Down Core Oxygen Isotopic Measurements Of Diatom δsup18/supO From The Guaymas Basin, Gulf Of California

Anthony J. Menicucci, Howard J. Spero, Robert Thunell

Research output: Contribution to conferencePoster

Abstract

The Guaymas Basin (GB), Gulf of California (27º53’N, 111º40’W ), is an evaporative basin, with sea surface temperatures (SST) varying between ~30 o C (summer) and ~15 o C (winter). Productivity is controlled mostly by seasonal upwelling starting in fall (early November) and extending into spring. We are currently analyzing δ 18 O diatom from a boxcore (BC-43) using microfluorination (Menicucci, et al. 2013). This boxcore was previously analyzed for UK '37 alkenones and 210 Pb activity (Goni, et al. 2001). Residual BC-43 material was sampled at ~2cm intervals. Samples were cleaned to isolate diatoms from other sediments, then equilibrated in water with δ 18 O water = +85‰ for 70 hours at 21 o C prior to vacuum dehydroxylation and microfluorination. The latter equilibration was done to account for fractionation between covalently bound O and OH - groups during vacuum dehydroxylation, preserving the original δ 18 O diatom value.

We present δ 18 O diatom data from BC-43 samples covering 27cm, equivalent to >225 years of sediment accumulation. δ 18 O data are converted to temperature (T) based on an existing calibration (Leclerc and Labeyrie 1987). Our data suggest δ 18 O diatom values record a T range of 22-18 o C, corresponding to the mixed layer depth and the chlorophyll maximum during the fall bloom. These T values are offset from SST data by a mean of 5 o C for the same sample intervals. However, δ 18 O diatom values from the most recent samples suggest a ~2 o C increase in diatom T relative to SST during the last 35 years. This subsurface warming may be due to decreased fall upwelling, increased mixed layer and chlorophyll maximum depths, and/or the timing of the peak diatom bloom. Such correlations are being investigated and the latest results will be presented.

Original languageAmerican English
StatePublished - Dec 15 2015
Externally publishedYes
EventAGU Fall Meeting -
Duration: Dec 13 2019 → …

Conference

ConferenceAGU Fall Meeting
Period12/13/19 → …

Disciplines

  • Earth Sciences

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