Rayleigh wave tomography in the North Atlantic: high resolution images of the Iceland, Azores and Eifel mantle plumes

<p>The North Atlantic Oscillation (NAO) has been widely recognized as one of the main patterns of atmospheric variability over the northern hemisphere, helping to understand variations on the North Atlantic Jet (NAJ) position and its influence on storm-tracks, atmospheric blocking and Rossby Wave breaking. Among several relevant teleconnection patterns identified through different timescales, the most prominent ones are found for northern Europe during winter months, when positive (negative) phases of NAO are related to wetter (drier) conditions. Although it is not well defined yet, an opposite connection is observed for the Mediterranean region, where negative NAO values are often associated with high precipitation. Therefore, the main goal of this study is to identify which regions and periods of the year are the most susceptible to abundant NAO-related precipitation throughout the Italian Peninsula. For doing so, the last 42 years period (1979-2020) was analysed using the Fifth Generation ECMWF Atmospheric ReAnalysis of the Global Climate (ERA5). The NAO index was calculated using the Mean Sea Level Pressure (MSLP) extracted from the nearest gridpoints to Reykjavik, Ponta Delgada, Lisbon and Gibraltar, with a time resolution of one hour and horizontal spatial resolution of 0.25&#186;x0.25&#186;. Both NAO index and MSLP time series were validated for different timescales (hourly, daily, monthly and seasonal) using the Automated Surface Observing System data and the Climatic Research Unit (CRU) high-resolution dataset (based on measured data). High correlations, ranging from 0.92 to 0.98, were found for all stations, timescales and evaluated parameters. To quantify the influence of NAO over the Mediterranean region, the monthly averaged ERA5 &#8216;total precipitation&#8217; data over the Italian Peninsula [35-48&#186; N; 5-20&#186; E] were used. As expected, the results concerning NAO x Precipitation presented the best correlations when analysed monthly, confirming some of the already known NAO signatures over the Italian Peninsula: higher correlations during winter and over the Tyrrhenian coast, and lower correlations during summer and over the Apennines, the Adriatic Sea and the Ionian Sea. On the other hand, the precipitation over the Alps and the Tunisian coast presented a remarkable signature of positive NAO values that, despite a lower statistical significance (85-90%), is in agreement with recent findings of observational studies. In addition, significant negative correlations were identified for the spring and autumn months over the Tyrrhenian area. Among those, the high correlations found during May are particularly interesting, as they follow the behaviour described in recent studies performed using the same high-resolution dataset (ERA5), which have identified an increased number of cyclones over the Mediterranean during this month. This connection suggests that NAO could also be used to explore the potential penetration of the North Atlantic depressions into the Mediterranean Basin.&#160;</p><p>Keywords: NAO; Teleconnections; ERA5; ReAnalysis; Mediterranean; Climatology.</p>

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Effects of High Resolution and Spinup Time on Modeled North Atlantic Circulation

Journal of Physical Oceanography ◽

10.1175/jpo-d-18-0141.1 ◽

2019 ◽

Vol 49 (5) ◽

pp. 1159-1181 ◽

Cited By ~ 4

Author(s):

Christopher Danek ◽

Patrick Scholz ◽

Gerrit Lohmann

Keyword(s):

High Resolution ◽

North Atlantic ◽

Horizontal Resolution ◽

Quasi Equilibrium ◽

Low Resolution ◽

The North ◽

Resolution Model ◽

High Horizontal Resolution ◽

High Resolution Model ◽

The North Atlantic

AbstractThe influence of a high horizontal resolution (5–15 km) on the general circulation and hydrography in the North Atlantic is investigated using the Finite Element Sea Ice–Ocean Model (FESOM). We find a stronger shift of the upper-ocean circulation and water mass properties during the model spinup in the high-resolution model version compared to the low-resolution (~1°) control run. In quasi equilibrium, the high-resolution model is able to reduce typical low-resolution model biases. Especially, it exhibits a weaker salinification of the North Atlantic subpolar gyre and a reduced mixed layer depth in the Labrador Sea. However, during the spinup adjustment, we see that initially improved high-resolution features partially reduce over time: the strength of the Atlantic overturning and the path of the North Atlantic Current are not maintained, and hence hydrographic biases known from low-resolution ocean models return in the high-resolution quasi-equilibrium state. We identify long baroclinic Rossby waves as a potential cause for the strong upper-ocean adjustment of the high-resolution model and conclude that a high horizontal resolution improves the state of the modeled ocean but the model integration length should be chosen carefully.

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Lagrangian data in a high-resolution numerical simulation of the North Atlantic

Journal of Marine Systems ◽

10.1016/s0924-7963(01)00015-x ◽

2001 ◽

Vol 29 (1-4) ◽

pp. 157-176 ◽

Cited By ~ 76

Author(s):

Zulema D Garraffo ◽

Arthur J Mariano ◽

Annalisa Griffa ◽

Carmela Veneziani ◽

Eric P Chassignet

Keyword(s):

Numerical Simulation ◽

High Resolution ◽

North Atlantic ◽

The North ◽

The North Atlantic ◽

Lagrangian Data

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The North Atlantic Subpolar Gyre in Four High-Resolution Models

Journal of Physical Oceanography ◽

10.1175/jpo2720.1 ◽

2005 ◽

Vol 35 (5) ◽

pp. 757-774 ◽

Cited By ~ 116

Author(s):

A. M. Treguier ◽

S. Theetten ◽

E. P. Chassignet ◽

T. Penduff ◽

R. Smith ◽

...

