scholarly journals Reduced misclosure of global sea-level budget with updated Tongji-Grace2018 solution

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fengwei Wang ◽  
Yunzhong Shen ◽  
Qiujie Chen ◽  
Yu Sun
Keyword(s):  
Sea Level ◽  
Spherical Harmonic ◽  
Mass Change ◽  
Global Ocean ◽  
Argo Data ◽  
Ocean Mass ◽  
Grace Data ◽  
Budget Equation ◽  
Global Sea Level ◽  
Gravity Recovery

AbstractThe global sea-level budget is studied using the Gravity Recovery and Climate Experiment (GRACE) solutions, Satellite Altimetry and Argo observations based on the updated budget equation. When the global ocean mass change is estimated with the updated Tongji-Grace2018 solution, the misclosure of the global sea-level budget can be reduced by 0.11–0.22 mm/year compared to four other recent solutions (i.e. CSR RL06, GFZ RL06, JPL RL06 and ITSG-Grace2018) over the period January 2005 to December 2016. When the same missing months as the GRACE solution are deleted from altimetry and Argo data, the misclosure will be reduced by 0.06 mm/year. Once retained the GRACE C20 term, the linear trends of Tongji-Grace2018 and ITSG-Grace2018 solutions are 2.60 ± 0.16 and 2.54 ± 0.16 mm/year, closer to 2.60 ± 0.14 mm/year from Altimetry–Argo than the three RL06 official solutions. Therefore, the Tongji-Grace2018 solution can reduce the misclosure between altimetry, Argo and GRACE data, regardless of whether the C20 term is replaced or not, since the low-degree spherical harmonic coefficients of the Tongji-Grace2018 solution can capture more ocean signals, which are confirmed by the statistical results of the time series of global mean ocean mass change derived from five GRACE solutions with the spherical harmonic coefficients truncated to different degrees and orders.

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.

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>

Assessing Global Ocean and Continental Mass Change from 17 years of GRACE/-FO: the role of coastal buffer zones

2020 ◽  
Author(s):  
Benjamin D. Gutknecht ◽  
Andreas Groh ◽  
Denise Cáceres ◽  
Martin Horwath
Keyword(s):  
Sea Level ◽  
Linear Trend ◽  
Mass Change ◽  
Global Ocean ◽  
Buffer Zones ◽  
Systematic Analysis ◽  
Ocean Mass ◽  
Phase Bias ◽  
Land Water

<p>Following the ESA CCI Sea Level Budget Closure (SLBC) project's work of 2017–2019, we present updated time-series of</p><ul><li>Global Ocean Mass Change (OMC) and</li> <li>Continental Mass Change (CMC),</li> </ul><p>both including continuous measurements by GRACE-FO. By least-squares adjusting a multi-parameter fit to monthly resolved OMC, we estimate the linear trend of Global Ocean mass change over all presently available GRACE/-FO months since April 2002 to be 2.41 ± 0.22 mm/a, with an acceleration of 0.10 mm a<sup>-</sup><sup>2</sup> over the same period.</p><p>A systematic analysis of the computed ocean response ("monthly fingerprints") to on-shore mass changes by means of solving the sea level equation implies that the common method of re-scaling the 'inner' buffered ocean may lead to OMC overestimations up to 10 per cent. We present this effect as a function of coastal buffer width for a global and for a 'truncated' global ocean (Lat ≤ ±65°), since the latter case, as seen e.g. in conjunction with radar altimetry, can lead to more than five per cent overestimated OMC. Furthermore, the use of coastal buffers seems to induce phase bias in the annual oscillation, which may explain the observed phase shift in the monthly budget between GRACE OMC and the sum of contributing continental components (i.e. ice sheets, glaciers, land water storage).</p><p>As a supplementary product of the SLBC project, we present GRACE/-FO derived mass change series 2002-04/present for continents (excluding Greenland and Antarctica). Consistent integration of out-leaking signal over coastal buffer zones, and subtraction of GAD-corrected mean OMC therein, leads to agreement with independently-assessed joint land water and glacier mass change data, well within uncertainty bounds.</p>

scholarly journals Heterogeneous oceanic mass distribution in GRACE observations and its leakage effect

2020 ◽  
Vol 221 (1) ◽  
pp. 603-616
Author(s):  
Shuang Yi ◽  
Kosuke Heki
Keyword(s):  
Ocean Model ◽  
The Arctic ◽  
Global Ocean ◽  
The Sea Of Japan ◽  
Observation Data ◽  
Ocean Reanalysis ◽  
Ocean Mass ◽  
Grace Data ◽  
Leakage Effect ◽  
Gravity Recovery

