Inversion of marine heat flow measurements by expansion of the temperature decay function

TL;DR

This paper introduces a linearized iterative method to invert marine heat flow measurements, enabling estimation of sediment temperature and thermal conductivity from non-linear decay data.

Contribution

It presents a novel first-order Taylor series expansion approach for inverting non-linear temperature decay functions in marine heat flow measurements.

Findings

Method is robust and reliable based on synthetic data tests.

Successfully applied to real cruise data and needle probe measurements.

Provides a practical algorithm for marine heat flow analysis.

Abstract

Marine heat flow data, obtained with a Lister-type probe, consists of two temperature decay curves, frictional and heat pulse decay. Both follow the same physical model of a cooling cylinder. The mathematical model describing the decays is non-linear as to the thermal sediment parameters thus a direct inversion is not possible. To overcome this difficulty, the model equations are expanded using a first-orderTaylor series. The linearised model equations are used in an iterative scheme to invert the temperature decay for undisturbed temperature and thermal conductivity of the sediment. The inversion scheme is tested first for its theoretical limitations using synthetic data. Inversion of heat flow measurements obtained during a cruise of R/V SONNE in 1996 and needle probe measurements in material of known thermal conductivity show that the algorithm is robust and gives reliable results. The programme can be obtained from the authors.