## Abstract

In heavily fished areas, upward looking acoustic Doppler current profilers (ADCPs), moored at depth, may

be the only option for long-term current measurements. Arrays of ADCP moorings that cross a current can thus

be the optimal strategy for monitoring the volume flux. These instruments only measure water properties at the

instrument, not through the water column, however. By itself, an ADCP array, therefore, does not give flux

estimates of specific water masses unless temperature and salinity profiles can be derived from the velocity

profiles. This is the opposite of the classical problem of determining currents from temperature and salinity

observations, and in principle it should be possible to solve it by inverting the classical dynamic method. As

for the classical method, this problem requires additional reference information. Using observations from the

Faroe Current between Iceland and the Faroe Islands, it is demonstrated that this procedure can indeed be used

by applying empirical orthogonal function (EOF) analysis to CTD and ADCP data from a section that crosses

this current. It is found that one of the empirical velocity modes is highly correlated to the dominant temperature

and salinity modes. Employing this relationship, ADCP measurements are used to reconstruct temperature and

salinity fields with the same temporal resolution as the velocity field. For the Atlantic inflow of the Faroe Current,

the reconstructed fields are found to explain 60% of the temperature and 44% of the observed salinity variances

be the only option for long-term current measurements. Arrays of ADCP moorings that cross a current can thus

be the optimal strategy for monitoring the volume flux. These instruments only measure water properties at the

instrument, not through the water column, however. By itself, an ADCP array, therefore, does not give flux

estimates of specific water masses unless temperature and salinity profiles can be derived from the velocity

profiles. This is the opposite of the classical problem of determining currents from temperature and salinity

observations, and in principle it should be possible to solve it by inverting the classical dynamic method. As

for the classical method, this problem requires additional reference information. Using observations from the

Faroe Current between Iceland and the Faroe Islands, it is demonstrated that this procedure can indeed be used

by applying empirical orthogonal function (EOF) analysis to CTD and ADCP data from a section that crosses

this current. It is found that one of the empirical velocity modes is highly correlated to the dominant temperature

and salinity modes. Employing this relationship, ADCP measurements are used to reconstruct temperature and

salinity fields with the same temporal resolution as the velocity field. For the Atlantic inflow of the Faroe Current,

the reconstructed fields are found to explain 60% of the temperature and 44% of the observed salinity variances

Original language | English |
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Pages (from-to) | 527-534 |

Number of pages | 8 |

Journal | Journal of Atmospheric and Oceanic Technology |

Volume | 21 |

DOIs | |

Publication status | Published - 2004 |