Climate changes modulated the history of Arctic iodine during the Last Glacial Cycle

Iodine has a significant impact on promoting the formation of new ultrafine aerosol particles and accelerating tropospheric ozone loss, thereby affecting radiative forcing and climate. Therefore, understanding the long-term natural evolution of iodine, and its coupling with climate variability, is key to adequately assess its effect on climate on centennial to millennial timescales. Here, using two Greenland ice cores (NEEM and RECAP), we report the Arctic iodine variability during the last 127,000 years. We find the highest and lowest iodine levels recorded during interglacial and glacial periods, respectively, modulated by ocean bioproductivity and sea ice dynamics. Our sub-decadal resolution measurements reveal that high frequency iodine emission variability occurred in pace with Dansgaard/Oeschger events, highlighting the rapid Arctic ocean-ice-atmosphere iodine exchange response to abrupt climate changes. Finally, we discuss if iodine levels during past warmer-than-present climate phases can serve as analogues of future scenarios under an expected ice-free Arctic Ocean. We argue that the combination of natural biogenic ocean iodine release (boosted by ongoing Arctic warming and sea ice retreat) and anthropogenic ozone-induced iodine emissions may lead to a near future scenario with the highest iodine levels of the last 127,000 years.

Demographic history and range modelling of the East Mediterranean Abies cilicica

The Mediterranean Basin is one of the 36 global hotspots of biodiversity and it is rich in endemic tree species. The complex geological history of the region throughout the Neogene and Quaternary periods that were marked with several palaeoclimatic transformations was a major factor triggering the genetic divergence of lineages in tree species in the region. The ongoing global climate change is the main factor threatening Mediterranean biodiversity. The risk of population decline related to aridization is the highest in the case of endemics, especially for cold-adapted conifers, such as Abies cilicica. The Cilician fir grows in the East Mediterranean mountains that constitute a local centre of endemism within the region. The species range is fragmented and small-size populations prevail. Previous studies have suggested that the last glacial cycle led to a significant reduction in the species range and might have initiated genetic divergence. As a result, two lineages are currently recognized at the subspecies level, A. cilicica subsp. isaurica (Turkey) and A. cilicica subsp. cilicica (Turkey, Syria, and Lebanon). The predictions about the impact of future climate changes in the East Mediterranean suggest a profound reduction of precipitation and overall warming that may put the remnant populations of A. cilicica at a risk of decline. Here, we used the Bayesian approach to investigate the demographic history of endemic A. cilicica. Specifically, we estimated the probable time of the intraspecies divergence to verify previous assumptions about the species’ evolutionary history. Additionally, niche modelling was used to outline the potential range of changes in the past and to indicate glacial refugia in where the species persisted climate crisis. This approach was also used to explore the possible influence of the future climate changes on the distribution of A. cilicica in the region. Our results demonstrate that the divergence between the Lebanese and the Turkish populations that occurred ~220 ka years BP coincided with the Riss glaciation. According to palaeoecological data, in the East Mediterranean, that glacial period caused a severe reduction in the populations of woody species due to the aridity of the climate. At that time, the Lebanese-Syrian part of the range was likely disconnected from the main range. The second split was induced by the last glacial cycle ~60 ka years BP and led to the separation of the Central Taurus and East Taurus population and, consequently, to the formation of the two subspecies. Niche modelling for the last glacial maximum has allowed us to locate the probable refugia for A. cilicica in the western Anatolia and Syria-Lebanon area. A projection of the future possible distribution of the species indicates a serious reduction of the range during this century.

Low-altitude periglacial activity in southeastern Australia during the late Pleistocene

Only a small area of the Australian mainland was glaciated during the Pleistocene, whereas periglacial deposits are far more common, indicating that cold environments were extensive and a major influence on landscape evolution. Here we identify representative low-elevation examples of scree slopes and frost action, together with fans and valley fills, indicating pronounced erosion cycles during the Pleistocene. To date the deposits, we explore approaches using radiocarbon, optically stimulated luminescence, and profile dating using the cosmogenic nuclide 10Be. The radiocarbon and optical ages show that screes, alluvial valley fill, and fans were deposited between 66–13 ka during the coldest part of the last glacial cycle, and within the previous glacial cycle. Exposure dating indicates further landscape erosion cycles back to the mid Pleistocene. Together, the deposits indicate the frost cracking limit was ~1300 m lower at 680 ± 10 m and mean winter temperature was 8.2 ± 0.5°C colder than present. Periglacial conditions probably affected much of southeastern Australia. The treeless and dry conditions resulted in widespread erosion and increased run off. Combined with increased snow storage within catchments, rivers were paradoxically larger, with high seasonal discharge and sediment loads.

Luminescence Sensitivity of Rhine Valley Loess: Indicators of Source Variability?

Loess provides a valuable terrestrial record of past environmental conditions, including the dynamics and trajectories of air mass circulation responsible for dust transport. Here we explore variations in the luminescence sensitivity characteristics of sedimentary quartz and feldspar as possible tools for identifying changes in source down a loess-palaeosol sequence (LPS). Luminescence sensitivity is a rapidly measurable index which is the product of interplay between source lithology and the history of the quartz or feldspar clasts. Variations in sensitivity of down profile may therefore reflect changes in sediment provenance as well as other factors such as weathering through pedogenesis. We undertake an empirical investigation of the luminescence sensitivity of quartz and feldspar from different grain-size fractions from the Schwalbenberg LPS in the German Rhine valley. We compare samples from a 30 m core spanning the last full glacial cycle with samples of oxygen isotope stage (OIS) 3–2 age exposed within nearby profile. We find an overall inverse relationship between quartz and feldspar sensitivity, as well as variability in sensitivity between different quartz grain sizes. Statistical analyses yield a significant correlation between IR50 sensitivity from unprocessed sediments and clay content, and feldspar sensitivity and Si/Al ratios down the core. Since Si/Al ratios may indicate changes in provenance, the latter correlation suggests that IR50 measurements on unprocessed samples may be used to provide a reliable, rapid scan of source variability over millennial timescales.

Geomorphological, chronological, and paleoenvironmental context of the Mousterian site at Roca San Miguel (Arén, Huesca, Spain) from the penultimate to the last glacial cycle

The Roca San Miguel (RSM) archaeological site was occupied during Mousterian times. Here we present a geoarchaeological and paleoenvironmental reconstruction of the site. Five stratigraphic units (A to E) formed by different archaeological levels are identified. Three optically stimulated luminescence (OSL) ages show that Unit A dates to between 169.6 ± 9.1 and 151.9 ± 11.1 ka, during the penultimate glacial period (PGP), and contains numerous signs of recurring hearths. Unit B is unexcavated. Unit C dates to between 118.9 ± 11.5 and 103.4 ± 6.9 ka (late Eemian–marine isotope stage (MIS) 5d) and shows an abundance of lithic remains as well as some faunal elements. Unit C is covered by Unit D, which incorporates materials moved downslope, and is dated at 81.2 ± 4.7 ka. These OSL ages concur with U/Th ages (129.3 ± 1.5 and 123.6 ± 0.6 ka) derived from a flowstone covered by both -C and D- post-flowstone units. Finally, Unit E covers the archaeological site, which was partially eroded during MIS2. The robust and well-constrained chronology of the RSM site and surroundings enables the establishment of its evolutionary model from the PGP to the last glacial cycle. The RSM site is the oldest Neanderthal occupation accurately dated in the Pre-Pyrenean region.