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.)

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

2011 ◽  
Vol 8 (3) ◽  
pp. 1535-1573
Author(s):  
T. Janjić ◽  
J. Schröter ◽  
R. Savcenko ◽  
W. Bosch ◽  
A. Albertella ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Gravity Data ◽  
Ocean Model ◽  
Sea Surface ◽  
Altimeter Data ◽  
Argo Data ◽  
Gravity Field Model ◽  
Gravity Fields ◽  
Ocean Topography ◽  
The Impact

Abstract. In this work we examine the impact of assimilation of multi-mission-altimeter data and the GRACE/GOCE gravity fields into the finite element ocean model (FEOM), with the focus on the Southern Ocean circulation. In order to do so, we use the geodetic approach for obtaining the dynamical ocean topography (DOT), that combines the multi-mission-altimeter data and the GRACE/GOCE gravity fields, and requires that both fields be spectrally consistent. The spectral consistency is achieved by filtering of the sea surface height and the geoid using profile approach. Combining the GRACE and GOCE data, a considerably shorter filter length resolving more DOT details can be used. In order to specify the spectrally consistent geodetic DOT we applied the Jekeli-Wahr filter corresponding to 241 km, 121 km, 97 km and 81 km halfwidths for the GRACE/GOCE based gravity field model GOCO01S and to the sea surface. More realistic features of the ocean assimilation were obtained in the Weddel gyre area due to increased resolution of the data fields, particularly for temperature field at the 800 m depth compared to Argo data.

Detection of Magnetic Signals from Ocean Circulation with Satellite Altimetry and Magnetometer

2020 ◽  
Author(s):  
Aaron Hornschild ◽  
Jan Saynisch-Wagner ◽  
Christopher Irrgang ◽  
Johannes Petereit ◽  
Maik Thomas
Keyword(s):  
Ocean Circulation ◽  
Satellite Altimetry ◽  
Sea Water ◽  
Sea Surface Height ◽  
Ocean Model ◽  
Sea Surface ◽  
Time Behavior ◽  
Electrically Conducting ◽  
Magnetic Signatures ◽  
Electromagnetic Signals

<p>Electrically conducting sea-water moves through Earth's magnetic field and generates electromagnetic signals itself. These signals can be detected by space borne Earth observation technologies, like the Swarm satellite magnetometer mission. In contrast to already successfully detected ocean tidal magnetic signatures, the magnetic signals from ocean circulation are still unidentified in observations. However, the electromagnetic signals from the ocean circulation would be an additional, interesting source of information.<br>We propose, that satellite altimetry can be helpful in order to detect magnetic signals from ocean circulation. Sea surface height measurements allow to estimate depth-integrated current velocities by using the geostrophic approximation, which describes a balance between sea surface height gradients and horizontal currents. With the resulting integrated electric current density, the magnetic signals from ocean circulation can be calculated using an electromagnetic induction solver. In a further step, the estimations are a basis for the  separation of magnetometer observations and for data assimilation.<br>Therefore, it is necessary that the geostrophic approach reflects the realistic time behavior of electromagnetic signals from ocean circulation. Ocean model data allows to verify this approach with respect to the identification of magnetic signals from ocean circulation in satellite magnetometer observations. We present this analysis and report about the feasibility of this approach regarding the Swarm mission and possible future missions.</p>

Interannual to Decadal Changes in the ECCO Global Synthesis

2007 ◽  
Vol 37 (2) ◽  
pp. 313-337 ◽  
Author(s):  
A. Köhl ◽  
D. Stammer ◽  
B. Cornuelle
Keyword(s):  
Southern Ocean ◽  
Ocean Circulation ◽  
North Atlantic ◽  
General Circulation ◽  
World Ocean ◽  
Circulation Model ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Global Ocean ◽  
The World

Abstract An estimate of the time-varying global ocean circulation for the period 1992–2002 was obtained by combining most of the World Ocean Circulation Experiment (WOCE) ocean datasets with a general circulation model on a 1° horizontal grid. The estimate exactly satisfies the model equations without artificial sources or sinks of momentum, heat, and freshwater. To bring the model into agreement with observations, its initial temperature and salinity conditions were permitted to change, as were the time-dependent surface fluxes of momentum, heat, and freshwater. The estimation of these “control variables” is largely consistent with accepted uncertainties in the hydrographic climatology and meteorological analyses. The estimated time-mean horizontal transports of volume, heat, and freshwater, which were largely underestimated in the previous 2° optimization performed by Stammer et al., have converged with time-independent estimates from box inversions over most parts of the World Ocean. Trends in the model’s heat content are 7% larger than those reported by Levitus and correspond to a global net heat uptake of about 1.1 W m−2 over the model domain. The associated model trend in sea surface height over the estimation period resembles the observations from Ocean Topography Experiment (TOPEX)/Poseidon over most of the global ocean. Sea surface height changes in the model are primarily steric but show contributions from mass redistributions from the subpolar North Atlantic Ocean and the Southern Ocean to the subtropical Pacific Ocean gyres. Steric contributions are primarily temperature based but are partly compensated by salt variation. However, the North Atlantic and the Southern Ocean reveal a clear contribution of salt to large-scale sea level variations.

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.

scholarly journals Changes in Ocean Heat Content Caused by Wave-Induced Mixing in a High-Resolution Ocean Model

2018 ◽  
Vol 48 (5) ◽  
pp. 1139-1150 ◽  
Author(s):  
Lachlan Stoney ◽  
Kevin J. E. Walsh ◽  
Steven Thomas ◽  
Paul Spence ◽  
Alexander V. Babanin
Keyword(s):  
High Resolution ◽  
Ocean Circulation ◽  
Heat Content ◽  
Circulation Model ◽  
Additional Term ◽  
Ocean Model ◽  
Ocean Heat Content ◽  
Sea Surface ◽  
Wave Heights ◽  
Wave Induced

Abstract A parameterization of turbulent mixing from unbroken surface waves is included in a 16-yr simulation within a high-resolution ocean circulation model (MOM5). This “surface wave mixing” (SWM) derives from the wave orbital motion and is parameterized as an additional term in a k-epsilon model. We show that SWM leads to significant changes in sea surface temperatures but smaller changes in ocean heat content, and show the extent to which these changes can reduce pre-existing model biases with respect to observed data. Specifically, SWM leads to a widespread improvement in sea surface temperature in both hemispheres in summer and winter, while for ocean heat content the improvements are less clear. In addition, we show that introducing SWM can lead to an accumulation of wave-induced ocean heat content between years. While it has been well established that secular positive trends exist in global wave heights, we find that such trends are relatively unimportant in driving the accumulation of wave-induced ocean heat content. Rather, in response to the new source of mixing, the simulated ocean climate evolves toward a new equilibrium with greater total ocean heat content.

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