Skill tests of three-dimensional tidal currents in a global ocean model: A look at the North Atlantic

AbstractIn the framework of a sea ice–ocean general circulation model coupled to an energy balance atmospheric model, an intensity oscillation of Southern Hemisphere (SH) westerly winds affects the global ocean circulation via not only the buoyancy-driven teleconnection (BDT) mode but also the Ekman-driven teleconnection (EDT) mode. The BDT mode is activated by the SH air–sea ice–ocean interactions such as polynyas and oceanic convection. The ensuing variation in the Antarctic meridional overturning circulation (MOC) that is indicative of the Antarctic Bottom Water (AABW) formation exerts a significant influence on the abyssal circulation of the globe, particularly the Pacific. This controls the bipolar seesaw balance between deep and bottom waters at the equator. The EDT mode controlled by northward Ekman transport under the oscillating SH westerly winds generates a signal that propagates northward along the upper ocean and passes through the equator. The variation in the western boundary current (WBC) is much stronger in the North Atlantic than in the North Pacific, which appears to be associated with the relatively strong and persistent Mindanao Current (i.e., the southward flowing WBC of the North Pacific tropical gyre). The North Atlantic Deep Water (NADW) formation is controlled by salt advected northward by the North Atlantic WBC.

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Tracking the Paleocene-Eocene Thermal Maximum in the North Atlantic: A Shelf-to-Basin Analysis With a Regional Ocean Model

Paleoceanography and Paleoclimatology ◽

10.1029/2018pa003371 ◽

2018 ◽

Vol 33 (12) ◽

pp. 1324-1338 ◽

Cited By ~ 1

Author(s):

Kalev G. Hantsoo ◽

Lee R. Kump ◽

Bernd J. Haupt ◽

Timothy J. Bralower

Keyword(s):

North Atlantic ◽

Ocean Model ◽

Basin Analysis ◽

The North ◽

Thermal Maximum ◽

Regional Ocean Model ◽

The North Atlantic

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Marine productivity response to Heinrich events: a model-data comparison

Climate of the Past ◽

10.5194/cp-8-1581-2012 ◽

2012 ◽

Vol 8 (5) ◽

pp. 1581-1598 ◽

Cited By ~ 23

Author(s):

V. Mariotti ◽

L. Bopp ◽

A. Tagliabue ◽

M. Kageyama ◽

D. Swingedouw

Keyword(s):

North Atlantic ◽

General Circulation ◽

Circulation Model ◽

Global Ocean ◽

Biogeochemical Model ◽

Heinrich Events ◽

The North ◽

Heinrich Event ◽

The North Atlantic ◽

Marine Productivity

Abstract. Marine sediments records suggest large changes in marine productivity during glacial periods, with abrupt variations especially during the Heinrich events. Here, we study the response of marine biogeochemistry to such an event by using a biogeochemical model of the global ocean (PISCES) coupled to an ocean-atmosphere general circulation model (IPSL-CM4). We conduct a 400-yr-long transient simulation under glacial climate conditions with a freshwater forcing of 0.1 Sv applied to the North Atlantic to mimic a Heinrich event, alongside a glacial control simulation. To evaluate our numerical results, we have compiled the available marine productivity records covering Heinrich events. We find that simulated primary productivity and organic carbon export decrease globally (by 16% for both) during a Heinrich event, albeit with large regional variations. In our experiments, the North Atlantic displays a significant decrease, whereas the Southern Ocean shows an increase, in agreement with paleo-productivity reconstructions. In the Equatorial Pacific, the model simulates an increase in organic matter export production but decreased biogenic silica export. This antagonistic behaviour results from changes in relative uptake of carbon and silicic acid by diatoms. Reasonable agreement between model and data for the large-scale response to Heinrich events gives confidence in models used to predict future centennial changes in marine production. In addition, our model allows us to investigate the mechanisms behind the observed changes in the response to Heinrich events.

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Efficient carbon drawdown allows for a high future carbon uptake in the North Atlantic

10.5194/egusphere-egu21-3894 ◽

2021 ◽

Author(s):

Nadine Goris ◽

Jerry Tjiputra ◽

Are Ohlsen ◽

Jörg Schwinger ◽

Siv Lauvset ◽

...

Keyword(s):

North Atlantic ◽

High Latitude ◽

Deep Convection ◽

Deep Ocean ◽

Nutrient Supply ◽

Global Ocean ◽

Carbon Uptake ◽

Model Ensemble ◽

The North ◽

The North Atlantic

As one of the major carbon sinks in the global ocean, the North Atlantic is a key player in mediating and ameliorating the ongoing global warming. Projections of the North Atlantic carbon sink in a high-CO2 future vary greatly among models, with some showing that a slowdown in carbon uptake has already begun and others predicting that this slowdown will not occur until nearly 2100.Discrepancies among models largely originate because of differences in the efficiency of the high-latitude transport of carbon from the surface to the deep ocean. This transport occurs through biological production, deep convection and subsequent transport via the deep western boundary current. For an ensemble of 11 CMIP5-models, we studied the efficiency of this transport and identified two indicators of contemporary model behavior that are highly correlated with a model&#180;s projected future carbon-uptake. The first indicator is the high latitude summer pCO2sea-anomaly of a model, which is tightly linked to winter mixing and nutrient supply, but also to deep convection. The second indicator is the fraction of the anthropogenic carbon-inventory stored below 1000-m depth, indicating how efficient carbon is transported into the deep ocean. By comparing to the observational database, these indicators allow us to better constrain the model ensemble, and demonstrate that the models with more efficient surface to deep transport are best aligned with current observations. These models also show the largest future North Atlantic carbon uptake, which we then conclude is the more plausible future evolution. We further study if the high correlations between our contemporary indicators and a model&#180;s future North Atlantic carbon uptake is also upheld for the next model generation, CMIP6. We hypothesize that this is the case and that our indicators can not only help us to constrain the CMIP6 model ensemble but also inform us about progress made between CMIP5 and CMIP6 in terms of North Atlantic carbon uptake, winter mixing, nutrient supply, deep convection and transport of carbon into the deep ocean.