Keyword(s):

High Resolution ◽

North Atlantic ◽

Ocean Model ◽

Quantitative Comparison ◽

Subpolar Gyre ◽

Reykjanes Ridge ◽

The North ◽

North Atlantic Subpolar Gyre ◽

The North Atlantic ◽

High Resolution Models

Abstract The authors present the first quantitative comparison between new velocity datasets and high-resolution models in the North Atlantic subpolar gyre [1/10° Parallel Ocean Program model (POPNA10), Miami Isopycnic Coordinate Ocean Model (MICOM), ⅙° Atlantic model (ATL6), and Family of Linked Atlantic Ocean Model Experiments (FLAME)]. At the surface, the model velocities agree generally well with World Ocean Circulation Experiment (WOCE) drifter data. Two noticeable exceptions are the weakness of the East Greenland coastal current in models and the presence in the surface layers of a strong southwestward East Reykjanes Ridge Current. At depths, the most prominent feature of the circulation is the boundary current following the continental slope. In this narrow flow, it is found that gridded float datasets cannot be used for a quantitative comparison with models. The models have very different patterns of deep convection, and it is suggested that this could be related to the differences in their barotropic transport at Cape Farewell. Models show a large drift in watermass properties with a salinization of the Labrador Sea Water. The authors believe that the main cause is related to horizontal transports of salt because models with different forcing and vertical mixing share the same salinization problem. A remarkable feature of the model solutions is the large westward transport over Reykjanes Ridge [10 Sv (Sv ≡ 106 m3 s−1) or more].

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Instability-Driven Benthic Storms below the Separated Gulf Stream and the North Atlantic Current in a High-Resolution Ocean Model

Journal of Physical Oceanography ◽

10.1175/jpo-d-17-0261.1 ◽

2018 ◽

Vol 48 (10) ◽

pp. 2283-2303 ◽

Cited By ~ 3

Author(s):

René Schubert ◽

Arne Biastoch ◽

Meghan F. Cronin ◽

Richard J. Greatbatch

Keyword(s):

Energy Transfer ◽

High Resolution ◽

Kinetic Energy ◽

North Atlantic ◽

Gulf Stream ◽

Eddy Kinetic Energy ◽

North Atlantic Current ◽

The North ◽

The North Atlantic ◽

Atlantic Current

AbstractBenthic storms are important for both the energy budget of the ocean and for sediment resuspension and transport. Using 30 years of output from a high-resolution model of the North Atlantic, it is found that most of the benthic storms in the model occur near the western boundary in association with the Gulf Stream and the North Atlantic Current, in regions that are generally collocated with the peak near-bottom eddy kinetic energy. A common feature is meander troughs in the near-surface jets that are accompanied by deep low pressure anomalies spinning up deep cyclones with near-bottom velocities of up to more than 0.5 m s−1. A case study of one of these events shows the importance of both baroclinic and barotropic instability of the jet, with energy being extracted from the jet in the upstream part of the meander trough and partly returned to the jet in the downstream part of the meander trough. This motivates examining the 30-yr time mean of the energy transfer from the (annual mean) background flow into the eddy kinetic energy. This quantity is shown to be collocated well with the region in which benthic storms and large increases in deep cyclonic relative vorticity occur most frequently, suggesting an important role for mixed barotropic–baroclinic instability-driven cyclogenesis in generating benthic storms throughout the model simulation. Regions of the largest energy transfer and most frequent benthic storms are found to be the Gulf Stream west of the New England Seamounts and the North Atlantic Current near Flemish Cap.

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RAS-NAAD: 40-yr High-Resolution North Atlantic Atmospheric Hindcast for Multipurpose Applications (New Dataset for the Regional Mesoscale Studies in the Atmosphere and the Ocean)

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-19-0190.1 ◽

2020 ◽

Vol 59 (5) ◽

pp. 793-817 ◽

Cited By ~ 5

Author(s):

Alexander Gavrikov ◽

Sergey K. Gulev ◽

Margarita Markina ◽

Natalia Tilinina ◽

Polina Verezemskaya ◽

...

Keyword(s):

High Resolution ◽

Ocean Circulation ◽

North Atlantic ◽

Three Dimensional ◽

Vertical Direction ◽

Lateral Boundary Condition ◽

Three Dimensional Model ◽

Free Atmosphere ◽

The North ◽

The North Atlantic

AbstractWe present in this paper the results of the Russian Academy of Sciences North Atlantic Atmospheric Downscaling (RAS-NAAD) project, which provides a 40-yr 3D hindcast of the North Atlantic (10°–80°N) atmosphere at 14-km spatial resolution with 50 levels in the vertical direction (up to 50 hPa), performed with a regional setting of the WRF-ARW 3.8.1 model for the period 1979–2018 and forced by ERA-Interim as a lateral boundary condition. The dataset provides a variety of surface and free-atmosphere parameters at sigma model levels and meets many demands of meteorologists, climate scientists, and oceanographers working in both research and operational domains. Three-dimensional model output at 3-hourly time resolution is freely available to the users. Our evaluation demonstrates a realistic representation of most characteristics in both datasets and also identifies biases mostly in the ice-covered regions. High-resolution and nonhydrostatic model settings in NAAD resolve mesoscale dynamics first of all in the subpolar latitudes. NAAD also provides a new view of the North Atlantic extratropical cyclone activity with a much larger number of cyclones as compared with most reanalyses. It also effectively captures highly localized mechanisms of atmospheric moisture transports. Applications of NAAD to ocean circulation and wave modeling are demonstrated.

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