Assessment of GRACE/GRACE Follow-On Estimates of Global Mean Ocean Mass Change

2021 ◽  
Author(s):  
Jae-Seung Kim ◽  
Ki-Weon Seo ◽  
Jianli Chen ◽  
Clark Wilson
Keyword(s):  
Sea Level ◽  
Sea Water ◽  
Ocean Dynamics ◽  
Water Density ◽  
Partial Explanation ◽  
Steric Sea Level ◽  
Isostatic Adjustment ◽  
Ocean Mass ◽  
Global Mean Sea Level ◽  
Global Mean

Abstract Global mean sea level has increased ~3.5 mm/yr over several decades due to increases in ocean mass and changes in sea water density. Ocean mass, accounting for about two-thirds of the increase, can be directly measured by the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GFO) satellites. An independent measure is obtained by combining satellite altimetry (measuring total sea level change) and Argo float data (measuring steric changes associated with sea water density). Many previous studies have reported that the two estimates of global mean ocean mass (GMOM) change are in good agreement within stated confidence intervals. Recently, particularly since 2016, estimates by the two methods have diverged. A partial explanation appears to be a spurious variation in steric sea level data. An additional contributor may be deficiencies in Glacial Isostatic Adjustment (GIA) corrections and degree-1 spherical harmonic (SH) coefficients. We found that erroneous corrections for GIA contaminate GRACE/GFO estimates as time goes forward. Errors in GIA corrections affect degree-1 SH coefficients, and degree-1 errors may also be associated with ocean dynamics. Poor estimates of degree-1 SH coefficients are likely an important source of discrepancies in the two methods of estimating GMOM change.

scholarly journals Global ocean freshening, ocean mass increase and global mean sea level rise over 2005–2015

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
William Llovel ◽  
S. Purkey ◽  
B. Meyssignac ◽  
A. Blazquez ◽  
N. Kolodziejczyk ◽  
...  
Keyword(s):  
Sea Level ◽  
Global Ocean ◽  
Last Deglaciation ◽  
Mean Sea Level ◽  
Isostatic Adjustment ◽  
Ocean Mass ◽  
Grace Data ◽  
Global Mean Sea Level ◽  
Gravity Recovery ◽  
Global Mean

AbstractGlobal mean sea level has experienced an unabated rise over the 20th century. This observed rise is due to both ocean warming and increasing continental freshwater discharge. We estimate the net ocean mass contribution to sea level by assessing the global ocean salt budget based on the unprecedented amount of in situ data over 2005–2015. We obtain the ocean mass trends of 1.30 ± 1.13 mm · yr−1 (0–2000 m) and 1.55 ± 1.20 mm · yr−1 (full depth). These new ocean mass trends are smaller by 0.63–0.88 mm · yr−1 compared to the ocean mass trend estimated through the sea level budget approach. Our result provides an independent validation of Gravity Recovery And Climate Experiment (GRACE)-based ocean mass trend and, in addition, places an independent constraint on the combined Glacial Isostatic Adjustment – the Earth’s delayed viscoelastic response to the redistribution of mass that accompanied the last deglaciation- and geocenter variations needed to directly infer the ocean mass trend based on GRACE data.

Closing the global mean sea level budget from altimetry, GRACE/GRACE Follow-On and Argo data (2005-present)

2021 ◽  
Author(s):  
Anne Barnoud ◽  
Anny Cazenave ◽  
Julia Pfeffer ◽  
Michaël Ablain ◽  
Adrien Guérou ◽  
...  
Keyword(s):  
Sea Level ◽  
Systematic Bias ◽  
Satellite Mission ◽  
Argo Data ◽  
Steric Sea Level ◽  
Mean Sea Level ◽  
Ocean Mass ◽  
Salinity Data ◽  
Global Mean Sea Level ◽  
Global Mean

