scholarly journals Causal dependences between the coupled ocean-atmosphere dynamics over the Tropical Pacific, the North Pacific and the North Atlantic

2018 ◽  
Author(s):  
Stéphane Vannitsem ◽  
Pierre Ekelmans
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Thermohaline Circulation ◽  
Tropical Pacific ◽  
Ocean Dynamics ◽  
The North ◽  
Ocean Atmosphere ◽  
The North Atlantic ◽  
The North Pacific ◽  
The Tropical Pacific

Abstract. The causal dependences between the dynamics of three different coupled ocean-atmosphere basins, The North Atlantic, the North Pacific and the Tropical Pacific region, NINO3.4, have been explored using data from three reanalyses datasets, namely the ORA-20C, the ORAS4 and the ERA-20C. The approach is based on the Convergent Cross Mapping (CCM) developed by Sugihara et al. (2012) that allows for evaluating the dependences between observables beyond the classical teleconnection patterns based on correlations. The use of CCM on these data mostly reveals that (i) the Tropical Pacific (NINO3.4 region) only influences the dynamics of the North Atlantic region through its annual climatological cycle; (ii) the atmosphere over the North Pacific is dynamically forcing the North Atlantic on a monthly basis; (iii) on longer time scales (interannual), the dynamics of the North Pacific and the North Atlantic are influencing each other through the ocean dynamics, suggesting a connection through the thermohaline circulation. These findings shed a new light on the coupling between these three different important regions of the globe. In particular they call for a deep reassessment of the way teleconnections are interpreted, and for a more rigorous way to evaluate causality and dependences between the different components of the climate system.

scholarly journals Causal dependences between the coupled ocean–atmosphere dynamics over the tropical Pacific, the North Pacific and the North Atlantic

2018 ◽  
Vol 9 (3) ◽  
pp. 1063-1083 ◽  
Author(s):  
Stéphane Vannitsem ◽  
Pierre Ekelmans
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Thermohaline Circulation ◽  
Tropical Pacific ◽  
Ocean Dynamics ◽  
The North ◽  
Ocean Atmosphere ◽  
The North Atlantic ◽  
The North Pacific ◽  
The Tropical Pacific

Abstract. The causal dependences (in a dynamical sense) between the dynamics of three different coupled ocean–atmosphere basins, the North Atlantic, the North Pacific and the tropical Pacific region (Nino3.4), have been explored using data from three reanalysis datasets, namely ORA-20C, ORAS4 and ERA-20C. The approach is based on convergent cross mapping (CCM) developed by Sugihara et al. (2012) that allows for evaluating the dependences between variables beyond the classical teleconnection patterns based on correlations. The use of CCM on these data mostly reveals that (i) the tropical Pacific (Nino3.4 region) only influences the dynamics of the North Atlantic region through its annual climatological cycle; (ii) the atmosphere over the North Pacific is dynamically forcing the North Atlantic on a monthly basis; (iii) on longer timescales (interannual), the dynamics of the North Pacific and the North Atlantic are influencing each other through the ocean dynamics, suggesting a connection through the thermohaline circulation. These findings shed a new light on the coupling between these three different regions of the globe. In particular, they call for a deep reassessment of the way teleconnections are interpreted and for a more rigorous way to evaluate dynamical dependences between the different components of the climate system.

scholarly journals The Development of a Statistical Forecast Model for Changma

2013 ◽  
Vol 28 (6) ◽  
pp. 1304-1321 ◽  
Author(s):  
Seung-Eon Lee ◽  
Kyong-Hwan Seo
Keyword(s):  
Wave Propagation ◽  
North Atlantic ◽  
North Pacific ◽  
Forecast Model ◽  
Tropical Pacific ◽  
The North ◽  
Sst Anomaly ◽  
The North Atlantic ◽  
The North Pacific ◽  
The Tropical Pacific

Abstract Forecasting year-to-year variations in East Asian summer monsoon (EASM) precipitation is one of the most challenging tasks in climate prediction because the predictors are not sufficiently well known and the forecast skill of the numerical models is poor. In this paper, a statistical forecast model for changma (the Korean portion of the EASM system) precipitation is proposed that was constructed with three physically based predictors. A forward-stepwise regression was used to select the predictors that included sea surface temperature (SST) anomalies over the North Pacific, the North Atlantic, and the tropical Pacific Ocean. Seasonal predictions with this model showed high forecasting capabilities that had a Gerrity skill score of ~0.82. The dynamical processes associated with the predictors were examined prior to their use in the prediction scheme. All predictors tended to induce an anticyclonic anomaly to the east or southeast of Japan, which was responsible for transporting a large amount of moisture to the southern Korean Peninsula. The predictor in the North Pacific formed an SST front to the east of Japan during the summertime, which maintained a lower-tropospheric baroclinicity. The North Atlantic SST anomaly induced downstream wave propagation in the upper troposphere, developing anticyclonic activity east of Japan. Forcing from the tropical Pacific SST anomaly triggered a cyclonic anomaly over the South China Sea, which was maintained by atmosphere–ocean interactions and induced an anticyclonic anomaly via northward Rossby wave propagation. Overall, the model used for forecasting changma precipitation performed well (R = 0.85) and correctly predicted information for 16 out of 19 yr of observational data.

