GRACE observing a small scale ocean mass increase in the Bohai Sea

2020 ◽  
Author(s):  
Dapeng Mu ◽  
Tianhe Xu
Keyword(s):  
Sea Level ◽  
Spatial Resolution ◽  
Bohai Sea ◽  
Sediment Accumulation ◽  
Sea Level Change ◽  
Groundwater Depletion ◽  
The Bohai Sea ◽  
Level Change ◽  
Ocean Mass ◽  
Mass Increase

<p>The Gravity Recovery and Climate Experiment (GRACE) satellite mission has profoundly advanced our knowledge of contemporary sea level change. Owing to the coarse spatial resolution and leakage issue across the land-ocean boundary, it is challenged for GRACE to detect mass changes over a region smaller than its spatial resolution, especially a semi-enclosed basin that is adjacent to land with significant mass variation. In this contribution, we find that GRACE is capable of recovering mass increase in the Bohai Sea, which is adjacent to the North China Plain that has been experiencing significant groundwater depletion. This water mass increase, only amounting to 0.45 Gt/yr, is demonstrated by a reconstruction that is implemented with multisource data, including altimeter observations, steric estimates, and hydrology model. The reconstructed mass signal rejects the detection of sediment accumulation by GRACE, but it does not exclude the possibility that sediment accumulation may occur at local scale. Compared with the “true” mass increase, the mass increase observed by GRACE spherical harmonic coefficients (SHCs) is seriously compromised (i.e., signal magnitudes are substantially reduced) due to leakage issue. Our reconstruction results exemplify that elaborate data-processing is necessary for specific cases. On the other hand, the recently released mascons, which are resolved with constraints and require no further processing, suggest improved seasonal cycles in the Bohai Sea that are in agreement with altimeter observations. However, the rates derived from the mascons cannot properly represent the real ocean mass increase for the Bohai Sea, because the mascons underestimate the rates or contain some artificial effect. Nevertheless, the mascons provide new insights into regional sea level change relative to the traditional SHCs.</p>

scholarly journals An investigation of mass changes in the Bohai Sea observed by GRACE

2020 ◽  
Vol 94 (9) ◽  
Author(s):  
Dapeng Mu ◽  
Tianhe Xu ◽  
Guochang Xu
Keyword(s):  
Sea Level ◽  
Spatial Resolution ◽  
Bohai Sea ◽  
Water Mass ◽  
Sea Level Change ◽  
Groundwater Depletion ◽  
Reconstruction Technique ◽  
The Bohai Sea ◽  
Level Change ◽  
Mass Increase

Abstract The Gravity Recovery and Climate Experiment (GRACE) satellite mission has profoundly advanced our knowledge of contemporary sea level change. Owing to the coarse spatial resolution and leakage issue across the land–ocean boundary, it is challenging (even impossible) for GRACE to detect mass changes over a region smaller than its spatial resolution, especially a semi-enclosed basin (e.g., the Bohai Sea) that is adjacent to land with significant mass variation. In this contribution, the causes for the GRACE RL06 mass changes in the Bohai Sea are investigated using a reconstruction technique that is implemented with multisource data, including altimeter observations, steric estimates, and land mass changes from GRACE RL06 mascon solution. Our results by the reconstruction technique demonstrate that the GRACE annual cycles are primarily caused by water mass changes rather than sediment changes. On the other hand, the mass trends from both reconstructed signals and those observed by the GRACE RL06 spherical harmonic coefficients (SHCs) are small, ranging from − 0.38 mm/year to 0.51 mm/year (depending on different data sources). Given that our estimated accuracies are > 0.8 mm/year (the real accuracies should be larger), our reconstructed results cannot directly confirm the presence of sediment accumulation or water mass increase; however, analysis of only the altimetry data suggests the mass trends are due to water mass increase, which would amount to ~ 0.44 Gt/year. Further investigation suggests that the mass trends in the Bohai Sea suffer from a − 2.9 mm/year leakage-in effect from groundwater depletion in the North China and about 2.5 mm/year signal attenuation (resulting in a ~ 2.5 mm/year remaining trend that is roughly equivalent to the leakage-in trend, consequently leading to the small mass trend in the Bohai Sea). Our reconstruction results exemplify that elaborate data processing is necessary for specific cases. We also test whether the recently released RL06 mascon solutions that are resolved with constraints and require no further processing would improve the agreement with altimeter observations. We find that the seasonal cycles are improved relative to the RL06 SHCs; however, the rates derived from the mascon solutions cannot properly represent the altimeter-derived ocean mass estimates for the Bohai Sea, probably because the mascon solutions underestimate the rates or contain some processing artifacts. Nevertheless, the mascon solutions show enhanced signals, which offer new opportunities to investigate regional sea level change.