<p>Change in the global mean sea level (GMSL) is the sum of changes in the global mean steric sea level and global mean ocean mass. Over the 1993-2016 period, the GMSL budget was found to be closed, as shown by many independent studies. However, non-closure of the sea level budget after 2016 has been recently reported when using altimetry, Argo and GRACE/GRACE Follow-On data (Chen et al., GRL, 2020). This non-closure may result from errors in one or more components of the sea level budget (altimetry-based GMSL, Argo-based steric sea level or GRACE-based ocean mass). In this study, we investigated possible sources of errors affecting atlimetry and Argo data used to assess closure of the GMSL budget. Concerning altimetry data, we compared the wet tropospheric correction (WTC) applied to Jason-3 data (the reference satellite mission used for the GMSL computation since 2016) with that from the SARAL/AltiKa mission, and found no systematic bias between the radiometer measurements from these two missions. Besides, preliminary comparisons of GMSL trends (using the WTC ECMWF model) between different missions do not suggest discrepancies larger than 0.4 mm/yr over 2016-present. While further analyses are still needed, we find unlikely that non-closure of the sea level budget results from errors of the altimetry system. Concerning Argo data, since 2016, salinity data from different processing groups display strong discrepancies, likely due to instrumental problems and data editing issues. Good agreement is found between all available Argo-based thermosteric products. Given that the halosteric component should be negligible in global average, we re-examined the sea level budget since 2016 using only the thermosteric component and found significant improvement in the budget closure, although it is not yet fully closed. This suggests that the observed discrepancies in the Argo-based halosteric component largely contribute to the non-closure of the GMSL budget in the recent years.</p>

scholarly journals Effect of La Niña on The Global Mean Sea Level And North Pacifc Ocean Mass Over 2005-2011

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
Habib B. Dieng ◽  
Anny Cazenave ◽  
Benoit Meyssignac ◽  
Olivier Henry ◽  
Karina von Schuckmann ◽  
...  
Keyword(s):  
Sea Level ◽  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Mean Sea Level ◽  
The North ◽  
Ocean Mass ◽  
La Nina ◽  
Global Mean Sea Level ◽  
Global Mean

AbstractInterannual fluctuations of the global mean sea level are highly correlated with El Niño-Southern Oscillation (ENSO) events, with positive/negative anomalies during El Niño/La Niña. In a previous study we showed that during the 1997 - 1998 El Niño, a positive anomaly observed in the global mean sea level was mostly caused by an increase of the ocean mass component rather than by steric (thermal) effects. This result was related to an increase of precipitation over the tropical ocean and a deficit in land water storage. In the present study, we investigate the effect of the recent 2008 and 2011 La Niña events on the satellite altimetry-based global mean sea level. We find that the large global mean sea level drop associated with the 2011 La Niña results from the combined decrease of the steric and ocean mass components, with a slightly dominant contribution from the latter. We show that the ocean mass contribution to the global mean sea level drop is spatially confined over the north eastern tropical Pacific (just as was found previously for the 1997 - 1998 El Niño, but with opposite sign). Corresponding ocean mass spatial pattern is closely correlated to observed sea level and steric spatial patterns over the duration of the La Niña event. This is also observed for previous El Niño and La Niña events. Such a drop in ocean mass during ENSO in the eastern part of the tropical Pacific has not been reported before. It is possibly related to a temporary decrease in the net precipitation over the north eastern Pacific (opposite situation was found during the 1997 - 1998 El Niño).

