The Deep Western Boundary Current at Cape Farewell: results from a moored current meter array

Bacon, Sheldon and Saunders, Peter M. (2010) The Deep Western Boundary Current at Cape Farewell: results from a moored current meter array. Journal of Physical Oceanography, 40 (4), 815-829. (doi:10.1175/2009JPO4091.1).

Abstract

An analysis ismade of data from 30 Aanderaa recording currentmeters (RCMs) set on ninemoorings located
east of Cape Farewell, the southern tip of Greenland. The purpose of the measurements was to allow for the
estimation of transport in the deep western boundary current (DWBC) below a depth of about 1500 m. The
records commenced in September 2005 and lasted from9.5 to 11.5months.After calibration of the rawdata, 12-h
averages of temperature and current were derived and the latter employed to estimate the flow across and along
the array direction. The 9.5-month average transport of water colder than 38Cwas found to be 7.8 Sv (1 Sv[13
106 m3 s21) with a standard error of 0.8 Sv. For water denser than su527.85 kg m23, the transport is calculated
as 4.5 Sv. Whether either of these values is significantly different fromcomparablemeasurementsmade 500 km
upstream cannot be determined. In marked contrast, for su . 27.8 kg m23, the transport is estimated as only
9.0 Sv, smaller than the widely accepted value of 13 Sv for nearby measurements made in 1978. A reevaluation
of the calculations and assumptions made then allows one to determine the uncertainty of the earlier estimate
and thereby conclude that the difference between the previous and present measurements is significant, that is,
that the transport has decreased between 1978 and 2005–06. Aweakening of the transport during the 9.5-month
period is also observed, along with a warming and an increase in salinity in the core of the DWBC. These latter
changes are shown to be consistent with interannual variability rather than a long-term trend.

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