Surface ocean warming and acidification driven by rapid carbon release precedes Paleocene-Eocene Thermal Maximum

Abstract

The Paleocene-Eocene Thermal Maximum (PETM) is recognized by a major negative carbon isotope (δ 13 C) excursion (CIE) signifying an injection of isotopically light carbon into exogenic reservoirs, the mass, source, and tempo of which continue to be debated. Evidence of a transient precursor carbon release(s) has been identified in a few localities, although it remains equivocal whether there is a global signal. Here, we present foraminiferal δ 13 C records from a marine continental margin section, which reveal a 1.0 to 1.5‰ negative pre-onset excursion (POE), and concomitant rise in sea surface temperature of at least 2°C and a decline in ocean pH. The recovery of both δ 13 C and pH before the CIE onset and apparent absence of a POE in deep-sea records suggests a rapid (< ocean mixing time scales) carbon release, followed by recovery driven by deep-sea mixing. Carbon released during the POE is therefore likely more similar to ongoing anthropogenic emissions in mass and rate than the main CIE.

Shallow Water Records of the PETM: Novel Insights From NE India (Eastern Tethys)

“…As our carbon isotope values do not reach pre‐event values, we suggest that the PETM is truncated at the top of the section. We also note a small deviation to lower values before the PETM (∼24–∼25 m; Figure 3) which has also been recognized in pedogenic records (Bowen et al., 2015) and other shallow water sections, e.g., the New Jersey Shelf, the Tasman Sea with similar amplitudes of 1–2‰ (Babila et al., 2022; Elling et al., 2019; Self‐trail et al., 2012) and termed preonset excursion (POE; Bowen et al., 2015). Akin to other records, the carbon isotope values recover to pre‐POE values before descending into the PETM.…”

“…These settings are key linkages between continental and open‐marine environments. While shallow water sections with a clearly defined PETM excursion have been described across both clastic and carbonate dominated shelves, few of these combine an integrated isotope and biostratigraphy (Babila et al., 2022; Beasley et al., 2021; Li et al., 2020; Orue‐Etxebarria et al., 2001; Scheibner et al., 2005; Sluijs & Brinkhuis, 2009; Sluijs et al., 2007a, 2007b; Stassen et al., 2012; Zamagni et al., 2012a; Zhang et al., 2013, 2019). Most Tethyan platforms are dominated by coralgal reefs in the Paleocene, but the composition often changes to larger benthic foraminifera (LBF) dominated systems across the event, with a loss of corals and algal groups (Scheibner & Speijer, 2008; Zamagni et al., 2012b).…”

Shelf Ecosystems Along the U.S. Atlantic Coastal Plain Prior to and During the Paleocene‐Eocene Thermal Maximum: Insights Into the Stratigraphic Architecture

“…A taphonomic bias causing this decline cannot be fully excluded, as it coincides with a strong decrease of B. virginiana, a thin-shelled, small species, which is presumably susceptible to dissolution (Nguyen et al, 2009). The fining trend in the sediment and the increased dissolution detected during the POE interval do mimic some PETM characteristics (Babila et al, 2022), but no distinct kaolinite influx is recorded. Attributing the pre-PETM abundance increase of biogroup 2 to specific environmental changes is thus not straightforward.…”

“… South Dover Bridge: (a) δ 18 O foram (‰); (b) Mg/Ca (mmol/mol) with 3% error bars (based on benthic foraminifera, Paleocene: Cibicidoides alleni , Paleocene‐Eocene Thermal Maximum (PETM): Anomalinoides acutus ); (c) δ 11 B (‰) and error interval (gray lines, Babila et al., 2022); (d) calculated seawater δ 18 O (‰); (e) seafloor temperature estimates (°C) based on Mg/Ca, δ 18 O with a linear δ 18 O sw (red diamonds, linear trend derived from coupling of the Mg/Ca with the δ 18 O foram data) and with a fixed δ 18 O sw of −1.2‰ for the PETM interval (gray triangles); (f) CaCO 3 content (%) and kaolinite content (% of whole clay suite—black line); (g) Grain‐size distributions (%) based on Laser Diffraction Particle Size Analyses and mean grain‐size based on Folk and Ward (1957, black line in μm). …”

“…Pink lines and dots indicate δ 13 C benthic+bulk for a doubling of the sedimentation rate to 4.8 cm/kyr up until the top of the POE, purple dots if sedimentation rate pre‐ and post‐POE is presumed as 2.4 cm/kyr. Black lines indicate the δ 11 B peak with error interval (gray lines, Babila et al., 2022), with doubled sedimentation rate in the gray box (dashed lines).…”