Abstract. The Lateglacial (14,700–11,700 cal BP) is a key climate period marked by rapid but contrasted changes in the Northern Hemisphere. Indeed, regional climate differences have been evidenced during the Lateglacial in Europe and the Northern Mediterranean areas. However, past climate patterns are still debated since temperature and precipitation changes are poorly investigated towards the lower European latitudes. Lake Matese in Southern Italy is a key site in the Central Mediterranean to investigate climate patterns during the Lateglacial. This study uses a multi-proxy approach including magnetic susceptibility, geochemistry (XRF core scanning), pollen data and molecular biomarkers like branched Glycerol Dialkyl Glycerol Tetraethers (brGDGTs) to reconstruct climate changes and their impacts at Matese. Palaeotemperatures and -precipitation patterns are quantitatively inferred from pollen assemblages (multi-method approach: Modern Analogue Technique, Weighted Averaging Partial Least Squares regression, Random Forest, and Boosted Regression Trees) and brGDGTs calibrations. The results are compared to a latitudinal selection of regional climate reconstructions in Italy to better understand climate processes in Europe and in the circum-Mediterranean region. A warm Bølling–Allerød and a marked cold Younger Dryas are revealed in all climate reconstructions inferred from various proxies (chironomids, ostracods, speleothems, pollen, brGDGTs), showing no latitudinal differences in terms of temperatures across Italy. During the Bølling–Allerød, no significant changes in terms of precipitation are recorded, however, a contrasted pattern is visible during the Younger Dryas. Slightly wet conditions are recorded south of latitude 42° N whereas dry conditions are recorded north of latitude 42° N. During the Younger Dryas, cold conditions can be attributed to the southward position of North Atlantic sea-ice and of the Polar Frontal JetStream whereas the increase of precipitation is Southern Italy seems to be linked to relocation of Atlantic storm tracks into the Mediterranean, induced by the Fennoscandian ice sheet and the North European Plain. On the contrary, during the Bølling–Allerød warm conditions can be linked to the northward position of North Atlantic sea-ice and of the Polar Frontal JetStream.

Abstract. Climatic changes in southern Europe during the Holocene are characterised by a strong spatial and temporal heterogeneity whose patterns are still poorly understood, notably the presence or not of a Holocene thermal maximum (HTM; 10,000–6,000 cal. BP). The reconstructed climatic patterns also differ according to the proxies used (e.g., pollen, chironomid) and the latitude of the data. Here, a multi-proxy approach combining pollen and lipid biomarkers (branched Glycerol Dialkyl Glycerol Tetraethers, brGDGTs) is applied to the Canroute sedimentological sequence to reconstruct the climatic variation over the last 15,000 years in southern Massif Central, France. This area is poorly documented in terms of vegetation and climate. To provide reliable climate reconstructions, we have (1) performed a multi-method comparison based on transfer functions applied to pollen (MAT, WA-PLS, BRT) and molecular biomarkers (brGDGTs), (2) investigated the role of modern databases/calibrations in climate reconstructions. Three different calibration databases were tested for pollen data: one global based on a Eurasian Pollen Database, and two regional databases corresponding to Mediterranean/Temperate Europe and Temperate Europe/Scandinavian databases respectively. Nine global calibrations were tested for lipid biomarkers including eight for soil and one for peat. The use of different modern databases highlights the importance of considering environmental and ecological constraints when using transfer functions on pollen sequences. Pollen and brGDGT-inferred climate trends are consistent, notably for the Lateglacial, the Early and Late Holocene. However, the reconstructions notably differ concerning the presence of a Holocene thermal maximum with the Modern Analogue Technique (MAT) pollen-based method but not apparent with the BRT pollen method nor brGDGT. The temperature reconstructions estimated from the two independent pollen and lipid proxies are then compared to regional published climate signals (chironomids, pollen, molecular biomarkers) to better derive global regional climatic patterns in South Europe. Altogether, our results from the Canroute sequence and those already available in southern Europe reveal that for the Lateglacial and Early Holocene, the regional climate trends are coherent between sites and proxies, supporting the reliability of their reconstructions despite some discrepancies. During the Holocene, the temperature signal of Canroute does not indicate the clear presence of a pronounced mid-Holocene thermal maximum, but rather stable and warmer temperature compared to Lateglacial ones and overall negative anomalies compared to modern annual temperatures.

