From The Daily Mail
- The Little Ice Age brought colder-than-average temps around the 17th century
- Researchers say temperatures in deep Pacific lag behind those at the surface
- As a result, parts of the deep Pacific is now cooling from long ago Little Ice Age
As much of the ocean responds to the rising temperatures of today’s world, the deep, dark waters at the bottom of the Pacific Ocean appear to be doing the exact opposite.
A Harvard study has found that parts of the deep Pacific may be getting cooler as the result of a climate phenomenon that occurred hundreds of years ago.
Around the 17th century, Earth experienced a prolonged cooling period dubbed the Little Ice Age that brought chillier-than-average temperatures to much of the Northern Hemisphere.
Though it’s been centuries since this all played out, researchers say the deep Pacific appears to lag behind the waters closer to the surface, and is still responding to the Little Ice Age.
‘Climate varies across all timescales,’ said Peter Huybers, a professor at the Harvard John A. Paulson School of Engineering and Applied Sciences.
‘Some regional warming and cooling patterns, like the Little Ice Age and Medieval Warm Period, are well known.
‘Our goal was to develop a model of how the interior properties of the ocean respond to changes in surface climate.’
The Medieval Warm Period was a period lasting between the 9th and 12th centuries during which Earth’s climate leaned on the warmer side.
It was followed not long after by the Little Ice Age, which lasted from the 16th through 19th century, though some argue it began even earlier.
According to researchers from the Woods Hole Oceanographic Institution and Harvard University, this long-ago cooling period could still be showing its face in the temperatures of the deep ocean.
‘If the surface ocean was generally cooling for the better part of the last millennium, those parts of the ocean most isolated from modern warming may still be cooling,’ said Jake Gebbie, a physical oceanographer at Woods Hole Oceanographic Institution.
To test this, the team compared measurements taken during the 1870s by scientists on the HMS Challenger to modern data.
During the study in the late 1800s, the researchers of the time dropped thermometers deep down into the ocean between 1872 and 1876, collecting more than 5,000 measurements in total.
‘We screened this historical data for outliers and considered a variety of corrections associated with pressure effects on the thermometer and stretching of the hemp rope used for lowering thermometers,’ Huybers said.
As expected, the comparisons showed most of the world’s ocean has been warming up over the last century.
In the deep Pacific Ocean, however, temperatures are dropping. This effect could be seen at a depth of around 2 kilometers (1.2 miles).
H/T David L Hagen and MarkW
And the from Phys.org.
January 4, 2019 by Bob Yirka, Phys.org report
“The model showed that the Pacific Ocean cooled over the course of the 20th century at depths of 1.8 to 2.6 kilometers. The amount is still not precise, but the researchers suggest it is most likely between 0.02 and 0.08° C. That cooling, the researchers suggest, is likely due to the Little Ice Age, which ran from approximately 1300 until approximately 1870. Prior to that, there was a time known as the Medieval Warm Period, which had caused the deep waters of the Pacific to warm just prior to the cooling it is now experiencing.”
More information: G. Gebbie et al. The Little Ice Age and 20th-century deep Pacific cooling, Science (2019). DOI: 10.1126/science.aar8413