Multidecadal Climate Variability in the Southern Region of the California Current System During the Last 1,800 Years

How climate warming is going to affect the multidecadal climate variability in the North Pacific remains an open question. Here we present a record of this type of variability inferred from carbon productivity and sea surface temperature (SST) proxies in high-resolution sediment records from the Southern California Current System (CCS). The reconstruction covers similar to 1,800 years of the Common Era and is associated with the latitudinal migration of the CCS tropical boundary at multidecadal timescales. Inorganic carbon proxies and a Globigerinoides ruber Mg/Ca summer SST reconstruction are associated with the intrusion of the tropical waters in the Southern CCS and organic carbon proxies with the strength of the California Current (CC). From these and other sediment components, we derived a principal component that captures the balance between tropical and subarctic waters in the study region. This principal component record shows further connections with land moisture records, which suggests a link with Pacific basin scale climate reorganization. The results show periods of reduced Pacific multidecadal climate variability associated with cold periods in the Northern Hemisphere (NH). We propose a mechanism related with the southward migration of the westerlies during relatively cool periods in the NH and a southward shift of the North Pacific Current, which could have reduced the advection of subarctic waters to the subtropical region.Consejo Nacional de Ciencia y Tecnología, Paraguay6 month embargo; first published online 22 January 2020This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Tracing the strength of the southwest monsoon using boron isotopes in the eastern Arabian Sea

Here we present the first boron isotope-based pCO2sw (pCO2 of seawater) reconstruction from the eastern Arabian Sea using the planktic foraminifera species Globigerinoides ruber. Our results from sediment core AAS9/21 show that pCO2sw varied between ~160 and 300?µatm during the last 23?kyr. The ?pCO2, the sea-air pCO2 difference, is relatively small during the last glacial maximum and becomes more negative toward the Holocene, with the exception of a significant excess during the last deglaciation centered on the Bølling-Ållerød. Throughout the record, ?pCO2 is predominantly negative, probably as a result of enhanced biological productivity (and higher nutrient and carbon utilization) during the southwest monsoon. A reduction in ?pCO2 during the last glacial maximum is therefore consistent with a reduction in the strength of this monsoon system

Instrumental validation of Globigerinoides ruber Mg/Ca as a proxy for NE Pacific summer SST

Accurate reconstruction of sea surface temperature (SST) is a high research priority, given that it is such a crucial variable in the Earth’s climate system. The Mg/Ca composition of Globigerinoides ruber (white) has been calibrated and applied for a number of tropical and extratropical paleo?SST reconstructions, though validation studies of the proxy against instrumental observations are relatively scarce. Here we present a validation of G. ruber Mg/Ca?derived SSTs against instrumental summer values, firstly from the modern seasonal water column perspective, and secondly from a 20th century observational time series. The study occurs in the San Lázaro Basin (SLB), one of the marginal basins in the NE Pacific known for very high sedimentation rates, excellent preservation, laminated sequences, and the ability to record upwelling processes on high?resolution timescales, from interannual climatic variability (El Niño / Southern Oscillation (ENSO)) to interdecadal (e.g., the Pacific Decadal Oscillation (PDO)). Results suggest that the proxy best reflects the summer season. The proxy?instrument time?series comparison for summer SSTs displays remarkable agreement, driven largely by ENSO cycles for the past century, with some events missing due to scarcity of foraminiferal specimens and/or lack of sufficient temporal resolution. This study validates the G. ruber Mg/Ca proxy for summer SSTs in this region, and suggests its high fidelity to reconstruct summer SST from SLB over longer timescales to record multi?decadal and multi?centennial variabilities

Field-based validation of a diagenetic effect on G. ruber Mg/Ca paleothermometry: Core top results from the Aegean Sea (eastern Mediterranean)

Recent work across the Mediterranean Sea has illustrated the salinity and overgrowth effects on planktonic foraminiferal Mg/Ca, which potentially confound the use of this as a temperature proxy for paleoceanographic reconstructions. To test and verify these effects, we present new Aegean Sea results which reveal Mg/Ca values that were unreasonably high to be explained by temperature or salinity variations alone, confirming that foraminiferal Mg/Ca is affected by diagenesis. We have specifically targeted Globigerinoides ruber (w, sensu stricto), from a series of modern core tops spanning a strong sea surface salinity gradient and a minor sea surface temperature range, along a north?south Aegean Sea transect. Scanning Electron Microscopy analyses show that G. ruber specimens were covered by microscale euhedral crystallites of inorganic precipitates. This secondary calcite phase seems to be responsible for the anomalously high Mg/Ca ratios and likely formed near the sediment/water interface from CaCO3 supersaturated interstitial seawater. We also have clear evidence of diagenetic alteration in a north?south direction along the Aegean Sea, possibly depending on salinity and calcite saturation state gradients. These observations illustrate the necessity of alternative techniques (e.g., flow?through time resolved analysis or laser ablation inductively coupled plasma mass spectrometry) to potentially overcome these diagenetic issues and develop a more reliable and sensitive temperature proxy in similar subtropical settings characterized by high salinity, excessive evaporation, and restricted circulation

