Constraining multiple controls on planktic foraminifera Mg/Ca

Holland, Katherine D.; Branson, Oscar; Haynes, L.; Hönisch, Bärbel; Allen, Katherine A.; Russell, A. D.; Fehrenbacher, Jennifer S.; Spero, Howard J.; Eggins, Stephen

doi:10.1016/j.gca.2020.01.015

Cited by 26 publications

(90 citation statements)

References 87 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Finally, Mg/Ca-temperature reconstructions from Site 1209 yield a temperature increase of 4 to 5°C (3), which is consistent with a synthesis of model and data estimates of global sea-surface temperature change (39). However, we note that profound uncertainties exist on the paleosensitivity of the Mg/Ca proxy due to low Mg/Ca sw and possible amplifying factors (e.g., seawater pH and DIC) (40). Given the available proxy evidence from ODP Site 1209, we thus conclude that this larger than previously estimated amount of time is missing from the planktic foraminiferal proxy records.…”

Section: Discussionsupporting

confidence: 79%

The seawater carbon inventory at the Paleocene–Eocene Thermal Maximum

Haynes

Hönisch

2020

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

The Paleocene–Eocene Thermal Maximum (PETM) (55.6 Mya) was a geologically rapid carbon-release event that is considered the closest natural analog to anthropogenic CO2 emissions. Recent work has used boron-based proxies in planktic foraminifera to characterize the extent of surface-ocean acidification that occurred during the event. However, seawater acidity alone provides an incomplete constraint on the nature and source of carbon release. Here, we apply previously undescribed culture calibrations for the B/Ca proxy in planktic foraminifera and use them to calculate relative changes in seawater-dissolved inorganic carbon (DIC) concentration, surmising that Pacific surface-ocean DIC increased by +1,010−646+1,415 µmol/kg during the peak-PETM. Making reasonable assumptions for the pre-PETM oceanic DIC inventory, we provide a fully data-driven estimate of the PETM carbon source. Our reconstruction yields a mean source carbon δ13C of −10‰ and a mean increase in the oceanic C inventory of +14,900 petagrams of carbon (PgC), pointing to volcanic CO2 emissions as the main carbon source responsible for PETM warming.

show abstract

Section: Discussionsupporting

confidence: 79%

The seawater carbon inventory at the Paleocene–Eocene Thermal Maximum

Haynes

Hönisch

2020

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, their work shows that pH sensitivity is observed in some species (e.g., O. universa , G. ruber , and G. bulloides ) and not others (e.g., T. sacculifer ). Building on this carbonate system control, Holland et al (2020) suggest that not pH but changes in DIC drive variations in O. universa Mg/Ca, with an increase in DIC corresponding to an increase in Mg/Ca; however, further work is needed to explore the possible DIC sensitivity across a range of species.…”

Section: Methodsmentioning

confidence: 99%

“…Existing records demonstrate large‐scale cooling in regions proximal to Antarctica and the North Atlantic (Hartman et al, 2018; Kuhnert et al, 2009; Levy et al, 2016; Lewis et al, 2007; Majewski & Bohaty, 2010; Sangiorgi et al, 2018; Shevenell et al, 2004; Super et al, 2018; Verducci et al, 2007), reorganization of polar frontal systems (Kuhnert et al, 2009; Verducci et al, 2007), and intensification of equatorial upwelling and overturning circulation (Holbourn et al, 2013, 2014). For example, the continuous, orbitally resolved Mg/Ca‐sea surface temperature (SST) and planktic isotope record from the Pacific sector of the Southern Ocean shows a 6°C to 7°C cooling and freshening preceding the main glaciation step by 300 kyr (Shevenell et al, 2004), although nonthermal effects (e.g., pH and dissolved inorganic carbon [DIC]) on Mg/Ca must be considered and warrant caution when interpreting the nature and extent of cooling (Gray & Evans, 2019; Holland et al, 2020). The timing of these changes has led to the idea that meridional heat/moisture transport and an early thermal isolation of the Antarctic continent played a fundamental role in triggering ice growth (Shevenell et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Initiation of the Western Pacific Warm Pool at the Middle Miocene Climate Transition?

