Atmospheric CO2 across the Plio-Pleistocene

The study of climate parameters and their feedback mechanisms have becomeexceedingly important in light of anthropogenic CO2release and its initiation ofclimate change. In this thesis, I investigate the interaction between different climateparameters during Late Pleistocene climate cycles and the Mid-Pleistocene transition(MPT). I use ocean sediment core-derived foraminiferal shells and geochemicalanalyses to reconstruct surface water temperature, salinity, and atmospheric CO2from a new site U1476 in the Mozambique Channel. I show for the first time thata peak in glacial Indian Ocean surface salinity creates a particularly salty AgulhasLeakage during Late Pleistocene deglaciations. This may influence changes inglobal climate by altering the surface salinity budgets at deep water convection sites,potentially driving a more vigorous overturning circulation. Late Pleistocene climatetransitions established during the MPT “900kyr event”, when glacial ice volumesignificantly increased forming a 100kyr cycle. I demonstrate that ice sheets duringthe early MPT sustained glacial ice volume, despite increases in summer durationinsolation and temperature. The data combined with newpCO2reconstructionssuggest that the early de-coupling of ice sheet dynamics caused a disruption in theforcing of earth’s internal feedback mechanisms, leading to the global phenomenonof the “900kyr event”. ThepCO2data was reconstructed using multi-collectorinductively coupled plasma mass spectrometry (MC-ICPMS) boron isotope analysis.I present accuracy and precision data of boron isotope standard measurements conducted on a new Nu plasma II instrument. Best results were achieved afteradopting a PFA cyclonic spray chamber, 1011Ωresistors, and concentrated solutions.My additional laboratory test studies provide evidence that cleaning large samples,as used in boron isotope analyses, can be efficiently conducted without the necessityfor scaling reagents. My research concludes that Late Pleistocene Indian Oceancirculation and early Pleistocene ice sheet dynamics are important internal climatedrivers that have the potential for shaping Pleistocene climate when coupled withinsolation- or atmospheric CO2 change

A rapid, simple, and low-blank pumped ion-exchange column chromatography technique for boron purification from carbonate and seawater matrices

Funding: This work is supported by the European Research Council under the European Union's Horizon 2020 research and innovation program (Grant 805246) to J.W.B.R., H.J., a Natural Environmental Research Council (NERC)-IAPETUS2 Doctoral Training Programme (DTP) Studentship to NE/S007431/1 C.X., a NERC-IAPETUS DTP Studentship NE/RO12253/1 to M.T., a Leverhulme Trust Early Career Fellowship ECF-2023-199 to H.J., a NERC UK IODP grant NE/P000878/1 to S.B. and S.N., and a Taiwanese MOST Grant 111-2116M-002-032-MY3 to S.N.Boron isotope ratios (δ11B) are used across the Earth Sciences and are increasing analyzed by Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS). Accurate δ11B MC-ICPMS analysis requires boron purification from the sample matrix using ion-exchange column chromatography. However, the traditional gravity-drip column method is time-consuming and prone to airborne contamination due to its long duration and open resin surface. To address these issues, we designed a novel, simple, and reliable column chromatography technique called “peri-columns.” This method uses a peristaltic pump to generate vacuum on a commonly used column set up. This method uses sealed collection beakers and does not require solutions to pass through pump tubing, minimizing contamination. The duration is reduced by eight-fold, processing 12 samples in just 1.5 hr. It also yields low and consistent total procedural blanks, averaging 11 pg. The efficiency and efficacy of this method were tested by repeated boron purification from calcium carbonate and high-sodium matrices with international and in-house reference materials. The results matched those obtained using the gravity column method and fell within our laboratory long-term and international certified values. The mean δ11B and 2SD (standard deviation) of repeatedly processed NIST 8301f were 14.57 ± 0.26‰ (n = 31), NIST 8301c was 24.19 ± 0.33‰ (n = 10), STAiG-F1 was 16.20 ± 0.26‰ (n = 13), and seawater was 39.52 ± 0.32‰ (n = 10). All the components of our techniques are commercially available, and it is easily adaptable to other laboratories and isotope systems.Publisher PDFPeer reviewe

A simple, low-blank batch purification method for high-precision boron isotope analysis

