Surface water temperature in the Northwest Pacific Ocean fluctuated widely between 800,000 and 750,000 years ago according to a new study conducted by a team of researchers from the National Institute of Polar Research (NIPR) and Ibaraki University. The researchers analyzed the oxygen isotopes of some fossils of foraminiferous, amoeboid marine microorganisms found on the island of Honshu, Japan.
According to the researchers, these changes were due to the discharge in this marine area of massive amounts of water derived from ice melting in the North Atlantic. This study could also be useful to understand climate change in the same area in the future.
According to the researchers, in fact, in order to assess the anthropogenic effects on ongoing climate change, it is necessary to make comparisons with the climates and environmental conditions that have occurred in the past, changes that naturally had no anthropogenic causes.
The study, published in the Earth and Planetary Science Letters, describes the methods researchers used to collect and then analyze fossils of four species of foraminifera taken from the MIS layer19. This sediment layer refers to a hot interglacial period of 790,000 to 760,000 years ago.
Based on previous studies that had shown that low oxygen isotope values of foraminiferous fossils correspond to higher water temperatures, the researchers came to the conclusion that there must be, in addition to the glacial-interglacial cycle that repeats on time scales of tens of thousands of years, other cycles related to water temperature.
Specifically, this temperature would oscillate in an extreme way, of about 7°, every few thousand years. In addition, analyses seem to show that these changes have occurred due to the outflow of water from icebergs in the North Atlantic.
“Surprisingly, the changes in the North Atlantic have caused dramatic fluctuations in water temperature in the remote Pacific Northwest,” says Yuki Haneda, NIPR scientist and one of the authors of the study. “We believe that the fossils collected from the outcrop are a tracer that integrates the data reported from deep water sediments. The composite section of Chiba is the global boundary stratification section and point (GSSP) of the lower-middle Pleistocene boundary and offers a remarkable understanding of global environmental changes during that period. We want to improve our understanding of climate change during MIS19 to predict future climate change more accurately.”