SUMMARY Signal leakage between the land and ocean is a challenge in using Gravity Recovery and Climate Experiment (GRACE) observation data to study global mass redistributions. Although the leakage occurs in both directions, more attention has been paid to the land-to-ocean leakage and less to the ocean-to-land leakage. Here, we show that the ocean-to-land leakage is non-uniform and non-negligible and propose a new forward modelling method to fully consider bi-directional leakages with the help of the global Ocean ReAnalysis System ORAS5. This observation-driven model could significantly reduce the variations in ocean grids and thus decrease the ocean-to-land leakage. The results with different treatment of the ocean signal leakage are compared. We find that failing to consider the ocean-to-land leakage will cause an underestimation of ∼20 per cent in the seasonal variation and will introduce a bias of several giga-tons in the secular trend. Although the uniform and non-uniform model have similar results in the global average of seasonal mass variations, the non-uniform ocean model is necessary in most places, especially near the Arctic Ocean, the Sea of Japan and the Gulf of Carpentaria. Despite these achievements, we also point out that there is still much room for improvement in ocean mass models, particularly in long-term trends. Our results indicate the importance of the ocean-to-land leakage correction in the mass estimation in coastal land areas using the GRACE data.

Interannual Variability in Global Ocean Mass Derived from 18+ Years of GRACE and GRACE-FO Satellite Gravimetry

2021 ◽  
Author(s):  
Benjamin D. Gutknecht ◽  
Andreas Groh ◽  
Martin Horwath
Keyword(s):  
Gravity Field ◽  
Sea Level ◽  
Linear Trend ◽  
Mass Change ◽  
Global Ocean ◽  
Mass System ◽  
Quasi Biennial Oscillation ◽  
Data Set ◽  
Ocean Mass ◽  
Major Mode

<p>The combined 18+ years long time series of observations of the Earth's gravity field from the satellite missions GRACE and GRACE-FO provides us with an unprecedented opportunity to analyse mass change and re-distribution in the Earth system. Furthermore, as the mission continues, we may also gain more insight into those types of variability in the water mass system that act over time scales of several years and possibly even decades.</p><p>For our analysis presented here, we updated the previous Ocean Mass Change (OMC) product by the ESA CCI Sea Level Budget Closure project, including (1) corrections for Glacial Isostatic Adjustment, (2) restorement of GAD background fields, (3) subtraction of atmospheric mean fields, and (4) replacement of dedicated low-degree coefficients for centre-of-mass, oblateness (TN14) and C30 (TN14) in the spherical harmonic gravity field solutions. We applied least-squares minimisation of the residual of a multi-parameter functional fit to the OMC series, including i.a. linear trend, semi-/annual signals, and an optional quadratic fit. We analysed the complete residual series based on the four monthly GRACE and GRACE-FO RL06 solutions from CSR/GFZ/JPL and ITSG-Grace2018 after removal of linear trend and seasonal cycles.</p><p>The remaining signal shows clear evidence of interannual oscillations and correlates (>0.5) with the Multivariate ENSO index (MEI). By spectral analysis and by an independent simulated-annealing approach, we locate several primary modes of the residual between 130 and 29 months. The phase of the lowest of these partial frequencies approximates that of solar flux data representing the solar cycle and the shortest major mode resembles the frequency of the Quasi Biennial Oscillation. However, minor phase-shifts and a direct physical link in this regard are not yet fully understood. When we include the extra modes in our OMC minimisation approach, it can be shown that recent acceleration in global ocean mass may indeed be smaller than previously anticipated by quadratic fitting while neglecting longer wavelengths.</p><p>Furthermore, the extrapolation of the fit including three prominent interannual modes between 29 and 130 months is able to predict recent La Niña related negative ocean mass anomalies. Our findings might support and integrate in similar analyses of the global sea level and other ECVs elsewhere. However, we must emphasise that an analysis of near-decadal oscillations from a sub-20 year lasting data set is yet to become more stable with increasing observation length from GRACE-FO.</p>

scholarly journals GRACE-derived ice-mass loss spread over Greenland

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
H. Nahavandchi ◽  
G. Joodaki ◽  
V. Schwarz
Keyword(s):  
Mass Loss ◽  
Sea Level ◽  
Satellite Data ◽  
Greenland Ice Sheet ◽  
Grace Data ◽  
Noise Structure ◽  
Global Sea Level ◽  
Warming World ◽  
Gravity Recovery ◽  
Over Time

AbstractThe Gravity Recovery and Climate Experiment (GRACE) monthly satellite data is used to examine the extent and magnitude of Greenland ice sheet melting for 2003-2012. We show that the well documented Greenland ice mass loss in the southern region spread to northwest Greenland in the period from2007 to 2010 and 2010 to 2012 by estimating ice mass variability over time in Greenland. The ice-mass melting is estimated to –183±11 Gt/yr. This estimation means that Greenland is still losing much more ice than gained, and continuing to contribute to global sea level rise in a warming world. Unlike other recent studies, our method employs a non-isotropic filter. A nonisotropic filter is used to decorrelate the GRACE data, since the GRACE noise structure has a non-isotropic nature.

scholarly journals The Balance and Abnormal Increase of Global Ocean Mass Change From Land Using GRACE