Data products from the ESA CCI Sea Level Budget Closure project

2020 ◽  
Author(s):  
Martin Horwath ◽  
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Sea Level Changes ◽  
Ocean Mass ◽  
Data Products ◽  
Global Mean Sea Level ◽  
The Individual ◽  
Land Water ◽  
Global Mean

<p>Studies of the sea-level budget are a means of assessing our ability to quantify and understand sea-level changes and their causes. ESA's Climate Change Initiative (CCI) projects include Sea Level CCI, Greenland Ice Sheet CCI, Antarctic Ice Sheet CCI, Glaciers CCI and the Sea Surface Temperature CCI, all addressing Essential Climate Variables (ECVs) related to sea level. The cross-ECV project CCI Sea Level Budget Closure used different products for the sea level and its components, based on the above CCI projects in conjunction with in situ data for ocean thermal expansion (e.g., Argo), GRACE-based assessments of ocean mass change, land water and land ice mass change, and model-based data for glaciers and land hydrology. The involvement of the authors of the individual data products facilitated consistency and enabled a unified treatment of uncertainties and their propagation to the overall budget closure. </p><p>After conclusion of the project, the developed data products are now available for science users and the public. This poster summarizes the project results with a focus on presenting these data products. They include time series (for the periods 1993-2016 and 2003-2016) of global mean sea level changes and global mean sea level contributions from the steric component, from the ocean mass component and from the individual mass contributions by glaciers, the Greenland Ice Sheet, the Antarctic Ice Sheet and changes in land water storage. They are designed and documented in the consistent framework of ESA SLBC_cci and include uncertainty measures per datum. Additional more comprehensive information, such as geographic grids underlying the global means, are available for some components.</p><p>For the long-term trend, the budget is closed within uncertainties on the order of 0.3 mm/yr (1 sigma). Moreover, the budget is also closed within uncertainties for interannual variations.</p>

Global sea-level and ocean-mass budgets using advanced data products and uncertainty characterisation

2021 ◽  
Author(s):  
Martin Horwath ◽  
Anny Cazenave ◽  
Keyword(s):  
Time Series ◽  
Sea Level ◽  
Satellite Altimetry ◽  
Sea Level Change ◽  
Mass Change ◽  
Level Change ◽  
Ocean Mass ◽  
Global Mean Sea Level ◽  
Global Sea Level ◽  
Global Mean

<p>Studies of the global sea-level budget (SLB) and ocean-mass budget (OMB) are essential to assess the reliability of our knowledge of sea-level change and its contributors. The SLB is considered closed if the observed sea-level change agrees with the sum of independently assessed steric and mass contributions. The OMB is considered closed if the observed ocean-mass change is compatible with the sum of assessed mass contributions. </p><p>Here we present results from the Sea-Level Budget Closure (SLBC_cci) project conducted in the framework of ESA’s Climate Change Initiative (CCI). We used data products from CCI projects as well as newly-developed products based on CCI products and on additional data sources. Our focus on products developed in the same framework allowed us to exercise a consistent uncertainty characterisation and its propagation to the budget closure analyses, where the SLB and the OMB are assessed simultaneously. </p><p>We present time series of global mean sea-level changes from satellite altimetry; new time series of the global mean steric component generated from Argo drifter data with incorporation of sea surface temperature data; time series of ocean-mass change derived from GRACE satellite gravimetry; time series of global glacier mass change from a global glacier model; time series of mass changes of the Greenland Ice Sheet and the Antarctic Ice Sheet both from satellite radar altimetry and from GRACE; as well as time series of land water storage change from the WaterGAP global hydrological model. Our budget analyses address the periods 1993–2016 (covered by the satellite altimetry records) and 2003–2016 (covered by GRACE and the Argo drifter system). In terms of the mean rates of change (linear trends), the SLB is closed within uncertainties for both periods, and the OMB, assessable for 2003–2016 only, is also closed within uncertainties. Uncertainties (1-sigma) arising from the combined uncertainties of the elements of the different budgets considered are between 0.26 mm/yr and 0.40 mm/yr, that is, on the order of 10% of the magnitude of global mean sea-level rise, which is 3.05 ± 0.24 mm/yr and 3.65 ± 0.26 mm/yr for 1993-2016 and 2003-2016, respectively. We also assessed the budgets on a monthly time series basis. The statistics of monthly misclosure agrees with the combined uncertainties of the budget elements, which amount to typically 2-3 mm for the 2003–2016 period. We discuss possible origins of the residual misclosure.</p>

scholarly journals Higher than present global mean sea level recorded by an Early Pliocene intertidal unit in Patagonia (Argentina)

