The University of Southampton
University of Southampton Institutional Repository

Is a decline of AMOC causing the warming hole above the North Atlantic in observed and modeled warming patterns?

Is a decline of AMOC causing the warming hole above the North Atlantic in observed and modeled warming patterns?
Is a decline of AMOC causing the warming hole above the North Atlantic in observed and modeled warming patterns?
The pattern of global mean temperature (GMT) change is calculated by regressing local surface air temperature (SAT) to GMT for an ensemble of CMIP5 models and for observations over the last 132 years. Calculations are based on the historical period and climate change scenarios. As in the observations the warming pattern contains a warming hole over the subpolar North Atlantic. Using a bivariate regression of SAT to GMT and an index of the Atlantic meridional overturning circulation (AMOC), the warming pattern is decomposed in a radiatively forced part and an AMOC fingerprint. The North Atlantic warming hole is associated with a decline of the AMOC. The AMOC fingerprint resembles Atlantic multidecadal variability (AMV), but details of the pattern change when the AMOC decline increases, underscoring the nonlinearity in the response.

The warming hole is situated south of deep convection sites, indicating that it involves an adjustment of the gyre circulation, although it should be noted that some models feature deep convection in the middle of the subpolar gyre. The warming hole is already prominent in historical runs, where the response of the AMOC to GMT is weak, which suggests that it is involved in an ocean adjustment that precedes the AMOC decline. In the more strongly forced scenario runs, the warming hole over the subpolar gyre becomes weaker, while cooling over the Nordic seas increases, consistent with previous findings that deep convection in the Labrador and Irminger Seas is more vulnerable to changes in external forcing than convection in the Nordic seas, which only reacts after a threshold is passed.
pattern detection, regression analysis, ensembles, model evaluation/performance, climate variability, trends
0894-8755
8373-8379
Drijfhout, Sybren
a5c76079-179b-490c-93fe-fc0391aacf13
van Oldenborgh, Geert Jan
d031304b-5788-4307-8fac-a01a3917adc9
Cimatoribus, Andrea
aeb0ef6f-e4b6-44aa-854c-7d86c5c16978
Drijfhout, Sybren
a5c76079-179b-490c-93fe-fc0391aacf13
van Oldenborgh, Geert Jan
d031304b-5788-4307-8fac-a01a3917adc9
Cimatoribus, Andrea
aeb0ef6f-e4b6-44aa-854c-7d86c5c16978

Drijfhout, Sybren, van Oldenborgh, Geert Jan and Cimatoribus, Andrea (2012) Is a decline of AMOC causing the warming hole above the North Atlantic in observed and modeled warming patterns? Journal of Climate, 25 (24), 8373-8379. (doi:10.1175/JCLI-D-12-00490.1).

Record type: Article

Abstract

The pattern of global mean temperature (GMT) change is calculated by regressing local surface air temperature (SAT) to GMT for an ensemble of CMIP5 models and for observations over the last 132 years. Calculations are based on the historical period and climate change scenarios. As in the observations the warming pattern contains a warming hole over the subpolar North Atlantic. Using a bivariate regression of SAT to GMT and an index of the Atlantic meridional overturning circulation (AMOC), the warming pattern is decomposed in a radiatively forced part and an AMOC fingerprint. The North Atlantic warming hole is associated with a decline of the AMOC. The AMOC fingerprint resembles Atlantic multidecadal variability (AMV), but details of the pattern change when the AMOC decline increases, underscoring the nonlinearity in the response.

The warming hole is situated south of deep convection sites, indicating that it involves an adjustment of the gyre circulation, although it should be noted that some models feature deep convection in the middle of the subpolar gyre. The warming hole is already prominent in historical runs, where the response of the AMOC to GMT is weak, which suggests that it is involved in an ocean adjustment that precedes the AMOC decline. In the more strongly forced scenario runs, the warming hole over the subpolar gyre becomes weaker, while cooling over the Nordic seas increases, consistent with previous findings that deep convection in the Labrador and Irminger Seas is more vulnerable to changes in external forcing than convection in the Nordic seas, which only reacts after a threshold is passed.

This record has no associated files available for download.

More information

Published date: December 2012
Keywords: pattern detection, regression analysis, ensembles, model evaluation/performance, climate variability, trends
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 348342
URI: http://eprints.soton.ac.uk/id/eprint/348342
ISSN: 0894-8755
PURE UUID: 7dc8234a-2f93-4f14-86b6-6ef8467d463b

Catalogue record

Date deposited: 12 Feb 2013 11:53
Last modified: 27 Apr 2022 07:24

Export record

Altmetrics

Contributors

Author: Geert Jan van Oldenborgh
Author: Andrea Cimatoribus

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×