120 Years of AMOC Variability Reconstructed From Observations Using the Bernoulli Inverse. Issue 18 (20th September 2021)

• Record Type: Journal Article
• Authors: Fraser, Neil J.; Cunningham, Stuart A.
• Is Part Of: Geophysical research letters. Volume 48:Issue 18(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-20
• Subjects: AMOC -- climate -- Atlantic -- observation -- AMV -- AMO; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL093893
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Determining the long‐term nature of the Atlantic Meridional Overturning Circulation (AMOC) presents a major step in understanding ocean temperature forcing, and is crucial both for placing the recently observed AMOC slowdown in the context of climate change and for predicting future climate. We present a time series for AMOC strength over the last 120 years which is derived solely from observations. Application of the Bernoulli inverse to hydrography yields the general geostrophic circulation in the North Atlantic without requiring additional sea surface height information, allowing AMOC evaluation in the pre‐satellite era. AMOC varies on a multidecadal timescale, leading the Atlantic Multidecadal Variability (AMV) in sea surface temperature by 2.5 years. We consider the dynamics of the implied AMOC/AMV coupling, and hypothesize that the low‐frequency variability in both parameters is driven by large‐scale density anomalies circulating in the AMOC. Plain Language Summary: The large‐scale ocean currents which influence the Earth's climate system are driven in large part by gradients in the sea surface. However, sea surface height measurements are scarce before 1993, when satellite observations began, limiting our knowledge of ocean currents over climate‐relevant time scales. Here, we use a method for determining sea surface height which does not require satellite data. We can therefore estimate the current strength in the North Atlantic over the last 120 years. We find that changes in the current strength are closely tied to changes in sea surface temperature. Key Points: Atlantic Meridional Overturning Circulation (AMOC) variability leads Atlantic Multidecadal Variability (AMV) by 2.5 years AMV is strongly coupled to ocean dynamics AMOC variability associated with circulation of large‐scale density anomalies