The global structure of the annual and semiannual sea surface height variability from Geosat altimeter data

1992 ◽  
Vol 97 (C11) ◽  
pp. 17813-17828 ◽  
Author(s):  
Gregg A. Jacobs ◽  
George H. Born ◽  
Mike E. Parke ◽  
Patrick C. Allen
Keyword(s):  
Sea Surface Height ◽  
Global Structure ◽  
Sea Surface ◽  
Altimeter Data

scholarly journals On the Relationship between Regional Ocean Heat Content and Sea Surface Height

2017 ◽  
Vol 30 (22) ◽  
pp. 9195-9211 ◽  
Author(s):  
John T. Fasullo ◽  
Peter R. Gent
Keyword(s):  
Time Scales ◽  
Low Frequency ◽  
Heat Content ◽  
Sea Surface Height ◽  
Ocean Heat Content ◽  
Ocean Dynamics ◽  
Sea Surface ◽  
Altimeter Data ◽  
Model Control ◽  
The Relationship

Abstract An accurate diagnosis of ocean heat content (OHC) is essential for interpreting climate variability and change, as evidenced for example by the broad range of hypotheses that exists for explaining the recent hiatus in global mean surface warming. Potential insights are explored here by examining relationships between OHC and sea surface height (SSH) in observations and two recently available large ensembles of climate model simulations from the mid-twentieth century to 2100. It is found that in decadal-length observations and a model control simulation with constant forcing, strong ties between OHC and SSH exist, with little temporal or spatial complexity. Agreement is particularly strong on monthly to interannual time scales. In contrast, in forced transient warming simulations, important dependencies in the relationship exist as a function of region and time scale. Near Antarctica, low-frequency SSH variability is driven mainly by changes in the circumpolar current associated with intensified surface winds, leading to correlations between OHC and SSH that are weak and sometimes negative. In subtropical regions, and near other coastal boundaries, negative correlations are also evident on long time scales and are associated with the accumulated effects of changes in the water cycle and ocean dynamics that underlie complexity in the OHC relationship to SSH. Low-frequency variability in observations is found to exhibit similar negative correlations. Combined with altimeter data, these results provide evidence that SSH increases in the Indian and western Pacific Oceans during the hiatus are suggestive of substantial OHC increases. Methods for developing the applicability of altimetry as a constraint on OHC more generally are also discussed.

Contributions of Wind Forcing and Surface Heating to Interannual Sea Level Variations in the Atlantic Ocean

2006 ◽  
Vol 36 (9) ◽  
pp. 1739-1750 ◽  
Author(s):  
Cécile Cabanes ◽  
Thierry Huck ◽  
Alain Colin de Verdière
Keyword(s):  
Atlantic Ocean ◽  
Sea Level ◽  
Wind Stress ◽  
Large Scale ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Altimeter Data ◽  
Local Response ◽  
Sea Level Variability ◽  
Sea Level Variations

Abstract Interannual sea surface height variations in the Atlantic Ocean are examined from 10 years of high-precision altimeter data in light of simple mechanisms that describe the ocean response to atmospheric forcing: 1) local steric changes due to surface buoyancy forcing and a local response to wind stress via Ekman pumping and 2) baroclinic and barotropic oceanic adjustment via propagating Rossby waves and quasi-steady Sverdrup balance, respectively. The relevance of these simple mechanisms in explaining interannual sea level variability in the whole Atlantic Ocean is investigated. It is shown that, in various regions, a large part of the interannual sea level variability is related to local response to heat flux changes (more than 50% in the eastern North Atlantic). Except in a few places, a local response to wind stress forcing is less successful in explaining sea surface height observations. In this case, it is necessary to consider large-scale oceanic adjustments: the first baroclinic mode forced by wind stress explains about 70% of interannual sea level variations in the latitude band 18°–20°N. A quasi-steady barotropic Sverdrup response is observed between 40° and 50°N.

Obtaining sea surface height signals from ERS‐1 altimeter data

1993 ◽  
Vol 16 (3) ◽  
pp. 241-251 ◽  
Author(s):  
Rashmi Sharma ◽  
M. M. Ali
Keyword(s):  
Sea Surface Height ◽  
Sea Surface ◽  
Altimeter Data

scholarly journals Temporal and spatial characteristics of sea surface height variability in the North Atlantic Ocean

Ocean Science ◽  
2006 ◽  
Vol 2 (2) ◽  
pp. 147-159 ◽  
Author(s):  
D. Cromwell
Keyword(s):  
North Atlantic ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Altimeter Data ◽  
Atlantic Basin ◽  
North Atlantic Basin ◽  
The North ◽  
Second Mode ◽  
Leading Mode ◽  
The North Atlantic