High sea surface temperatures in tropical warm pools during the Pliocene

The western warm pools of the Atlantic and Pacific oceans are a critical source of heat and moisture for the tropical climate system. Over the past five million years, global mean temperatures have cooled by 3–4 °C. Yet, present reconstructions of sea surface temperatures indicate that temperature in the warm pools has remained stable during this time. This stability has been used to suggest that tropical sea surface temperatures are controlled by a thermostat-like mechanism that maintained consistent temperatures. Here we reconstruct sea surface temperatures in the South China Sea, Caribbean Sea and western equatorial Pacific Ocean for the past five million years, using a combination of the Mg/Ca-, TEX86H- and -surface-temperature proxies. Our data indicate that during the period of Pliocene warmth from about 5 to 2.6 million years ago, the western Pacific and western Atlantic warm pools were about 2 °C warmer than today. We suggest that the apparent lack of warmth seen in the previous reconstructions was an artefact of low seawater Mg/Ca ratios in the Pliocene oceans. Taking this bias into account, our data indicate that tropical sea surface temperatures did change in conjunction with global mean temperatures. We therefore conclude that the temperature of the warm pools of the equatorial oceans during the Pliocene was not limited by a thermostat-like mechanism

Calibration of the boron isotope proxy in the planktonic foraminifera Globigerinoides ruber for use in palaeo-CO2 reconstruction

The boron isotope-pH proxy, applied to mixed-layer planktic foraminifera, has great potential for estimating past CO2 levels, which in turn is crucial to advance our understanding of how this greenhouse gas influences Earth’s climate. Previous culture experiments have shown that, although the boron isotopic compositions of various planktic foraminifera are pH dependent, they do not agree with the aqueous geochemical basis of the proxy. Here we outline the results of culture experiments on Globigerinoides ruber (white) across a range of pH

Toward a Cenozoic history of atmospheric CO₂

The geological record encodes the relationship between climate and atmospheric carbon dioxide (CO2) over long and short timescales, as well as potential drivers of evolutionary transitions. However, reconstructing CO2 beyond direct measurements requires the use of paleoproxies and herein lies the challenge, as proxies differ in their assumptions, degree of understanding, and even reconstructed values. In this study, we critically evaluated, categorized, and integrated available proxies to create a high-fidelity and transparently constructed atmospheric CO2 record spanning the past 66 million years. This newly constructed record provides clearer evidence for higher Earth system sensitivity in the past and for the role of CO2 thresholds in biological and cryosphere evolution.</p

Non-motor symptoms burden, mood, and gait problems are the most significant factors contributing to a poor quality of life in non-demented Parkinson's disease patients: Results from the COPPADIS Study Cohort

[Objective] To identify factors related to a poor health-related and global quality of life (QoL) in a cohort of non-demented Parkinson's disease (PD) patients and compare to a control group.[Methods] The data correspond to the baseline evaluation of the COPPADIS-2015 Study, an observational, 5-year follow-up, multicenter, evaluation study. Three instruments were used to assess QoL: (1) the 39-item Parkinson's disease Questionnaire (PDQ-39), (2) a subjective rating of global QoL (PQ-10), and (3) the EUROHIS-QOL 8-item index (EUROHIS-QOL8). Multiple linear regression methods were used to evaluate the direct impact of different variables on these QoL measures.[Results] QoL was worse in PD patients (n = 692; 62.6 ± 8.9 years old, 60.3% males) than controls (n = 206; 61 ± 8.3 years old, 49.5% males): PDQ-39, 17.1 ± 13.5 vs 4.4 ± 6.3 (p < 0.0001); PQ-10, 7.3 ± 1.6 vs 8.1 ± 1.2 (p < 0.0001); EUROHIS-QOL8, 3.8 ± 0.6 vs 4.2 ± 0.5 (p < 0.0001). A high correlation was observed between PDQ-39 and Non-Motor Symptoms Scale (NMSS) (r = 0.72; p < 0.0001), and PDQ-39 and Beck Depression Inventory-II (BDI-II) (r = 0.65; p < 0.0001). For health-related QoL (PDQ-39), non-motor symptoms burden (NMSS), mood (BDI-II), and gait problems (Freezing Of Gait Questionnaire [FOGQ]) provided the highest contribution to the model (β = 0.32, 0.28, and 0.27, respectively; p < 0.0001); whereas mood and gait problems contributed the most to global QoL (PQ-10, β = -0.46 and −0.21, respectively; EUROHIS-QOL8, β = -0.44 and −0.23, respectively).[Conclusions] QoL is worse in PD patients than in controls. Mood, non-motor symptoms burden, and gait problems seem to be the most relevant factors affecting health-related and global perceived QoL in non-demented PD patients.Peer reviewe