Rapid Communication of Upper‐Ocean Salinity Anomaly to Deep Waters of the Iceland Basin Indicates an AMOC Short‐Cut

Chafik, Léon; Holliday, N. Penny

doi:10.1029/2021gl097570

Cited by 8 publications

(7 citation statements)

References 20 publications

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“…14f, g). We recall that an exceptionally cold anomaly, termed the cold blob, occurred in the SPNA in 2015 (Ruiz-Barradas et al, 2018;Chafik et al, 2019). The analysis presented here shows that while the onset of this strong cooling started in 2004 in the eastern SPNA (red curve in Fig.…”

Section: Relationship Between Sea Level and Surface Buoyancy Forcingmentioning

confidence: 56%

“…These tendencies reversed abruptly in 2011-2015. During the latter time interval, the subtropical gyre warmed considerably, which led to an accelerated sea level rise along the US southeastern coast with rates up to 5 times the global mean (Domingues et al, 2018;Volkov et al, 2019b), while a strong cooling occurred in the subpolar North Atlantic in 2013-2015 (Chafik et al, 2019).…”

Section: The Imprint Of Ssh Tripole In the Subpolar North Atlanticmentioning

confidence: 99%

“…Ocean and atmosphere dynamics induce regional sea level changes with amplitudes that are often several times greater than the global mean sea level rise of about 3.5 mm yr −1 (Meyssignac and Cazenave, 2012;Cazenave et al, 2014;Volkov et al, 2017;Chafik et al, 2019). On timescales from seasonal to longer, this dynamic sea level variability (after the global mean sea level has been subtracted) is mainly due to changes in the density of water column, driven by surface buoyancy fluxes and the advection of heat and freshwater by ocean currents (Gill and Niiler, 1973;Ferry et al, 2000;Volkov and van Aken, 2003;Cabanes et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

“…This warming was associated with the positive phase of the Atlantic Multidecadal Oscillation (e.g., Enfield et al, 2001), partly driven by the strengthening of the North Atlantic Current (NAC) and the AMOC (Msadek et al, 2014). A cooling tendency in the SPNA started in 2006, and it ended with an exceptionally cold anomaly in 2015, termed the "cold blob" (Ruiz- Barradas et al, 2018;Chafik et al, 2019). Several studies have attributed the cold blob observed in the SPNA to the dramatic wintertime heat loss event in 2014-2015 (Josey et al, 2018;Grist et al, 2016;Duchez et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Interannual to decadal sea level variability in the subpolar North Atlantic: the role of propagating signals

Volkov

Schmid²,

Chomiak³

et al. 2022

Ocean Sci.

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Abstract. The gyre-scale, dynamic sea surface height (SSH) variability signifies the spatial redistribution of heat and freshwater in the ocean, influencing the ocean circulation, weather, climate, sea level, and ecosystems. It is known that the first empirical orthogonal function (EOF) mode of the interannual SSH variability in the North Atlantic exhibits a tripole gyre pattern, with the subtropical gyre varying out of phase with both the subpolar gyre and the tropics, influenced by the low-frequency North Atlantic Oscillation. Here, we show that the first EOF mode explains the majority (60 %–90 %) of the interannual SSH variance in the Labrador and Irminger Sea, whereas the second EOF mode is more influential in the northeastern part of the subpolar North Atlantic (SPNA), explaining up to 60 %–80 % of the regional interannual SSH variability. We find that the two leading modes do not represent physically independent phenomena. On the contrary, they evolve as a quadrature pair associated with a propagation of SSH anomalies from the eastern to the western SPNA. This is confirmed by the complex EOF analysis, which can detect propagating (as opposed to stationary) signals. The analysis shows that it takes about 2 years for sea level signals to propagate from the Iceland Basin to the Labrador Sea, and it takes 7–10 years for the entire cycle of the North Atlantic SSH tripole to complete. The observed westward propagation of SSH anomalies is linked to shifting wind forcing patterns and to the cyclonic pattern of the mean ocean circulation in the SPNA. The analysis of regional surface buoyancy fluxes in combination with the upper-ocean temperature and salinity changes suggests a time-dependent dominance of either air–sea heat fluxes or advection in driving the observed SSH tendencies, while the contribution of surface freshwater fluxes (precipitation and evaporation) is negligible. We demonstrate that the most recent cooling and freshening observed in the SPNA since about 2010 were mostly driven by advection associated with the North Atlantic Current. The results of this study indicate that signal propagation is an important component of the North Atlantic SSH tripole, as it applies to the SPNA.

