Rapid 20th century warming in the Gulf of Maine reversed the very long-term cooling that had occurred there over the 900 recent years, according to new research that combines an examination of the shells of long-lived ocean quahogs and climate model simulations.
The warming is “likely due to increased concentrations of greenhouse gases in the atmosphere and changes in the circulation of the western North Atlantic,” according to the article, “The rapid warming of the 20th century reverses the cooling of 900 years in the Gulf of Maine”, published in Communications Earth & Natural environment, an open access journal of Mother Nature Portfolio.
“Given future projections of atmospheric greenhouse gas concentrations and pressure, this warming trend in the Gulf of Maine is likely to continue, leading to increases in temperature proceeds and potentially devastating on the ecological and economic plan in the region in the future, ”says the doc.
“What this report shows – both clams and climate model simulations – is that at the end of the years 300 there were quite dramatic changes and the Gulf of Maine started to warm up, reversing 900 years of cooling that had been driven primarily by volcanoes,” said Nina Whitney, lead author of the paper. Whitney is a NOAA Postdoctoral Fellow in Climate and Global Change in the Department of Physical Oceanography at the Woods Hole Oceanographic Institution (WHOI) and completed her Ph.D. at Iowa Point out University, where the research presented in this article began.
“Clam and climate model simulations suggest that greenhouse gas forcings cause not only changes in surface temperature affecting the Gulf of Maine, but also changes in ocean circulation. The paths and strengths of different ocean currents bringing water into the Gulf of Maine have changed as the region has warmed,” says Whitney.
Scientists reconstructed 300 years of hydrographic variability in the Gulf of Maine by discerning geochemical records of oxygen, nitrogen, and radiocarbon isotopes previously published at from Arctica islandica (ocean quahog) shells from the Gulf of Maine.
Ocean quahogs, which can live up to about 500 years and grow their shells in annual increments somewhat analogous to tree rings, have been absolutely dated by researchers and have served as good recorders of ocean situations, according to Whitney.
The chemical signatures of seashells have provided researchers with a multi-proxy approach to studying changes in ocean conditions. Oxygen isotopes served as proxies for seawater temperature and salinity; nitrogen and radiocarbon isotopes were proxies for the water mass resource. The researchers placed the geochemical results in a broader temporal and spatial context by analyzing fully coupled climate model simulations from the Community Earth Program Product-Past Millennium Ensemble.
“The rate of warming observed in the Gulf of Maine over the past century has exceeded the average global warming of the oceans. This has important consequences for the region’s ecosystems and fisheries, and therefore for the local economy,” says the paper’s co-author, Caroline Ummenhofer, associate. researcher in the Department of Physical Oceanography at OMSI.
“Our new study combines paleo indirect evidence from bivalves with climate models to place this rapid warming of the Gulf of Maine in a long-term context. Using an ensemble of state-of-the-art climate model simulations allows us to distinguish ocean temperature trends due to internal climate dynamics from those due to anthropogenic influences. We find that the rate of warming since the turn of the 20 century in the Gulf of Maine stands out in the context of 1000 recent years, and reverses a very long-term trend of several centuries. cooling trend that occurred until the end of the years
. Such a long-term context is crucial for adapting regional fisheries and managing natural resources in vulnerable marine ecosystems in a warming climate,” says Ummenhofer.
“The results are important because we reveal when recent warming in the Gulf of Maine began and provide the likely causes of the warming,” says Alan Wanamaker, co-author of the paper and professor in the Department of Geological and Atmospheric Sciences at the University. ‘Iowa Condition College..
“It was very satisfying to revisit my PhD research in the Gulf of Maine with more tools and new insights offered by Nina Whitney and the team,” says Wanamaker. “The reality is that it took about 300 years to cool by 2°C and only 20 years to warm up by 2°C. Unfortunately, warming in the Gulf of Maine is likely to continue and worsen in coming decades with negative impacts on the entire ecosystem.”