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Alessio Rovere ◽  
Marta Pappalardo ◽  
Sebastian Richiano ◽  
Marina Aguirre ◽  
Michael R. Sandstrom ◽  
...  
Keyword(s):  
Sea Level ◽  
Differential Gps ◽  
Intertidal Environment ◽  
Mean Sea Level ◽  
Early Pliocene ◽  
Isostatic Adjustment ◽  
Strontium Isotope Stratigraphy ◽  
Geological Unit ◽  
Global Mean Sea Level ◽  
Global Mean

AbstractReconstructions of global mean sea level from earlier warm periods in Earth’s history can help constrain future projections of sea level rise. Here we report on the sedimentology and age of a geological unit in central Patagonia, Argentina, that we dated to the Early Pliocene (4.69–5.23 Ma, 2σ) with strontium isotope stratigraphy. The unit was interpreted as representative of an intertidal environment, and its elevation was measured with differential GPS at ca. 36 m above present-day sea level. Considering modern tidal ranges, it was possible to constrain paleo relative sea level within  ±2.7 m (1σ). We use glacial isostatic adjustment models and estimates of vertical land movement to calculate that, when the Camarones intertidal sequence was deposited, global mean sea level was 28.4 ± 11.7 m (1σ) above present. This estimate matches those derived from analogous Early Pliocene sea level proxies in the Mediterranean Sea and South Africa. Evidence from these three locations indicates that Early Pliocene sea level may have exceeded 20m above its present level. Such high global mean sea level values imply an ice-free Greenland, a significant melting of West Antarctica, and a contribution of marine-based sectors of East Antarctica to global mean sea level.

scholarly journals A new assessment of global mean sea level from altimeters highlights a reduction of global trend from 2005 to 2008

2009 ◽  
Vol 6 (1) ◽  
pp. 31-56 ◽  
Author(s):  
M. Ablain ◽  
A. Cazenave ◽  
G. Valladeau ◽  
S. Guinehut
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Tide Gauge ◽  
Mean Sea Level ◽  
Error Budget ◽  
Isostatic Adjustment ◽  
Global Trend ◽  
Tide Gauge Measurements ◽  
Global Mean Sea Level ◽  
Global Mean

Abstract. A new error budget assessment of the global Mean Sea Level (MSL) determined by TOPEX/Poseidon and Jason-1 altimeter satellites between January 1993 and June 2008 is presented. We discuss all potential errors affecting the calculation of the global MSL rate. We also compare altimetry-based sea level with tide gauge measurements over the altimetric period. This allows us to provide a realistic error budget of the MSL rise measured by satellite altimetry. These new calculations highlight a reduction in the rate of sea level rise since 2005, by ~2 mm/yr. This represents a 60% reduction compared to the 3.3 mm/yr sea level rise (glacial isostatic adjustment correction applied) measured between 1993 and 2005. Since November 2005, MSL is accurately measured by a single satellite, Jason-1. However the error analysis performed here indicates that the recent reduction in MSL rate is real.

scholarly journals Sea-level stands from the Western Mediterranean over the past 6.5 million years

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Oana A. Dumitru ◽  
Jacqueline Austermann ◽  
Victor J. Polyak ◽  
Joan J. Fornós ◽  
Yemane Asmerom ◽  
...  
Keyword(s):  
Sea Level ◽  
Western Mediterranean ◽  
Glacial Isostatic Adjustment ◽  
Mean Sea Level ◽  
The Past ◽  
Isostatic Adjustment ◽  
Future Warming ◽  
Global Mean Sea Level ◽  
Global Mean

