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Abstract. The mid-Cretaceous was a period of unusually active tectonism that drove enhanced volcanic outgassing and high seafloor spreading rates. This intense tectonic activity is coincident with dramatic events in the marine environment, including oceanic anoxic events 1 (Aptian-Early Albian) and 2 (Cenomanian/Turonian boundary), high biological turnover rates, and a thermal maximum. In this study, a series of mid-Cretaceous ocean general circulation model experiments were completed using the

This paper assesses the potential impacts of climate change on the mid-Atlantic coastal (MAC) region of the United States. In order of increasing uncertainty, it is projected that sea level, temperature and streamflow will increase in the MAC region in response to higher levels of atmospheric CO 2 . A case study for Delaware based on digital elevation models suggests that, by the end of the 21st century, 1.6% of its land area and 21% of its wetlands will be lost to an encroaching sea. Sea-level rise will also result in higher storm surges, causing 100 yr floods to occur 3 or 4 times more frequently by the end of the 21st century. Increased accretion in coastal wetlands, however, which may occur in response to increases in CO 2 , temperature, and streamflow, could mitigate some of the flooding effect of sea-level rise. Warming alone will result in northward displacements of some mobile estuarine species and will exacerbate the already low summer oxygen levels in mid-Atlantic estuaries because of increased oxygen demand and decreased oxygen solubility. Streamflow increases could substantially degrade water quality, with significant negative consequences for submerged aquatic vegetation and birds. Though climate change may have some positive impacts on the MAC region, such as increased coastal tourism due to warming and some ecological benefits from less-frequent harsh winters, most impacts are expected to be negative. Policies designed to minimize adverse ecological impacts of human activities on coastal ecosystems in the mid-Atlantic, such as decreases in nutrient loading of watersheds, could help mitigate some of the risks associated with future climate variability and change in this region.

A series of general circulation model experiments utilizing GENESIS have been completed for the mid‐Cretaceous based on geography, variable atmospheric carbon dioxide concentrations (2 to 6 times present‐day concentrations), and variable poleward oceanic heat flux (.6 to 1.2 × 1015 W increased from present day). By combining all three major variables (CO2, geography, and oceanic heat flux), the distribution of mid‐Cretaceous temperatures can be achieved. In the simulations, increased CO2 is required to promote global warmth, and increased oceanic heat flux is required to prevent the tropics from overheating with higher levels of CO2. Four times present‐day CO2 with 1.2 × 1015 W provided the best match to the distribution of mid‐Cretaceous data. The best match to the Cretaceous observations was achieved with a globally averaged surface temperature increase of 6.2°C, at the lower end of past estimates of mid‐Cretaceous warmth. This value may be a better estimate of mid‐Cretaceous global warming. Finally, the model experiments can be used to provide a “paleocalibration” of the global warming expected for a doubling of atmospheric carbon dioxide. The best estimates for the mid‐Cretaceous appear to be a 2.5 to 4.0°C sensitivity, in the mid to upper range of the sensitivity of current climate models used to assess future global change.

Eocene surface ocean terrestrial data defines the nature of the problem of Eocene climates. The solution must involve reinterpretation of at least one major source of information.