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Title: Argo Observations of the Deep Mixing Band in the Southern Ocean: A Salinity Modeling Challenge

Journal Article · · Journal of Geophysical Research. Oceans
DOI:https://doi.org/10.1029/2018jc014275· OSTI ID:1611902
ORCiD logo [1];  [1];  [1]
  1. National Center for Atmospheric Research (NCAR), Boulder, CO (United States)
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The Southern Ocean plays an important role in mediating oceanic uptake of CO2 and heat due to a strong meridional overturning circulation. Gridded Argo float data for 2004–2017 were used to evaluate subsurface processes at the mixed layer depth (MLD) that occur in a narrow deep mixing band. Shifts in the value of the Turner Angle at the MLD indicate that early in the season the MLD deepens slowly as it encounters and is stabilized by a subsurface salt maximum. By September mixing has penetrated this salinity feature and the rate of deepening is faster once the MLD is deeper than the depth where the maximum salinity occurs (~150–200 m). This distinctive salinity layer is the result of surface Ekman transport of fresh water from the south and subsurface advection of high-salinity water from the north. Two configurations of the Community Earth System Model (CESM) ocean-ice forced hindcast experiments—one with 1° and the other with 0.1° horizontal resolution (Parallel Ocean Program low and high resolutions [POP-LR and POP-HR], respectively)—are compared with the Argo data for 2005–2009. POP-LR has a shallow MLD bias common to many Fifth Coupled Models Intercomparison Project (CMIP5) models, while POP-HR has a mix of deep and shallow MLD biases. While both models were able to replicate the large-scale processes leading to formation of a high-salinity layer, the salinity feature in POP-HR is too strong and deep. Neither model was able to replicate the vertical mixing processes leading to penetration of the subsurface salt maximum.

Research Organization:
University Corporation for Atmospheric Research, Boulder, CO (United States)
Sponsoring Organization:
USDOE Office of Science (SC)
Grant/Contract Number:
SC0012605; FOA‐0001036
OSTI ID:
1611902
Alternate ID(s):
OSTI ID: 1479596
Journal Information:
Journal of Geophysical Research. Oceans, Vol. 123, Issue 10; ISSN 2169-9275
Publisher:
American Geophysical UnionCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 12 works
Citation information provided by
Web of Science

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Cited By (3)

Global Impacts of Subseasonal (<60 Day) Wind Variability on Ocean Surface Stress, Buoyancy Flux, and Mixed Layer Depth journal December 2019
Sustained ocean changes contributed to sudden Antarctic sea ice retreat in late 2016 journal January 2019
Max Planck Institute Earth System Model (MPI-ESM1.2) for the High-Resolution Model Intercomparison Project (HighResMIP) journal January 2019

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54 ENVIRONMENTAL SCIENCES
oceanography
Southern Ocean
mixed layer
turner angle
argo
model
salinity