They say the bodies of water on Earth hold a lot of mysteries that humans have not fully explored. This does not only refer to the vast ocean but also to the different lakes and rivers.
In the southwest region of Japan, at the bottom of Lake Nakaumi, there are tiny shells that may contain the secrets of the East Asian Summer Monsoon.
Predicting the pattern for the rainy season has been practiced for as long as history can remember. Farmers from different corners of the world anticipate the air and precipitation that are conducive to growing crops.
However, there will be times that the pattern would fail. There are crops that died because some areas were left without rainfall. On the other hand, some parts of the land are frequented with rain leaving crops and homes flooded.
A team of researchers looked into the tiny shells called Ostracoda shells to better understand why East Asian summer monsoons vary at the centennial scale. This variation on the summer monsoon is peculiar as the scientific community previously believed that the pattern should hold to be relatively steady.
The tiny shells were said to have recorded under 500 million years worth of data showing the effects of sunshine and climate shifts.
Katsura Yamada, The research author, and professor in the Department of Geology and Faculty of Science at Shinshu University explains that the driving mechanism for variations in the East Asian summer monsoons is still unclear. Because of this, his team of researchers used the oxygen isotopes from adult Ostracoda shells to reconstruct the variations in southwestern Japan for the last 3000 years.
To be able to get samples of shells from the present day to 3000 years ago, Yamada and his team cored sections of the lake.
The analysis process of the scientists involved measuring the specific ratio between slightly different versions of oxygen called isotopes. Higher rates of nitrogen in the atmosphere would produce a different version of oxygen as compared to those times when nitrogen is less abundant. This process of identifying the isotope ratio offers a glimpse into the precise composition of the atmosphere even if it was from 1000 years ago.
In the research, the scientists have found out that it was insolation, a solar activity, that affected the centennial scale variation in the East Asian summer monsoon.
This means that during sunny periods, the East Asian monsoon pattern is dominated by the insolation. On the other hand, during the cooling-off periods, such as glacial ice ages, other factors such as wind patterns and other climatic phenomena were the determinants for that period's monsoon pattern.
Yamada pointed out that the research paved the way for their next goal which is to clarify the relationship between other climatic phenomena and the East Asian monsoon variations.
