The Atlantic Multidecadal Oscillation and its relation to rainfall and river flows in the continental U.S.

Enfield, David B.; Mestas-Nuñez, Alberto M.; Trimble, Paul

doi:10.1029/2000gl012745

Cited by 2,539 publications

(2,353 citation statements)

References 12 publications

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“…The influence of AMO variability on regional drought in the United States is well established (Enfield et al 2001;McCabe et al 2004;McCabe and Palecki 2006;Ortegren et al 2011). The summer mean location of the Bermuda high also is significantly related to warmseason drought variability in the Southeast via its influence on moisture advection into the region (Stahle and Cleaveland 1993;Katz et al 2003;Diem 2006;Ortegren et al 2011).…”

Section: B Interdecadal Drought Variabilitymentioning

confidence: 95%

“…The summer mean location of the Bermuda high also is significantly related to warmseason drought variability in the Southeast via its influence on moisture advection into the region (Stahle and Cleaveland 1993;Katz et al 2003;Diem 2006;Ortegren et al 2011). AMO1 is associated with increased drought frequency in the Atlantic coastal Southeast (Enfield et al 2001;McCabe et al 2004). Conversely, AMO1 is associated with multidecadal regimes of increased summer wetness in the Gulf of Mexico coastal states, including Mississippi, Louisiana, and eastern Texas (Ortegren et al 2011).…”

Section: B Interdecadal Drought Variabilitymentioning

confidence: 99%

“…noaa.gov/psd/data/climateindices/list/). We collected the AMO index (Enfield et al 2001) from NOAA's Earth System Research Laboratory for 1950-2011 (AMO short) and the extended version covering 1895-2011 (AMO long). The climate indices were converted to binary format based on positive and negative phase.…”

Section: Identifying Larger-scale Ocean-atmosphere Influences On Tmentioning

confidence: 99%

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Tropical Cyclones and Drought Amelioration in the Gulf and Southeastern Coastal United States

et al. 2013

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Precipitation from land-falling tropical cyclones (TCs) has a significant hydroclimatic influence in the southeastern United States, particularly during drought years. The frequency with which TCs ended drought conditions was examined for southeastern coastal states from Texas to North Carolina during 1895-2011. The region was divided into the Gulf Coast states (GCS) and the southeastern Atlantic coast states (ACS). The spatiotemporal patterns of tropical cyclone drought busters (TCDBs) were analyzed. Larger-scale ocean-atmosphere influences on TCDBs were examined using chi-squared analysis. The ACS experienced TCDBs more frequently and farther inland compared to the GCS. The number of TCDBs has significantly increased with time in the ACS. TCDBs numbers in the GCS did not exhibit significant increases, but the area alleviated of drought conditions increased significantly in the last 117 years. The dominant larger-scale oceanatmosphere forcing of TCDBs was a combination of a warm Atlantic Ocean ABSTRACTPrecipitation from land-falling tropical cyclones (TCs) has a significant hydroclimatic influence in the southeastern United States, particularly during drought years. The frequency with which TCs ended drought conditions was examined for southeastern coastal states from Texas to North Carolina during 1895-2011. The region was divided into the Gulf Coast states (GCS) and the southeastern Atlantic coast states (ACS). The spatiotemporal patterns of tropical cyclone drought busters (TCDBs) were analyzed. Larger-scale oceanatmosphere influences on TCDBs were examined using chi-squared analysis. The ACS experienced TCDBs more frequently and farther inland compared to the GCS. The number of TCDBs has significantly increased with time in the ACS. TCDBs numbers in the GCS did not exhibit significant increases, but the area alleviated of drought conditions increased significantly in the last 117 years. The dominant larger-scale ocean-atmosphere forcing of TCDBs was a combination of a warm Atlantic Ocean [positive Atlantic multidecadal oscillation index (AMO1)] and weak westerlies [negative North Atlantic Oscillation index (NAO2)]. AMO1 leads to an increase in the number of TCs throughout the North Atlantic basin, and NAO2 increases the likelihood of TC landfall by controlling the steering of TCs toward the southeastern United States.

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Section: B Interdecadal Drought Variabilitymentioning

confidence: 95%

Section: B Interdecadal Drought Variabilitymentioning

confidence: 99%

Section: Identifying Larger-scale Ocean-atmosphere Influences On Tmentioning

confidence: 99%

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Tropical Cyclones and Drought Amelioration in the Gulf and Southeastern Coastal United States

et al. 2013

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“…In particular, the AMO modifies the precipitation over the tropical Atlantic region (Enfield et al 2001;McCabe et al 2004;Knight et al 2006;Mohino et al 2011) and the hurricane frequency, mostly notably during boreal summer (Goldenberg et al 2001;Zhang and Delworth 2006;Chylek and Lesins 2008;Dunstone et al 2011). In the midlatitudes, the AMO was shown to modify the precipitation and temperature over the surrounding region both in boreal summer (Sutton and Hodson 2005;Seager et al 2008) and winter (Ting et al 2011;Ionita et al 2012;Ting et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Mechanisms Determining the Winter Atmospheric Response to the Atlantic Overturning Circulation

