Analysis of the factors exciting the ocean–atmosphere heat interaction in the North Atlantic using satellite and vessel data

Abstract In this paper, the atmospheric teleconnections of the tropical Atlantic SST variability are investigated in a series of coupled ocean–atmosphere modeling experiments. It is found that the tropical Atlantic climate not only displays an apparent interhemispheric link, but also significantly influences the North Atlantic Oscillation (NAO) and the El Niño–Southern Oscillation (ENSO). In spring, the tropical Atlantic SST exhibits an interhemispheric seesaw controlled by the wind–evaporation–SST (WES) feedback that subsequently decays through the mediation of the seasonal migration of the ITCZ. Over the North Atlantic, the tropical Atlantic SST can force a significant coupled NAO–dipole SST response in spring that changes to a coupled wave train–horseshoe SST response in the following summer and fall, and a recurrence of the NAO in the next winter. The seasonal changes of the atmospheric response as well as the recurrence of the next winter’s NAO are driven predominantly by the tropical Atlantic SST itself, while the resulting extratropical SST can enhance the atmospheric response, but it is not a necessary bridge of the winter-to-winter NAO persistency. Over the Pacific, the model demonstrates that the north tropical Atlantic (NTA) SST can also organize an interhemispheric SST seesaw in spring in the eastern equatorial Pacific that subsequently evolves into an ENSO-like pattern in the tropical Pacific through mediation of the ITCZ and equatorial coupled ocean–atmosphere feedback.

Download Full-text

Atmospheric Response to Arctic and Antarctic Sea Ice: The Importance of Ocean–Atmosphere Coupling and the Background State

Journal of Climate ◽

10.1175/jcli-d-16-0564.1 ◽

2017 ◽

Vol 30 (12) ◽

pp. 4547-4565 ◽

Cited By ~ 58

Author(s):

Doug M. Smith ◽

Nick J. Dunstone ◽

Adam A. Scaife ◽

Emma K. Fiedler ◽

Dan Copsey ◽

...

Keyword(s):

Sea Ice ◽

North Atlantic ◽

Arctic Sea Ice ◽

Atmospheric Response ◽

The North ◽

Antarctic Sea Ice ◽

Arctic Sea ◽

Ocean Atmosphere ◽

The North Atlantic ◽

Background State

The atmospheric response to Arctic and Antarctic sea ice changes typical of the present day and coming decades is investigated using the Hadley Centre global climate model (HadGEM3). The response is diagnosed from ensemble simulations of the period 1979 to 2009 with observed and perturbed sea ice concentrations. The experimental design allows the impacts of ocean–atmosphere coupling and the background atmospheric state to be assessed. The modeled response can be very different to that inferred from statistical relationships, showing that the response cannot be easily diagnosed from observations. Reduced Arctic sea ice drives a local low pressure response in boreal summer and autumn. Increased Antarctic sea ice drives a poleward shift of the Southern Hemisphere midlatitude jet, especially in the cold season. Coupling enables surface temperature responses to spread to the ocean, amplifying the atmospheric response and revealing additional impacts including warming of the North Atlantic in response to reduced Arctic sea ice, with a northward shift of the Atlantic intertropical convergence zone and increased Sahel rainfall. The background state controls the sign of the North Atlantic Oscillation (NAO) response via the refraction of planetary waves. This could help to resolve differences in previous studies, and potentially provides an “emergent constraint” to narrow the uncertainties in the NAO response, highlighting the need for future multimodel coordinated experiments.

Download Full-text

Letter to the editor: Are the North Atlantic Oscillation and the Southern Oscillation related in any time-scale?

Annales Geophysicae ◽

10.1007/s00585-000-0247-z ◽

2000 ◽

Vol 18 (2) ◽

pp. 247-251 ◽

Cited By ~ 2

Author(s):

R. García ◽

P. Ribera ◽

L. Gimenoo ◽

E. Hernández

Keyword(s):