Sosdian

Lear

2020

Paleoceanog and Paleoclimatol

View full text Add to dashboard Cite

Across the middle Miocene, Earth's climate underwent a major cooling and expansion of the Antarctic ice sheet. However, the associated response and development of the tropical climate system is not fully understood, in part because this is influenced by both global climate and also low-latitude tectonic gateways and paleoceanography. Here we use combined δ 18 O and Mg/Ca of planktic foraminifera to reconstruct the thermal history and changes in hydrology from the Indo-Pacific region from 16.5 to 11.5 Ma. During the warmth of the early middle Miocene, our records indicate a dynamic ocean-atmosphere system in the Indo-Pacific region, with episodes of saltier and warmer tropical surface waters associated with high pCO 2 and retreat of the Antarctic ice sheet. We show that across the Middle Miocene Climate Transition (MMCT) surface ocean temperatures in the Indo-Pacific cooled by~2°C, synchronous with the advance of the Antarctic ice sheet. The associated cooling in the Southern Ocean appears to have started earlier and was stronger. Further, we show that western Pacific Ocean warmed and eastern tropical Indian Ocean freshened following the MMCT, likely caused by the constriction of the Indonesian Seaway and reduced connectivity between the Pacific and Indian Oceans following Antarctic glaciation. The MMCT therefore represented a key phase in the evolution of the West Pacific Warm Pool and associated tropical climate dynamics.

show abstract

“…To estimate mixed layer temperatures, we used the exponential equation for T. sacculifer (without sac, 350–500 μm) of (Anand et al, 2003) derived from sediment trap samples:

Mg / Ca = 0.347 \exp ((), 0.09 \times normalT)

A comparison of temperature estimates using the equations of Nürnberg et al (1996) derived from culture experiments on T. sacculifer and the core top calibration of Dekens et al (2002) on T. sacculifer without sac (250–350 μm) shows differences of <1°C (Figure S3 in the supporting information). Several recent studies discussed nonthermal influences, such as pH and salinity, on Mg/Ca variability in foraminiferal calcite (e.g., Gray & Evans, 2019; Holland et al, 2020; Tierney et al, 2019). These authors found a negligible sensitivity of T. sacculifer to changes in pH.…”

Section: Methodsmentioning

confidence: 99%

“…Mg/Ca‐derived temperatures are presented on both, a corrected and an uncorrected scale. The covariance between temperature and seawater carbon chemistry (dissolved inorganic carbon [DIC] concentration and carbonate ion ([CO 3 ] 2− ) saturation) also influences temperature estimates on short timescales (Holland et al, 2020). The late Miocene/early Pliocene variability of these parameters, however, is unknown.…”

Section: Methodsmentioning

confidence: 99%

Variability of the Indian Monsoon in the Andaman Sea Across the Miocene‐Pliocene Transition

Jöhnck

Kuhnt

Holbourn

et al. 2020

Paleoceanog and Paleoclimatol

View full text Add to dashboard Cite

We reconstructed the variability of the Earth's strongest hydrological system, the Indian monsoon, over the interval 6.24 to 4.91 Ma at International Ocean Discovery Program (IODP) Expedition 353 Site U1448 in the Andaman Sea. We integrated high-resolution benthic and planktic foraminiferal carbon and oxygen isotopes with Mg/Ca measurements of the mixed layer foraminifer Trilobatus sacculifer to reconstruct the isotopic composition of seawater (δ 18 O sw) and the gradient between planktic and benthic foraminiferal δ 13 C. A prominent increase in mixed layer temperatures of~4°C occurred between 5.55 and 5.28 Ma, accompanied by a change from precession-to obliquity-driven variability in planktic δ 18 O and δ 18 O sw. We suggest that an intensified cross-equatorial transport of heat and moisture, paced by obliquity, led to increased summer monsoon precipitation during warm stages after 5.55 Ma. Transient cold stages were characterized by reduced mixed layer temperatures and summer monsoon failure, thus resembling late Pleistocene stadials. In contrast, an overall cooler background climate state with a strengthened biological pump prevailed prior to 5.55 Ma. These findings highlight the importance of internal feedback processes for the long-term evolution of the Indian monsoon.

show abstract

Constraining multiple controls on planktic foraminifera Mg/Ca

Cited by 26 publications

References 87 publications

The seawater carbon inventory at the Paleocene–Eocene Thermal Maximum

The seawater carbon inventory at the Paleocene–Eocene Thermal Maximum

Initiation of the Western Pacific Warm Pool at the Middle Miocene Climate Transition?

Variability of the Indian Monsoon in the Andaman Sea Across the Miocene‐Pliocene Transition

Contact Info

Product

Resources

About