Atmospheric Control on the Thermohaline Circulation

2009 ◽  
Vol 39 (1) ◽  
pp. 234-247 ◽  
Author(s):  
Arnaud Czaja
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
North Pacific ◽  
Thermohaline Circulation ◽  
High Surface ◽  
Subpolar Gyre ◽  
Atlantic Sector ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific

Abstract In an attempt to elucidate the role of atmospheric and oceanic processes in setting a vigorous ocean overturning circulation in the North Atlantic but not in the North Pacific, a comparison of the observed atmospheric circulation and net surface freshwater fluxes over the North Atlantic and Pacific basins is conducted. It is proposed that the more erratic meridional displacements of the atmospheric jet stream over the North Atlantic sector is instrumental in maintaining high surface salinities in its subpolar gyre. In addition, it is suggested that the spatial pattern of the net freshwater flux at the sea surface favors higher subpolar Atlantic salinity, because the geographical line separating net precipitation from net evaporation is found well south of the time-mean gyre separation in the North Pacific, whereas the two lines tend to coincide in the North Atlantic. Numerical experiments with an idealized two-gyre system confirm that these differences impact the salinity budget of the subpolar gyre. Further analysis of a coupled climate model in which the Atlantic meridional overturning cell has been artificially weakened suggests that the more erratic jet fluctuations in the Atlantic and the shift of the zero [net evaporation minus precipitation (E − P)] line are likely explained by features independent of the state of the thermohaline circulation. It is thus proposed that the atmospheric circulation helps “locking” high surface salinities and an active coupling between upper and deep ocean layers in the North Atlantic rather than in the North Pacific basin.

scholarly journals Portraying the Impact of the Tibetan Plateau on Global Climate

2020 ◽  
Vol 33 (9) ◽  
pp. 3565-3583 ◽  
Author(s):  
Haijun Yang ◽  
Xingchen Shen ◽  
Jie Yao ◽  
Qin Wen
Keyword(s):  
Tibetan Plateau ◽  
North Atlantic ◽  
Thermohaline Circulation ◽  
Global Climate ◽  
Tropical Pacific ◽  
The Tibetan Plateau ◽  
The North ◽  
The North Atlantic ◽  
The Impact ◽  
The Tropical Pacific

AbstractAs the most extensive highland in the world, the Tibetan Plateau (TP) plays an important role in shaping the global climate. Quantifying the effect of the TP on global climate is the first step for a full understanding of the TP’s standing on planet Earth. Through coupled model sensitivity experiments, we draw a panorama of the TP’s global impact in this paper. Our model results show that the absence of the TP would result in a 4°C colder and 10% drier climate in the Northern Hemisphere (NH). The TP has a striking remote effect on the North Atlantic. Removing the TP would enhance the westerlies in the mid- to high latitudes of the NH and weaken the easterlies over the tropical Pacific. More moisture would be relocated from the tropical Pacific to the North Atlantic, shutting down the Atlantic thermohaline circulation, which would eventually result in more than 15°C colder and 20% drier climate over the North Atlantic. Our model results suggest that the presence of the TP may have contributed greatly to the hospitable modern climate in the NH, by promoting the establishment of the thermohaline circulation in the Atlantic, and therefore enhancing the northward ocean heat transport and atmosphere moisture transport across the equator.

scholarly journals A Hemispheric Mechanism for the Atlantic Multidecadal Oscillation

2007 ◽  
Vol 20 (11) ◽  
pp. 2706-2719 ◽  
Author(s):  
Mihai Dima ◽  
Gerrit Lohmann
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
North Pacific ◽  
Thermohaline Circulation ◽  
Atlantic Multidecadal Oscillation ◽  
Sea Surface ◽  
The North ◽  
Sea Surface Temperature Anomalies ◽  
The North Atlantic ◽  
The North Pacific

Abstract The physical processes associated with the ∼70-yr period climate mode, known as the Atlantic multidecadal oscillation (AMO), are examined. Based on analyses of observational data, a deterministic mechanism relying on atmosphere–ocean–sea ice interactions is proposed for the AMO. Variations in the thermohaline circulation are reflected as uniform sea surface temperature anomalies in the North Atlantic. These anomalies are associated with a hemispheric wavenumber-1 sea level pressure (SLP) structure in the atmosphere that is amplified through atmosphere–ocean interactions in the North Pacific. The SLP pattern and its associated wind field affect the sea ice export through Fram Strait, the freshwater balance in the northern North Atlantic, and consequently the strength of the large-scale ocean circulation. It generates sea surface temperature anomalies with opposite signs in the North Atlantic and completes a negative feedback. The authors find that the time scale of the cycle is associated with the thermohaline circulation adjustment to freshwater forcing, the SST response to it, the oceanic adjustment in the North Pacific, and the sea ice response to the wind forcing. Finally, it is argued that the Great Salinity Anomaly in the late 1960s and 1970s is part of AMO.

