The melting of ice that occurred about 125,000 years ago in both Greenland and Antarctica caused sea levels to rise about 10 meters above their current position during the last interglacial period. A study carried out by an international team and published this Wednesday in Nature Communications quantifies for the first time the timing, magnitude and rates of this melting, finding that this melting altered global ocean circulation.
This study is led by professors Eelco Rohling and Fiona Hibbert from the Australian National University in Canberra and involves the researcher from the Marine Research Center of the University of Vigo, CIM-UVigo, Gianluca Marino, who explains that the article includes the results of a project that started in 2014, when he was still working at this Australian university. “We were particularly interested in studying the relationships between climate and sea level during the period from the penultimate ice age to the last interglacial period and in investigating the causes that caused it,” emphasizes the researcher.
Sea level rises of up to 3 meters per century
The study concludes that the melting occurred very rapidly, causing sea level rise rates of up to 3 meters per century, and that this rise was mainly due to the loss of ice from the Antarctic ice sheet. The last interglacial period was the most recent time when sea level rose above its current position. During this period, global temperatures were between 0.5 C and 2 C above pre-industrial levels (late 19th century). The importance of this study lies, as its authors emphasize, in the information it provides about the processes that govern sea level rise when the two polar ice sheets melt in response to warmer climate conditions than existed in the pre-industrial era.
The research also reveals that this melting of polar ice occurred first in Antarctica and then in Greenland and that it was the warming of the Southern Ocean at the beginning of the last interglacial period that caused the loss of Antarctic ice and, consequently, what altered global ocean circulation.
“Antarctica is not a sleeping, insensitive giant as was believed”
According to the authors, the project has shown that “Antarctica is not a sleeping, insensitive giant, as has long been believed.” On the contrary, the data indicate that it can change very significantly on timescales that are highly relevant to society. According to them, in the current climate, anthropogenic greenhouse gases are causing rapid atmospheric and oceanic warming in both polar regions at the same time, which causes simultaneous melting in Antarctica and Greenland. Furthermore, today’s climate disturbance is greater than that which occurred during the last interglacial. As a result, they insist that it is foreseeable that the rates of sea level rise that develop in the coming centuries could be even higher than those found in the last interglacial period.
“High rates of sea level rise reduce adaptation opportunities, pose a great challenge for planning effective coastal protection strategies and increase the vulnerability of communities living in these types of areas,” explains Marino, who emphasizes that there are currently 680 million people living in areas that are less than 10 meters above sea level and that the forecast is that in the coming decades this number will increase by almost 50%.
“There is not much we can do to limit the increase”
When asked whether we have time to mitigate these consequences or, at least, slow them down, Marino is clear: “there is not much we can do to limit the rise in sea level over the next century”, something that the latest report from the IPCC, the Intergovernmental Panel on Climate Change, which was published a few weeks ago, also warned about. “Both Greenland and Antarctica will continue to lose ice mass throughout the 21st century and beyond”, emphasizes the CIM researcher, who explains that this is because the ice sheets are large and take a long time to respond (“equilibrate”) to climate forcing. “However, by considerably reducing greenhouse gas emissions and with them the associated climate consequences, we should also be able to limit the rise in sea level, but, to achieve this, we need to act immediately!” insists Marino.
Gianluca Marino é investigador distinguido na Universidade de Vigo, institución á que se incorporou a través do Programa de captación do talento investigador excelente en 2018 e membro do Grupo de Xeoloxía Mariña e Ambiental do CIM-UVigo, quen apoia o seu traballo de investigación a través das axudas concedidas pola Xunta de Galicia a través do Programa Operativo FEDER/FSE Galicia 2014-2020. Ostenta tamén a distinción de profesor titular honorario na Research School of Earth Sciences da Australian National University, de Canberra, Australia. Nas súas investigacións emprega ferramentas xeoquímicas, micropaleontolóxicas, sedimentolóxicas e de estatística probabilística para determinar cuantitativamente o tempo, a magnitude e as taxas de cambio climático no pasado como análogos do cambio climático actual. “Neste estudo en concreto o meu traballo centrouse en contribuír á interpretación dos datos e a situar a evidencia do nivel do mar no contexto doutros parámetros climáticos, como temperatura e CO2”, explica o investigador.
Source: DUVI
