More moisture was produced due to warmer ocean temperatures and more
powerful monsoons. This moisture helped the ice sheets to expand.
A new study suggests that the Earth's transition into a whole new glacial
cycle, which occurred between 670,000 and 800,000 years ago, was caused by
warming.
The study was released in May in Nature, a renowned publication of peer
review in science.
The late Middle Pleistocene Transition (MPT) is when the ice age warming
took place. Global glacial cycles, which are periods of time throughout ice
ages when glaciers advance across the Earth's surface, underwent a permanent
change during the MPT.
A drill core taken from South-West Iberia was examined by a team of
European experts for data on upper ocean temperatures and Mediterranean
vegetation cover.
Drill cores are cylindrical samples collected from the earth's crust or
from an ice sheet, and they reveal chronologically arranged layers of silt
or ice. These data serve as gauges for current precipitation and westerlies
(westerly winds).
These records were coupled with new data on West Pacific Ocean surface
temperatures and East Asia Summer Monsoon (EASM) intensity by the
researchers.
The researchers were able to develop models to replicate the late MPT
climate using this data.
The statistics revealed that throughout this time, both the severity of the
summer monsoon in East Asia and the amount of winter precipitation in
southwest Europe both increased.
What led to the harsh weather conditions?
According to the study, these unusually severe weather conditions were
caused by a "nearly continuous moisture supply from both oceans" that was
transported northward by the westerlies.
Researchers hypothesized that this in turn contributed to the ice sheets'
expansion during the late MPT.
The MPT heralds the start of a long-lasting, worldwide change in glacial
eras. Previously, the climate on Earth was defined by shorter, weaker
glacial periods that occurred on 40,000-year cycles, according to a
SciTechDaily story on the research paper.
But after the MPT, Earth's climate underwent a drastic change and
transitioned to 100,000-year cycles of glacial periods, where the glacial
periods, albeit less frequent, lasted longer and were more severe.
The glaciers had to have expanded in size from their pre-MPT levels to
produce this transformation, which, as previously established, was fueled by
the increased moisture brought on by warmer ocean temperatures.
The "warm" ice age was a major contributor to the shift in the
40,000–100,000–year glacial cycle, even if the exact causes of this
transformation are still unknown.
According to Dr. André Bahr, an associate professor of earth sciences at
Heidelberg University, "such expansion of the continental glaciers was
necessary to trigger the shift from the 40,000-year cycles to the
100,000-year cycles we experience today, which was critical for the Earth's
later climate evolution."