AbstractSea-level reconstructions are important for understanding past ice sheet variability and its response to past and future warming. Here we present Neogene and Quaternary sea-level snapshots using phreatic overgrowths on speleothems (POS) from caves on Mallorca, Spain. POS are excellent sea level index points because of their clear relationship to sea level and precise U–Pb chronology. We find that local sea-level before and at the onset of the Messinian Salinity Crisis was at 33.3 ± 0.25 m (6.54 ± 0.37 Ma) and 31.8 ± 0.25 m (5.86 ± 0.60 Ma) above present levels, respectively. We further present global mean sea level (GMSL) estimates, i.e. local sea level corrected for glacial isostatic adjustment and long-term uplift, for three other POS. The results show that GMSL during the Pliocene–Pleistocene Transition was 6.4 m (− 2.0–8.8 m) at 2.63 ± 0.11 Ma and during the beginning and the end of the Mid-Pleistocene Transition was − 1.1 m (− 5.6–2.4 m) and 5 m (1.5–8.1 m), respectively. These estimates provide important constraints for the past evolution of sea level and show that local sea level prior to the MSC was similar to the highest stand during the Pliocene, with markedly lower position afterwards.

Sea level fingerprints due to ongoing land ice melt in altimetry data

2021 ◽  
Author(s):  
Lorena Moreira ◽  
Anny Cazenave
Keyword(s):  
Sea Level ◽  
Regional Scale ◽  
Water Storage ◽  
Altimetry Data ◽  
Ice Melt ◽  
Atmospheric Loading ◽  
Ocean Mass ◽  
Global Mean Sea Level ◽  
Land Water ◽  
Global Mean

<p>The Global Mean Sea Level (GMSL) is rising at a rate of 3.3 mm/year over the altimetry era but at regional scale the behaviour is quite different. In some regions, the sea level rates are up to 2-3 times the global mean rate. The mechanisms behind these discrepancies are explained through the differences in the processes that affect the sea level at different scales. The concept of budget is used to express the superposition of signals that contribute to the change in sea level. At regional scale, apart from the contributions from steric and ocean mass components which are also present in the GMSL budget, the budget is also affected by atmospheric loading component and the static factors component. The static terms (also called fingerprints) include solid Earth’s deformations and gravitational changes in response to mass redistributions caused by land ice melt and land water storage changes. The goal of this study is to detect the fingerprints of the static factors using satellite altimetry-based sea level grids corrected for steric and ocean mass effects. Our preliminary results show a statistically significant correlation between observed and modelled fingerprints in some regions of the oceanic basins.</p>

scholarly journals A new assessment of the error budget of global mean sea level rate estimated by satellite altimetry over 1993–2008

Ocean Science ◽  
2009 ◽  
Vol 5 (2) ◽  
pp. 193-201 ◽  
Author(s):  
M. Ablain ◽  
A. Cazenave ◽  
G. Valladeau ◽  
S. Guinehut
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Satellite Altimetry ◽  
Tide Gauge ◽  
Mean Sea Level ◽  
Error Budget ◽  
Isostatic Adjustment ◽  
Tide Gauge Measurements ◽  
Global Mean Sea Level ◽  
Global Mean

Abstract. A new error budget assessment of the global Mean Sea Level (MSL) determined by TOPEX/Poseidon and Jason-1 altimeter satellites between January 1993 and June 2008 is presented using last altimeter standards. We discuss all potential errors affecting the calculation of the global MSL rate. We also compare altimetry-based sea level with tide gauge measurements over the altimetric period. Applying a statistical approach, this allows us to provide a realistic error budget of the MSL rise measured by satellite altimetry. These new calculations highlight a reduction in the rate of sea level rise since 2005, by ~2 mm/yr. This represents a 60% reduction compared to the 3.3 mm/yr sea level rise (glacial isostatic adjustment correction applied) measured between 1993 and 2005. Since November 2005, MSL is accurately measured by a single satellite, Jason-1. However the error analysis performed here indicates that the recent reduction in MSL rate is real.

Sign in / Sign up

Export Citation Format

Share Document