Corals : Indicators Of The Changing Sea

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Corals: Indicators of the Changing Sea Throughout the 4.5 billion years of its existence, Earth’s climate has oscillated between episodes of cold and warmth during different periods in its history. Earth has experienced periods of ice ages where continental-sized glaciers covered the planet. During Earth’s warmest periods, the polar regions of the world today were completely ice free. Though there were no humans on Earth billions of years ago to describe these dramatic climate variations, Earth was still able to keep records of the past. Climate archives have proven to be significant in providing clues of past climates and also gives us information to help predict future climatic events. Climate archives contain many indicators of past…show more content…
Corals as climate archives Corals harbour millions of sea creatures that can only thrive in warm shallow waters in tropical or subtropical oceans. Andrea Grottoli (2001) describes corals as good climate archives because they are widely distributed, their banding patterns are strong dating tools, and their records can span several centuries (from 5 to 25 Myr ago). Corals secrete layers of calcium carbonate (CaCO3) which form their skeletons. The organisms that produce CaCO3 are sensitive to temperature changes in the ocean; thus, when the water temperature changes, the CaCO3 densities in the skeletons also change (Grottoli, 2001). The layers from corals have annual banding patterns which help date the changes that scientists discover. Light-coloured layers appear during the summer when growth is rapid and dark layers form in the winter when growth is slowed down (Figure 1). By studying these banding patterns, scientists can determine the season and temperature of the water these corals grew in and date them accordingly. Scientists drill into corals and take samples which provide accurate information about sea level, temperature and salinity at different times in history. Therefore, by interpreting this data obtained from corals, scientists are provided with a way to reconstruct past climate changes.
Sea surface temperature Seasonal records of sea surface temperature in tropical regions
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