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Section: Relationship Between Sea Level and Surface Buoyancy Forcingmentioning

confidence: 56%

Section: The Imprint Of Ssh Tripole In the Subpolar North Atlanticmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Interannual to decadal sea level variability in the subpolar North Atlantic: the role of propagating signals

Volkov

Schmid²,

Chomiak³

et al. 2022

Ocean Sci.

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“…Understanding how these patterns will continue to amplify in a more stratified upper ocean 42 and other GSA 40,42,41 resulting from Arctic processes 43 will help shed light on foreseeing AMOC collapse. Also, the maintenance of the AMOC observing system along with continued paleoclimate simulations in climate and ocean model development and evaluation, will provide more accurate information on the AMOC prediction.…”

Section: Discussionmentioning

confidence: 99%

The state of the AMOC revealed from the Subpolar North Atlantic Sea Surface Salinity

Xu,

Dai,

Wright

2024

Preprint

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As a critical regulator of the global climate system, the Atlantic Meridional Overturning Circulation (AMOC) has attracted huge attention since its bimodal state change could abruptly alter climate1–5. The subpolar sea surface temperature (SST) has been used as a fingerprint to predict the state change of AMOC3,6–8. Although the subpolar SST agrees well with the variability of AMOC in recent years, it is under debate whether the subpolar SST can represent the abrupt state change of AMOC since its physical role remains unclear9. In contrast, it is well-known that the freshwater flux in high latitudes is a key to AMOC stability10–13. To foresee the AMOC collapse based on salinity, we investigate the relationship of SST and SSS with various AMOC mean states from the Paleoclimate Modeling Intercomparison Project phase 4 (PMIP4). It is found that SST does not agree with changes in AMOC mean state under various climate conditions, while the sea surface salinity (SSS) within the subpolar North Atlantic (SPNA) does. Our results indicate that about 3.5 PSU drop in SPNA SSS is required for AMOC collapse to totally shut down. It's worth noting that no significant salinity trend was observed in the SPNA, implying the stability of deep water formation in recent decades. More attention should be paid to monitoring salinity variations in the SPNA and studying the anthropogenic-induced ice melting and alterations in the water cycle in high latitudes.

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North Atlantic Ocean Circulation and Related Exchange of Heat and Salt Between Water Masses

Berglund

Döös

Groeskamp

et al. 2023

Geophysical Research Letters

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The circulation in the Atlantic Ocean is a key component of the Earth's climate system (Bindoff et al., 2019;Bower et al., 2019;Weijer et al., 2020). The Atlantic Meridional Overturning Circulation (AMOC) transports surface water to the northernmost parts of the Atlantic Ocean. On its way, the water looses heat and freshens, which results in a net increase in density. These changes are due to a combination of air-sea interactions, such as heat fluxes through the surface or evaporation and precipitation, and through internal mixing (Berglund et al., 2017;Bower et al., 2019;Lozier, 2012). When the water reaches the northern parts of the Atlantic Ocean it is sufficiently dense to sink and return southwards. This watermass transformation from light to dense waters is gradual on its northward path and to a large extent subsurface within the North Atlantic Current and in the Subpolar Gyre in a depth range of 800-1,500 m (Chafik & Rossby, 2019;Evans et al., 2022;Zhang & Thomas, 2021).In the present study, we will investigate to what extent this subsurface transformation is due to mixing with other water masses and thus not only due to the heat and freshwater fluxes through the sea surface. The northward heat transport, associated with the AMOC, is considered to be one of the reasons for the relatively mild climate of

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Rapid Communication of Upper‐Ocean Salinity Anomaly to Deep Waters of the Iceland Basin Indicates an AMOC Short‐Cut

Cited by 8 publications

References 20 publications

Interannual to decadal sea level variability in the subpolar North Atlantic: the role of propagating signals

Interannual to decadal sea level variability in the subpolar North Atlantic: the role of propagating signals

The state of the AMOC revealed from the Subpolar North Atlantic Sea Surface Salinity

North Atlantic Ocean Circulation and Related Exchange of Heat and Salt Between Water Masses

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