Abstract. We investigate the spatial and temporal variability of sea surface height (SSH) in the North Atlantic basin using satellite altimeter data from October 1992–January 2004. Our primary aim is to provide a detailed description of such variability, including that associated with propagating signals. We also investigate possible correlations between SSH variability and atmospheric pressure changes as represented by climate indices. We first investigate interannual SSH variations by deriving the complex empirical orthogonal functions (CEOFs) of altimeter data lowpass-filtered at 18 months. We determine the spatial structure of the leading four modes (both in amplitude and phase) and also the associated principal component (PC) time series. Using wavelet analysis we derive the time-varying spectral density of the PCs, revealing when particular modes were strongest between 1992–2004. The spatial pattern of the leading CEOF, comprising 30% of the total variability, displays a 5-year periodicity in phase; signal propagation is particularly marked in the Labrador Sea. The second mode, with a dominant 3-year signal, has strong variability in the eastern basin. Secondly, we focus on the Azores subtropical frontal zone. The leading mode (35%) is strong in the south and east of this region with strong variations at 3- and 5-year periods. The second mode (21%) has a near-zonal band of low variance between  22°–27° N, sandwiched between two regions of high variance. Thirdly, we lowpass filter the altimeter data at a cutoff of 30 days, instead of 18 months, in order to retain signals associated with propagating baroclinic Rossby waves and/or eddies. The leading mode is the annual steric signal, around 46% of the SSH variability. The third and fourth CEOFs,  11% of the remaining variability, are associated with westward propagation which is particularly dominant in a "waveband" between 32°–36° N. For all three cases considered above, no significant cross-correlation is found between the North Atlantic Oscillation index and the amplitude of the leading four PCs of interannual SSH variability. The only exception is an anti-correlation found over the North Atlantic basin between the NAO and the 4th PC. In the subtropical front, the East Atlantic Pattern index is anti-correlated with the leading PC for SSH variations lowpass filtered at 30 days. Further investigation of forcing mechanisms is suggested using hindcasts from ocean general circulation models.

scholarly journals Temporal and spatial characteristics of sea surface height variability in the North Atlantic Ocean

2006 ◽  
Vol 3 (3) ◽  
pp. 609-636 ◽  
Author(s):  
D. Cromwell
Keyword(s):  
North Atlantic ◽  
Principal Components ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Frontal Region ◽  
Altimeter Data ◽  
The North ◽  
Second Mode ◽  
Leading Mode ◽  
The North Atlantic

Abstract. We investigate the spatial and temporal variability of sea surface height (SSH) in the North Atlantic basin using altimeter data from October 1992–January 2004. Our primary aim is to provide a fuller description of such variability, particularly that associated with propagating signals. We also investigate possible correlations between SSH variability and climate indices. We first investigate interannual SSH variations by deriving the complex empirical orthogonal functions (CEOFs) of altimeter data lowpass-filtered at 18 months. We determine the spatial structure of the leading four modes (both in amplitude and phase) and also the associated principal components (PCs). Using wavelet analysis we derive the time-varying spectral density of the PCs revealing when particular modes are strongest between 1992–2004. The spatial pattern of the leading CEOF, comprising 30% of the total variability, has a 5-year period. Signal propagation with a 5-year period is also observed in the Labrador Sea. The second mode, with a dominant 3-year signal, has strong variability in the eastern basin. We next focus on the Azores subtropical frontal region. The leading mode (35%) is strong in the south and east of this region. The second mode (21%) has a near-zonal band of low variance between ~22°–27° N sandwiched between two regions of high variance. We then lowpass filter the altimeter data at a cutoff of 30 days, instead of 18 months, in order to retain signals associated with propagating baroclinic Rossby waves. The leading mode is the annual steric signal, around 46% of the SSH variability. The third and fourth CEOFs, 11% of the remaining variability, are associated with westward propagation which is particularly dominant in a ''waveband'' between 32°–36° N. No significant cross-correlation is found between the North Atlantic Oscillation index and the amplitude of the leading two principal components of interannual SSH variability. The East Atlantic Pattern index, however, is correlated with the principal components of the two leading modes of SSH variability, particularly with PC2 in the Azores subtropical frontal region. Further investigation of forcing mechanisms is suggested using hindcasts from ocean general circulation models.

scholarly journals Impact of combining GRACE and GOCE gravity data on ocean circulation estimates

Ocean Science ◽  
2012 ◽  
Vol 8 (1) ◽  
pp. 65-79 ◽  
Author(s):  
T. Janjić ◽  
J. Schröter ◽  
R. Savcenko ◽  
W. Bosch ◽  
A. Albertella ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Ocean Circulation ◽  
Gravity Data ◽  
Sea Surface Height ◽  
Ocean Model ◽  
Weddell Sea ◽  
Sea Surface ◽  
Altimeter Data ◽  
Surface Drifters ◽  
Ocean Topography

Abstract. With the focus on the Southern Ocean circulation, results of assimilation of multi-mission-altimeter data and the GRACE/GOCE gravity data into the finite element ocean model (FEOM) are investigated. We use the geodetic method to obtain the dynamical ocean topography (DOT). This method combines the multi-mission-altimeter sea surface height and the GRACE/GOCE gravity field. Using the profile approach, the spectral consistency of both fields is achieved by filtering the sea surface height and the geoid. By combining the GRACE and GOCE data, a considerably shorter filter length can be used, which results in more DOT details. We show that this increase in resolution of measured DOT carries onto the results of data assimilation for the surface data. By assimilating only absolute dynamical topography data using the ensemble Kalman filter, we were able to improve modeled fields. Results are closer to observations which were not used for assimilation and lie outside the area covered by altimetry in the Southern Ocean (e.g. temperature of surface drifters or deep temperatures in the Weddell Sea area at 800 m depth derived from Argo composite.)

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