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Greenland melting signatures in model simulations and oceanic observations

10.5194/egusphere-egu21-8225 ◽

2021 ◽

Author(s):

Sophie Stolzenberger ◽

Roelof Rietbroek ◽

Claudia Wekerle ◽

Bernd Uebbing ◽

Jürgen Kusche

Keyword(s):

North Atlantic ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ocean Model ◽

Freshwater Flux ◽

Model Simulations ◽

The North ◽

Sea Level Anomalies ◽

The North Atlantic ◽

The Impact

The impact of Greenland freshwater on oceanic variables in the North Atlantic has been controversially discussed in the past. Within the framework of the German research project GROCE (Greenland Ice Sheet Ocean Interaction), we present a comprehensive study using ocean modelling results including and excluding the Greenland freshwater flux. The aim of this study is whether signatures of Greenland ice sheet melting found in ocean model simulations are visible in the observations. Therefore, we estimate changes in temperature, salinity, steric heights and sea level anomalies since the 1990s. The observational database includes altimetric and gravimetric satellite data as well as Argo floats. We will discuss similarities/differences between model simulations and observations for smaller regions around Greenland in the North Atlantic. As these experiments are available for two different horizontal resolutions, we will furthermore be able to assess the effects of an increased model resolution.

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Variability of the Oceanic Mixed Layer, 1960–2004

Journal of Climate ◽

10.1175/2007jcli1798.1 ◽

2008 ◽

Vol 21 (5) ◽

pp. 1029-1047 ◽

Cited By ~ 64

Author(s):

James A. Carton ◽

Semyon A. Grodsky ◽

Hailong Liu

Keyword(s):

Mixed Layer ◽

North Atlantic ◽

Southern Oscillation ◽

Mixed Layer Depth ◽

Global Ocean ◽

Boreal Summer ◽

Layer Depth ◽

The North ◽

The North Atlantic ◽

Mixed Layers

Abstract A new monthly uniformly gridded analysis of mixed layer properties based on the World Ocean Atlas 2005 global ocean dataset is used to examine interannual and longer changes in mixed layer properties during the 45-yr period 1960–2004. The analysis reveals substantial variability in the winter–spring depth of the mixed layer in the subtropics and midlatitudes. In the North Pacific an empirical orthogonal function analysis shows a pattern of mixed layer depth variability peaking in the central subtropics. This pattern occurs coincident with intensification of local surface winds and may be responsible for the SST changes associated with the Pacific decadal oscillation. Years with deep winter–spring mixed layers coincide with years in which winter–spring SST is low. In the North Atlantic a pattern of winter–spring mixed layer depth variability occurs that is not so obviously connected to local changes in winds or SST, suggesting that other processes such as advection are more important. Interestingly, at decadal periods the winter–spring mixed layers of both basins show trends, deepening by 10–40 m over the 45-yr period of this analysis. The long-term mixed layer deepening is even stronger (50–100 m) in the North Atlantic subpolar gyre. At tropical latitudes the boreal winter mixed layer varies in phase with the Southern Oscillation index, deepening in the eastern Pacific and shallowing in the western Pacific and eastern Indian Oceans during El Niños. In boreal summer the mixed layer in the Arabian Sea region of the western Indian Ocean varies in response to changes in the strength of the southwest monsoon.

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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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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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Bioturbational structures in the North Atlantic: new approaches for studying cores

The Paleontological Society Special Publications ◽

10.1017/s2475262200006663 ◽

1992 ◽

Vol 6 ◽

pp. 106-106

Author(s):

Shaoping Fu ◽

Friedrich Werner

Keyword(s):

North Atlantic ◽

Sediment Cores ◽

Three Dimensional ◽

Bedding Plane ◽

Lateral Migration ◽

Core Diameter ◽

The North ◽

Biogenic Structures ◽

Sediment Cover ◽

The North Atlantic

General environmental correlation, established for trace fossils, is hard to apply to modern sediment cores, for which environmental factors can be measured directly - at least with regard to the top layers. Reasons for this difficulty are obvious: (1) Outcrop volume is limited by the core diameter. (2) Biogenic structures are hard to see, because they have not yet been “developed” by diagenetic processes. (3) Cores are traditionally studied in vertical cuts, in which search patterns parallel to bedding plane - typical for deep-sea environment - are poorly expressed. Therefore cores from the North Atlantic were studied not only by traditional X-ray radiography (both vertical and horizontal cuts), but by computer tomography (CT), which renders series of sections parallel to the bedding plane, as well as a three-dimensional picture, without destroying the valuable core.On the Iceland-Faeroe Ridge, the distribution of ichnocoenoses appears to be largely controlled by microenvironments in connection with local channel systems and their lateral migration. In a local, ridge-parallel channel system at the southern slope, a core from the NE flank shows a vertical alternation of Zoophycos, Trichichnus, and Planolites communities correlating with fluctuations of CaCO3 and the fraction >63μm. In contrast to this, on the opposite slope, sediments are uniform and dominated by Scolicia. On the colder N slope of the ridge, topography is more uniform and the water motion is sluggish. The characteristic and dominant ichnogenus is Chondrites. On top of the ridge the sediment cover becomes very thin, contains large amounts of dropstones, but still Chondrites is dominant.

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