This work was supported by NERC IAPETUS PhD Studentships NE/RO12253/1 to M.T., J.C.B. and E.L., an IAPETUS2 PhD Studentship NE/S007431/1 to C.X.; S.N. was supported by the MOST 111-2116M-002-032-MY3 Grant; J.W.B.R acknowledges support from NERC (Grant NE/N011716/1) and from the European Research Council under the European Union's Horizon 2020 research and innovation program (Grant agreement 805246).Boron (B) isotopes are widely used in the Earth sciences to trace processes ranging from slab recycling in the mantle to changes in ocean pH and atmospheric CO2. Boron isotope analysis is increasingly achieved by multi-collector inductively coupled plasma mass spectrometry, which requires separation of B from the sample matrix. Traditional column chromatography methods for this separation have a well-established track record but are time consuming and prone to contamination from airborne blank. Here, we present an extensive array of tests that establish a novel method for B purification using a batch method. We discuss the key controls and limitations on sample loading, matrix removal and B elution including sample volume, ionic strength, buffer to acid ratio and elution volume, all of which may also help optimize column-based methods. We find consistent, low procedural blanks of 10 ± 16 pg and excellent reproducibility: 10 ng NIST RM 8301 foram [8301f] yields 14.58 ± 0.11‰ 2SD n = 15; 2.5 ng 8301f yields 14.60 ± 0.19‰ 2SD, n = 31; and overall long term 2SD on n = 218 samples pooling different sample sizes yields 14.62 ± 0.21‰ 2SD. This method also offers significant advantages in throughput, allowing the processing of 24 samples in ∼5 hr. This boron batch method thus provides a fast, reproducible, low-blank method for purification of boron for high precision isotopic analyses.Peer reviewe

A rapid, simple, and low-blank pumped ion-exchange column chromatography technique for boron purification from carbonate and seawater matrices

Funding: This work is supported by the European Research Council under the European Union's Horizon 2020 research and innovation program (Grant 805246) to J.W.B.R., H.J., a Natural Environmental Research Council (NERC)-IAPETUS2 Doctoral Training Programme (DTP) Studentship to NE/S007431/1 C.X., a NERC-IAPETUS DTP Studentship NE/RO12253/1 to M.T., a Leverhulme Trust Early Career Fellowship ECF-2023-199 to H.J., a NERC UK IODP grant NE/P000878/1 to S.B. and S.N., and a Taiwanese MOST Grant 111-2116M-002-032-MY3 to S.N.Boron isotope ratios (δ11B) are used across the Earth Sciences and are increasing analyzed by Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS). Accurate δ11B MC-ICPMS analysis requires boron purification from the sample matrix using ion-exchange column chromatography. However, the traditional gravity-drip column method is time-consuming and prone to airborne contamination due to its long duration and open resin surface. To address these issues, we designed a novel, simple, and reliable column chromatography technique called “peri-columns.” This method uses a peristaltic pump to generate vacuum on a commonly used column set up. This method uses sealed collection beakers and does not require solutions to pass through pump tubing, minimizing contamination. The duration is reduced by eight-fold, processing 12 samples in just 1.5 hr. It also yields low and consistent total procedural blanks, averaging 11 pg. The efficiency and efficacy of this method were tested by repeated boron purification from calcium carbonate and high-sodium matrices with international and in-house reference materials. The results matched those obtained using the gravity column method and fell within our laboratory long-term and international certified values. The mean δ11B and 2SD (standard deviation) of repeatedly processed NIST 8301f were 14.57 ± 0.26‰ (n = 31), NIST 8301c was 24.19 ± 0.33‰ (n = 10), STAiG-F1 was 16.20 ± 0.26‰ (n = 13), and seawater was 39.52 ± 0.32‰ (n = 10). All the components of our techniques are commercially available, and it is easily adaptable to other laboratories and isotope systems.Peer reviewe

A Rapid, Simple, and Low‐Blank Pumped Ion‐Exchange Column Chromatography Technique for Boron Purification From Carbonate and Seawater Matrices

International audienceBoron isotope ratios (δ 11 B) are used across the Earth Sciences and are increasing analyzed by Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS). Accurate δ 11 B MC-ICPMS analysis requires boron purification from the sample matrix using ion-exchange column chromatography. However, the traditional gravity-drip column method is time-consuming and prone to airborne contamination due to its long duration and open resin surface. To address these issues, we designed a novel, simple, and reliable column chromatography technique called "peri-columns." This method uses a peristaltic pump to generate vacuum on a commonly used column set up. This method uses sealed collection beakers and does not require solutions to pass through pump tubing, minimizing contamination. The duration is reduced by eight-fold, processing 12 samples in just 1.5 hr. It also yields low and consistent total procedural blanks, averaging 11 pg. The efficiency and efficacy of this method were tested by repeated boron purification from calcium carbonate and high-sodium matrices with international and in-house reference materials. The results matched those obtained using the gravity column method and fell within our laboratory long-term and international certified values. The mean δ 11 B and 2SD (standard deviation) of repeatedly processed NIST 8301f were 14.57 ± 0.26‰ (n = 31), NIST 8301c was 24.19 ± 0.33‰ (n = 10), STAiG-F1 was 16.20 ± 0.26‰ (n = 13), and seawater was 39.52 ± 0.32‰ (n = 10). All the components of our techniques are commercially available, and it is easily adaptable to other laboratories and isotope systems. Plain Language Summary Scientists use boron isotope ratios to study changes in seawater acidity, atmospheric carbon dioxide levels, pollution, and volatile cycling in the Earth. To measure these changes, they need to purify boron from a carbonate matrix, such as foraminifera and coral fossils or seawater, using ionexchange column chromatography. However, the traditional gravity-drip column method is time-consuming and prone to airborne contamination. To address this issue, we developed a new technique called "pericolumns," where we connect manufactured columns to a peristaltic pump. The pump creates a vacuum, which pulls the liquid through columns faster than gravity. This new method is around eight times faster than the existing gravity method and, due to the shorter timescale and the closed nature of the columns, produces lower levels of contamination. We tested this technique using several international and in-house reference materials and found that it produced the same boron isotope ratio results as the traditional method but faster and cleaner

