Microscopic Algae Fossils Help Unlock Mysteries Of Climate Change
April Flowers for redOrbit.com – Your Universe Online
One of the fastest warming regions on the planet – and the fastest warming part of the Southern Hemisphere – is the western Antarctic Peninsula. This warming has been the subject of scientific debate, especially in light of recent instrumental records of both atmospheric and oceanic warming from the region. Holding an equivalent of 5 meters of global sea level rise locked in ice, the Antarctic ice sheet is becoming increasingly vulnerable to collapse as the atmosphere and oceans continue to warm.
A new study from Cardiff University, published in a recent issue of Nature Geoscience, has traced glacial ice entering the ocean along the western Antarctic Peninsula using a unique 12,000-year record of microscopic marine algae fossils. The findings reveal that in the late Holocene – approximately 3500 – 250 years ago – the atmosphere had a more significant impact on warming along the western Antarctic Peninsula than oceanic circulation did.
Prior to 3500 years ago, this was not the case, nor is it the case in the modern environment. This late Holocene atmospheric warming was cyclic – with cycles ranging from 400 – 500 years in duration. They are also linked to the increasing strength of the El Nino Southern Oscillation phenomenon, a climate pattern centered in the low-latitude Pacific Ocean that exerts an equatorial influence on high latitude climate.
According Dr. Jennifer Pike, a professor at Cardiff’s School of Earth and Ocean Sciences: “Our research is helping to understand the past dynamic behavior of the Antarctic Peninsula Ice Sheet. The implications of our findings are that the modern observations of ocean-driven warming along the western Antarctic Peninsula need to be considered as part of a natural centennial timescale cycle of climate variability, and that in order to understand climate change along the Antarctic Peninsula, we need to understand the broader climate connections with the rest of the planet.”
A very distinctive ratio of oxygen isotopes exists in ice derived from land. The current research is the highest resolution application in coastal Antarctic marine sediments of a technique to measure the oxygen isotope ratios of microscopic marine algae fossils (diatom silica). The oxygen isotope ratio of the sea water in which marine algae live is altered when a large amount of glacial ice is discharged into the coastal ocean, creating a clear imprint in the fossils that reveals the environmental conditions of the time.
To reconstruct the amount of glacial ice entering the coastal ocean in the past 12,000 years, and to determine whether the variations in the amount of ice discharged were the result of changes in the ocean or atmospheric environment, the scientists used the oxygen isotope ratio of the fossils.
Professor Melanie Leng from the British Geological Survey and Chair of Isotope Geosciences in the Department of Geology at the University of Leicester, said, “Technologically the analysis of the oxygen isotope composition of diatom silica is extremely difficult, the British Geological Survey is one of a very few research organisations in the world that can undertake this type of analysis.”
“For this research project the methodology has been developed over the last five years with the specific aim of investigating the different amounts of melting in the polar regions. It’s fair to say we are world leading pioneers in this technique.”