Journal
JOURNAL OF MARINE SYSTEMS
Volume 187, Issue -, Pages 250-259Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jmarsys.2018.08.002
Keywords
Antarctica; Ross Sea [755-780 degrees S, 162-167 degrees E]; CTD profilers; Sea ice; Ice thickness; Weddell seals; Salinity correction
Funding
- University of Otago
- NIWA
- Deep South National Challenge
- University of Alaska Anchorage
- National Science Foundation (NSF) Office of Polar Programs [ANT-0838892]
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The high-latitude oceans surrounding Antarctica are substantially undersampled compared to lower latitudes. Mammal based instruments such as Conductivity-Temperature-Depth Satellite Relay Data Loggers (CTD-SRDLs) present one possible solution. Unfortunately, these are subject to instrument-dependent offsets in absolute salinity. This study investigates a set of satellite-transmitted data collected by CTD-SRDLs mounted on Weddell seals (Leptonychotes weddellii) in the South-western Ross Sea in 2011. The uncorrected salinity offset between devices was found to be up to 1.4 g kg(-1), making the data unsuitable for some oceanographic studies without correction. Here, a correction method was developed that uses profiles from pairs of CTD-SRDLs that are considered to be co-located and to sample the same body of water if they occur within defined time and space windows. Using least squares, a best-fit solution to the matrix of offsets in co-located pairs was found that reduces salinity offsets between the CTD-SRDLs. These offsets are smaller than the original offsets by a factor of 10. A calibrated reference instrument, that was co-located with some of the devices, provided further improvement in the absolute accuracy of all the CTD-SRDLs. Using the corrected CTD-SRDL data we estimate the rejection of salt into the water column by sea ice formation, and derived the time evolution of sea ice thickness in the South-western Ross Sea. Our estimates of regional sea ice thickness are in agreement with direct sea ice thickness measurements taken over a limited area in November 2011, providing further affirmation of our method.
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