Sea-Level Fingerprints Due to Present-Day Water Mass Redistribution in Observed Sea-Level Data

Satellite altimetry over the oceans shows that the rate of sea-level rise is far from uniform, with reported regional rates up to two to three times the global mean rate of rise of ~3.3 mm/year during the altimeter era. The mechanisms causing the regional variations in sea-level trends are dominated by ocean temperature and salinity changes, and other processes such as ocean mass redistribution as well as solid Earth’s deformations and gravitational changes in response to past and ongoing mass redistributions caused by land ice melt and terrestrial water storage changes (respectively known as Glacial Isostatic Adjustment (GIA) and sea-level fingerprints). Here, we attempt to detect the spatial trend patterns of the fingerprints associated with present-day land ice melt and terrestrial water mass changes, using satellite altimetry-based sea-level grids corrected for the steric component. Although the signal-to-noise ratio is still very low, a statistically significant correlation between altimetry-based sea-level and modelled fingerprints is detected in some ocean regions. We also examine spatial trend patterns in observed GRACE ocean mass corrected for atmospheric and oceanic loading and find that some oceanic regions are dominated by the fingerprints of present-day water mass redistribution.

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

Scientific Reports ◽

10.1038/s41598-019-54239-2 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 5

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.

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

10.5194/egusphere-egu21-10174 ◽

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

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.&#160;Here we present results from the Sea-Level Budget Closure (SLBC_cci) project conducted in the framework of ESA&#8217;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.&#160;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&#8211;2016 (covered by the satellite altimetry records) and 2003&#8211;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&#8211;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 &#177; 0.24 mm/yr and 3.65 &#177; 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&#8211;2016 period. We discuss possible origins of the residual misclosure.

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

10.21203/rs.3.rs-1182933/v1 ◽

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.

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Regional and interannual variability in sea level over 2002–2009 based on satellite altimetry, Argo float data and GRACE ocean mass

Ocean Dynamics ◽

10.1007/s10236-010-0324-0 ◽

2010 ◽

Vol 60 (5) ◽

pp. 1193-1204 ◽

Cited By ~ 33

Author(s):

William Llovel ◽

Stéphanie Guinehut ◽

Anny Cazenave

Keyword(s):

Interannual Variability ◽

Sea Level ◽

Satellite Altimetry ◽

Argo Float ◽

Ocean Mass

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Comparison of Satellite Altimetry to Tide Gauge Measurement of Sea Level: Predictions of Glacio-Isostatic Adjustment

Journal of Climate ◽

10.1175/1520-0442(2002)015<3291:cosatt>2.0.co;2 ◽

2002 ◽

Vol 15 (22) ◽

pp. 3291-3300 ◽

Cited By ~ 4

Author(s):

James A. Clark ◽

Paul E. Haidle ◽

L. Nichole Cunningham

Keyword(s):

Sea Level ◽

Satellite Altimetry ◽

Tide Gauge ◽

Isostatic Adjustment ◽

Gauge Measurement

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Sea-level rise in the Mediterranean Sea by 2050: Roles of terrestrial ice melt, steric effects and glacial isostatic adjustment

Global and Planetary Change ◽

10.1016/j.gloplacha.2014.10.007 ◽

2014 ◽

Vol 123 ◽

pp. 55-66 ◽

Cited By ~ 23

Author(s):

Gaia Galassi ◽

Giorgio Spada

Keyword(s):

Sea Level Rise ◽

Mediterranean Sea ◽

Sea Level ◽

Steric Effects ◽

Glacial Isostatic Adjustment ◽

Ice Melt ◽

Isostatic Adjustment ◽

The Mediterranean

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Global sea-level budget and ocean-mass budget, with focus on advanced data products and uncertainty characterisation

10.5194/essd-2021-137 ◽

2021 ◽

Author(s):

Martin Horwath ◽

Benjamin D. Gutknecht ◽

Anny Cazenave ◽

Hindumathi Kulaiappan Palanisamy ◽

Florence Marti ◽

...

Keyword(s):

