A collective of scientists from Canada and the United States gathered data regarding the Atlantic Ocean’s temperature over the past three millennia. They did so by analyzing thermometer data and ice and sediment cores drilled from the sea bed and ice sheets.
The samples allowed the scientists to look through layers of chemical clues and microbes to reconstruct the past. They were collected from an 80-meter-deep lake in the Canadian Arctic called South Sawtooth Lake because fluctuations in Atlantic sea surface temperatures significantly impact the waters.
The titanium in the sediment cores told the story of the Atlantic Ocean temperatures from the past 2,900 years, revealing changes from decade to decade. The team found that between 100BC to AD420 were the warmest conditions (aside from recent decades), between 1300 to 1870 were the coolest, and the past decade has been the hottest of all.
The scientists wrote:
Temperatures have steadily increased since the 15th-century minimum; the rate and magnitude of warming over the last few centuries are unprecedented in the entire record, leading to the last decade which was the warmest in the past 2,900 years.
The team then compared other evidence from across the North Atlantic to back up South Sawtooth Lake’s findings. They collected sediment cores off the south coast of Iceland. Those samples revealed clues as to what happened over the past two centuries only. Nevertheless, the data collected from them show that the population of turborotalita quinqueloba – a tiny, shelled, single-celled organisms which like cold waters – has been declining at an accelerating pace since 100 years ago and has reached unprecedented low values in the last decade.
The team concludes that recent Atlantic Ocean warming is unparalleled in the past 2,900 years. And while natural factors could be at play, human-induced warming from fossil fuel consumption is likely a significant influence.
The IPCC found that the ocean has absorbed over 93% of the excess heat from greenhouse gas emissions over the past 50 years. Furthermore, satellite data shows that the Arctic sea ice shrank to its second-lowest extent since records began, and another study found that even the deepest parts of the ocean are warming.
