Comparison of eastern tropical Pacific TEX86 and Globigerinoides ruber Mg/Ca derived sea surface temperatures: Insights from the Holocene and Last Glacial Maximum

Hertzberg, J. E.; Schmidt, M. W.; Bianchi, Thomas S.; Smith, Richard; Shields, Michael R.; Marcantonio, Franco

doi:10.1016/j.epsl.2015.11.050

Cited by 31 publications

(36 citation statements)

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“…From the LGM to the Holocene, the EPWP δ 18 O subsurface values decreased (an increase in temperatures and/or decrease in δ 18 O seawater values), whereas the cold tongue δ 18 O subsurface values increased (a decrease in temperatures and/or an increase in δ 18 O seawater values). The limited subsurface records available do not show a consistent spatial pattern and suggest temperatures were 1–2 °C cooler or 1–2 °C warmer in the EEP (Ford et al, ; Hertzberg et al, ; Pena et al, ; Sadekov et al, ). The spatial subsurface temperature and δ 18 O seawater pattern within the EEP is currently poorly constrained.…”

Section: Resultsmentioning

confidence: 99%

“…The EEP regional surface δ 18 O (this study; Koutavas et al, ) and the balance of SST records indicate there was spatial heterogeneity in cooling during the LGM relative to modern. Surface temperatures in the EPWP and western equatorial Pacific warm pool were ~2.5 °C cooler during the LGM, whereas the EEP cold tongue was ~1.5 °C cooler (Benway et al, ; de Garidel‐Thoron et al, ; Hertzberg et al, ; Kienast et al, ; Koutavas et al, ; Koutavas & Sachs, ; Lea et al, , ; Leduc et al, ; Rosenthal et al, ; Stott et al, ). This suggests the EPWP and western equatorial Pacific warm pool primarily respond to p CO 2 ‐radiative forcing (and associated feedbacks), while the cold tongue responds to p CO 2 ‐radiative and dynamic forcing.…”

Section: Resultsmentioning

confidence: 99%

“…To reconstruct the surface and subsurface conditions across the EEP, we generated additional surface and subsurface dwelling foraminifera stable isotope data and used previously published records (Figure , Tables and , and Data Set S1; Benway et al, ; Faul et al, ; Koutavas & Lynch‐Stieglitz, ; Lea et al, ; Leduc et al, , ; Lyle et al, ; Martínez et al, ; Patrick & Thunell, ; Pena et al, ; Sadekov et al, ; Spero et al, ; Spero & Lea, ). Additional surface and subsurface dwelling foraminifera (Table , age model: Hertzberg et al, ) were analyzed at sites on the Cocos Ridge (MV1014‐07MC: 6°14.037′N, 86°2.613′W, 1,995 m water depth and MV1014‐08JC: 6°14.038′N, 86°2.613′W, 1,993 m water depth) and Carnegie Ridge (MV1014‐09MC: 0°41.630′S, 85°19.995′W, 2,452 m water depth and MV1014‐17JC: 0°10.832′S, 85°52.004′W, 2,867 m water depth) for the Holocene and LGM. Approximately 10–20 specimens of G .…”

Section: Methodsmentioning

confidence: 99%

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A Deep Eastern Equatorial Pacific Thermocline During the Last Glacial Maximum

Ford

McChesney

Hertzberg

et al. 2018

Geophysical Research Letters

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The mean state and variability of the tropical Pacific is influenced by the depth of the thermocline. During the Last Glacial Maximum (~21,000 years ago), the zonal sea surface temperature gradient across the equatorial Pacific was reduced and productivity was generally lower than modern. To understand the thermocline depth's role in determining the Last Glacial Maximum tropical mean state, we reconstruct the upper ocean δ18O profile from multiple species of planktic foraminifera. We synthesize existing records of surface and subsurface dwelling foraminifera to reconstruct the vertical δ18O gradient throughout the eastern equatorial Pacific. We find the thermocline was deeper during the Last Glacial Maximum than the Holocene throughout the eastern equatorial Pacific region. The thermocline depth's role in the dynamic forcing of the cold tongue contributed to the reduced zonal SST gradient across the equatorial Pacific, decreased productivity, and presumably impacted El Niño‐Southern Oscillation variability relative to the Holocene.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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A Deep Eastern Equatorial Pacific Thermocline During the Last Glacial Maximum