scholarly journals THE VERTICAL LAND MOTION OF TIDE GAUGE AND ABSOLUTE SEA LEVEL RISE IN BOHAI SEA

2019 ◽  
Vol IV-2/W5 ◽  
pp. 601-606
Author(s):  
D. Zhou ◽  
W. Sun ◽  
Y. Fu ◽  
X. Zhou
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Bohai Sea ◽  
Tide Gauge ◽  
Sea Level Change ◽  
Tide Gauges ◽  
Sea Level Changes ◽  
The Bohai Sea ◽  
Level Change ◽  
Vertical Land Motion

<p><strong>Abstract.</strong> The ground vertical movement of the tide gauges around the Bohai sea was firstly analyzed by using the observation data from 2009 to 2017 of the nine co-located GNSS stations. It was found that the change rate of ground vertical motion of four stations was in the same order of magnitude as the sea level change. In particular, the land subsidence rate of BTGU station reaches 11.47&amp;thinsp;mm/yr, which should be paid special attention to in the analysis of sea level change. Then combined with long-term tide gauges and the satellite altimetry results, the sea level changes in the Bohai sea and adjacent waters from 1993 to 2012 were analyzed. The relative and absolute sea level rise rates of the sea area are 3.81&amp;thinsp;mm/yr and 3.61&amp;thinsp;mm/yr, respectively, both are higher than the global average rate of change. At the same time, it is found that the vertical land motion of tide gauge stations is the main factor causing regional differences in relative sea level changes.</p>

Age and source of coastal loess in Shandong Peninsula, Bohai Sea, China: Implications for dust aggradation in respond to sea-level change

2022 ◽  
Vol 54 ◽  
pp. 100767
Author(s):  
Xiaodong Miao ◽  
E. Chongyi ◽  
Shujian Xu ◽  
Qiansuo Wang ◽  
Paul R. Hanson ◽  
...  
Keyword(s):  
Sea Level ◽  
Bohai Sea ◽  
Sea Level Change ◽  
Shandong Peninsula ◽  
Level Change

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

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

Sea-level and climate signatures recorded in the 1 Myr continental margin deposits from the Bohai Sea

2020 ◽  
Author(s):  
Zhengquan Yao ◽  
Xuefa Shi ◽  
Yanguang Liu ◽  
Shuqing Qiao
Keyword(s):  
Grain Size ◽  
Sea Level ◽  
Continental Margin ◽  
Principal Components ◽  
Bohai Sea ◽  
Sediment Accumulation ◽  
Fine Fraction ◽  
The Bohai Sea ◽  
Floodplain Deposits ◽  
And Sea Level

&lt;p&gt;Sediment accumulation in the continental margin is largely influenced by both sea-level fluctuations and climate changes during the Quaternary Period. However, the response of sediment accumulation to these changes at orbital timescale, remains poorly understood, mainly due to (i) the scarce of sedimentary records with high-resolution chronology and (ii) the difficulty of distinguishing the role of sea-level from climate signals. Here we present sediment color reflectance (c*), grain size and total organic carbon (TOC) data of core BH08 (212.4 m; ~1 Myr) recovered from the Bohai Sea, China. The chronology of core BH08 was constrained at orbital timescale by using magnetostratigraphy and astronomical tuning methods. Sedimentary facies analysis suggests that the core sequence is dominated by alternations of deltaic system and floodplain deposits. Principal components analysis on grain size data reveals two principal components (PCs), including PC1 (31&amp;#8211;500 &amp;#181;m, coarse fraction) and PC2 (18&amp;#8211;66 &amp;#181;m, fine fraction). Comparison of PC1, PC2, c* and TOC with sedimentary environments, we found that PC1 and c* corresponds well with cycles of deltaic and floodplain deposits at ~100/40-kyr cycles, while PC2 and TOC display ~20-kyr cycle, in addition to the ~100/40-kyr cycles. We interpret that PC1 and c* are mainly sea-level dependent, whereas PC2 and TOC are controlled by a combination of monsoonal climate and sea level. We suggest that Milankovitch-scale monsoon climate controlled the sediments supply to the Bohai Sea during the last 1 Myr, while the redistribution of sediments by marine process (e.g. tidal currents) seem to have obscured the monsoonal signal in the grain size proxy (e.g. PC1) which is sensitive to sea-level change. Our results provide an example of climate and sea-level influenced sediment accumulation in the shallow continental margin influenced by monsoonal climate in an icehouse world.&lt;/p&gt;

