Importance of density-compensated temperature change for deep North Atlantic Ocean heat uptake

Mauritzen, Cecilie; Melsom, Arne; Sutton, Rowan

doi:10.1038/ngeo1639

Cited by 38 publications

(41 citation statements)

References 35 publications

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“…As a consequence of an AMOC strengthening related to a positives AMO signal in the late 1990s (Parker et al, 2007), our analysis would suggest NADO heat content to rise for more than a decade after a peak in circulation strength, which is in good agreement with observations from the North Atlantic (Mauritzen et al, 2012). Studies by Guemas et al (2013) and Balmaseda et al (2013) demonstrate that ocean heat uptake plays a crucial role in understanding the GMT hiatus over the last decade.…”

Section: Discussionsupporting

confidence: 78%

“…Using observational data, Mauritzen et al (2012) also report a decadal time lag between upper ocean (which is highly correlated with the AMOC at lags between zero and 3 yr in our model ensemble, not shown) and deep-ocean heat content in the northern North Atlantic. Meehl et al (2011) investigated deep-ocean heat uptake anomalies during decades exhibiting a hiatus in the GMT over the 21st century in global warming model simulations and found a difference of about 1.3 × 10 22 J for the global deep-ocean heat uptake rate per decade below 750 m and 0.2 × 10 22 J for the Atlantic Basin compared to reference decades.…”

Section: Discussionmentioning

confidence: 99%

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The role of the North Atlantic overturning and deep ocean for multi-decadal global-mean-temperature variability

et al. 2014

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Abstract. Earth's climate exhibits internal modes of variability on various timescales. Here we investigate multi-decadal variability of the Atlantic meridional overturning circulation (AMOC), Northern Hemisphere sea-ice extent and global mean temperature (GMT) in an ensemble of CMIP5 models under control conditions. We report an inter-annual GMT variability of about ±0.1 • C originating solely from natural variability in the model ensemble. By decomposing the GMT variance into contributions of the AMOC and Northern Hemisphere sea-ice extent using a graph-theoretical statistical approach, we find the AMOC to contribute 8 % to GMT variability in the ensemble mean. Our results highlight the importance of AMOC sea-ice feedbacks that explain 5 % of the GMT variance, while the contribution solely related to the AMOC is found to be about 3 %. As a consequence of multi-decadal AMOC variability, we report substantial variations in North Atlantic deep-ocean heat content with trends of up to 0.7 × 10 22 J decade −1 that are of the order of observed changes over the last decade and consistent with the reduced GMT warming trend over this period. Although these temperature anomalies are largely densitycompensated by salinity changes, we find a robust negative correlation between the AMOC and North Atlantic deepocean density with density lagging the AMOC by 5 to 11 yr in most models. While this would in principle allow for a self-sustained oscillatory behavior of the coupled AMOCdeep-ocean system, our results are inconclusive about the role of this feedback in the model ensemble.

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Section: Discussionsupporting

confidence: 78%

Section: Discussionmentioning

confidence: 99%

The role of the North Atlantic overturning and deep ocean for multi-decadal global-mean-temperature variability

et al. 2014

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“…While most of the warming of the world ocean has occurred in the upper 2,000 m, the significance of the amount of heat stored in the deep ocean has become increasingly clear (Purkey and Johnson 2010;Mauritzen et al, 2012). Approximately 19% of excess heat associated with contemporary global warming has gone into the deep ocean below 2,000 m, and a large part of it has entered the ocean through abyssal waters that sink in the Southern Ocean (Rhein et al, 2013).…”

Section: Observed Temperature Trendsmentioning

confidence: 99%

Southern Ocean Warming

Sallée¹,

Cnrs²

2018

Oceanog

105

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“…Though there is evidence in the literature of changes in deep waters of the North Atlantic, during the time span of our time series the deep ocean in the Atlantic Iberian basin has remained stable. Examples of observed changes include decadal density-compensated temperature anomalies formed in the subpolar gyre and then propagated equatorward [Mauritzen et al, 2012]; and rapid freshening of the deep North Atlantic over past decades [Dickson et al, 2002;Curry et al, 2003;Atkinson et al, 2012]. Atkinson et al [2012] found a decreasing southward transport in the 3000-4700 m layer (LNADW) along 25 N, coincident with a density compensated cooling and freshening of the Denmark Strait Overflow Water in the Deep Western Boundary Current at that latitude.…”

Section: Deep Watersmentioning

confidence: 99%

Interannual variability of the northwestern Iberia deep ocean: Response to large‐scale North Atlantic forcing

et al. 2015

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The oceanic hydrography of the north-easternmost region of the North Atlantic subtropical gyre has been monitored since 2003 by three sections extending between 100 and 200 nautical miles from the Spanish NW and N coast into the Atlantic and the Bay of Biscay. The sections were occupied twice a year from 2003 to 2010, annually after that, and measure the whole water column (>5000 m). Correlation of series in the vertical and among sections, autocorrelation and estimates of the effect of the noise induced by the mesoscale field, all indicate that observed signatures are robust changes of water masses at the regional scale. The hydrographic time series are not characterized by smooth trends but instead by shifts that persist through consecutive cruises. The most notable features include a shift to more saline central waters around 2005 after which they remained stable, and a decrease in thermohaline properties of the Labrador Sea Water from autumn 2008 to 2010. Years with a strong winter North Atlantic Oscillation (NAO) index are characterized by shifts in thermohaline properties across most of the intermediate levels, with the most notable event being the warming and increasing salinity that followed the large NAO index drop of 2010. The observations are consistent with current understanding of the large-scale functioning of the North Atlantic, which predicts a northeastward expansion of subtropical temperate waters in the eastern boundary as a response to NAO forcing. The observed variability is discussed in relationship to large-scale circulation.

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Importance of density-compensated temperature change for deep North Atlantic Ocean heat uptake

Cited by 38 publications

References 35 publications

The role of the North Atlantic overturning and deep ocean for multi-decadal global-mean-temperature variability

The role of the North Atlantic overturning and deep ocean for multi-decadal global-mean-temperature variability

Southern Ocean Warming

Interannual variability of the northwestern Iberia deep ocean: Response to large‐scale North Atlantic forcing

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