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This paper presents for the first time the global latitude structure and seasonal variability of the ionospheric response to the forced from below DE3 and DE2 tides during the period of time January 2008–March 2009. The COSMIC hmF2 and SABER temperature data have been utilized in order to define the ionospheric DE3 and DE2 tidal response to the DE3 and DE2 temperature tides propagating from below. The COSMIC DE3 and DE2 hmF2 tidal oscillations are derived by the same method as the tides seen the SABER temperatures. It has been shown that the longitude wave‐4 and wave‐3 hmF2 structures observed respectively in September and May 2008 are forced mainly by DE3 (wave‐4) and DE2 (wave‐3) temperature tides coming from below. The longitude wave‐3 hmF2 structure observed in January 2008 however is forced by the combined action of the DE2 temperature tide coming from below and the SPW3 probably generated in‐situ.

Both ground‐ and satellite‐based airglow imaging have significantly contributed to understanding the low‐latitude ionosphere, especially the morphology and dynamics of the equatorial ionization anomaly (EIA). The NASA Global‐scale Observations of the Limb and Disk (GOLD) mission focuses on far‐ultraviolet airglow images from a geostationary orbit at 47.5°W. This region is of particular interest at low magnetic latitudes because of the high magnetic declination (i.e., about ‐20°) and proximity of the South Atlantic magnetic anomaly. In this study, we characterize an exciting feature of the nighttime EIA using GOLD observations from October 5, 2018 to June 30, 2020. It consists of a wavelike structure of a few thousand kilometers seen as poleward and equatorward displacements of the EIA‐crests. Initial analyses show that the synoptic‐scale structure is symmetric about the dip equator and appears nearly stationary with time over the night. In quasi‐dipole coordinates, maxima poleward displacements of the EIA‐crests are seen at about ± 12° latitude and around 20 and 60° longitude (i.e., in geographic longitude at the dip equator, about 53°W and 14°W). The wavelike structure presents typical zonal wavelengths of about 6.7 × 103 km and 3.3 × 103 km. The structure's occurrence and wavelength are highly variable on a day‐to‐day basis with no apparent dependence on geomagnetic activity. In addition, a cluster or quasi‐periodic wave train of equatorial plasma depletions (EPDs) is often detected within the synoptic‐scale structure. We further outline the difference in observing these EPDs from FUV images and in situ measurements during a GOLD and Swarm mission conjunction. Key Points Characteristics of a wavelike structure in the nighttime equatorial ionization anomaly are reported using GOLD far‐ultraviolet observations The structure is symmetric about the dip equator, appears stationary with time over the night, and is highly variable on a day‐to‐day basis A cluster or quasi‐periodic wave train of equatorial plasma depletions is often detected within the synoptic structure

The Last Glacial Maximum (LGM, 21 000 years ago) is one of the suite of paleoclimate simulations included in the current phase of the Coupled Model Intercomparison Project (CMIP6). It is an interval when insolation was similar to the present, but global ice volume was at a maximum, eustatic sea level was at or close to a minimum, greenhouse gas concentrations were lower, atmospheric aerosol loadings were higher than today, and vegetation and land-surface characteristics were different from today. The LGM has been a focus for the Paleoclimate Modelling Intercomparison Project (PMIP) since its inception, and thus many of the problems that might be associated with simulating such a radically different climate are well documented. The LGM state provides an ideal case study for evaluating climate model performance because the changes in forcing and temperature between the LGM and pre-industrial are of the same order of magnitude as those projected for the end of the 21st century. Thus, the CMIP6 LGM experiment could provide additional information that can be used to constrain estimates of climate sensitivity. The design of the Tier 1 LGM experiment (lgm) includes an assessment of uncertainties in boundary conditions, in particular through the use of different reconstructions of the ice sheets and of the change in dust forcing. Additional (Tier 2) sensitivity experiments have been designed to quantify feedbacks associated with land-surface changes and aerosol loadings, and to isolate the role of individual forcings. Model analysis and evaluation will capitalize on the relative abundance of paleoenvironmental observations and quantitative climate reconstructions already available for the LGM.

