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

Abstract

The Palaeocene-Eocene Thermal Maximum, approximately 55 million years ago, was a period of rapid warming linked to a massive release of carbon to the ocean-atmosphere system 1 . This warming event was also marked by widespread dissolution of carbonates at the sea floor 2 . The acidification of deep waters was generally more extensive and severe in the Atlantic and Caribbean, with more modest changes in the Southern and Pacific oceans 3-5 . Here we use the UVic ESCM global climate model to show that corrosive deep water spreading from the North Atlantic can explain the spatial variations in carbonate dissolution during the Palaeocene-Eocene Thermal Maximum. In our simulations, highly corrosive waters accumulate in the deep North Atlantic at the onset of the event. Several thousand years after an imposed atmospheric carbon release, warming of the deep ocean destabilizes the North Atlantic water column and triggers deep-water formation. This deep convection causes the corrosive bottom water to spill over an equatorial sill into the South Atlantic. The bottom water then spreads through the Southern and Pacific oceans, progressively gaining alkalinity. We conclude that the pattern of sediment dissolution simulated along the path taken by the corrosive water is consistent with most dissolution estimates from the sediment record.The Palaeocene-Eocene Thermal Maximum (PETM) is a warming event of significant interest because of its relevance to present-day climate change. This palaeoclimate event illustrates how a large and rapid release of carbon can impact physical, chemical and biological systems worldwide 6-8 . Numerous studies have estimated the rate and magnitude of the carbon release to compare the PETM with modern climate change, including approaches based on climate sensitivity 9,10 , seafloor CaCO 3 dissolution 2,3,11 , and C-isotope records 3,12 . Methods based on the intensity of dissolution, such as changes in the position of the lysocline and the calcite compensation depth, are particularly useful as these variables relate directly to the amount of carbon entering the ocean without assuming an isotopic ratio. However, seafloor dissolution was not globally uniform during the PETM (ref. 3), complicating estimates of the accompanying global rise in atmospheric CO 2 .

Expanded oxygen minimum zones during the late Paleocene‐early Eocene: Hints from multiproxy comparison and ocean modeling

“…The state of past circulation in the late Paleocene is highly uncertain [e.g., Nunes and Norris, 2006;Zeebe and Zachos, 2007;Lunt et al, 2010Lunt et al, , 2012Alexander et al, 2015]. Lunt et al [2010] demonstrate that an atmospheric CO 2 and surface warming threshold could exist, beyond which any further CO 2 rise and surface warming leads to a disproportionately larger increase in temperature in the intermediate waters than (Figure 3a).…”

Carbonate Dissolution Enhanced by Ocean Stagnation and Respiration at the Onset of the Paleocene‐Eocene Thermal Maximum

“…Previous modeling studies investigated the response of the ocean carbon cycle to the PETM carbon perturbation (Panchuk et al, ; Ridgwell & Schmidt, ; Zeebe et al, ). Until now, however, the effects of transient changes in ocean circulation on the organic (Winguth et al, ) and inorganic (Alexander et al, ) carbon cycles have been addressed separately and thus interactions between them remain poorly quantified. Yet interactions between inorganic and organic components of the ocean carbon cycle have the potential for producing synergistic effects in the response of ocean biogeochemistry to climate change.…”

Predominant east to west colonizations across major oceanic barriers: Insights into the phylogeographic history of the hydroid superfamily Plumularioidea, suggested by a mitochondrial DNA barcoding marker

“…We use the term "colonization" to denote that the extant species is found in a location different than the one inferred to be occupied by its ancestor. the middle/end of the Eocene, when oceans started to cool after a major global warming period (e.g., Alexander, Meissner, & Bralower, 2015;Lear, Bailey, Pearson, Coxall, & Rosenthal, 2008;Pearson & Palmer, 2000;Zachos et al, 2005). A great part of the extant genera of the Plumularioidea probably persisted through the warm temperatures and climate disruptions of the middle Miocene ( Figure 3; e.g., Zachos, Pagani, Sloan, Thomas, & Billups, 2001;Retallack, 2002), which induced extinctions in other groups (e.g., Sepkoski, 1992,).…”