Deep-Ocean Bottom Pressure Measurement: Drift Removal and Performance

Abstract

Abstract Sixteen records from seven Digiquartz deep-ocean bottom pressure sensors have been in deployments of 3–12 month duration under the Gulf Stream in depths of 3300 to 4400 m. Particular attention is given (i) to characterizing any observed drift in their calibration in relation to their construction (bellows or Bourdon-tube) and to their prior history of pressurization, and (ii) to estimating and removing this drift from the records. Bellows-type sensors exhibited significant drift (0.2 to 0.85 db) in all of their deployments. Bourdon-tube sensors had less drift in their first deployment (0 to 0.45 db), and in subsequent deployments had either no drift or a small drift with different shape that may have been due to clock-frequency drift. An exponential decay with time [∼exp(−αt)] was found to best represent the drifts, such a curve was fit in a least-squares sense to each pressure record and then subtracted from it Careful attention is given to estimating the uncertainty of the residual “dedrifted” ...