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Increase in global temperatures by 2°C could result in melting of Antarctic ice sheets increasing the sea levels by 20 meters

Increase in global temperatures by 2°C could result in melting of Antarctic ice sheets increasing the sea level by 20 meters

During the Pliocene geological epoch, three million years ago, Earth faced a rise in temperature. The latest research funded by the Marsden Fund involving researchers from the Antarctic Research Centre, Waikato University and other nations has found that one-third of the ice sheet melted in Antarctica during this period causes a rise in current sea level by 20 meters in the centuries to come. 

Past changes in sea level were measured by drilling of cores at the Whanganui Basin in New Zealand. It contains marine sediments of the highest resolution in the entire planet. Then a record of worldwide change in the sea-level was constructed with much more precision than previously estimated.

During the Pliocene period, the concentrations of carbon dioxide in the atmosphere were more than 400 ppm and the temperature of Earth was two Celsius higher than pre-industrial times. Warming exceeding two celsius might lead to widespread melting in Antarctica dragging the future of the planet back to three million years before. 

Worldwide protests under the hashtag #FridaysForFuture were organized under the leadership of Greta Thunberg as people have realized the urgency to keep the levels of global warming below that of the target of two degrees Celsius set by the Paris Agreement. She criticized the United Nations for not acting on the evidence provided by the scientific community. 

The current rate of worldwide emissions might take us back to the Pliocene period within 2030 thereby passing the target of the Paris Agreement. A pressing question is how fast would the sea levels rise. As per a special report on oceans and cryosphere by  IPCC (Intergovernmental Panel on Climate Change) polar ice caps and glaciers are losing mass at an alarming rate, making it difficult to constrain the contribution of Antarctic ice sheets to a future rise in sea level. Following the current trend of emissions, the global sea level is likely to rise by 1.2 meters by the end of the century with an upper limit of two meters. 

In 2015, sediment cores deposited during the Pliocene, preserved under Whanganui Basin were drilled. Timothy Naish, working for 30 years in this area detected more than 50 fluctuations in the worldwide sea level in the last 3.5 million years in the history of the planet. Sea levels changed in response to the climate cycles also known as Milankovitch cycles. These are caused due to long-term changes in the orbit of the Earth every 20,000, 40,000 and 100,000 years. 

Sea levels are estimated to have been varied by several meters but the exact number has been difficult to obtain due to the deformation processes of Earth and the cycles’ incomplete nature. In the research, a theoretical relationship between particle size carried by waves on the continental shelf and the depth till seabed were used. This was then applied to 800 meters of drill core and outcrop that represented sediment sequences spanning a period of 2.5 to 3.3 million years before. 

Fluctuations in the global sea level in the Pliocene were between five to twenty-five meters. This figure is adjusted to the local tectonic land movements and regional changes in the sea level due to gravitational and crustal changes also termed as PlioSeaNZ sea-level record. 

During the Pliocene period, the geography of the continents, oceans, and size of polar ice sheets was similar to the present times, with an ice sheet on Greenland in the warmest times. Melting of this ice sheet would lead from five to 25 meters of the rise in sea level at the Whanganui Basin. 90 percent of heat from global warming has gone to the ocean, mainly to the Southern Ocean on the margins of the ice sheet at Antarctica. 

Deepwater upwelling in addition to entering ice shelf cavities is observed around Antarctica now. The ice sheet is thinning the fastest around the Amundsen Sea of West Antarctica, where maximum ocean heating is observed. One-third of the ice sheet of Antarctica equalling nearly 20 meters of the rise in sea level is situated below the sea level which can collapse from ocean heating. 

Thus if global temperatures are allowed to rise more than two degrees celsius, huge portions of the ice sheet could get melted in the coming times, changing the entire shoreline of the world. 

Kohnen-Station

Researchers detect radioactive interstellar dust in the Antarctic Ice

In new research, scientists have found evidence of dust from a nearby supernova under several thousand pounds of Antarctic snow. Our solar system not only comprises of celestial objects such as planets, moon, sun but also a lot of dust that might have originated from the interstellar sources. A group of researchers in Germany, Austria and Australia is in the search of the presence of dust on Earth to understand the circumstances in which the solar system is moving forward. The study has been published in the Physical Review Letters. 

Dominik Koll, first author of the study and a PhD candidate from Australian National University mentioned he is very excited to learn about the stellar explosions and structures present around our planet which have faraway origins. Scientists transported fresh snow which is not more than 20 years old, weighing almost 1100 pounds from the Kohnen Station located in Antarctica to Munich, Germany.

Then the snow was melted in the laboratory, filtered and evaporated for collecting dust and other micrometeorites. Dust was incinerated and put into Accelerator Mass Spectrometer. It is used to create charged ions from the sample, pass through the magnet and then into a particle accelerator before finally sending to a detector. This technique is useful for collecting only specific atomic isotopes. 

The team wanted to find iron-60, a radioactive isotope released by the supernova. It can also have other sources such as the matter irradiated by the cosmic rays. For guaranteeing it to be interstellar dust, researchers also searched for manganese-53 and compared the ratio of iron-60 to manganese-53 to the ratio expected if there was no presence of interstellar dust. A lot more iron-60 was found than expected from the cosmic rays. 

Thomas Faestermann, TU Munich explained that it was previously established that iron-60 was deposited in the solar system by a nearby supernova in the past 1.5 to 3 million years. Its prolonged presence on Earth indicates it is coming from a remaining dust cloud from a supernova.

These studies show better conditions of the interstellar environment through which Sun is travelling. It has been detected that the Sun is in a “Local Bubble” where the density of the interstellar medium is quite less than average possibly due to a recent supernova. It contains the Local Interstellar Cloud which has a higher density than the Bubble. We can know more about these regions from the dust found in Antarctica. 

There are lots of findings remaining as the Antarctic ice could lead an exposition of the history of an ancient supernova. 

Journal Reference: Physical Review Letters.