Sea Level ◽

Satellite Altimetry ◽

Water Storage ◽

Ice Sheet ◽

Mass Budget ◽

Ocean Mass ◽

Global Sea Level ◽

Land Water ◽

Global Mean ◽

Mass Component

Abstract. Studies of the global sea-level budget (SLB) and the global ocean-mass budget (OMB) are essential to assess the reliability of our knowledge of sea-level change and its contributions. Here we present datasets for times series of the SLB and OMB elements developed in the framework of ESA's Climate Change Initiative. We use these datasets to assess the SLB and the OMB simultaneously, utilising a consistent framework of uncertainty characterisation. The time series, given at monthly sampling, include global mean sea-level (GMSL) anomalies from satellite altimetry; the global mean steric component from Argo drifter data with incorporation of sea surface temperature data; the ocean mass component from Gravity Recovery and Climate Experiment (GRACE) satellite gravimetry; the contribution from global glacier mass changes assessed by a global glacier model; the contribution from Greenland Ice Sheet and Antarctic Ice Sheet mass changes, assessed from satellite radar altimetry and from GRACE; and the contribution from land water storage anomalies assessed by the WaterGAP global hydrological model. Over the period Jan 1993–Dec 2016 (P1, covered by the satellite altimetry records), the mean rate (linear trend) of GMSL is 3.05 ± 0.24 mm yr−1. The steric component is 1.15 ± 0.12 mm yr−1 (38 % of the GMSL trend) and the mass component is 1.75 ± 0.12 mm yr−1 (57 %). The mass component includes 0.64 ± 0.03 mm yr−1 (21 % of the GMSL trend) from glaciers outside Greenland and Antarctica, 0.60 ± 0.04 mm yr−1 (20 %) from Greenland, 0.19 ± 0.04 mm yr−1 (6 %) from Antarctica, and 0.32 ± 0.10 mm yr−1 (10 %) from changes of land water storage. In the period Jan 2003–Aug 2016 (P2, covered by GRACE and the Argo drifter system), GMSL rise is higher than in P1 at 3.64 ± 0.26 mm yr−1. This is due to an increase of the mass contributions (now about 2.22 ± 0.15 mm yr−1, 61 % of the GMSL trend), with the largest increase contributed from Greenland. The SLB of linear trends is closed for P1 and P2, that is, the GMSL trend agrees with the sum of the steric and mass components within their combined uncertainties. The OMB budget, which can be evaluated only for P2, is also closed, that is, the GRACE-based ocean-mass trend agrees with the sum of assessed mass contributions within uncertainties. Combined uncertainties (1-sigma) of the elements involved in the budgets are between 0.26 and 0.40 mm yr−1, about 10 % of GMSL rise. Interannual variations that overlie the long-term trends are coherently represented by the elements of the SLB and the OMB. Even at the level of monthly anomalies the budgets are closed within uncertainties, while also indicating possible origins of remaining misclosures.

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Sea Level Trend and Fronts in the South Atlantic Ocean

Geosciences ◽

10.3390/geosciences10060218 ◽

2020 ◽

Vol 10 (6) ◽

pp. 218

Author(s):

Laura A. Ruiz-Etcheverry ◽

Martin Saraceno

Keyword(s):

Atlantic Ocean ◽

Sea Level ◽

Satellite Altimetry ◽

South Atlantic ◽

South Atlantic Ocean ◽

The South ◽

Steric Height ◽

Ocean Mass ◽

Sea Level Trend ◽

Height Component

The understanding of the physical drivers of sea level trend is crucial on global and regional scales. In particular, little is known about the sea level trend in the South Atlantic Ocean in comparison with other parts of the world. In this work, we computed the South Atlantic mean sea level (SAMSL) trend from 25 years of satellite altimetry data, and we analyzed the contributions of steric height (thermosteric and halosteric components) and ocean mass changes for the period 2005–2016 when all the source data used (Argo, GRACE and satellite altimetry) overlap. The SAMSL trend is 2.65 ± 0.24 mm/yr and is mostly explained by ocean mass trend, which is 2.22 ± 0.21 mm/yr. However, between 50° S–33° S, the steric height component constitutes the main contribution in comparison with the ocean mass component. Within that latitudinal band, three regions with trend values higher than the SAMSL trend are observed when considering 25 years of satellite SLA. In the three regions, a southward displacement of the Subtropical, Subantarctic, and Polar Fronts is observed. The southward shift of the fronts is associated with the strengthening and polar shift of westerly winds and contributes to a clear thermosteric trend that translates to the SLA trend observed in those regions.

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Improving the representation of ice-sheet mass changes in the global inversion for sea-level contributions

10.5194/egusphere-egu2020-7999 ◽

2020 ◽

Author(s):

Matthias O. Willen ◽

Bernd Uebbing ◽

Martin Horwath ◽

Jürgen Kusche ◽

Roelof Rietbroek ◽

...

Keyword(s):

Sea Level ◽

A Priori ◽

Ice Sheets ◽

Ice Sheet ◽

Mass Change ◽

Altimetry Data ◽

Isostatic Adjustment ◽

Ocean Mass ◽

First Results ◽

Ocean Altimetry

Global-mean sea level rises (GMSLR) by 3.1-3.5 mm a-1 (1993-2017) and of which about 50 % can be attributed to changes in global-mean ocean mass due to hydrological variations, mass changes of land glaciers, and mass changes of the major ice sheets in Greenland and Antarctica. The ice-sheet contributions account for more than the half of the contemporary ocean mass change and can be observed with time-variable gravimetry by the Gravity Recovery and Climate Experiment (GRACE) and its follow-on mission (GRACE-FO). In addition, geometric surface changes due to the volume change of ice sheets is also observed by polar altimetry missions. Of particular importance here is the signal of glacial isostatic adjustment (GIA) which is superimposed with ice mass change.Conventionally, the gravimetry and ice-altimetry observations are processed independently. For ocean applications, a global fingerprint inversion (Rietbroek et al., 2016) allows to estimate individual mass and steric contributors to the sea-level budget by combining GRACE and ocean-altimetry data in a joint approach. To improve the estimates of the ice-sheet contributions to GMSLR, we present first results from additionally incorporating independent ice-altimetry data over Greenland and Antarctica into the fingerprint inversion. We examine the sensitivity of the sea-level contributions to the additional ice-altimetry data (from ERS-2, Envisat, ICESat, CryoSat-2 missions) and provide validation against independent estimates. In our standard runs, GIA is accounted for as an a-priori correction during the inversion. However, we demonstrate the potential and limitations of a regional inverse approach in which GIA is separated from ice mass change over Antarctica using GRACE and ice altimetry. In our future work, we aim to parametrise and co-estimate GIA within the global inversion framework.

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

10.5194/egusphere-egu21-10950 ◽

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

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&#8217;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.

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