2020 ◽  
Vol 7 (5) ◽  
Author(s):  
Taoyong Jin ◽  
Xiaolong Li ◽  
C. K. Shum ◽  
Hao Ding ◽  
Xinyu Xu
Keyword(s):  
Mass Change ◽  
Global Ocean ◽  
Ocean Mass ◽  
Abnormal Increase ◽  
Land Using

A new working group on the Regional Assessments of Glacier MAss Change (RAGMAC)

2020 ◽  
Author(s):  
Michael Zemp ◽  
Matthias H. Braun ◽  
Alex S. Gardner ◽  
Bert Wouters ◽  
Geir Moholdt ◽  
...  
Keyword(s):  
Sea Level ◽  
Working Group ◽  
International Association ◽  
Temporal Distribution ◽  
Mass Change ◽  
Mountain Range ◽  
Spatio Temporal ◽  
Point Data ◽  
Release Data ◽  
Global Sea Level

<p>Retreating and thinning glaciers are icons of climate change and impact the local hazard situation, regional runoff as well as global sea level. For past IPCC reports, regional glacier change assessments were challenged by the small number and heterogeneous spatio-temporal distribution of in situ measurement series and uncertain representativeness for the respective mountain range as well as by spatial limitations of current satellite altimetry (only point data) and gravimetry (coarse resolution). Towards IPCC SROCC, there have been considerable improvements with respect to available geodetic datasets. Geodetic volume change assessments for entire mountain ranges have become possible thanks to recently available and comparably accurate DEMs. At the same time, advances have been made in processing methods for radar altimetry (CryoSat-2 swath processing), as well as new spaceborne laser altimetry (ICESat-2) and gravimetry (GRACE-FO) missions are in orbit and about to release data products to the science community. This opens new opportunities for regional evaluations of results from different methods as well as for truly global assessments of glacier mass changes and related contributions to sea-level rise. At the same time, the glacier research and monitoring community is facing new challenges related to data size, formats, and availability as well as new questions with regard to best practises for data processing chains and for related uncertainty assessments.</p><p>In this PICO presentation, we introduce a new working group of the International Association of Cryospheric Sciences (IACS) on Regional Assessments of Glacier Mass Change (RAGMAC; https://cryosphericsciences.org/activities/wg-ragmac/). The overall goal of this working group (WG) is bringing together the research community that is assessing regional glacier mass changes from various observation technologies and to come up with a new consensus estimate of global glacier mass changes and related uncertainties. The WG is organized in three work packages, two related to different remote sensing technologies (WG1: glaciological and geodetic DEM-differencing methods, WG2: altimetry and gravimetry) and a third that aims at regional comparisons of corresponding results. Participation is open to everybody who is willing to actively contribute to one or several of these work packages.</p>

How Salty Is the Global Ocean: Weighting It All or Tasting It a Sip at a Time?

2020 ◽  
Author(s):  
Rui Ponte ◽  
Qiang Sun ◽  
Chao Liu ◽  
Xinfeng Liang
Keyword(s):  
Sea Ice ◽  
Sea Level ◽  
Hydrological Cycle ◽  
Global Ocean ◽  
Data Quality Control ◽  
Argo Data ◽  
Terrestrial Water ◽  
Control Procedures ◽  
Global Mean Sea Level

<div class="page" title="Page 1"> <div class="section"> <div class="layoutArea"> <div class="column"> <p>Global ocean mean salinity <em>S </em>is a key indicator of the Earth's hydrological cycle and the exchanges of freshwater between the terrestrial water and ice reservoirs and the ocean. We explore two different ways of determining how salty the ocean is: (1) use in situ salinity measurements to taste the ocean a sip at a time and obtain a sample average; (2) use space gravimetry to weigh the whole ocean including sea-ice, and then separate sea-ice effects to infer changes in liquid freshwater content and thus <em>S</em>. Focusing on the 2005-2019 period, we assess monthly series of <em>S </em>derived from five different in situ gridded products, based mostly but not exclusively on Argo data, versus a series obtained from GRACE and GRACE Follow-On data and available sea ice mass estimates.</p> <p>There is little consistency in <em>S </em>series from the two methods for all time scales examined (seasonal, interannual, long-term trend). In situ series show larger variability, particularly at the longest scales, and are somewhat incoherent with the GRACE-derived series. In addition, there are wide spread differences among all the in situ <em>S </em>series, which denote their considerable sensitivity to choice of data, quality control procedures, and mapping methods. Results also suggest that in situ <em>S </em>values are prone to systematic biases, with most series showing increases after around 2014 that are equivalent to a drop in barystatic sea level of tens of centimeters! Estimates derived from GRACE are much smaller in magnitude and consistent with contributions of freshwater to the global mean sea level budgets, and they are thus more reliable than in situ-based <em>S </em>estimates. The existence of GRACE-derived estimates can serve as a consistency check on in situ measurements, revealing potential unknown biases and providing a way to cross-calibrate the latter data.</p> </div> </div> </div> </div>

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