Recent comments in /f/science

Dalmah t1_j8lw912 wrote

Reply to comment by hotdogbo in New study shows Acceleration of global sea level rise imminent past 1.8℃ planetary warming by 9273629397759992

The surface of the Pacific Ocean stands about 40 cm higher than the Atlantic Ocean with respect to the 1000-decibar surface, and the North Atlantic and North Pacific stand respectively about 14 and 17 cm higher than the South Atlantic and Pacific.

How are they gonna measure sea level rise when its not even a uniform level in the first place?

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avogadros_number OP t1_j8ltl1b wrote

Reply to During the mid-Cretaceous approximately 94.5 million years ago the worlds oceans became nearly uninhabitable as rapid degassing of volcanic carbon dioxide altered seawater carbonate chemistry, triggering a global-scale episode of reduced marine oxygen levels known as Oceanic Anoxic Event 2. by avogadros_number

>During the Jurassic and Cretaceous, global events of widespread low-oxygen conditions (Oceanic Anoxic Events) were recorded in marine strata associated to major perturbations in the carbon cycle. These disturbances were linked to rapid global warming, probably caused by a release of carbon dioxide in the atmosphere due to degassing related to large-scale volcanism, dissociation of methane hydrates and thermogenic methane.

>Many authors have studied the Oceanic Anoxic Events (OAEs) following the original definition by Schlanger and Jenkyns (1976). Nine OAEs are recognized as of global significance and three of them are considered as major events: T-OAE, OAE1a and OAE2. The first, also called Toarcian OAE or Posidonienschiefer event, occurred in the Early Jurassic (~183 Ma) and was first identified by Jenkyns (1980) in northern Europe. The second, also called early Aptian OAE or Selli Event, occurred in the late Early Cretaceous (~120 Ma) and was first observed by Coccioni et al. (1987) in Italy. The third global event, also called Cenomanian – Turonian OAE or Bonarelli Event, occurred in the early Late Cretaceous (~93 Ma) and was noticed by Schlanger and Jenkyns (1976) when comparing subsurface data from the Deep Sea Drilling Project to outcrops; with the most famous being the Livello Bonarelli in the Umbrian Apennines of Italy.

>- The expression of the Oceanic Anoxic Event 2 (OAE2) in the northeast of Brazil (Sergipe-Alagoas Basin)

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avogadros_number OP t1_j8lt3mi wrote

Reply to comment by [deleted] in During the mid-Cretaceous approximately 94.5 million years ago the worlds oceans became nearly uninhabitable as rapid degassing of volcanic carbon dioxide altered seawater carbonate chemistry, triggering a global-scale episode of reduced marine oxygen levels known as Oceanic Anoxic Event 2. by avogadros_number

They absolutely are. Of all of the mass extinction events and minor extinction events, one of them (the end-Cretaceous) is more commonly attributed to bolide impact, though not without prior effects from the Deccan Traps. The End-Permian (Siberian Traps), and End-Triassic (Central Atlantic Volcanic Province - CAMP) are certainly attributed to volcanism, as are a number of other extinction events such as AOE 2 and others. Not all large impact events lead to extinctions or mass extinctions (> 75% of all species go extinct within a relatively short geological time span). For example, the Manicouagan Impact Crater, located in Quebec, Canada has a diameter of ~100 km and occurred more than 12 million years before the end of the Triassic with no extinctions associated with the event.

The greatest cause of extinction events - mass or otherwise, whether from volcanism, impact events, orbital cycles, etc. results from the subsequent changes in atmospheric and ocean chemistry. This doesn't bode well for our current climate trajectory.

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avogadros_number OP t1_j8lr8h1 wrote

Reply to comment by [deleted] in During the mid-Cretaceous approximately 94.5 million years ago the worlds oceans became nearly uninhabitable as rapid degassing of volcanic carbon dioxide altered seawater carbonate chemistry, triggering a global-scale episode of reduced marine oxygen levels known as Oceanic Anoxic Event 2. by avogadros_number

FYI the link you provide says nothing about diatoms, benthic or planktonic.

However, in "The origin of Cretaceous black shales: a change in the surface ocean ecosystem and its triggers (2015)" the authors state

>During OAE 2, up to 25% of marine invertebrate species became extinct

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