Coral reefs in the Pacific

[NCWDave]

My 50 years of wreck / reef / wall diving in SE Asia, Hawaii and Mayan reef has unscientifically been spectacular. Just out of curiosity how old are the planet's reefs? What has the temperature profile been during that period? As the planet warms what areas will degrade? What areas will proliferate? btw where does limestone come from?

[StuM]

Originally Posted by NCWDave

Just out of curiosity how old are the planet's reefs?

It depends on what you mean by "old" and "reefs"

• Individual corals can live for up to about 5000 years.
• The GBR was mainly dry land about 10,000 years ago.
• The oldest coral skeletons on which the GBR grows date back about 500,000 years
• The types of coral that form today's tropical reefs first appeared about 240 million years ago.
• Chazy Fossil Reef is reckoned to be about 480 million years old

[jackdale]

Originally Posted by StuM

[*]Chazy Fossil Reef is reckoned to be about 480 million years old[/LIST]

BTW

"These rocks are often called "The World's Oldest Coral Reefs" (Raymond, 1924), but could be more appropriately termed "The World's Oldest Reefs in Which Coral Occur," but that's a little wordy. Although coral are present, they were recent developments in the biotic world and were not the dominant framebuilder. "

https://dec.vermont.gov/geological-s...-geology/Chazy

[NCWDave]

Good read! https://dec.vermont.gov/geological-s...-geology/Chazy TY! I was kinda asking a couple loaded questions. I really struggle with the concept that an ocean a couple degrees warmer and or a tiny change in the amount of CO2 (a gas that makes up a total of .04% of our atmosphere) will have a devastating effect on the reefs. If we have a 5% rise in CO2 it will be .002% of our atmosphere(if i got the math right). We are supposed to believe a couple few degrees warmer and .002% change in the atmosphere will be devastating? Coral reefs are millions of years old. They have existed even flourished through extensive changes in climate and atmospheric conditions. https://en.wikipedia.org/wiki/Global_temperature_record

[StuM]

Another good read:

Corals of the World

One quote from there which is relevant to your last post:
Much of the Middle Cretaceous was characterised by release of carbon dioxide due to extensive volcanism around the continental plate margins and this, together with the accumulation of organic matter associated with sea level changes, may have increased the acidity of much of the ocean surface. Ocean and atmospheric temperatures over a range of latitudes from the equator to the poles were much higher than they are now. This would have varied greatly over time, but subtropical conditions may have periodically extended to 45°N and possibly 70°S, and there were no polar ice caps. These conditions would have resulted in weaker ocean currents than we have today. Corals would have been far more widely dispersed and there would have been a much greater development of distinctive regional provinces.

(Middle Cretaceous was about 100 million years ago)

[Don C L]

If you don't believe really tiny things can have huge consequences then you've never tried to sleep in a room with one mosquito.

[jackdale]

Originally Posted by NCWDave

Good read! https://dec.vermont.gov/geological-s...-geology/Chazy TY! I was kinda asking a couple loaded questions. I really struggle with the concept that an ocean a couple degrees warmer and or a tiny change in the amount of CO2 (a gas that makes up a total of .04% of our atmosphere) will have a devastating effect on the reefs. If we have a 5% rise in CO2 it will be .002% of our atmosphere(if i got the math right). We are supposed to believe a couple few degrees warmer and .002% change in the atmosphere will be devastating? Coral reefs are millions of years old. They have existed even flourished through extensive changes in climate and atmospheric conditions. https://en.wikipedia.org/wiki/Global_temperature_record

I am not sure where you get the 5% rise in CO2. Prior to the Industrial revolution CO2 level were approximately 285 ppm. They are currently 415 ppm. That is approximately a 50% increase in a known greenhouse gas. Using carbon isotope analysis that increase can be attributed to the burning of fossil fuel. It is called the Suess effect.

Since the mid-18th century we have added 1.5 trillion tonnes of CO2 to the system. About 30% of that has been added to the oceans which has lowered the pH level. "Since the beginning of the Industrial Revolution, the pH of surface ocean waters has fallen by 0.1 pH units. Since the pH scale, like the Richter scale, is logarithmic, this change represents approximately a 30 percent increase in acidity". (see https://www.pmel.noaa.gov/co2/story/...idification%3F for more information).

As well the heat capacity of water is higher than that of air. As a result, much of the heat from anthropogenic global warming has gone into the oceans.

https://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/

All of this is occurring at a time when natural cycles such as solar cycles and Milankovitch cycles would have us in a cooling phase.
https://climate.nasa.gov/faq/14/is-t...lobal-warming/
https://climate.nasa.gov/blog/2949/w...rrent-warming/

Coral reefs are subject to both increased water temperature and to lower pH levels.

