South China Sea depths (in meters). Map courtesy Silent World Foundation.
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On July 25, 2023 Anonymous commented (with
some additions by Pete):
The depth issues in the South China Sea (SCS) are not as simple as shallow and deeper parts. There is a collection of interconnected basins linked by deep valleys (or undersea canyons). Submarines can hide under water levels of differing temperature and salinity.
There is at least 100 years of bathymetric data in the SCS collected by the British, US, French, Dutch, Japanese and now Chinese navies. Most of this data is kept secret although there are some public, but crude, sea depth maps, like the one above.
There are many ways of detecting submarines the oldest being naked eye visual, acoustic/sonar and magnetic anomaly (used in the destruction of submarines as far back as 1918). Magnetic anomaly detection needs to be very close range (certainly less than a mile at most) measuring a submarine's magnetic abnormality vs background magnetism. The volcanic areas in the SCS are very different from the magnetic uniformity found in the North Sea or the Baltic.
Most submarines as well as surface warships have a reduced Magnetic signature through the process of Degaussing.
Here is also a list of ASW detection aspects that might be available to China's "SEAWEB".
French strategic writers
Bonnet's study has many things to say about:
-
the increasing importance of SSKs and nuclear subs in Southeast Asian and
SCS waters.
- relatively low amount of publicity about ways through the Philippine islands.
-
well understood by some, though secret in detail, paths for nuclear
submarines though the Philippine and Indonesian archipelagos.
-
US and Chinese secrecy about viable submarine paths and sensor arrays
throughout the SCS especially within the so-called "Dangerous Ground"
in the Spratly Islands
-
China's sensor buildups on and between its new militarized reefs since
the 2010s eg. Fiery Cross, Mischief and Subi reefs.
-
China's evolution in SSBN development including Type 094
"Jins" with JL-2 SLBMs (that can already hit Australia). There is an
expectation Type 096 "Tangs" will soon be developed with ever longer
range JL-3s that from the SCS (including "Dangerous Ground") waters may have the range to hit the
continental US.
Other interesting Hérodote volumes are many, including:
- Seas
and Oceans, Volume 163, Issue 4,
2016 eg. Camille
Morel's Threats
beneath the seas: Vulnerabilities in the global cable network