Ocean anoxia 93 million years ago linked to warming

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Ocean anoxia, a condition where oceans are severely depleted in dissolved oxygen, can have devastating impacts on marine life. One such event, Oceanic Anoxic Event 2 (OAE2), occurred about 93.5 million years ago and lasted for up to 700,000 years. New research suggests that OAE2 was caused by global warming, as evidenced by deep-sea sediments that show a sharp increase in the abundance of a specific type of bacteria that thrives in warm, low-oxygen environments.

Ocean Anoxia 93 Million Years Ago: A Deep Dive into Marine Deoxygenation

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Published on: January 17, 2015 Description: Hugh Jenkyns goes through the contingent facts that made him discover that the earth underwent peridos of global anoxia.

The discovery of the Oceanic Anoxic Events (H.Jenkyns)

Imagine a world where vast stretches of the ocean are devoid of oxygen, creating toxic environments that threaten marine life. This phenomenon, known as marine anoxia, has occurred throughout Earth’s history, with one notable event taking place approximately 93 million years ago during the Cretaceous period.

Marine Anoxia Event 2: A Case Study

Oceanic Anoxic Event 2 (OAE2) stands as a prime example of marine anoxia. It occurred across the Cenomanian-Turonian boundary and lasted for up to 700,000 years. During this period, large portions of the ocean became severely depleted in dissolved oxygen, leading to devastating impacts on marine ecosystems.

Volcanic Activity and Climate Warming: The Culprits Behind OAE2

Scientists believe that volcanic eruptions from the Caribbean Large Igneous Province and the High Arctic Large Igneous Province played a significant role in triggering OAE2. These eruptions released enormous amounts of carbon dioxide into the atmosphere, causing global temperatures to rise. The warmer climate led to increased weathering of land, releasing nutrients into the oceans and stimulating primary productivity. However, this surge in productivity ultimately consumed more oxygen, resulting in widespread deoxygenation.

Unveiling Ancient Secrets Through Deep-Sea Sediments

Researchers have turned to deep-sea sediments to uncover the secrets of OAE2. By studying biomarkers, chemical compounds preserved in marine sediments, scientists can reconstruct past environmental conditions. These biomarkers reveal that sea surface temperatures increased by ~5-8°C during OAE2, accompanied by a rise in organic carbon content and a decline in oxygen levels.

The Consequences of Ocean Anoxia

The widespread deoxygenation during OAE2 had profound consequences for marine life. Benthic foraminifera, bottom-dwelling microorganisms, were particularly vulnerable and experienced a significant decline in abundance. The expansion of oxygen minimum zones, areas with extremely low oxygen levels, further stressed marine ecosystems.

Lessons from the Past for the Future

The study of OAE2 provides valuable insights into the potential impacts of ongoing climate change on our oceans. As global temperatures continue to rise, oxygen minimum zones are expanding, threatening marine biodiversity and fisheries. Understanding the role of warmer oceans in the cycling of oxygen and nutrients is crucial for mitigating the future impacts of climate change on marine ecosystems.

Wrapping Up

Ocean anoxia 93 million years ago serves as a stark reminder of the profound impact that climate change can have on marine environments. By studying ancient episodes of marine anoxia, scientists gain valuable knowledge that can help us understand and address the challenges facing our oceans today.

FAQ’s

1. What was Ocean Anoxic Event 2?

Ocean Anoxic Event 2 (OAE2) was a period of widespread deoxygenation in the oceans that occurred approximately 93 million years ago during the Cretaceous period. It lasted for up to 700,000 years and had devastating impacts on marine ecosystems.

2. What caused OAE2?

Volcanic eruptions from the Caribbean Large Igneous Province and the High Arctic Large Igneous Province released enormous amounts of carbon dioxide into the atmosphere, causing global temperatures to rise. The warmer climate led to increased weathering of land, releasing nutrients into the oceans and stimulating primary productivity. However, this surge in productivity ultimately consumed more oxygen, resulting in widespread deoxygenation.

3. How do scientists study OAE2?

Scientists study OAE2 by analyzing biomarkers, chemical compounds preserved in deep-sea sediments. These biomarkers reveal past environmental conditions, such as sea surface temperatures, organic carbon content, and oxygen levels.

4. What were the consequences of OAE2?

The widespread deoxygenation during OAE2 had profound consequences for marine life. Benthic foraminifera, bottom-dwelling microorganisms, were particularly vulnerable and experienced a significant decline in abundance. The expansion of oxygen minimum zones, areas with extremely low oxygen levels, further stressed marine ecosystems.

5. What lessons can we learn from OAE2?

The study of OAE2 provides valuable insights into the potential impacts of ongoing climate change on our oceans. As global temperatures continue to rise, oxygen minimum zones are expanding, threatening marine biodiversity and fisheries. Understanding the role of warmer oceans in the cycling of oxygen and nutrients is crucial for mitigating the future impacts of climate change on marine ecosystems.

Links to additional Resources:

1. www.nature.com/articles/s41467-022-34922-w 2. www.sciencedirect.com/science/article/abs/pii/S0012825222006061 3. www.agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2022GC010807.