Ford

McChesney

Hertzberg

et al. 2018

Geophysical Research Letters

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“…Thermocline temperatures of the Last Glacial Maximum are expected to be substantially colder than those of the Plio-Pleistocene transition (Ford et al, 2012). However, in comparison to tropical east Pacific thermocline temperatures of the Last Glacial Maximum (on average ∼ 14-16 • C), which are derived from Mg / Ca data of G. tumida from Site 849 (Ford et al, 2015) and N. dutertrei from Sites 08JC and 17JC (Hertzberg et al, 2016) (Fig. 1a), deep-thermocline temperatures of G. crassaformis at Site 849 from the ∼ 2.75 to 2.4 Ma interval appear to be too low.…”

Section: Mg / Ca-based Temperature Datamentioning

confidence: 99%

Thermocline state change in the eastern equatorial Pacific during the late Pliocene/early Pleistocene intensification of Northern Hemisphere glaciation

et al. 2018

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Abstract. The late Pliocene/early Pleistocene intensification of Northern Hemisphere glaciation (iNHG) ∼ 2.5 million years ago (marine isotope stages, MIS, 100-96) stands out as an important tipping point in Earth's climate history, which strongly influenced oceanographic and climatic patterns including trade wind and upwelling strength in the eastern equatorial Pacific (EEP). The thermocline depth in the EEP, in turn, plays a pivotal role in the Earth's climate system: small changes in its depth associated with short-term climate phenomena such as the El Niño-Southern Oscillation can affect surface-water properties and the ocean-atmosphere exchange. However, thermocline dynamics in the EEP during the iNHG still remain unclear. While numerous studies have suggested a link between a thermocline shoaling in the EEP and Northern Hemisphere ice growth, other studies have indicated a stable thermocline depth during the iNHG; consequently, a causal relationship between thermocline dynamics and ice-sheet growth has been excluded. In light of these contradictory views, we have generated geochemical (planktic foraminiferal δ 18 O, δ 13 C and Mg / Ca), sedimentological (sand accumulation rates) and faunal (abundance data of thermocline-dwelling foraminifera) records for Ocean Drilling Program Site 849 located in the central region of the EEP. Our records span the interval from ∼ 2.75 to 2.4 Ma (MIS G7-95), which is critical for understanding thermocline dynamics during the final phase of the iNHG. Our new records document a thermocline shoaling from ∼ 2.64 to 2.55 Ma (MIS G2-101) and a relatively shallow thermocline from ∼ 2.55 Ma onwards . This indicates a state change in thermocline depth at Site 849 shortly before the final phase of the iNHG. Ultimately, our data support the hypothesis that (sub-)tropical thermocline shoaling may have contributed to the development of large Northern Hemisphere ice sheets.

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“…The ini tial mile stones, such as the first at tempt to de duce gla cial trop i cal SSTs us ing Mg/Ca (Hastings et al, 1998), the first cal i bra tions made on cul tured whole shells , or the first detailed sed i ment trap cal i bra tions (Anand et al, 2003;Martínez-Botí et al, 2011), was fol lowed by new ones fo cus ing mostly on its con fi dent use on tar geted key (morpho)spe cies (e.g., Globigerinoides ruber) on both short (mod ern or late Quater nary; Steinke et al, 2005;Thirumalai et al, 2014;Antonarakou et al, 2015) and lon ger time scales over the past 17 My (Wara et al, 2005; Me dina-Elizalde and Lea, 2005;Medina-Elizalde et al, 2008;Lear et al, 2015). Es pe cially for the mod ern ma te rial (core-tops, plank ton tows and sed i ment traps), in which the Mg/Ca sig nal is com pli cated by the com bined in fluence of en vi ron men tal pa ram e ters (e.g., sa lin ity, cal cite sat u ration state; Kisakürek et al, 2008;Hoogakker et al, 2009;Kontakiotis et al, 2011;van Raden et al, 2011;Hönisch et al, 2013;Hertzberg and Schmidt, 2013;Hertzberg et al, 2016) and/or bi o log i cal pro cesses (Hathorne et al, 2009;Wit et al, 2010;Bolton et al, 2011;Nehrke et al, 2013;Spero et al, 2015), prog ress has been rapid be cause of im prove ments in an a lyt i cal in stru men ta tion and meth ods (Haley and Klinkhammer, 2002;Benway et al, 2003;Klinkhammer et al, 2004;Rosenthal et al, 2004;Greaves et al, 2008;. More over, the prog ress has been made in elu ci dating the im pact of chang ing sea wa ter Mg/Ca ra tios on Mg/Ca palaeothermometry (Me dina-Elizalde et al, 2008;Hasiuk and Lohmann, 2010;Broecker and Yu, 2011;Ev ans and Müller, 2012;…”

Section: Introductionmentioning

confidence: 99%