Mechanisms Accounting for Interannual Variability of Advective Heat Transport in the North Atlantic Upper Layer

Abstract A recent state estimate covering the period 1992–2010 from the Estimating the Circulation and Climate of the Ocean (ECCO) project is utilized to quantify the roles of air–sea heat fluxes and advective heat transport convergences in setting upper-ocean heat content anomalies H in the North Atlantic Ocean on monthly to interannual time scales. Anomalies in (linear) advective heat transport convergences, as well as Ekman and geostrophic contributions, are decomposed into parts that are due to velocity variability, temperature variability, and their covariability. Ekman convergences are generally dominated by variability in Ekman mass transports, which reflect the instantaneous response to local wind forcing, except in the tropics, where variability in the temperature field plays a significant role. In contrast, both budget analyses and simple dynamical arguments demonstrate that geostrophic heat transport convergences that are due to temperature and velocity variability are anticorrelated, and thus their separate treatment is not insightful. In the interior of the subtropical gyre, the sum of air–sea heat fluxes and Ekman heat transport convergences is a reasonable measure of local atmospheric forcing, and such forcing explains the majority of H variability on all time scales resolved by ECCO. In contrast, in the Gulf Stream region and subpolar gyre, ocean dynamics are found to be important in setting H on interannual time scales. Air–sea heat fluxes damp anomalies created by the ocean and thus are not set by local atmospheric variability.

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The Combined Effects of SST and the North Atlantic Subtropical High-Pressure System on the Atlantic Basin Tropical Cyclone Interannual Variability

Atmosphere ◽

10.3390/atmos12030329 ◽

2021 ◽

Vol 12 (3) ◽

pp. 329

Author(s):

Albenis Pérez-Alarcón ◽

José C. Fernández-Alvarez ◽

Rogert Sorí ◽

Raquel Nieto ◽

Luis Gimeno

Keyword(s):

High Pressure ◽

Interannual Variability ◽

Central America ◽

North Atlantic ◽

The West ◽

The Bahamas ◽

Pressure System ◽

North Atlantic Subtropical High ◽

The North ◽

The North Atlantic

The combined effect of the sea surface temperature (SST) and the North Atlantic subtropical high-pressure system (NASH) in the interannual variability of the genesis of tropical cyclones (TCs) and landfalling in the period 1980–2019 is explored in this study. The SST was extracted from the Centennial Time Scale dataset from the National Oceanic and Atmospheric Administration (NOAA), and TC records were obtained from the Atlantic Hurricane Database of the NOAA/National Hurricane Center. The genesis and landfalling regions were objectively clustered for this analysis. Seven regions of TC genesis and five for landfalling were identified. Intercluster differences were observed in the monthly frequency distribution and annual variability, both for genesis and landfalling. From the generalized least square multiple regression model, SST and NASH (intensity and position) covariates can explain 22.7% of the variance of the frequency of TC genesis, but it is only statistically significant (p < 0.1) for the NASH center latitude. The SST mostly modulates the frequency of TCs formed near the West African coast, and the NASH latitudinal variation affects those originated in the Lesser Antilles arc. For landfalling, both covariates explain 38.7% of the variance; however, significant differences are observed in the comparison between each region. With a statistical significance higher than 90%, SST and NASH explain 33.4% of the landfalling variability in the archipelago of the Bahamas and central–eastern region of Cuba. Besides, landfalls in the Gulf of Mexico and Central America seem to be modulated by SST. It was also found there was no statistically significant relationship between the frequency of genesis and landfalling with the NASH intensity. However, the NASH structure modulates the probability density of the TCs trajectory that make landfall once or several times in their lifetime. Thus, the NASH variability throughout a hurricane season affects the TCs trajectory in the North Atlantic basin. Moreover, we found that the landfalling frequency of TCs formed near the West Africa coast and the central North Atlantic is relatively low. Furthermore, the SST and NASH longitude center explains 31.6% (p < 0.05) of the variance of the landfalling intensity in the archipelago of the Bahamas, while the SST explains 26.4% (p < 0.05) in Central America. Furthermore, the 5-year moving average filter revealed decadal and multidecadal variability in both genesis and landfalling by region. Our findings confirm the complexity of the atmospheric processes involved in the TC genesis and landfalling.

