In:
Ocean Science, Copernicus GmbH, Vol. 16, No. 4 ( 2020-07-23), p. 863-874
Abstract:
Abstract. The strength of the Atlantic meridional overturning circulation
(AMOC) at 26∘ N has now been continuously measured by the RAPID
array over the period April 2004–September 2018. This record provides unique
insight into the variability of the large-scale ocean circulation,
previously only measured by sporadic snapshots of basin-wide transport from
hydrographic sections. The continuous measurements have unveiled striking
variability on timescales of days to a decade, driven largely by
wind forcing, contrasting with previous expectations about a slowly varying
buoyancy-forced large-scale ocean circulation. However, these measurements
were primarily observed during a warm state of the Atlantic multidecadal
variability (AMV) which has been steadily declining since a peak in
2008–2010. In 2013–2015, a period of strong buoyancy forcing by the
atmosphere drove intense water-mass transformation in the subpolar North
Atlantic and provides a unique opportunity to investigate the response of
the large-scale ocean circulation to buoyancy forcing. Modelling studies
suggest that the AMOC in the subtropics responds to such events with an
increase in overturning transport, after a lag of 3–9 years. At
45∘ N, observations suggest that the AMOC may already be
increasing. Examining 26∘ N, we find that the AMOC is no longer
weakening, though the recent transport is not above the long-term mean.
Extending the record backwards in time at 26∘ N with ocean
reanalysis from GloSea5, the transport fluctuations at 26∘ N are
consistent with a 0- to 2-year lag from those at 45∘ N, albeit with
lower magnitude. Given the short span of time and anticipated delays in the
signal from the subpolar to subtropical gyres, it is not yet possible to
determine whether the subtropical AMOC strength is recovering nor how the
AMOC at 26∘ N responds to intense buoyancy forcing.
Type of Medium:
Online Resource
ISSN:
1812-0792
DOI:
10.5194/os-16-863-2020
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2020
detail.hit.zdb_id:
2183769-7
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