Ocean dust identifies oldest ice near South America dating back 1.5 million years

Earth’s climate has experienced significant changes over its billions of years of history, including numerous periods when ice grew on Earth. Today, ice cores capture snapshots of the climate at the time, both through their geochemical composition and through the dust and debris that has been preserved over thousands of years, making it difficult to understand these periods in Earth’s history. can be a valuable resource.

High dust content in ice cores is often indicative of an ice age, as continental shelf exposure, reduced rainfall, increased aridity, and winds can increase dust transport. There may be.

The oldest known continuous ice record in Antarctica (Epica Dome C, a European ice coring project at Antarctic Dome C) dates back 800,000 years, but an international collaboration of scientists has They are trying to extend it to 1.5 million years.

This explains why the Earth’s climate cycles (switching between glacial and interglacial periods) were periodic for about 41,000 years ago, up to 1.2 million years ago, and irregular between 700,000 and 1.2 million years ago. This is because it is viewed in terms of a long period of time (known as the mid-Pleistocene transition period). Since then, a cycle of about 100,000 years has continued since 700,000 years ago.

Such efforts are difficult because topography can disrupt the ice stratigraphy as glaciers move over land, and basal melt can erase records. Therefore, extensive research is required to identify suitable locations for core drilling.

The rapid recovery of discovered cores includes optical logging (a laser is lowered below the core and backscattered light is measured as an indicator of dust content) used to identify the oldest ice. , which involves the upper ice layer melting to reach the basal ice faster. .

A new study published in the journal Climate of the Past finds that the International Ocean Discovery Program site U1537, near South America, is a strong candidate for dating the oldest ice based on its marine dust content. It is suggested that there is.

Dr. Jessica Ng of the Scripps Institution of Oceanography and colleagues compared marine dust from ice cores from the southern Atlantic ocean drilling project site 1090 and ice cores from site U1537, and found correlations between ages and ice cores from South America, Australia, and New Zealand. The origin was identified. Site U1537 was considered the most suitable marine dust record to compare with the ice dust from Epica Dome C in Antarctica.

The researchers generated an artificial oldest ice record that was pattern-matched to the marine dust record at site U1537 and experimented with manually offsetting the record to determine the accuracy of the correlation. Records from Sites 1090 and U1537 are consistent up to 800,000 years ago, but the correlation has declined since then, suggesting that the spatial variation in dust input across the high-latitude Southern Hemisphere in the 40,000-year global scenario is may be indicated.

A further goal of establishing the oldest ice is to be able to understand why the mid-Pleistocene transition occurred and what its consequences were. Dr. Ng and his team cite previous research that identified thick ice sheets caused by tectonic activity and eroded regolith (a surface layer of loose dust and rock) that enables glacial cooling as potential causes. We ultimately determined that further research is needed to establish a causal relationship.

Overall, this study shows that climate cycles spanning approximately 40,000 and 100,000 years produce different feedback signals on Earth, with significant implications for our ability to understand the regularities of change in planetary systems and their impacts. It is important because it gives.

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