The deep ocean in the North Atlantic has provided evidence of climate change over the past millennium, according to a recently published study led by researchers from the Woods Hole Oceanographic Institution (WHOI) and University College London. The study, titled “Surface climate signals transmitted rapidly to deep North Atlantic throughout last millennium” and published in Science, examines sediment records from the North Atlantic that corroborate surface and deep ocean warming and freshening trends.
Unlike previous studies focusing on surface climate data, this research emphasizes the significant role of the deep ocean in reflecting climate changes. By analyzing sediment cores from the region south of Iceland, where cold, dense waters sink and fill the deep North Atlantic, scientists discovered a consistent connection between surface and deep ocean temperatures throughout the past 1,200 years. This timeframe encompasses climate oscillations such as the warm Medieval Climate Anomaly (around 850-1250 Common Era, CE) and the cold Little Ice Age (approximately 1400-1850 CE), as well as current warming trends.
The researchers removed tiny fossil shells of foraminifera, single-celled organisms found in surface and deep water, from the sediment cores to study their chemistry. This analysis provided valuable insights into the ocean’s environment during the periods in which these foraminifera were alive. Importantly, the study indicates that while the Earth’s surface has experienced significant warming over the past century, the deep ocean has absorbed and stored more than 90% of the excess heat, mitigating the surface temperature increase.
One notable finding from the research is that the deep ocean exhibited cooling from the Medieval Climate Anomaly to the Little Ice Age, implying a heat exchange process where the deep ocean released heat back into the atmosphere, reducing surface cooling during the Little Ice Age. This phenomenon also explains the deep ocean’s role in mitigating modern surface warming.
The study emphasizes the significance of incorporating deep ocean data to enhance our understanding of climate variability. By comparing surface records with deep ocean information, researchers were able to observe similarities between 20th-century changes and ongoing warming trends, providing increased confidence in the reliability of ancient surface and deep ocean temperature readings.
자주 묻는 질문 (FAQ) :
Q: What evidence of climate change was discovered in the North Atlantic?
A: Sediment records from the North Atlantic indicate surface and deep ocean warming and freshening trends throughout the past millennium.
Q: What is the role of the deep ocean in mitigating climate change?
A: The deep ocean absorbs and stores more than 90% of the excess heat, reducing surface temperature increases and mitigating modern warming.
Q: How did the deep ocean contribute to reducing surface cooling during the Little Ice Age?
A: The deep ocean gave back heat to the atmosphere, countering surface cooling during the Little Ice Age.
Q: What are foraminifera, and how were they used in the study?
A: Foraminifera are single-celled organisms found in both surface and deep water. By analyzing the chemistry of their fossil shells, researchers gained insights into past ocean environments.
Q: Why is studying the deep ocean important for understanding climate change?
A: Incorporating deep ocean data enhances our understanding of climate variability and helps reduce reliance on climate models for studying Earth’s climate variations.