from the surface to the seafloor and under sea ice, provides a new perspective on AABW in the Australian‐Antarctic Basin. Over 2 years of data from the floats illuminate AABW properties with unprecedented detail, simultaneously sampling AABW at multiple locations, year‐round, throughout the basin. Calibrating each float individually with nearby, quasi‐simultaneous shipboard profiles ensures the highest quality salinity data, with estimated accuracy of ±0.005 or better. Pathways of Ross Sea and Adélie Land Bottom Water (RSBW and ALBW), defined by their unique temperature and salinity characteristics, are mapped along the continental slope from their respective sources. The main pathway of RSBW, identified by its characteristic deep salinity maximum, is inferred to be inshore of the 3,700 m isobath, where it cools and freshens westward along the slope before interacting with ALBW near 140°E. A pulse of very cold and very fresh (nearly −0.6°C, 34.82 g kg−1) ALBW appears in February 2019, highlighting temporal variability on daily scales near its source. Deep Argo has greatly enhanced our view of AABW in the Australian‐Antarctic Basin and will prove to be an essential tool for monitoring future changes in the deep ocean by drastically increasing observations in a cost‐effective way. Plain Language Summary: Antarctic Bottom Water (AABW) is both a crucially important component of Earth's climate, with the capacity to store heat and carbon in the abyssal ocean for centuries, and one of the hardest water masses to monitor. New instruments have been developed to do just that. Deep Argo floats are able to take measurements of temperature and salinity from the surface to seafloor and can continue to profile safely while under winter sea ice. 12 Deep Argo floats were deployed in the Australian‐Antarctic Basin and have been continuously profiling for over two years, producing an unprecedented observational data set of AABW properties. We map out pathways of AABW from two source regions: the Ross Sea and Adélie Land. The Ross Sea Bottom Water tends to flow westward hugging the slope, but there is some leakage into the deeper ocean. Near 140°E, Adélie Land Bottom Water flows down the slope, sometimes in pulses, usually slicing under Ross Sea Bottom Water and through a narrow bathymetric saddle between a seamount and the slope. Deep Argo floats offer a window into the deep ocean, enhancing our understanding of AABW and allowing for continuous monitoring of its variability. Key Points: Deep Argo floats map Antarctic Bottom Water properties year‐round and under‐ice in the Australian‐Antarctic Basin from 2018 to 2020Floats reveal Antarctic Bottom Water (AABW) pathways in unprecedented detail and show some Ross Sea Bottom Water hugs the slope and some descends to the deep oceanPulses of Adélie Land Bottom Water descending the slope interact with Ross Sea and Bottom Water (RSBW) and drive short‐term (∼1 day) variability near 140°E
- Subjects
BOTTOM water (Oceanography); SEAWATER; OCEANOGRAPHY; ABYSSAL zone; MARINE habitats
- Publication
Journal of Geophysical Research. Oceans, 2021, Vol 126, Issue 12, p1
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2021JC017935