Climatic changes are one of the most important concerns of human on earth today. Though there are many factors which result in gradual changes in climate, people are alarmed on what the climate will be in future. The question of whether such changes occurred in the past and the possible causation of climate change is very vital. According to research, there were some forces in the past that resulted in changes in the environment. For that reason, it is possible that the same forces are responsible for climatic change. Some of the sources that helped in determining past climatic conditions include coral beds, fossils, dendrochronology, geochemical studies, glaciological and geological among others (Bradley 2006). In addition to climatic changes, a quaternary period is associated with radical environmental changes which are estimated to occur between 2 and 3 million years long and is characterized by co-occurring glaciations. This paper is aimed at discussing extensively sediment cores, how they were extracted and how people interpret information from them about all the climate change throughout the quaternary.
Sediment Cores
Sediment cores are materials collected in the seabed of oceans. The samples are cylindrical shaped and the scientists use this samples to determine the past climatic conditions (Rothwell 2006, 15). Throughout the years, millions of dead marine organisms and planktons are found floating on the ocean. These materials are normally collected by scientists due to their benefit in determining the past climatic conditions. Within the materials are recently dead organisms and others are older materials which are found deep in the ocean. The deeply seated materials are used to establish the past environmental conditions. However, scientists collect all the materials regardless of the time in which they occurred. They put the materials in cylindrical cores in order to reconstruct the past climatic condition of the oceans. The sediment cores which include the dead organisms and the planktons are very vital in determining the ocean’s composition and temperatures in the past.
Moreover, the sediments cores occur in layers. More recent sediments are located on top of the previous year’s cores. For that reason, the bottom layer cores are the oldest while the uppermost sediment layer is the recent as stated by Rothwell (2006, 29). This aspect is very important to scientist since they can be able to evaluate the past climatic conditions based on the sediment layers. In most cases, the layers act as a comparison factor in evaluating the past climatic conditions. Furthermore, the sediments show changes in the ocean structure as confirmed in the light sediments having many shells and dark sediments having few shells. One of the most important fossils found in the sediment is foraminifera which has a carbonate shell. According to research, these species are prone to climate variations despite the fact that they are rarely found in continental sediments due to a concentration of silt, sand, and clay in continental areas. Evaluation of deep-seated foraminifers’ fossils shows the temperature conditions in the deep sea. Also, a lot of continental erosion has been confirmed in ocean shelves due to rapid changing of the environmental conditions.
Extraction of Sediment Cores
The extraction of sediment cores is a very expensive procedure that requires special equipment for collection and is mostly done in isolated oceanic areas. During extraction, a lot of samples is collected and stored for future reference. Due to the expensive nature of sediment extraction, the Natural Environment Research established a National Oceanography Center (BOSCORF) which is the central extraction center and the scientist could use the samples in evaluation thereafter. After the collection, the cores are normally divided into two equal parts and put in plastic bags separately. One half which is occasionally referred to as the archive half is not used for evaluation and is kept untouched for many years. The other half is used by the scientist for evaluation and sampling, this is normally referred to as the working half. The sediment cores are then returned to the National Oceanography Center where it is stored at 4°C for the availability to other users mostly scientists. During extraction of sediments, deeply seated cores are targeted mainly because they provide a more detailed information about the past climatic changes and variations in the course of time as stated by Rabineau (2004, 92). Due to the advancing technology, cores are resampled to increase the knowledge and skills of the scientists in an evaluation.
According to Mudroch, A (1995) in Manual of aquatic sediment sampling, there are three methods of extraction of the sediments. The first method is gravity coring which is done on oceans. The force of gravity enables the core sampler to drop down the ocean hence recuperating a sample of cores that are used to ascertain the presence of fossils. As a result, the scientists can evaluate the patterns of climatic changes such as monsoons and ice ages. This method is very cheap as well as easy to apply. Vibracoring is another method which is based on the vibrations of the samples. The vibrations of the sample enable infiltration of the cores over a duration of time. The subject material in this method is very vital as they can reduce the number of samples collected. Furthermore, drilling method can also be used in extraction. In this method, a driller is used to remove the core samples. However, excessive force should not be used while using this method as it can lead to fractures of the samples (Mudroch, 1995).The samples are carefully stored and maintained in order to provide accurate information about the past climatic conditions.
Interpreting Information from Sediment Cores
The sediment cores are very necessary for establishing the past climatic conditions as far as the Quaternary period is concerned. For instance, gas bubbles occasionally trapped in the ice have clues on the number of atmospheric gases present in the atmosphere. In the same way, the ice cores are dated back 500,000 years ago, the sediment cores are dated approximately 200 million years ago. Moreover, a lot of sediments is found in the sea floor creating layers of 5.6 miles which is 9 km in an estimate. The composition of this sediments is mainly shells of oceanic organisms. Since many organisms are found in specific environmental conditions, the scientist can use this information to establish variations in water temperature of the past years.
Apart from establishing the past water temperatures, the scientists can use the sediment cores in association with the fossils and pollen to establish the environmental conditions and sea temperatures. They used the sediments in analyzing the presence of ice in the past. For instance, if the sediments show evidence that they contracted quickly, the scientist are ascertained of a warmer period in the past. Warmer periods makes the ice sheet to disappear immediately after 3.5 million years. According to Asikainen (2006, 105), high susceptibility of grain size, stratigraphy, crystallinity and clay mineralogy shows the evidence of warmer conditions in the pats while low susceptibility of the aspects indicates cold conditions.
Moreover, the past wind and water currents can be estimated easily using the sediment cores when there are large deposits. Most of the ocean organisms use the planktons and food reserves found on the ocean surface. When the organisms die, they decompose and the nutrients remain on the ocean floor. In most cases especially in the diatom plants, the organisms and their nutrients are carried upwards by strong ocean currents so that other organism can utilize (Jian 2014, 320). This is known as upwelling and mostly applies in the diatom plants. The sediment cores found in the oceans are used to track the probability of upwelling hence the scientists can ascertain if there were strong oceanic currents or not. In addition, since upwelling occurs in presence of wind, the scientist can ascertain about the past weather patterns.
Also, the fossils are very vital in establishing the past temperature of the oceans. Foraminifera, diatoms and radiolarians shells contain oxygen (Rabineau 2004, 92). Studying this sediments will enable people to gauge the amount of oxygen that the sediments carried, either heavy or light. By estimating the amount of oxygen that was present, it is possible to deduce how the ocean was as far as its coldness is concerned. They can also help in determining the amount of ice that was present at the time of shell formation. Therefore, the shells will have more oxygen when the ocean is very cold and there is a lot of ice.
Conclusion
In conclusion, sediment cores are found and collected on the ocean floor. They are extracted by various methods such as drilling, gravity coring, and vibracoring. By extracting and using the sediments cores, the scientist is capable of establishing the past climatic conditions. Knowing the past climatic conditions is very important in predicting the future possible changes. As a result, people can know what and when to expect adverse changes in climate. Moreover, according to a research of Holocene sediments done on Yunnan, scientist ascertain that some of the climatic changes arise due to natural and human-influenced activities as stated by Zhang (2014, 7).
References
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