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Despite decades of research, the cause of deglaciations is not fully understood, leaving a critical gap in our understanding of Earth's climate system. During the most recent deglaciation (Termination I (T I)), abrupt declines in the stable carbon isotope ratio (δ¹³C) of benthic foraminifera occurred throughout the mid‐depth (1,500–2,500 m) Atlantic. The spatial pattern in δ¹³C anomalies was likely due to Atlantic Meridional Overturning Circulation (AMOC) weakening and the accumulation of respired carbon, which also yields negative excursions in carbonate ion concentration (). To investigate whether a similar pattern occurred during prior deglaciations, we developed δ¹³C and records from 1,800 and 2,300 m water depth in the Southwest Atlantic spanning the last 150 ka. The new records reveal negative δ¹³C and anomalies during Termination II (TII) and the smaller deglaciations of Marine Isotope Stages (MIS) 4/3, 5b/a, and 5d/c, suggesting AMOC weakening is a common feature of deglaciation. The anomalies are more pronounced in the shallower core following MIS 2, 4, and 6 and in the deeper core following MIS 5b and 5d. The depth‐dependent pattern is most likely due to shoaling of Northern Source Water during glacial maxima and deepening during interglacial intervals. Comparison of records from TI and TII suggests similar levels of carbon accumulation in the mid‐depth Atlantic. The Brazil Margin δ¹³C and results indicate the AMOC plays a key role in the series of events causing deglaciation, regardless of differences in orbital configuration, ice volume, and mean global temperature.

 

This paper presents fully kinetic particle simulations of plasma charging at lunar craters with the presence of lunar lander modules using the recently developed Parallel Immersed-Finite-Element Particle-in-Cell (PIFE-PIC) code. The computation model explicitly includes the lunar regolith layer on top of the lunar bedrock, taking into account the regolith layer thickness and permittivity as well as the lunar lander module in the simulation domain, resolving a nontrivial surface terrain or lunar lander configuration. Simulations were carried out to study the lunar surface and lunar lander module charging near craters at the lunar terminator region under mean and severe plasma environments. The lunar module’s position is also investigated to see its effect on the plasma charging relative to the craters. Differential surface charging was clearly resolved by the simulations. For the charging of a lunar lander module made of conducting materials, the results show a near-uniform potential close to that of its surrounding environment and moderate levels of local electric fields. Additionally, the risks associated with charging and discharging increase significantly under a more severe plasma charging environment as shown in the severe plasma environment cases. 

In paleoceanography, carbon and oxygen stable isotope ratios from benthic foraminifera are used as tracers of physical and biogeochemical properties of the deep ocean. We present the first version of the Ocean Carbon Cycling working group database,  of stable isotope ratios of oxygen and carbon from benthic foraminifera from deep ocean sediment cores from the Last Glacial Maximum (LGM, 23-20 ky before present (BP)) to the Holocene (<10 ky BP) with a particular focus on the early last deglaciation (20-15 ky BP). It includes 287 globally distributed coring sites, with metadata, isotopic and chronostratigraphic information, and age models. A quality check was performed for all data and age models. Sites with at least millennial resolution were preferred, because the main goal is to resolve ocean changes associated with the last deglaciation on at least millennial timescales. Software tools were produced to access and analyze the data, and are included with this publication. Deep water mass structure as well as differences between the early deglaciation and LGM are captured by the data in the compilation, even though its coverage is still sparse in many ocean regions. We find high correlations among time series calculated with different age models at sites that allow such analysis. The database provides a useful dynamical approach to map physical and biogeochemical changes of the ocean throughout the last deglaciation.

Custom python scripts to read and analyze the data base may be found in https://github.com/juanmuglia/OC3-python-scripts and in OC3-python-scripts.zip in this repository. plots_d13c.pdf and plots_d18o.pdf contain time series for all sites and available age models. 

We present the first version of the Ocean Circulation and Carbon Cycling (OC3) working group database, of oxygen and carbon stable isotope ratios from benthic foraminifera in deep ocean sediment cores from the Last Glacial Maximum (LGM, 23-19 ky) to the Holocene (<10 ky) with a particular focus on the early last deglaciation (19-15 ky BP). It includes 287 globally distributed coring sites, with metadata, isotopic and chronostratigraphic information, and age models. A quality check was performed for all data and age models, and sites with at least millennial resolution were preferred. Deep water mass structure as well as differences between the early deglaciation and LGM are captured by the data, even though its coverage is still sparse in many regions. We find high correlations among time series calculated with different age models at sites that allow such analysis. The database provides a useful dynamical approach to map physical and biogeochemical changes of the ocean throughout the last deglaciation.

 

Southern Ocean sea ice plays a central role in the oceanic meridional overturning circulation, transforming globally prevalent watermasses through surface buoyancy loss and gain. Buoyancy loss due to surface cooling and sea ice growth promotes the formation of bottom water that flows into the Atlantic, Indian, and Pacific basins, while buoyancy gain due to sea ice melt helps transform the returning deep flow into intermediate and mode waters. Because northward expansion of Southern Ocean sea ice during the Last Glacial Maximum (LGM; 19–23 kyr BP) may have enhanced deep ocean stratification and contributed to lower atmospheric CO₂levels, reconstructions of sea ice extent are critical to understanding the LGM climate state. Here, we present a new sea ice proxy based on the¹⁸O/¹⁶O ratio of foraminifera (δ¹⁸O_c). In the seasonal sea ice zone, sea ice formation during austral winter creates a cold surface mixed layer that persists in the sub‐surface during spring and summer. The cold sub‐surface layer, known as winter water, sits above relatively warm deep water, creating an inverted temperature profile. The unique surface‐to‐deep temperature contrast is reflected in estimates of equilibrium δ¹⁸O_c, implying that paired analysis of planktonic and benthic foraminifera can be used to infer sea ice extent. To demonstrate the feasibility of the δ¹⁸O_cmethod, we present a compilation ofN. pachydermaandCibicidoidesspp. results from the Atlantic sector that yields an estimate of winter sea ice extent consistent with modern observations.