Sea Level controls on Agulhas Leakage Salinity and the Atlantic Overturning Circulation

The Indian Ocean has been proposed as an important source of salt for North Atlantic deep-water convection sites, via the Agulhas Leakage, and may thus drive changes in the ocean’s overturning circulation. However, while past changes in Agulhas leakage volume have been explored, little is known about this water’s salt content, representing a major gap in our understanding of Agulhas salinity supply. Here, we present new planktonic foraminiferal Mg/Ca-derived sea surface temperatures (SST) and stable isotope-derived salinity reconstructions for the last 1.2Ma from the western Indian Ocean source waters of the Agulhas Leakage to investigate glacial-interglacial changes in surface water properties. We find that SST and relative salinity both increase during glaciation, leading to high salinity and SST during glacial maxima. We show that the onset of surface salinification and warming in the Indian Ocean occurs during a phase of rapid land-bridge exposure in the Indonesian archipelago induced by sea level lowering. We link these findings to new global climate model results which show that the export of salt from the Indian Ocean via the Agulhas Leakage can directly impact the deglacial Atlantic meridional overturning circulation and therefore global climate

A Rapid, Simple, and Low‐Blank Pumped Ion‐Exchange Column Chromatography Technique for Boron Purification From Carbonate and Seawater Matrices

Abstract Boron isotope ratios (δ11B) are used across the Earth Sciences and are increasing analyzed by Multi‐Collector Inductively Coupled Plasma Mass Spectrometry (MC‐ICPMS). Accurate δ11B MC‐ICPMS analysis requires boron purification from the sample matrix using ion‐exchange column chromatography. However, the traditional gravity‐drip column method is time‐consuming and prone to airborne contamination due to its long duration and open resin surface. To address these issues, we designed a novel, simple, and reliable column chromatography technique called “peri‐columns.” This method uses a peristaltic pump to generate vacuum on a commonly used column set up. This method uses sealed collection beakers and does not require solutions to pass through pump tubing, minimizing contamination. The duration is reduced by eight‐fold, processing 12 samples in just 1.5 hr. It also yields low and consistent total procedural blanks, averaging 11 pg. The efficiency and efficacy of this method were tested by repeated boron purification from calcium carbonate and high‐sodium matrices with international and in‐house reference materials. The results matched those obtained using the gravity column method and fell within our laboratory long‐term and international certified values. The mean δ11B and 2SD (standard deviation) of repeatedly processed NIST 8301f were 14.57 ± 0.26‰ (n = 31), NIST 8301c was 24.19 ± 0.33‰ (n = 10), STAiG‐F1 was 16.20 ± 0.26‰ (n = 13), and seawater was 39.52 ± 0.32‰ (n = 10). All the components of our techniques are commercially available, and it is easily adaptable to other laboratories and isotope systems

A simple, low-blank batch purification method for high-precision boron isotope analysis

Boron (B) isotopes are widely used in the Earth sciences to trace processes ranging from slab recycling in the mantle to changes in ocean pH and atmospheric CO2. Boron isotope analysis is increasingly achieved by multi-collector inductively coupled plasma mass spectrometry, which requires separation of B from the sample matrix. Traditional column chromatography methods for this separation have a well-established track record but are time consuming and prone to contamination from airborne blank. Here, we present an extensive array of tests that establish a novel method for B purification using a batch method. We discuss the key controls and limitations on sample loading, matrix removal and B elution including sample volume, ionic strength, buffer to acid ratio and elution volume, all of which may also help optimize column-based methods. We find consistent, low procedural blanks of 10 ± 16 pg and excellent reproducibility: 10 ng NIST RM 8301 foram [8301f] yields 14.58 ± 0.11‰ 2SD n = 15; 2.5 ng 8301f yields 14.60 ± 0.19‰ 2SD, n = 31; and overall long term 2SD on n = 218 samples pooling different sample sizes yields 14.62 ± 0.21‰ 2SD. This method also offers significant advantages in throughput, allowing the processing of 24 samples in ∼5 hr. This boron batch method thus provides a fast, reproducible, low-blank method for purification of boron for high precision isotopic analyses