et al. 2016

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In climate models, an intensification of the Atlantic meridional overturning circulation (AMOC) precedes a warming in the North Atlantic subpolar basin by a few years. In the IPSL-CM5A-LR model, this warming may explain the atmospheric response to the AMOC observed in winter, which resembles a negative phase of the North Atlantic Oscillation (NAO). To firmly establish the causality links between the ocean and the atmosphere and illustrate the underlying mechanisms in this model, ensembles of atmosphere-only simulations are conducted, prescribing the SST and sea ice anomalies that follow an AMOC intensification. In late winter, the North Atlantic SST and sea ice anomalies drive atmospheric circulation anomalies similar to those found in the coupled model. Simulations only driven by the SST anomalies related to the AMOC show that the largest oceanic influence is due to the warm subpolar SST anomaly, which enhances the oceanic heat release and decreases the lower-tropospheric baroclinicity in the region of maximum eddy growth, resulting in a weaker meridional eddy heat flux in the atmosphere. The transient eddy feedback leads to a negative NAO-like response. An AMOC intensification is also followed by less sea ice over the Labrador Sea and more sea ice over the Nordic seas. The simulations with full boundary forcing suggest that such anomalies act to strengthen both the poleward momentum flux and the upward heat flux into the polar stratosphere and lead to a stratospheric warming, which then reinforces the negative NAO signal in late winter.

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“…Most studies focus on the Atlantic meridional overturning circulation (AMOC) (Collins 2002;Pohlmann et al 2004;Collins et al 2006;Msadek et al 2010) or the upper-ocean heat content (Branstator et al 2012), which seem especially predictable and may influence climate fluctuations over the continents, being thus of particular socioeconomic interest. An influence of the Atlantic multidecadal oscillation (AMO), which has been suggested to largely result from AMOC fluctuations, on summer precipitation in North America and Europe, Atlantic hurricane activity, and other climatic features has been suggested by several empirical and modeling studies (e.g., Enfield et al 2001;Sutton and Hodson 2005;Knight et al 2006). Changes in the atmospheric circulation and a strengthening of the North Atlantic storm track have been attributed to the sustained weakening of the AMOC in most hosing and anthropogenic gas forcing experiments with climate models (e.g., Stouffer et al 2006;Brayshaw et al 2009;Woollings et al 2012), but control simulations provide a cleaner setup to detect the influence of the AMOC variability on the atmospheric circulation (Msadek and Frankignoul 2009;Teng et al 2011;Gastineau and Frankignoul 2012, hereafter GF12).…”

Section: Introductionmentioning

confidence: 99%

The Influence of the AMOC Variability on the Atmosphere in CCSM3

2013

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The influence of the Atlantic meridional overturning circulation (AMOC) variability on the atmospheric circulation is investigated in a control simulation of the NCAR Community Climate System Model, version 3 (CCSM3), where the AMOC evolves from an oscillatory regime into a red noise regime. In the latter, an AMOC intensification is followed during winter by a positive North Atlantic Oscillation (NAO). The atmospheric response is robust and controlled by AMOC-driven SST anomalies, which shift the heat release to the atmosphere northward near the Gulf Stream/North Atlantic Current. This alters the low-level atmospheric baroclinicity and shifts the maximum eddy growth northward, affecting the storm track and favoring a positive NAO. The AMOC influence is detected in the relation between seasonal upper-ocean heat content or SST anomalies and winter sea level pressure. In the oscillatory regime, no direct AMOC influence is detected in winter. However, an upper-ocean heat content anomaly resembling the AMOC footprint precedes a negative NAO. This opposite NAO polarity seems due to the southward shift of the Gulf Stream during AMOC intensification, displacing the maximum baroclinicity southward near the jet exit. As the mode has somewhat different patterns when using SST, the wintertime impact of the AMOC lacks robustness in this regime. However, none of the signals compares well with the observed influence of North Atlantic SST anomalies on the NAO because SST is dominated in CCSM3 by the meridional shifts of the Gulf Stream/ North Atlantic Current that covary with the AMOC. Hence, although there is some potential climate predictability in CCSM3, it is not realistic.

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The Atlantic Multidecadal Oscillation and its relation to rainfall and river flows in the continental U.S.

Abstract: Abstract.North

Cited by 2,539 publications

References 12 publications

Tropical Cyclones and Drought Amelioration in the Gulf and Southeastern Coastal United States

Tropical Cyclones and Drought Amelioration in the Gulf and Southeastern Coastal United States

Mechanisms Determining the Winter Atmospheric Response to the Atlantic Overturning Circulation

The Influence of the AMOC Variability on the Atmosphere in CCSM3

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