A revised sea level budget equation to accurately represent physical processes driving sea level rise

2020 ◽  
Author(s):  
Bramha Dutt Vishwakarma ◽  
Sam Royston ◽  
Ricardo E. M. Riva ◽  
Richard M. Westaway ◽  
Jonathan L. Bamber
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Sea Level Change ◽  
Ocean Bottom ◽  
Physical Processes ◽  
Level Change ◽  
Ocean Mass ◽  
The Earth ◽  
Regional Sea Level ◽  
Global Mean

&lt;p&gt;The sea level budget (SLB) equates changes in sea surface height (SSH) to the sum of various geo-physical processes that contribute to sea level change. Currently, it is a common practice to explain a change in SSH as a sum of ocean mass and steric change, assuming that solid-Earth motion is corrected for and completely explained by secular visco-elastic relaxation of mantle, due to the process of glacial isostatic adjustment. Yet, since the Solid Earth also responds elastically to changes in present day mass load near the surface of the Earth, we can expect the ocean bottom to respond to ongoing ocean mass changes. This elastic ocean bottom deformation (OBD) has been ignored until very recently because the contribution of ocean mass to sea level rise was thought to be smaller than the steric contribution and the resulting OBD was within observation system uncertainties. However, ocean mass change has increased rapidly in the last 2 decades. Therefore, OBD is no longer negligible and recent studies have shown that its magnitude is similar to that of the deep steric sea level contribution: a global mean of about 0.1 mm/yr but regional changes at some places can be more than 10 times the global mean. Although now an important part of the SLB, especially for regional sea level, OBD is considered by only a few budget studies and they treat it as a spatially uniform correction. This is due to lack of a mathematical framework that defines the contribution of OBD to the SLB. Here, we use a mass-volume framework to derive, for the first time, a SLB equation that partitions SSH change into its component parts accurately and it includes OBD as a physical response of the Earth system. This updated SLB equation is important for various disciplines of Earth Sciences that use the SLB equation: as a constraint to assess the quality of observational time-series; as a means to quantify the importance of each component of sea level change; and, to adequately include all processes in global and regional sea level projections. We recommend using the updated SLB equation for sea level budget studies. We also revisit the contemporary SLB with the updated SLB equation using satellite altimetry data, GRACE data, and ARGO data.&lt;/p&gt;

scholarly journals Arctic Sea Level Budget Assessment during the GRACE/Argo Time Period

2020 ◽  
Vol 12 (17) ◽  
pp. 2837
Author(s):  
Roshin P. Raj ◽  
Ole B. Andersen ◽  
Johnny A. Johannessen ◽  
Benjamin D. Gutknecht ◽  
Sourav Chatterjee ◽  
...  
Keyword(s):  
Sea Level ◽  
Sea Level Change ◽  
Mass Change ◽  
The Arctic ◽  
Altimeter Data ◽  
Significant Shift ◽  
Important Indicator ◽  
Level Change ◽  
Ocean Mass ◽  
Time Period

Sea level change is an important indicator of climate change. Our study focuses on the sea level budget assessment of the Arctic Ocean using: (1) the newly reprocessed satellite altimeter data with major changes in the processing techniques; (2) ocean mass change data derived from GRACE satellite gravimetry; (3) and steric height estimated from gridded hydrographic data for the GRACE/Argo time period (2003–2016). The Beaufort Gyre (BG) and the Nordic Seas (NS) regions exhibit the largest positive trend in sea level during the study period. Halosteric sea level change is found to dominate the area averaged sea level trend of BG, while the trend in NS is found to be influenced by halosteric and ocean mass change effects. Temporal variability of sea level in these two regions reveals a significant shift in the trend pattern centered around 2009–2011. Analysis suggests that this shift can be explained by a change in large-scale atmospheric circulation patterns over the Arctic. The sea level budget assessment of the Arctic found a residual trend of more than 1.0 mm/yr. This nonclosure of the sea level budget is further attributed to the limitations of the three above mentioned datasets in the Arctic region.

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