North Atlantic warming during global cooling at the end of the Cretaceous

Abstract

Differences in regional responses to climate fluctuations are well documented on short time scales (e.g., El Nino-Southern Oscillation), but with the exception of latitudinal temperature gradients, regional patterns are seldom considered in discussions of ancient greenhouse climates. Contrary to the expectation of global warming or global cooling implicit in most treatments of climate evolution over millions of years, this paper shows that the North Atlantic warmed by as much as 6 °C (1.5%c decrease in 8ls O values of planktic foraminifera) during the Maastrichtian global cooling interval. We suggest that warming was the result of the importation of heat from the South Atlantic. Decreasing North Atlantic 8ls O values are also associated with increasing gradients in planktic 8 13 C values, suggesting increasing surface-water stratification and a correlated strengthening of the North Atlantic Polar Front. If correct, this conclusion predicts arctic cooling during the late Maastrichtian. Beyond implications for the Maastrichtian, these data demonstrate that climate does not behave as if there is a simple global thermostat, even on geologic time scales.

Deccan volcanism, the KT mass extinction and dinosaurs

“…This view is countered by global oxygen isotope evidence of rapid short warming of 3-4ºC in ocean temperatures in zone CF1 of C29r (e.g. Li and Keller 1998b;Wilf et al 2003;MacLeod et al 2005) that appears to be related to enhanced CO 2 emissions from Deccan volcanism at that time. A rapid shift in 187 Os/ 188 Os ratios coincides with this warming and is interpreted to mark the onset of the main Deccan pulse in C29r (Robinson et al 2009).…”

CO2-forced climate thresholds during the Phanerozoic

“…Third, original carbonate is commonly altered diagenetically, leading to falsely cool temperatures (Pearson et al, 2001); however, this issue is less problematic for short-term events (Crowley and Zachos, 2000). Finally, for planktic d 18 O records it is important to have geographically widespread coverage for a given time slice before making inferences about global surface temperatures (e.g., MacLeod et al, 2005). Nevertheless, despite these drawbacks, benthic paleotemperatures are generally good integrators of globally averaged surface temperatures and rapid changes in d 18 O typically reflect either temperature or ice volume (e.g., Zachos et al, 2001).…”

Southern high latitude climate variability in the Late Cretaceous greenhouse world

“…Huber (1998) estimated Turonian to early Campanian Southern Ocean sea surface temperatures were from 20 to N 28°C and deep-water temperatures from 12 to 16°C. By the Maastrichtian sea surface and deep-water temperatures had cooled to 13°C and around 7°C (Barrera, 1994;Barrera and Savin, 1999;Li et al, 2000;MacLeod et al, 2005). There is increasing evidence that not only was the climate deteriorating in the Late Cretaceous, but it was also quite dynamic (Royer et al, 2004).…”

“…Most previous studies on small-scale (b1 Ma) climate variability in the last 12 million years of the Cretaceous have concentrated on oxygen isotope data from Ocean Drilling Program (ODP) and Deep Sea Drilling Sites (DSDP) from the Atlantic and Indian oceans (as summarized in MacLeod et al, 2005). With the exception of a few equatorial Pacific ODP sites (MacLeod et al, 2005), there are no oxygen isotope data from the southern hemisphere Pacific Ocean.…”