Typhoon-Induced Microseisms around the South China Sea

2020 ◽  
Vol 91 (6) ◽  
pp. 3454-3468
Author(s):  
Seongjun Park ◽  
Tae-Kyung Hong
Keyword(s):  
South China Sea ◽  
South China ◽  
Bottom Topography ◽  
Pressure Change ◽  
Ocean Waves ◽  
The South China Sea ◽  
Ocean Bottom ◽  
The South ◽  
China Sea ◽  
Regional Factors

Abstract Microseisms in frequencies of 0.05–0.5 Hz are a presentation of solid earth response to the ocean waves that are developed by atmospheric pressure change. The South China Sea provides a natural laboratory with a closed ocean environment to examine the influence of regional factors on microseism development as well as the nature of microseisms. The microseisms induced by typhoons crossing over the South China Sea are investigated. Typhoons are typical transient sources of varying strengths and locations. Primary microseisms develop nearly stationary in the northeastern South China Sea for most typhoons, suggesting effective environment for excitation of primary microseisms. Typhoon-induced secondary microseisms develop around the typhoon paths with time delays varying up to one day. Typhoon-induced microseism amplitudes are proportional to the ocean-wave amplitudes in the source regions, decaying with distance. Ocean waves develop following the typhoons for days. The dominant frequency of typhoon-induced microseisms increases with time due to the influence of dispersive ocean waves. The microseisms are affected by regional factors including crustal structures, coastal geometry, ocean depth, and ocean-bottom topography.

scholarly journals Pack-Ice Drift off East Antarctica and some Implications

1989 ◽  
Vol 12 ◽  
pp. 1-8 ◽  
Author(s):  
Allison Ian
Keyword(s):  
Sea Ice ◽  
Bottom Topography ◽  
Regional Climate ◽  
Qualitative Assessment ◽  
Ocean Bottom ◽  
Ice Dynamics ◽  
Antarctic Sea Ice ◽  
Ice Drift ◽  
Region Data ◽  
Autumn And Winter

Three satellite-tracked data buoys were deployed between 70° and 80°E south of 65°S in February-March 1985. These buoys were subsequently trapped within the expanding seasonal sea ice and drifted with the ice. The buoys measured air temperature and pressure, and water temperatures to 100 m depth. Data from the buoys are used to describe the ice drift and environment within the winter sea-ice zone in this region, both north and south of the Antarctic Divergence. Additional preliminary data from a further six buoys deployed in the same area in March 1987 are also presented. Besides providing information on the broad-scale drift of the ice in the Prydz Bay region, data from the buoys have shown: (i) the important role that ice drift plays in determining the autumn and winter expansion of Antarctic sea ice; (ii) the highly mobile nature of the ice, even hundreds of kilometres from the ice edge; (iii) the role that ocean-bottom topography has in determining ice drift over the continental shelf; and (iv) the modifying influence that an ice cover has on regional climate. A qualitative assessment is made of the relative importance of the major forces driving the ice, although the data are insufficient for a detailed study of the ice dynamics.

scholarly journals Evaluating Accuracy of HY-2A/GM-Derived Gravity Data With the Gravity-Geologic Method to Predict Bathymetry

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhijie Wei ◽  
Jinyun Guo ◽  
Chengcheng Zhu ◽  
Jiajia Yuan ◽  
Xiaotao Chang ◽  
...  
Keyword(s):  
Gravity Data ◽  
Bottom Topography ◽  
Gravity Anomalies ◽  
Processing Method ◽  
Ocean Bottom ◽  
Least Squares Collocation ◽  
Geological Structures ◽  
Data Processing Method ◽  
First Time ◽  
Assessment Result

For the first time, HY-2A/GM-derived gravity anomalies determined with the least-squares collocation method and ship-borne bathymetry released from the National Centers for Environmental Information (NCEI) are used to predict bathymetry with the gravity-geologic method (GGM) over three test areas located in the South China Sea (105–122°E, 2–26°N). The iterative method is used to determine density contrasts (1.4, 1.5, and 1.6 g/cm3) between seawater and ocean bottom topography, improving the accuracy of GGM bathymetry. The results show that GGM bathymetry is the closest to ship-borne bathymetry at check points, followed by SRTM15+V2.0 model and GEBCO 2020 model. It is found that in a certain range, the relative accuracy of GGM bathymetry tends to improve with the increase of depth. Different geological structures affect the accuracy of GGM bathymetry. In addition, the influences of gravity anomalies and data processing method on GGM bathymetry are analyzed. Our assessment result suggests that GGM can be widely applied to bathymetry prediction and that HY-2A/GM-derived gravity data are feasible with good results in calculating ocean depth.

