It’s a parallel comparison to what’s happening to this world, what with the record levels of carbon dioxide being amassed today and all. I’ve understood for years that climate change was a significant threat, but as more is discovered, it’s turning out to be a far more significant problem than I ever imagined.
Global climate change, fueled by skyrocketing levels of atmospheric carbon dioxide, is siphoning oxygen from today’s oceans at an alarming pace — so fast that scientists aren’t entirely sure how the planet will respond.
Their only hint? Look to the past.
In a study to be published this week in the journal Proceedings of the National Academy of Sciences, researchers from Florida State University did just that — and what they found brings into stark relief the disastrous effects a deoxygenated ocean could have on marine life.
Millions of years ago, scientists discovered, powerful volcanoes pumped Earth’s atmosphere full of carbon dioxide, draining the oceans of oxygen and driving a mass extinction of marine organisms.
“We wanted to reconstruct Early Jurassic ocean oxygen levels to better understand the mass extinction and the T-OAE,” said Theodore Them, a postdoctoral researcher at FSU who led the study. “We used to think of ocean temperature and acidification as a one-two punch, but more recently we’ve learned this third variable, oxygen change, is equally important.”
By analyzing the thallium isotope composition of ancient rocks from North America and Europe, the team found that ocean oxygen began to deplete well before the defined time interval traditionally ascribed to the T-OAE.
That initial deoxygenation, researchers say, was precipitated by massive episodes of volcanic activity — a process not altogether unlike the industrial emission of carbon dioxide we’re familiar with today.
“Over the past 50 years, we’ve seen that a significant amount of oxygen has been lost from our modern oceans,” Them said. “While the timescales are different, past volcanism and carbon dioxide increases could very well be an analog for present events.”
When the atmosphere is suffused with carbon dioxide, global temperatures climb, triggering a cascade of hydrological, biological and chemical events that conspire to sap the oceans of oxygen.
“It’s extremely important to study these past events,” Them said. “It seems that no matter what event we observe in Earth’s history, when we see carbon dioxide concentrations increasing rapidly, the result tends to be very similar: a major or mass extinction event. This is another situation where we can unequivocally link widespread oceanic deoxygenation to a mass extinction.”
Steps can still be taken to curb oxygen loss in the modern oceans. For example, conserving important wetlands and estuaries — along with other environments that absorb and store large amounts of carbon dioxide — could help to blunt the effects of harmful industrial emissions.