Taking advantage of the unique properties of sediments from the bottom of Lake Sawtooth in Canada̵
A team led by Francois Lapoint and Raymond Bradley of the Center for Climate Systems Research at the University of Massachusetts Amherst and Pierre France of the University of Quebec-INRS analyzed “perfectly preserved” annual layers of sediment accumulated in the north. which contain titanium left over from centuries of rock weathering. By measuring the concentration of titanium in the various layers, scientists can calculate the relative temperature and atmospheric pressure over time.
The newly expanded record shows that the coldest temperatures were found between about 1400-1600 AD, and the warmest interval occurred only in the last decade, the authors report. France added: “Our unique data set represents the first reconstruction of Atlantic surface temperatures in 3,000 years and will allow climatologists to better understand the mechanisms behind long-term changes in Atlantic behavior.”
When temperatures are cool over the North Atlantic, relatively low atmospheric pressure is found in much of Canada’s High Arctic and Greenland. This is due to slower snowmelt in this region and higher levels of titanium in the sediments. The opposite is true when the ocean is warmer – atmospheric pressure is higher, snow melts quickly and the concentration of titanium decreases.
Lapointe says, “Using these strong connections, it was possible to recover how temperatures on the surface of the Atlantic Ocean have fluctuated over the last 2,900 years, making it the longest record available at present.” Details appear this week in Notices of the National Academy of Sciences.
The researchers report that their recently reconstructed record is significantly related to several other independent Atlantic sediment records, ranging from northern Iceland to offshore Venezuela, confirming its reliability as an indicator of long-term oceanic ocean temperature variability over a wide range of oceans. The record is also similar to European temperatures over the past 2,000 years, they said.
Fluctuations in sea surface temperatures, known as the Atlantic Decade of Ten Decays (AMO), are also linked to other major climate shocks, such as droughts in North America and the severity of hurricanes. However, as sea surface temperature measurements go back a century or more, the exact length and variability of the AMO cycle is poorly understood.
Climate warming in the Arctic is now two or three times faster than the rest of the planet due to greenhouse gas emissions from fossil fuel combustion, warming may be intensified or reduced by natural climate variability, such as changes in surface temperature. The North Atlantic, which seems to vary within cycles of about 60-80 years.
Lapointe, which has carried out extensive field work in the Canadian Arctic over the past decade, notes that “In recent summers, high-pressure atmospheric systems – clear skies – have often prevailed over the region. Maximum temperatures often reach 20 degrees Celsius. , 68 degrees Fahrenheit, for many consecutive days or even weeks, as in 2019. This has had irreversible effects on snow cover, glaciers and ice caps, and permafrost. “
Bradley added, “The surface waters of the Atlantic Ocean have been constantly warm since about 1995. We don’t know if conditions will soon move to a cooler phase, which would give some relief to the accelerated warming of the Arctic. But if Atlantic warming continues, weather conditions conducive to more severe melting of Canadian Arctic ice caps and Greenland’s ice sheet can be expected in the coming decades. “
In 2019, the Greenland ice sheet lost more than 500 billion tons of mass, which was a record and this was due to unprecedented, stable weather conditions with high pressure. “
Lapointe notes, “Conditions like this are currently not properly captured by global climate models, underestimating the potential impacts of future warming in the Arctic.”
Arctic sea ice is increasingly melting from below by warming Atlantic water
Francois Lapointe et al, Annual permitted variability in Atlantic surface temperature over the last 2 900 years, Notices of the National Academy of Sciences (2020). DOI: 10.1073 / pnas.2014166117
Provided by the University of Massachusetts Amherst
Quote: The recent warming of the Atlantic Ocean, unprecedented for nearly 3,000 years (2020, October 14), retrieved on October 14, 2020 from https://phys.org/news/2020-10-atlantic-ocean-unprecedented-years .html
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