<div>The arid and semi-arid mountainous environment of the Southern Caucasus lies between the Black and Caspian Sea with elevations from below sea level to over 5000 m asl and has annual temperatures from -6˚ to 16˚C and precipitation between 200 - 2200 mm a year. Due to the large elevation changes in this mountainous zone, temperature and precipitation shifts occur quickly over short distances. The semi-arid regions here host a number of wetland contexts available for paleo-environmental research. However, recent investigations of branched glycerol dialkyl glycerol tetraethers (brGDGTs) records from a large wetland from the region note the changes in wetland development, from lake to peatland, impact the distribution of brGDGTs and the temperature reconstructions (Robles et al. 2022). To overcome these challenges Robles et al. (2022) applied a combination of global lake and soil calibrations to each section. New research on smaller wetlands, however, have found that these wetland transformations are not always as well defined and include periods of erosional soil inputs, open lake contexts, and eventual transformation to a wetland. In addition, soils from the region record a similar trend found in Gao et al., (2021) who found a temperature relationship with the MBT'6<sub>me</sub> suggesting the MBT'5<sub>me</sub> reconstructions do not fully capture the temperature profile. To address these issues we propose two avenues to reconstruct temperature and present our results. First, we evaluate the feasibility of utilizing a stepwise selection model for local configuration based on mixed samples (lake, wetland, soils) to overcome problems with changes in sediment overtime while capturing the temperature relationships between both the 5-methyl and 6-methyl brGDGT groups. Second, we utilize a probability based machine learning approach to estimate changes in source sediment distribution as the wetland transitions through time. We test both of these applications on downcore wetland sediments to evaluate our results. These results are compared with pollen reconstructions, aquatic pollen, non-pollen polymorphs, and XRF data in order to evaluate their success. We find that both methods can help provide better information for reconstructions.</div><div> </div><p>Robles, Mary, et al. "Impact of climate changes on vegetation and human societies during the Holocene in the South Caucasus (Vanevan, Armenia): A multiproxy approach including pollen, NPPs and brGDGTs." Quaternary Science Reviews 277 (2022): 107297. </p><p>Guo, Jingjing, et al. "Soil pH and aridity influence distributions of branched tetraether lipids in grassland soils along an aridity transect." Organic Geochemistry (2021): 104347. APA  </p><p> </p>

<p>Environmental conditions along the Algerian margin (AM) involve complex atmosphere-hydrosphere-biosphere interactions with superimposed anthropogenic activities on adjacent watersheds across the Holocene. Surface waters of the Atlantic Ocean entering the western Mediterranean Sea become the Algerian Current (AC) flowing along the North African coast and generating anticyclonic eddies. Upwelled waters are other recurring hydrological feature reflecting the instability of the AC. In this area, Holocene vegetation and paleohydrological dynamics have not yet been described. The marine core MD04-2801 (2,067 m water depth) has been analyzed to assess environmental and climatic conditions over the last 14 kyrs BP at a secular-scale resolution to fill this gap. A multi-proxy approach including terrestrial (pollen grains and continental non-pollen palynomorphs such as Glomus spores and freshwater microalgae) and marine (dinoflagellate cysts or dinocysts) palynological data as well as sedimentological data (grain-size analysis and clay mineral assemblages) and biomarkers (alkenones and n-alkanes) have been used to investigate the links between past sea surface hydrological conditions characterized by the over-representation of heterotrophic dinocyst taxa (especially <em>Brigantedinium</em> spp.) and regional environmental changes on nearby watersheds. Quantifications of hydrological and climate parameters are also estimated using the Modern Analogue Technique applied to dinocyst and pollen assemblages. Our data evidence linkages between continental dryness or moisture and surface ocean conditions. High productivity is recorded during the cold and arid climate conditions of the Younger Dryas (12.7 to 11.7 ka BP). During the Early-Middle Holocene (11.7 to 8.2 and 8.2 to 4.2 ka BP), fluvial discharges increase concomitantly with the colonization of coastlands by the Mediterranean forest and oligotrophic conditions in the AM. In contrast, aridification characterizes the Late Holocene with the notable 4.2 ka BP megadrought  between 4.3 and 3.9 ka BP. Comparison between with other paleoenvironmental records from the Gulf of Cadiz to the Siculo-Tunisian strait underlines a west to east climatic gradient at orbital and infra-orbital timescales, with marked cold-dry events at 9, 8.1, 7.3 and 6.5 ka BP. This zonal gradient is discussed to explain contradictory results from the Alboran Sea to Tunisia. Finally, the last 3 kyrs BP highlight the establishment of modern ocean production conditions reflecting both vertical mixing in the AM (wind-driven eddies of the AC) and nutrient-enriched fluvial discharges intensified by human land-use.</p>