The past two million years of eastern African climate variability is currently poorly constrained, despite interest in understanding its assumed role in early human evolution 1 – 4 . Rare palaeoclimate records from northeastern Africa suggest progressively drier conditions 2 , 5 or a stable hydroclimate 6 . By contrast, records from Lake Malawi in tropical southeastern Africa reveal a trend of a progressively wetter climate over the past 1.3 million years 7 , 8 . The climatic forcings that controlled these past hydrological changes are also a matter of debate. Some studies suggest a dominant local insolation forcing on hydrological changes 9 – 11 , whereas others infer a potential influence of sea surface temperature changes in the Indian Ocean 8 , 12 , 13 . Here we show that the hydroclimate in southeastern Africa (20–25° S) is controlled by interplay between low-latitude insolation forcing (precession and eccentricity) and changes in ice volume at high latitudes. Our results are based on a multiple-proxy reconstruction of hydrological changes in the Limpopo River catchment, combined with a reconstruction of sea surface temperature in the southwestern Indian Ocean for the past 2.14 million years. We find a long-term aridification in the Limpopo catchment between around 1 and 0.6 million years ago, opposite to the hydroclimatic evolution suggested by records from Lake Malawi. Our results, together with evidence of wetting at Lake Malawi, imply that the rainbelt contracted toward the Equator in response to increased ice volume at high latitudes. By reducing the extent of woodland or wetlands in terrestrial ecosystems, the observed changes in the hydroclimate of southeastern Africa—both in terms of its long-term state and marked precessional variability—could have had a role in the evolution of early hominins, particularly in the extinction of Paranthropus robustus . A multiple-proxy reconstruction for the catchment of the Limpopo River and of sea surface temperatures in the Indian Ocean provides evidence for hydroclimatic changes that may have been important in hominin evolution.

In the southern Indian Ocean, the position of the subtropical front – the boundary between colder, fresher waters to the south and warmer, saltier waters to the north – has a strong influence on the upper ocean hydrodynamics and biogeochemistry. Here we analyse a sedimentary record from the Agulhas Plateau, located close to the modern position of the subtropical front and use alkenones and coccolith assemblages to reconstruct oceanographic conditions over the past 300,000 years. We identify a strong glacial-interglacial variability in sea surface temperature and productivity associated with subtropical front migration over the Agulhas Plateau, as well as shorter-term high frequency variability aligned with variations in high latitude insolation. Alkenone and coccolith abundances, in combination with diatom and organic carbon records indicate high glacial export productivity. We conclude that the biological pump was more efficient and strengthened during glacial periods, which could partly account for the reported reduction in atmospheric carbon dioxide concentrations.

The understanding of the nature and behavior of ice sheets in past warm periods is important for constraining the potential impacts of future climate change. The Pliocene warm period (between 3.264 and 3.025 Ma) saw global temperatures similar to those projected for future climates; nevertheless, Pliocene ice locations and extents are still poorly constrained. We present results from the efforts to simulate mid-Pliocene Greenland Ice Sheets by means of the international Pliocene Ice Sheet Modeling Intercomparison Project (PLISMIP). We compare the performance of existing numerical ice sheet models in simulating modern control and mid-Pliocene ice sheets with a suite of sensitivity experiments guided by available proxy records. We quantify equilibrated ice sheet volume on Greenland, identifying a potential range in sea level contributions from warm Pliocene scenarios. A series of statistical measures are performed to quantify the confidence of simulations with focus on inter-model and inter-scenario differences. We find that Pliocene Greenland Ice Sheets are less sensitive to differences in ice sheet model configurations and internal physical quantities than to changes in imposed climate forcing. We conclude that Pliocene ice was most likely to be limited to the highest elevations in eastern and southern Greenland as simulated with the highest confidence and by synthesizing available regional proxies; however, the extent of those ice caps needs to be further constrained by using a range of general circulation model (GCM) climate forcings.