scholarly journals Simulated Response to Recent Freshwater Flux Change over the Gulf Stream and Its Extension: Coupled Ocean–Atmosphere Adjustment and Atlantic–Pacific Teleconnection

2011 ◽  
Vol 24 (15) ◽  
pp. 3971-3988 ◽  
Author(s):  
Liping Zhang ◽  
Lixin Wu ◽  
Jiaxu Zhang
Keyword(s):  
North Atlantic ◽  
Gulf Stream ◽  
Tropical Pacific ◽  
Late Winter ◽  
Freshwater Flux ◽  
The North ◽  
Flux Change ◽  
Ocean Atmosphere ◽  
The North Atlantic ◽  
The Tropical Pacific

Abstract Recent observation has shown that the dominant mode of the net freshwater flux variations over the North Atlantic Ocean is the significant trend of freshwater loss over the Gulf Stream region and its extension. In this paper, the coupled ocean–atmosphere response to this freshwater flux change is investigated based on a series of the Fast Ocean–Atmosphere Model coupled-model experiments. The model demonstrates that the freshwater loss over the Gulf Stream and its extension region directly forces an anomalous cyclonic gyre and triggers a SST dipole with cooling in the western subtropical and warming in the eastern subpolar North Atlantic. The freshwater loss also forces a significant response in the atmosphere with a negative NAO-like response in early winter and a basin-scale ridge resembling the eastern Atlantic mode (EAM) in late winter. The salinification also strengthens the Atlantic meridional overturning circulation and thus the poleward heat transport, leading to tropical cooling. The freshwater loss over the Gulf Stream and its extension also leads to an El Niño–like warming in the tropical Pacific and cooling in the North Pacific, similar to the responses in previous water-hosing experiments with an input of freshwater in the subpolar North Atlantic. The tropical Pacific responses subsequently strengthen the Northern Hemispheric atmospheric anomalies in early winter, but reverse them in late winter through an emanation of Rossby wave trains. Overall, the tropical Pacific air–sea coupling plays a damping role, while local air–sea coupling tends to enhance the ocean and atmospheric responses over the North Atlantic.

scholarly journals Warming of the North Pacific Ocean: Local Air–Sea Coupling and Remote Climatic Impacts

2007 ◽  
Vol 20 (11) ◽  
pp. 2581-2601 ◽  
Author(s):  
Lixin Wu ◽  
Chun Li
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Tropical Pacific ◽  
Meridional Overturning Circulation ◽  
Ocean Dynamics ◽  
Atmospheric Response ◽  
The North ◽  
The North Pacific ◽  
The Tropical Pacific

Abstract In this paper, global climatic response to the North Pacific oceanic warming is investigated in a series of coupled ocean–atmosphere modeling experiments. In the model, an idealized heating is imposed over the North Pacific Ocean, while the ocean and atmosphere remain fully coupled both locally and elsewhere. The model explicitly demonstrates that the North Pacific oceanic warming can force a significant change of the atmospheric circulation with a strong seasonal dependence. The seasonal marching of the atmospheric response over the North Pacific is characterized by a quasi-baratropic warm ridge in early winter, a transition to a quasi-baratropic warm trough in late winter, and then to a baroclinic response in summer with a trough and ridge, respectively, in the lower and upper troposphere. The North Pacific warming also forces a significant remote response over the tropical Pacific. In winter, the tropical Pacific response is characterized by a nearly uniform warming coupled with anomalous southerly cross-equatorial winds, while in summer it is dominated by an enhanced zonal SST gradient and anomalous equatorial easterlies. The tropical warming tends to be associated with a reduction of the upper-ocean meridional overturning circulation and equatorial ocean dynamics associated with a reduction of the Hadley circulation and the surface coupled wind–evaporation–SST feedback. The resulting tropical warming can further intensify the seasonal marching of the North Pacific atmospheric response. The global impacts of the North Pacific warming are also discussed.

The Role of Oscillating Southern Hemisphere Westerly Winds: Global Ocean Circulation

2020 ◽  
Vol 33 (6) ◽  
pp. 2111-2130
Author(s):  
Woo Geun Cheon ◽  
Jong-Seong Kug
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
North Pacific ◽  
Global Ocean ◽  
The North ◽  
Westerly Winds ◽  
The North Atlantic ◽  
Global Ocean Circulation ◽  
The Antarctic ◽  
The North Pacific

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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