[NCWDave]

TY for your reply jackdale. A nice presentation and all info to be considered. Percent increase, 5% or 50% we are still discussing a .04% element of our atmosphere. When the most sensational terms are always used (ie Trillions of tons) it tends to make me very suspicious. The global heat content shows a scary skyrocketing curve. How much have the oceans actually warmed in the last century? Solar cycles and Milankovitch cycles? plausible, warming after a recent Ice age? clearly. Coral reefs are indeed subject to climatic change. Over the last few million years how has the reefs fared in periods of massively higher temps and co2/ph levels? I appreciate civil conversation, forgive me if I seem jaded but I have lived through too many false "scientific" proficiency and end of the world scenarios. When I see only one side of any issue presented and others repressed I become very suspicious. I remember the pollution of the 60's and 70's. I also wonder how forcing the western heavy industry to unregulated countries like China have effected the health of the planet.

[StuM]

I just knew this was going to happen

[jackdale]

Originally Posted by NCWDave

TY for your reply jackdale. A nice presentation and all info to be considered. Percent increase, 5% or 50% we are still discussing a .04% element of our atmosphere.

Without that 0.4% of CO2, the earth would be 33C colder.
https://pubs.giss.nasa.gov/docs/2010...s_la09300d.pdf

The rate at which climate change is the issue.

PETM, the Paleocene – Eocene Thermal Maximum.

That’s the last time in earth history that things changed in a way similar to the way they are changing now. It was 55 million years ago, give or take a millenium.

https://climatecrocks.com/2011/06/29...tory-the-petm/

No scientific institution in any country on the the entire planet disputes the conclusions of the IPCC. What is the other side? How is it repressed?

[NCWDave]

You guys seem to put a lot more faith in science, especially science that is overwhelmingly funded buy government and including a very tidy financial and political motivation. I have seen "science" turn out wrong to many times. Accepting it as absolute? Nope.
edt; ty for the polite conversation n sharing your opinion

[Rucksta]

Go and have a look.

Don't accept the "science" without verification.
Coral reefs have been around longer than humans and will probably be around long after we've gone.

[jackdale]

Originally Posted by Rucksta

Go and have a look.

Don't accept the "science" without verification.
Coral reefs have been around longer than humans and will probably be around long after we've gone.

OK

"Abstract
Since the 1980s the frequency of warming events has intensified and simultaneously
widespread coral bleaching, and enhanced coral mortality have been observed. Yet,
it remains unpredictable how tropical coral reef communities will react to prolonged
5 adverse conditions. Possibly, coral reef systems are sufficiently robust to withstand
continued environmental pressures. But if coral mortality increases, what will platform
communities of the future look like? The co-evolution of early Paleogene carbonate
platforms and palaeoclimate may provide insight. Here we document the impact of
early Paleogene global warming on shallow-water carbonate platforms in the Tethys.
10 Between 59 and 55 Ma, three discrete stages in platform development can be identified
Tethys-wide: during the first stage carbonate platforms mainly consisted of coralgal
reefs; during the second – transitional – stage coralgal reefs thrived only at middle
latitudes and gave way to larger foraminifera as dominant carbonate producer in low
latitudes; finally, during the third stage, newly developing larger foraminifera lineages
15 completely took over the role as main carbonate-producing organisms in low to middle
latitudes. We postulate that rising temperatures led to a stepwise demise of Paleocene
coral reefs, giving way to an unprecedented expansion of larger foraminifera, dominating Tethyan platforms during the early Eocene.
"
https://hal.archives-ouvertes.fr/hal-00298253/document

[jackdale]

Threats to reefs:



https://oceanservice.noaa.gov/facts/...f-climate.html



https://oceanservice.noaa.gov/facts/...pollution.html



https://oceanservice.noaa.gov/facts/...erfishing.html

[NCWDave]

Again ty. now if you can lets dumb it down for me. Paleogene = 56 - 66 m years ago. Very very warm, most of the planet was tropical. (sounds like great diving) But was hard on coral reefs? Coral that we would recognize today? Coral reefs declined and shellfish prospered? What temp range are thought to be common in this period? I would think that if the entire planet was tropical or close to tropical the temps must have been extremely high compared to today. Is there any reliable data on atmosphere co2 or ocean ph? Are the massive limestone formations on the planet primarily foraminifera / shellfish? Are ancient coral formations a large component of today's lime stone? I will give this a rest for a bit and return to hal-002.