The Northwest Atlantic is a region of major climate change over the twentieth century, affected by the weakening of the Atlantic meridional overturning circulation. To assess whether the ability of this region to absorb anthropogenic CO 2 has been impacted by this change, we present the region's first long-term carbon isotope (δ 13 C) time series of fossil foraminifera spanning the past 4,000 years. These records reveal an unprecedented negative δ 13 C excursion driven by anthropogenic CO 2 penetration into the surface ocean, the "Suess effect" signal. This signal (amplitude −0.45‰) emerges in 1950 CE ± 15 with a decrease rate of 0.009 ± 0.001‰/yr. This marine signal is~30% of the atmospheric Suess effect and emerges over a century later. Based on current estimates of the ratio of δ 13 C DIC change to dissolved inorganic carbon change and limited constraints on surface ocean residence times, we calculate a mean anthropogenic CO 2 uptake rate of 0.6 ± 0.2 μmol/(kg yr) from 1950 to 2005. Plain Language SummarySince the industrial revolution, the burning of fossil fuels for human energy and transportation needs has caused an accumulation of carbon dioxide (CO 2 ) in the atmosphere. Over the same time period, nearly 30% of CO 2 emissions have been taken up by the ocean. This absorption is not uniform; therefore, understanding local CO 2 uptake rates is essential for assessing future ocean acidification risk. Our study investigates and presents the first long-term history of carbon for the Northwest Atlantic shelf region. The CO 2 emitted from fossil fuel burning has a distinct carbon isotope ratio compared to the preindustrial background level. Organisms called foraminifera incorporate the carbon isotope ratio of ocean carbon into their shells, which eventually sink to the seafloor where they are preserved in the sediments. For our analysis, we collected five sediment cores containing foraminifera from the NW Atlantic, resulting in carbon isotope records that span the last 4,000 years. We find evidence of fossil fuel-derived CO 2 in the NW Atlantic starting in 1950 and translate carbon isotope trends into estimates of fossil fuel CO 2 uptake rates by the surface ocean. Results from our study can be used to assess and predict future ocean acidification risk.
The abundance, distribution, and size of marine species are linked to temperature and nutrient regimes and are profoundly affected by humans through exploitation and climate change. Yet little is known about long-term historical links between ocean environmental changes and resource abundance to provide context for current and potential future trends and inform conservation and management. We synthesize >4000 years of climate and marine ecosystem dynamics in a Northwest Atlantic region currently undergoing rapid changes, the Gulf of Maine and Scotian Shelf. This period spans the late Holocene cooling and recent warming and includes both Indigenous and European influence. We compare environmental records from instrumental, sedimentary, coral, and mollusk archives with ecological records from fossils, archaeological, historical, and modern data, and integrate future model projections of environmental and ecosystem changes. This multidisciplinary synthesis provides insight into multiple reference points and shifting baselines of environmental and ecosystem conditions, and projects a near-future departure from natural climate variability in 2028 for the Scotian Shelf and 2034 for the Gulf of Maine. Our work helps advancing integrative end-to-end modeling to improve the predictive capacity of ecosystem forecasts with climate change. Our results can be used to adjust marine conservation strategies and network planning and adapt ecosystem-based management with climate change.
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