The dynamics of global change at the Paleocene-Eocene thermal maximum: A data-model comparison

Abstract

We integrate published stable isotopic, chemical, mineralogical, and biotic data from the onset of the Paleocene-Eocene thermal maximum (PETM) at Site 690, Maud Rise in the Southern Ocean. The integrated data set documents a sequence of environmental steps including warming of the ocean from the surface downward, and modification of its thermal and nutrient structure, acidification of the deep ocean, and the onset of continental weathering. The age of the events with respect to the onset of the PETM is calibrated with three different age models. The relative and absolute timing of the steps are compared with simulated temperature, salinity, calcite saturation, and dissolved PO 4 and O 2 , at different depths in the ocean, generated with the UVic Earth System Climate Model of intermediate complexity. The simulation supports the top to bottom transfer of heat and carbon, and generally agrees with age models in terms of the durations of leads and lags in temperature, C-isotope, and biotic responses. Moreover, the simulation shows that stratification increased and the nutricline strengthened at the onset of the PETM. These environmental changes explain the abundance of deep-dwelling nannoplankton and foraminifera during the early part of the event. The modeled calcite saturation is consistent with a harsh deep-sea habitat at the time of the benthic foraminiferal extinction.

Anthropogenic carbon release rate unprecedented during the past 66 million years

“…Our results do not support a 2-step carbon release 32 for which the effect of bioturbation and mixing with our estimated sedimentation rate at Millville would only damp, not obliterate, a prominent δ 13 C reversal midway through the onset. We note that a previous study determined leads/lags between climatic/biotic events at one PETM site 33 . However, the data and model results were not used to constrain the time interval of the onset.…”

Evidence for Shelf Acidification During the Onset of the Paleocene‐Eocene Thermal Maximum

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Sudden spreading of corrosive bottom water during the Palaeocene–Eocene Thermal Maximum

“…Although bioturbation has obscured the maximum sediment dissolution by mixing adjacent layers, less significant chemical erosion has been observed at Shatsky Rise in the North Pacific 16 and particularly in the Weddell Sea of the Southern Ocean 17 . The cause of this apparent inter-basinal [CO 3 2− ] gradient during the PETM has not been definitively identified; hypotheses include deep-water formation in the North Pacific 3 or spatial variations in the rate of bioturbation 11 .…”

“…Nonetheless, estimates of percent dissolution exist at various Ocean Drilling Program (ODP) and Deep Sea Drilling Project (DSDP) drilling sites 13,17,[22][23][24] . These estimates are compared with simulated percent dissolution in Fig.…”

“…Black rectangles show the eight rectangular regions used for time series inFig. 2. c, Simulated percent dissolution of sedimentary CaCO 3 (coloured shading), overlain with percent dissolution calculated from sedimentary data at the indicated ODP and DSDP sites (coloured points)17,[22][23][24] .…”