SOUTHERN Australia and nearby Pacific nations are likely to be the most seriously affected in the world by the continuing rise in sea levels, according to new research.
Since the late 19th century the sea level in the southwest Pacific has risen about 20 centimetres with the fastest rate occurring in the early decades of the 20th century, says Dr Patrick Moss of the University of Queensland.
Sea levels around the world rose at an average rate of 1.5 millimetres a year since 1880, but studies of tidal marshes in Tasmania show a rise of 4.2mm a year between 1900 and 1950.
“Sea levels in Tasmania remained relatively stable for much of the past 6000 years, but around 1880 they started rising drastically,” said Dr Moss, who co-wrote the study in conjunction with scientists from the UK, New Zealand and Australia.
Dr Moss said a jump in sea levels occurred after 1990.
“The rise in 1910 probably reflects the end of the little ice age, when temperatures were about one to two degrees cooler in the northern hemisphere than today,” he said.
“The 1990s peak is most likely indicative of human-induced climate change.”
While debate exists over whether the increasing depths of the oceans is a result of thermal expansion of existing water or the melting of ice, the ultimate cause is undoubtedly global warming.
Dr Moss said research suggests the earth has been free of ice at various periods during its existence, at which times sea levels could have been as much as 90-100 metres higher than today.
The results of the study published in the journal Earth and Planetary Science Letters indicate the comparatively higher levels in the southwest Pacific are the result of melting ice in the northern hemisphere.
“A large ice-melt is like a fingerprint,” Dr Moss said.
“When such a significant mass shifts around the earth’s surface we can detect its movement.
“Based on this, it appears likely that the primary source of sea level rise in the southern hemisphere is the Greenland Ice Sheet, but also mountain glaciers in Alaska, western North America and the Canadian Arctic.”
Dr Moss’s study is largely based on sediment layers in core samples taken from salt marshes near Little Swanport in Tasmania.
Dr Moss said the samples also provided physical evidence of the start of logging in Tasmania, when nuclear testing was at its peak globally and the introduction of unleaded petrol.