The deep sea guards secrets of Earth’s past. Its sediment layers silently record carbon cycles, climate shifts, and ecosystem upheavals. Among the vast oceans, the Pacific holds the most heat and carbon. Yet, it remains one of the least explored when it comes to long-term climate data.

“It’s easy to forget that two-thirds of our planet is covered with salty ocean water, especially when you don’t live near the coast,” said Professor Elizabeth Griffith from The Ohio State University. “It’s also hard to realize just how much of it we haven’t explored yet.”

Legacy data is thin. Only eight Pacific High sites have been sampled using modern drilling methods. These include Shatsky Rise, Hess Rise, Allison Guyot, Limalok Guyot, Lo-En Guyot, Ontong Java Plateau, Mid-Pacific Mountains, and Magellan Rise.

Most of our insights still rely on decades-old sediment cores, many of which are now partly degraded and depleted.

Pacific sediment holds a climate record

Pacific Highs are submerged geological plateaus, rich in carbonate sediments ideal for preserving past climate signals. These sites sit above the carbonate compensation depth, where shells of tiny organisms survive long enough to become fossilized.

During warmer epochs, the deep ocean turned acidic, eroding many fossil records. Yet, these Highs remained relatively untouched. Sediment cores from sites like Shatsky Rise have revealed Earth’s ancient greenhouse climates, mass extinctions, oceanic anoxic events, and recovery patterns.

But sediment continuity is not guaranteed. Currents and internal tides sometimes erode layers. That’s why scientists argue for multi-site sampling. More complete and widespread records help piece together zonal and latitudinal ocean changes over time.

Uncovering ancient climate clues

Technology has transformed ocean drilling. Ships like the JOIDES Resolution enabled long, continuous core recovery from multiple holes per site. This method replaced the earlier “spot-coring” that often missed climate transitions.

Still, many key events – like the Cretaceous-Paleogene boundary – are poorly represented in Pacific cores. New proxies now let researchers study microbial communities, biomarkers, and porewaters, but these methods need fresh sediment.

“When you’re extrapolating from such a huge time and spatial scale, you need more than one or two data points to get complete records and ground truth modeling,” said Professor Griffith.

Urgent need for Pacific sediment cores

Gaps in spatial data limit model accuracy. Researchers stress the importance of gathering new cores to improve climate models, reduce uncertainty, and capture ecological transitions.

Scientific drilling helps reconstruct circulation patterns, biological pump dynamics, and responses to warming and acidification. These insights are crucial for understanding how oceans will absorb excess CO₂ and how marine life will adapt – or collapse.

The 2024 Ohio State workshop emphasized community-led research planning. Experts recommended revisiting sites with excellent preservation, like Hess Rise, and launching new expeditions to still-unexplored Highs.

Global effort needed

Scientific progress depends on global cooperation. “One of the benefits of the ocean drilling community has always been that it’s a larger effort,” said Professor Griffith.

“Working with legacy core material is a crucial part of my research, but it will never replicate the experience of sailing on a deep-sea scientific drilling expedition and fostering international collaboration at sea,” noted study co-author Batoul Saad.

The loss of the U.S. riserless drillship threatens this effort. Funding cuts and aging infrastructure make it harder to pursue long-term sediment recovery missions.

Training the next generation

Pacific Highs are more than research sites. They are training grounds for the next wave of ocean scientists. Coordinated “expeditions” to core repositories and collaborative drilling missions centered on Pacific sediment cores will allow students and early-career researchers to engage deeply with Earth science.

“As individuals, much of the work of supporting science involves just being curious about the planet that we live on and that sustains us,” said Professor Griffith.

“Once you become curious, realizing how much you impact your surroundings leads to better decisions and new scientific discoveries.”

Sampling for future climate models

Future reconstructions of Earth’s climate will depend on how well we sample the past. New drilling, combined with legacy data and emerging tools, will help clarify what the Pacific has to tell us.

As climate models evolve, grounding them in physical evidence becomes critical. The Pacific’s buried layers might just hold the clues to predicting tomorrow’s Earth.

The study is published in the journal Paleoceanography and Paleoclimatology.

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Source: Earth.com