Abstract:

Spectral Absorption and Attenuation data (AC-s meter, Sea-Bird Scientific, WET Labs instrument) was collected underway using the R/V Point Sur flow-through system during the Spring cruise on March 29-April 3, 2016. The AC-s instrument was coupled with temperature and salinity from the ship flow-through system. The data includes the date, time, location, temperature, salinity, absorption (a) and attenuation (c) at 85 wavelengths. The ship flow-through system is located at 2-m depth.

Suggested Citation:

Inia M. Soto Ramos, Robert Arnone, Alan Weidemann, Wesley Goode. 2017. Spectral Absorption and Attenuation underway data (AC-s meter, Sea-Bird Scientific, WET Labs instrument) collected during Spring R/V Pelican Cruise, March 29 to April 3, 2016. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N74M92ZN

Purpose:

Inherent Optical Properties (IOP's) such as the attenuation and absorption coefficients provide information about the color of the ocean and therefore the optical constituents such as phytoplankton, colored dissolved organic matter and detritus.

Data Parameters and Units:

Year (YYYY), Month (MM), Day (DD), Hour (HH), Minutes (MM), Seconds (SS), Matlab_time (CTZ), Latitude (dd), Longitude (dd), Temperature (deg C), Salinity (psu), Attenuation coefficient (c; units: m-1; wavelengths: 401.2, 405.5, 409.6, 413.9, 417.8, 422.6, 427.0, 431.5, 435.6, 439.8, 444.4, 449.0, 453.6, 458.2, 462.7, 467.1, 472.0, 477.1, 481.8, 486.7, 491.1, 495.8, 500.5, 505.4, 510.4, 515.2, 520.3, 524.8, 529.4, 534.1, 538.5, 543.0, 547.6, 552.4, 556.9, 561.5, 565.6, 570.0, 574.1, 578.0, 582.0, 586.1, 590.3, 594.7, 599.1, 603.6, 608.3, 612.9, 617.4, 621.9, 626.2, 630.4, 634.7, 639.2, 643.3, 647.6, 652.1, 656.3, 660.9, 665.0, 669.3, 673.4, 677.6, 681.6, 685.6, 689.4, 693.1, 696.6, 700.2, 703.4, 706.8, 710.0, 713.2, 716.6, 719.7, 722.9, 725.4, 728.1, 731.1, 733.4, 735.6, 738.0, 739.9, 741.8, 743.5), Absorption coefficient (a; units: m-1; wavelengths: 403.9, 408.0, 412.1, 416.2, 420.6, 425.4, 429.9, 434.1, 438.2, 442.8, 447.4, 452.2, 456.6, 461.1, 465.7, 470.6, 475.4, 480.4, 485.2, 489.7, 494.4, 498.9, 503.6, 508.5, 513.5, 518.5, 523.0, 527.9, 532.5, 537.2, 541.6, 546.3, 550.7, 555.5, 560.1, 564.4, 568.6, 572.7, 576.6, 581.7, 586.1, 590.3, 594.5, 598.9, 603.3, 608.0, 612.5, 616.9, 621.4, 625.7, 630.0, 634.4, 638.5, 642.8, 647.1, 651.4, 655.8, 660.1, 664.6, 668.7, 672.9, 677, 681.2, 685.0, 688.9, 692.6, 696.0, 699.6, 702.9, 706.2, 709.5, 712.8, 715.8, 718.9, 722.2, 725.1, 727.8, 730.4, 732.7, 735.3, 737.0, 739.4, 741.5, 743.2, 744.8)

Methods:

A CTD (Seabird 19) and Spectral Absorption and Attenuation data (AC-s meter, Sea-Brid Scientific, WET Labs instrument) was connected to the underway flow-through system of the R/V Point Sur. To ensure stability and reliability, the ac-s instrument was placed in a temperature-stabilized water bath to dissipate the instruments’ heat and maintain a constant temperature. The ac-s and CTD was interfaced with a WET Labs DH4 data logger with additional inputs from the ship’s flow-through system (coordinates, time, and date). These inputs were required for the standard protocol corrections during the post processing of the ac-s data. The ac-s instruments were calibrated prior to and post cruise. Calibration of the ac-s included running Nanopure water through the systems using a gravity feed as the instruments were allowed to stabilize for some time interval (≈5 min to ≈10 min). The calibration procedure included obtaining the clear water calibration before and after cleaning the absorption and scattering tubes. An update to instrument device files was applied in real-time if it was deemed that new corrections were necessary to assure good quality measurements. Post processing of the ac-s data will follow the WET Labs protocols (http://www.seabird.com/ac-s). First, the ac-s data is merged and binned with the ship CTD data using the WetLabs Archive Processing Software (WAP). The software can be found here: http://www.seabird.com/software/wap-archive-processing. Water absorption corrections for temperature and salinity will be applied using the ships flow-through data following [Pegau et al., 1997; DOI: 10.1364/ao.36.006035]. The final correction was the scattering correction. For this, we used the method outline in Rottgers et al., 2013 (DOI: 10.1016/j.mio.2013.11.001)

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