North Atlantic Oscillation ◽

North Atlantic ◽

Southern Oscillation ◽

Singular Spectrum Analysis ◽

Atmospheric Dynamics ◽

Meteorology And Atmospheric Dynamics ◽

The North ◽

Ocean Atmosphere ◽

The North Atlantic ◽

The North Atlantic Oscillation

Abstract. The North Atlantic Oscillation (NAO) and the Southern Oscillation (SO) are compared from the standpoint of a possible common temporal scale of oscillation. To do this a cross-spectrum of the temporal series of NAO and SO indices was determined, finding a significant common oscillation of 6-8 years. To assure this finding, both series were decomposed in their main oscillations using singular spectrum analysis (SSA). Resulting reconstructed series of 6-8 years oscillation were then cross-correlated without and with pre-whitened, the latter being significant. The main conclusion is a possible relationship between a common oscillation of 6-8 years' that represents about 20% of the SO variance and about 25% of the NAO variance.Key words: Meteorology and atmospheric dynamics (climatology; ocean-atmosphere interactions)

Download Full-text

Ocean–Atmosphere Influences on Low-Frequency Warm-Season Drought Variability in the Gulf Coast and Southeastern United States

Journal of Applied Meteorology and Climatology ◽

10.1175/2010jamc2566.1 ◽

2011 ◽

Vol 50 (6) ◽

pp. 1177-1186 ◽

Cited By ~ 34

Author(s):

Jason T. Ortegren ◽

Paul A. Knapp ◽

Justin T. Maxwell ◽

William P. Tyminski ◽

Peter T. Soulé

Keyword(s):

United States ◽

North Atlantic ◽

Low Frequency ◽

Warm Season ◽

Spatiotemporal Variability ◽

Drought Variability ◽

The North ◽

Low Frequency Variability ◽

Ocean Atmosphere ◽

The North Atlantic

AbstractFrom the 344 state climate divisions in the conterminous United States, nine distinct regions of warm-season drought variability are identified using principal component analysis. The drought metric used is the Palmer hydrological drought index for the period 1895–2008. The focus of this paper is multidecadal drought variability in the Southeast (SEUS) and eastern Gulf South (EGS) regions of the United States, areas in which the low-frequency forcing mechanisms of warm-season drought are still poorly understood. Low-frequency drought variability in the SEUS and EGS is associated with smoothed indexed time series of major ocean–atmosphere circulation features, including two indices of spatiotemporal variability in the North Atlantic subtropical anticyclone (Bermuda high). Long-term warm-season drought conditions are significantly out of phase between the two regions. Multidecadal regimes of above- and below-average moisture in the SEUS and EGS are closely associated with slow variability in sea surface temperatures in the North Atlantic Ocean and with the summer mean position and mean strength of the Bermuda high. Multivariate linear regression indicates that 82%–92% of the low-frequency variability in warm-season moisture is explained by two of the three leading principal components of low-frequency variability in the climate indices. The findings are important for water resource managers and water-intensive industries in the SEUS and EGS. The associations identified in the paper are valuable for enhanced drought preparedness and forecasting in the study area and potentially for global models of coupled ocean–atmosphere variability.

Download Full-text

Will Global Warming Suppress North Atlantic Tripole Decadal Variability?

Journal of Climate ◽

10.1175/jcli-d-11-00164.1 ◽

2012 ◽

Vol 25 (6) ◽

pp. 2040-2055 ◽

Cited By ~ 5

Author(s):

Yun Yang ◽

Lixin Wu ◽

Changfang Fang

Keyword(s):

Global Warming ◽

North Atlantic ◽

Time Scale ◽

Decadal Variability ◽

Buoyancy Frequency ◽

The North ◽

Ocean Atmosphere ◽

The North Atlantic ◽

Partial Blocking ◽

Partial Coupling

Abstract In this paper, the modulations of the North Atlantic tripole (NAT) decadal variability from global warming are studied by conducting a series of coupled ocean–atmosphere experiments using the Fast Ocean Atmosphere Model (FOAM). The model reasonably captures the observed NAT decadal variability with a preferred time scale of about 11 years. With the aid of partial-blocking and partial-coupling experiments, it is found that the NAT decadal cycle can be attributed to oceanic planetary wave adjustment in the subtropical basin and ocean–atmosphere coupling over the North Atlantic. In a doubled CO2 experiment, the spatial pattern of the NAT is preserved; however, the decadal cycle is significantly suppressed. This suppression appears to be associated with the acceleration of oceanic planetary waves due to an increase of buoyancy frequency in global warming. This shortens the time from a decadal to an interannual time scale for the first-mode baroclinic Rossby waves to cross the subtropical North Atlantic basin, the primary memory for the NAT decadal variability in the model. The modeling study also found that the global warming does not modulate the North Atlantic air–sea coupling significantly, but it may be model dependent.

Download Full-text

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

10.5194/esd-2018-3 ◽

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.

Download Full-text