SAR Detection of Ocean Bottom Topography

2018 ◽  
pp. 147-176
Author(s):  
Qing Xu ◽  
Quanan Zheng ◽  
Shuangshang Zhang ◽  
Xiaofeng Li
Keyword(s):  
Bottom Topography ◽  
Ocean Bottom

scholarly journals Energetics of Eddy-Mean Flow Interactions in the Amery Ice Shelf Cavity

2021 ◽  
Vol 8 ◽  
Author(s):  
Yang Wu ◽  
Zhaomin Wang ◽  
Chengyan Liu ◽  
Liangjun Yan
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Ocean Circulation ◽  
Bottom Topography ◽  
Ocean Bottom ◽  
Mean Flow ◽  
Ice Shelf ◽  
Available Potential Energy ◽  
Amery Ice Shelf ◽  
Basal Melting

Previous studies demonstrated that eddy processes play an important role in ice shelf basal melting and the water mass properties of ice shelf cavities. However, the eddy energy generation and dissipation mechanisms in ice shelf cavities have not been studied systematically. The dynamic processes of the ocean circulation in the Amery Ice Shelf cavity are studied quantitatively through a Lorenz energy cycle approach for the first time by using the outputs of a high-resolution coupled regional ocean-sea ice-ice shelf model. Over the entire sub-ice-shelf cavity, mean available potential energy (MAPE) is the largest energy reservoir (112 TJ), followed by the mean kinetic energy (MKE, 70 TJ) and eddy available potential energy (EAPE, 10 TJ). The eddy kinetic energy (EKE) is the smallest pool (5.5 TJ), which is roughly 8% of the MKE, indicating significantly suppressed eddy activities by the drag stresses at ice shelf base and bottom topography. The total generation rate of available potential energy is about 1.0 GW, almost all of which is generated by basal melting and seawater refreezing, i.e., the so-called “ice pump.” The energy generated by ice pump is mainly dissipated by the ocean-ice shelf and ocean-bottom drag stresses, amounting to 0.3 GW and 0.2 GW, respectively. The EKE is generated through two pathways: the barotropic pathway MAPE→MKE→EKE (0.03 GW) and the baroclinic pathway MAPE→EAPE→EKE (0.2 GW). In addition to directly supplying the EAPE through baroclinic pathway (0.2 GW), MAPE also provides 0.5 GW of power to MKE to facilitate the barotropic pathway.

A Classification of Scientific Evidence in Geology

2001 ◽  
Vol 20 (1) ◽  
pp. 9-13 ◽  
Author(s):  
Cyril Galvin ◽  
Coastal Engineer
Keyword(s):  
Scientific Evidence ◽  
Bottom Topography ◽  
Continental Drift ◽  
Ocean Bottom ◽  
Lake Mead ◽  
Third Order ◽  
Simple Fact ◽  
First Order ◽  
Rock Types

All facts are not equal, nor are they equally theory-laden. Facts can be separated into a three-level, five-part classification. The three levels are first-, second-, and third-order evidences, going from most certain to least certain evidence. First-order evidence may be either a simple fact (one based directly on a measurement of length, time, or mass, or on an expert's identification) or a derivative fact (an induction from simple facts). Second-order evidence may be a simple inference (from insufficient first-order evidence) or a derivative inference (from the cumulative indication of simple facts, derivative facts, and simple inference). Third-order evidences are hypothetical explanations, known as theories to their proponents. Scientific examples of the five classes are as follows: Elevations, clast sizes, and rock types employed by J Harlen Breli to explain the Channeled Scablands are simple facts. The understanding of the Basin and Range of western North America as an extensional terrane is a derivative fact. The ocean bottom topography on maps by Heezen and Tharp are simple inferences. The thicknesses of the crust under Lake Mead or Lake Bonneville are derivative inferences. Many theories are third-order evidences, although successful theories can graduate to become first-order derivative facts, with sufficient first-order support. This classification developed from close readings of Oreskes's The Rejection of Continental Drift and Victor Baker's essay-review of that book in Earth Sciences History.

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