See complete methodology in Haskell et al. (2017). In summary:
This study is part of an effort aimed at characterizing the biological response to upwelling at SPOT on 21 cruises between January 2013 and June 2014; the Upwelling Regime In-Situ Ecosystem Efficiency (Up.R.I.S.E.E.) study.

O2/Ar and Triple Oxygen Isotopes (TOI): Samples for O2/Ar and TOI analysis were collected from Niskin bottles in 300 or 500 mL glass flasks equipped with airtight Louwers-Hapert valves (with three high-vacuum greased Viton O-rings in valve stem) and sidearms. Each bottle was poisoned with 150 uL saturated HgCl2, dried in an oven at 50 degrees C, preevacuated on a rotary vane vacuum pump (Pfeiffer Duo 2.5) for at least 5 min before evacuation on a stainless steel gas line using a turbo drag dry high vacuum pump (Alcatel Drytel 31). A vacuum of <1 mtorr was reached and held for at least 5 min, then the bottle was weighed. After sampling, the samples were equilibrated with the headspace for ~12–24 h on a shaking table at University of Southern California (USC), weighed, and drained. The headspace was analyzed in the laboratory of R. Stanley (Woods Hole Oceanographic Institution) for O2 and Ar by peak jumping and for 18O16O (m/z 34) and 17O16O (m/z 33) using a Thermofisher MAT 253 multicollector isotope ratio mass spectrometry. The TOI values are reported relative to atmospheric air as a standard, for which clean Woods Hole air stored in an electropolished 2 L stainless steel cylinder was used.

Gross Oxygen Production (GOP) Rates: Using estimates of vertical advection, diffusion, and gas exchange, we calculated the rates of GOP during each cruise. This dataset contains the calculated GOP rates, δ17O, δ18O, and 17Δ. Total euphotic zone GOP rates ranged from 161 +/- 44 mmol m-2 d-1 to 256 +/- 41 mmol m-2 d-1 in fall/winter,
and 175 ± 58 mmol m-2 d-1 to 477 ± 155 mmol m-2 d-1 in spring.

Oxygen mixed layer depths were determined as the depth at which the oxygen concentration was 0.5% different from the surface concentration. Oxygen was measured by using a Seabird SBE 43 oxygen sensor mounted on an SBE 9plus conductivity-temperature-depth (CTD) and calibrated by using Winkler titrations collected in duplicate at five depths on every CTD cast. For nine cruises (Up-13 to Up-21), the base of the euphotic zone was determined as the depth at which 1% of the surface photosynthetically available radiation (PAR) was measured. Prior to Up-13, there was no PAR sensor on the CTD unit. Since the deep chlorophyll a maximum (DCM, determined via CTD fluorescence) is almost always above the euphotic depth in the Southern California Bight, for the remainder of the cruises, the euphotic depth was defined as 10m below the DCM, except during Up-2, Up-3, and Up-4 because the DCM was within the mixed layer. For these three cruises, the euphotic depth is defined as 15m below the MLD.