DOI: 10.6075/j08s4nf2
title: CLIvar and MOde water Dynamics Experiment (CLIMODE) and Antarctic Intermediate Water (AAIW) Float Data Archive

description: Summary: Profiling float data, equivalent to Argo profiling floats, were collected as part of the NSF-funded CLIMODE experiment in the western North Atlantic's Eighteen Degree Water region, and in the southeast Pacific as part of an NSF-funded experiment to study the origins of Antarctic Intermediate Water. The 9 floats in the Atlantic and 3 floats in the Pacific were Webb ApexSBE floats built and configured by Webb Research, with Systeme Argos data sets decoded and provided by the U. Washington Argo lab (Swift, Riser). Each float carried core Argo sensors: pressure, temperature, salinity. Each float also had an Aanderaa Optode oxygen sensor. The floats were parked at 500 m depth and alternately profiled from 500 dbar and 1800 dbar to the surface every 5 days, which differs from Argo floats with 1000 m parking depth and 10 day frequency. (1) CLIMODE floats: The 9 CLIMODE floats were deployed during the first CLIMODE hydrographic cruise on the RV Oceanus, cruise OC419, in November, 2005. The archived data set includes the uncalibrated raw data, and data calibrated by S. Billheimer in 2011/2012 following Argo protocols for P, T, S and using an oxygen dependent correction based on nearly coincidental shipboard Winkler oxygen profiles for the oxygen data. Calibration is described in Billheimer et al. (GBC, submitted). The hydrographic survey data from the November, 2005 cruise and the 4 subsequent CLIMODE cruises are archived at the CCHDO (CLIVAR and Carbon Hydrographic Data Office) (https://cchdo.ucsd.edu, search for CLIMODE). CLIMODE - CLIvar MOde Water Dynamic Experiment. CLIMODE was a Process Study under US CLIVAR. The process study is briefly described on the US CLIVAR website https://usclivar.org/resources/process-studies. The objective was to study the formation, destruction and dynamics of 'Eighteen Degree Water' (EDW), the subtropical mode water of the North Atlantic. This project stemmed from two years of CLIVAR planning (with advice and support of both the Atlantic and US CLIVAR committees) to develop an experiment to attack a key process that was poorly understood and poorly represented in ocean climate models - i.e. the treatment of convection, eddy and mixing processes in setting properties of subtropical mode waters, the associated air-sea interaction, and the exchange of fluid between the mixed layer and the upper ocean. This profiling float component of CLIMODE was supported by the National Science Foundation Ocean Sciences Division under Grants No. 0424893 and 0960928. The principal investigator for this component of CLIMODE was Lynne D. Talley (Scripps Institution of Oceanography, UCSD). The lead principal investigator for CLIMODE was Terrence Joyce (Woods Hole Institution of Oceanography). Publications using these data: Billheimer, S., 2016. Annual and interannual evolution of Eighteen Degree Water and oxygen in the western North Atlantic. UC San Diego. ProQuest ID: Billheimer_ucsd_0033D_16065. Merritt ID: ark:/13030/m5j14r60. Retrieved from https://escholarship.org/uc/item/7fg7z021 Billheimer, S. and L. D. Talley, 2016. Annual cycle and destruction of eighteen degree water. J. Geophys. Res. Oceans,121, 14 pp., DOI: 10.1002/2016JC011799 Billheimer, S., L. D. Talley and T. R. Martz, 2021. Oxygen seasonality, utilization rate and impacts of vertical mixing in the Eighteen Degree Water region of the Sargasso Sea as observed by profiling biogeochemical floats. Global Biogeochemical Cycles, 35, e2020GB006824, https://doi.org/10.1029/2020GB006824 (2) AAIW ‘SAMFLOC’ floats: The 3 floats in the southeast Pacific were deployed in February, 2006, from the second of the two AAIW hydrographic survey cruises on the RV Knorr (Bernadette Sloyan, chief scientist). Configuration and operation of the AAIW floats was identical to that of the CLIMODE floats. The hydrographic survey data from the Jan-March, 2006 cruise and the prior Aug-Oct 2005 hydrographic cruise are archived at the CCHDO (CLIVAR and Carbon Hydrographic Data Office) (https://cchdo.ucsd.edu, search for AAIW). SAMFLOC (SubAntarctic Mixed layers, Fluxes and Overturning Circulation) was an international CLIVAR project to study formation of Subantarctic Mode Water and Antarctic Intermediate Water in the southeast Pacific, primarily through an austral winter 2005 hydrographic survey and following austral summer 2006 hydrographic survey. AAIW is a low salinity water mass that fills most of the southern hemisphere and the tropical oceans at about 800 to 1000 m depth. As the densest of the circumpolar Subantarctic Mode Waters (SAMW), the salinity minimum that lies at the top of the AAIW layer is formed as a thick, outcropping mixed layer in the southeastern Pacific just north of the Subantarctic Front (SAF). SAMW and AAIW formation have a major impact on the oceanic sink for anthropogenic CO2, whose largest uncertainty is at intermediate depths. In 2005 and 2006, we received NSF funding to carry out an austral winter and subsequent austral summer cruise to characterize the deep mixed layers in the SAMW/AAIW formation region in the SE Pacific. Shipboard measurements included CTD, salinity, oxygen, nutrients, XCTD, ADCP, LADCP, shipboard meteorology, CFCs, CO2, underway N2O and CO2, underway T/S/O2. We deployed 3 profiling ApexSBE floats with oxygen sensors, profiling floats for Argo, and a surface drifter with a pCO2 sensor. Subsequent to the cruises, in addition to analysis of these data sets, we used this funding and subsequent NSF funding (I. Cerovecki, M. Mazloff, L. Talley) to analyze output from the Southern Ocean State Estimate to provide a global context for formation of the SE Pacific SAMW. This profiling float component of SAMFLOC was a small addendum to the major hydrographic survey work that was supported by the National Science Foundation Ocean Sciences Division Grant OCE-0327544. The principal investigators were Lynne D. Talley and Teresa Chereskin (Scripps Institution of Oceanography, UCSD). Bernadette Sloyan of CSIRO in Hobart, Tasmania (Australia) was an international principal investigator.