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Extreme value distributions describe interannual variability in the North Atlantic spring bloom

10.1002/essoar.10507656.1 ◽

2021 ◽

Author(s):

Gregory Britten

Keyword(s):

Interannual Variability ◽

North Atlantic ◽

Spring Bloom ◽

Extreme Value ◽

Extreme Value Distributions ◽

The North ◽

The North Atlantic

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Interannual Variability in the Thermodynamics of Subduction over the North Atlantic

Journal of Physical Oceanography ◽

10.1175/1520-0485(2001)031<3284:ivitto>2.0.co;2 ◽

2001 ◽

Vol 31 (11) ◽

pp. 3284-3294 ◽

Cited By ~ 6

Author(s):

Alison J. McLaren ◽

Richard G. Williams

Keyword(s):

Interannual Variability ◽

North Atlantic ◽

The North ◽

The North Atlantic

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Interannual variability in the upper ocean in the North Atlantic, summer 1983 and 1986

Deep Sea Research Part A Oceanographic Research Papers ◽

10.1016/0198-0149(90)90057-3 ◽

1990 ◽

Vol 37 (7) ◽

pp. 1169-1175 ◽

Cited By ~ 6

Author(s):

H. Leach

Keyword(s):

Interannual Variability ◽

North Atlantic ◽

Upper Ocean ◽

The North ◽

The North Atlantic

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Transport and storage of anthropogenic C in the North Atlantic Subpolar Ocean

Biogeosciences ◽

10.5194/bg-15-4661-2018 ◽

2018 ◽

Vol 15 (14) ◽

pp. 4661-4682 ◽

Cited By ~ 1

Author(s):

Virginie Racapé ◽

Patricia Zunino ◽

Herlé Mercier ◽

Pascale Lherminier ◽

Laurent Bopp ◽

...

Keyword(s):

Interannual Variability ◽

North Atlantic ◽

General Circulation ◽

Meridional Overturning Circulation ◽

Intermediate Water ◽

Data Set ◽

The North ◽

Storage Rate ◽

The North Atlantic ◽

And Storage

Abstract. The North Atlantic Ocean is a major sink region for atmospheric CO2 and contributes to the storage of anthropogenic carbon (Cant). While there is general agreement that the intensity of the meridional overturning circulation (MOC) modulates uptake, transport and storage of Cant in the North Atlantic Subpolar Ocean, processes controlling their recent variability and evolution over the 21st century remain uncertain. This study investigates the relationship between transport, air–sea flux and storage rate of Cant in the North Atlantic Subpolar Ocean over the past 53 years. Its relies on the combined analysis of a multiannual in situ data set and outputs from a global biogeochemical ocean general circulation model (NEMO–PISCES) at 1∕2∘ spatial resolution forced by an atmospheric reanalysis. Despite an underestimation of Cant transport and an overestimation of anthropogenic air–sea CO2 flux in the model, the interannual variability of the regional Cant storage rate and its driving processes were well simulated by the model. Analysis of the multi-decadal simulation revealed that the MOC intensity variability was the major driver of the Cant transport variability at 25 and 36∘ N, but not at OVIDE. At the subpolar OVIDE section, the interannual variability of Cant transport was controlled by the accumulation of Cant in the MOC upper limb. At multi-decadal timescales, long-term changes in the North Atlantic storage rate of Cant were driven by the increase in air–sea fluxes of anthropogenic CO2. North Atlantic Central Water played a key role for storing Cant in the upper layer of the subtropical region and for supplying Cant to Intermediate Water and North Atlantic Deep Water. The transfer of Cant from surface to deep waters occurred mainly north of the OVIDE section. Most of the Cant transferred to the deep ocean was stored in the subpolar region, while the remainder was exported to the subtropical gyre within the lower MOC.

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The North Atlantic Eddy Heat Transport and Its Relation with the Vertical Tilting of the Gulf Stream Axis

Journal of Physical Oceanography ◽

10.1175/jpo-d-16-0172.1 ◽

2017 ◽

Vol 47 (6) ◽

pp. 1281-1289 ◽

Cited By ~ 6

Author(s):

A. M. Treguier ◽

C. Lique ◽

J. Deshayes ◽

J. M. Molines

Keyword(s):

Numerical Model ◽

Heat Transport ◽

North Atlantic ◽

Gulf Stream ◽

Mean Flow ◽

The North ◽

Spatial Shift ◽

Eddy Heat Flux ◽

Eddy Heat Transport ◽

The North Atlantic

AbstractCorrelations between temperature and velocity fluctuations are a significant contribution to the North Atlantic meridional heat transport, especially at the northern boundary of the subtropical gyre. In satellite observations and in a numerical model at ⅞° resolution, a localized pattern of positive eddy heat flux is found northwest of the Gulf Stream, downstream of its separation at Cape Hatteras. It is confined to the upper 500 m. A simple kinematic model of a meandering jet can explain the surface eddy flux, taking into account a spatial shift between the maximum velocity of the jet and the maximum cross-jet temperature gradient. In the Gulf Stream such a spatial shift results from the nonlinear temperature profile and the vertical tilting of the velocity profile with depth. The numerical model suggests that the meandering of the Gulf Stream could account, at least in part, for the large eddy heat transport (of order 0.3 PW) near 36°N in the North Atlantic and for its compensation by the mean flow.

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