Geography lecturer leads ground-breaking project that shines a light on fossil sunshine
Thursday, 15 December 2016
An international team of scientists led
by Dr Wesley Fraser has reconstructed the longest ever
record of past sunshine using fossil pollen grains collected from lake
sediments in Ghana, Africa. The study, published today in Scientific Reports, enables us to understand past changes in solar
input to the global system over the past 140,000 years. Previously we have had
to rely upon computer models to mathematically determine past solar inputs to
the Earth. "This work really is a
first; being able to peer back in time to understand how the Sun has driven our
global system over many of thousands of years is a very exciting prospect"
said joint-lead author Dr Phillip Jardine of the Open University.
The Sun is a key component of our
natural environment, driving a multitude of processes at Earth's surface, from
photosynthesis generating energy within plants, through to global-scale
circulation patterns in our oceans and atmosphere. Understanding more about how
the Sun has behaved in the past, and the influence this had on Earth's
environment, will help scientists predict future climate change.
Dr Jardine used a technique pioneered
by one of his co-authors, Dr Wesley Fraser of Oxford Brookes University, to
determine past changes in solar input, specifically changes in ultraviolet (UV)
radiation. Plants protect themselves from the harmful nature of ultraviolet
radiation by incorporating a number of specific chemical compounds into their
tissues that absorb and dissipate the energy of UV radiation. Pollen grains of
flowering plants are also provided protection by these UV-absorbing chemicals, and
thus act as a long-term recorder of ultraviolet radiation from the Sun.
Pollen grains are readily trapped in
lake sediments, where they can be preserved for millions of years. By
extracting material from Lake Bosumtwi, Ghana, the pollen that was released by
flowering plants thousands of years ago can be separated from the lake sediment
and chemically analysed for UV-absorbing chemical compounds. It is this
chemical signature within the ancient pollen grains that provides us with
information about past levels of solar ultraviolet radiation.
we have here is a new tool for Earth Science and Geographical research” said Dr Fraser. “The next steps will be to look further back through the fossil record
to try and understand how past changes in UV and solar radiation impacted upon
climate and biodiversity.”
This study is available now at www.nature.com/articles/srep39269
Jardine PE, Fraser WT, Lomax BH,
Sephton MA, Shanahan TM, Miller CS & Gosling WD (2016) Pollen and spores as
biological recorders of past ultraviolet irradiance. Scientific Reports. DOI: 10.1038/srep39269
Contact: Dr Phillip Jardine