Sub-decadal North Atlantic Oscillation variability in observations and the Kiel Climate Model

Reintges, Annika; Latif, Mojib; Park, Wonsun

doi:10.1007/s00382-016-3279-0

Cited by 22 publications

(30 citation statements)

References 29 publications

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“…The analysis of the climate model ensemble suggests a feedback between the ocean and the atmosphere on the subdecadal time scale, which contributes a small but significant part of the total variability. The derived mechanism from the CMIP5 models is consistent with surface observations analyzed by Reintges et al () and also confirms their results derived from a control integration of the Kiel Climate Model. Moreover, the close relation between oceanic heat loss and heat content tendencies in the SPG and STG regions is consistent with the findings of Williams et al ().…”

Section: Summary and Discussionsupporting

confidence: 90%

Coupled North Atlantic Subdecadal Variability in CMIP5 Models

2019

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The interaction between the atmosphere, specifically the North Atlantic Oscillation, and the North Atlantic Ocean circulation on subdecadal time scale is analyzed in a subset of models participating in the Coupled Model Intercomparison Project phase 5. From preindustrial control runs of at least 500‐year length, we derive anomaly patterns in the atmospheric and ocean circulation and of air‐sea heat exchange. All models simulate a distinct dipolar oceanic overturning anomaly at the subdecadal time scale, with centers at 30°N and 55°N. The dipolar overturning anomaly goes along with marked anomalies in the North Atlantic sea surface temperature and gyre circulation. Lag‐regression analyses demonstrate, with relatively small ensemble spread, how the atmosphere and the ocean circulation interact. The dipolar anomalies in the overturning are forced by North Atlantic Oscillation‐related wind stress curl anomalies. Anomalous surface heat fluxes in concert with anomalous vertical motions drive a meridional dipolar heat content anomaly in the upper ocean, and it is this dipolar heat content anomaly which carries the coupled system from one phase of the subdecadal cycle to the other by reversing the tendencies in the overturning circulation. The coupled subdecadal variability derived from the Coupled Model Intercomparison Project phase 5 models is characterized by three elements: a wind‐driven part steering the dipolar overturning anomaly, surface heat flux anomalies that support a heat buildup in the subpolar gyre region, and the heat storage memory which is instrumental in the phase reversal of the North Atlantic Oscillation.

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Section: Summary and Discussionsupporting

confidence: 90%

Coupled North Atlantic Subdecadal Variability in CMIP5 Models

2019

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“…Several feedback mechanisms between oceanic variability and quasi‐decadal NAO variations have been discussed on the basis of observations and climate modeling [ Reintges et al ., ]: (a) between SST and wind‐driven circulation; (b) between NAO and AMOC, and (c) through projections of SST anomalies back on the NAO. Herein, we show for the first time a deep circulation element that is in phase with the quasi‐decadal NAO mode; and as we believe that the LNADW transport within the DWBC is key to the AMOC, this behavior of the deep subpolar circulation might be representative of linking NAO, DWBC, and AMOC on quasi‐decadal time scales.…”

Section: Discussionmentioning

confidence: 99%

From interannual to decadal: 17 years of boundary current transports at the exit of the Labrador Sea

et al. 2017

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Over the past 17 years, the western boundary current system of the Labrador Sea has been closely observed by maintaining the 53°N observatory (moorings and shipboard station data) measuring the top‐to‐bottom flow field offshore from the Labrador shelf break. Volume transports for the North Atlantic Deep Water (NADW) components were calculated using different methods, including gap filling procedures for deployment periods with suboptimal instrument coverage. On average the Deep Western Boundary Current (DWBC) carries 30.2 ± 6.6 Sv of NADW southward, which are almost equally partitioned between Labrador Sea Water (LSW, 14.9 ± 3.9 Sv) and Lower North Atlantic Deep Water (LNADW, 15.3 ± 3.8 Sv). The transport variability ranges from days to decades, with the most prominent multiyear fluctuations at interannual to near decadal time scales (±5 Sv) in the LNADW overflow water mass. These long‐term fluctuations appear to be in phase with the NAO‐modulated wind fluctuations. The boundary current system off Labrador occurs as a conglomerate of nearly independent components, namely, the shallow Labrador Current, the weakly sheared LSW range, and the deep baroclinic, bottom‐intensified current core of the LNADW, all of which are part of the cyclonic Labrador Sea circulation. This structure is relatively stable over time, and the 120 km wide boundary current is constrained seaward by a weak counterflow which reduces the deep water export by 10–15%.

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“…The NAO reflects the variable strength and latitude of the dominant westerly winds (Woollings et al, ) and therefore exerts a strong influence on European SAT (supporting information Figure S2; Hurrell & Van Loon, ). Consistent with a large portion of central and eastern Europe exhibiting predominantly subdecadal SAT variability, the power spectrum of the NAO index has a statistically significant subdecadal peak (Hurrell & Van Loon, ; Moron et al, ; Reintges et al, ). The significant subdecadal variability in eastern and central Europe (Figure ) furthermore disappears if the SAT variability associated with the NAO is removed by regressing the SAT time series onto the NAO index (not shown), indicating that the subdecadal SAT peak in central and eastern Europe is linked to atmospheric variability.…”

Section: Sources Of Sat Variabilitymentioning

confidence: 93%

Time Scales and Sources of European Temperature Variability

Årthun

Kolstad

Eldevik

et al. 2018

Geophysical Research Letters

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Skillful predictions of continental climate would be of great practical benefit for society and stakeholders. It nevertheless remains fundamentally unresolved to what extent climate is predictable, for what features, at what time scales, and by which mechanisms. Here we identify the dominant time scales and sources of European surface air temperature (SAT) variability during the cold season using a coupled climate reanalysis, and a statistical method that estimates SAT variability due to atmospheric circulation anomalies. We find that eastern Europe is dominated by subdecadal SAT variability associated with the North Atlantic Oscillation, whereas interdecadal and multidecadal SAT variability over northern and southern Europe are thermodynamically driven by ocean temperature anomalies. Our results provide evidence that temperature anomalies in the North Atlantic Ocean are advected over land by the mean westerly winds and, hence, provide a mechanism through which ocean temperature controls the variability and provides predictability of European SAT.

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Sub-decadal North Atlantic Oscillation variability in observations and the Kiel Climate Model

Cited by 22 publications

References 29 publications

Coupled North Atlantic Subdecadal Variability in CMIP5 Models

Coupled North Atlantic Subdecadal Variability in CMIP5 Models

From interannual to decadal: 17 years of boundary current transports at the exit of the Labrador Sea

Time Scales and Sources of European Temperature Variability

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