et al. # a comprehensive database of paleoclimate records is needed to place recent warming into the longer-term context of natural climate variability. We present a global compilation of quality-controlled, published, temperature-sensitive proxy records extending back 12,000 years through the Holocene. Data were compiled from 679 sites where time series cover at least 4000 years, are resolved at sub-millennial scale (median spacing of 400 years or finer) and have at least one age control point every 3000 years, with cutoff values slackened in datasparse regions. The data derive from lake sediment (51%), marine sediment (31%), peat (11%), glacier ice (3%), and other natural archives. The database contains 1319 records, including 157 from the Southern Hemisphere. the multi-proxy database comprises paleotemperature time series based on ecological assemblages, as well as biophysical and geochemical indicators that reflect mean annual or seasonal temperatures, as encoded in the database. This database can be used to reconstruct the spatiotemporal evolution of Holocene temperature at global to regional scales, and is publicly available in Linked Paleo Data (LiPD) format.

No abstract

South-central Chile is one of the most geodynamically active areas in the world, characterised by frequent volcanic eruptions and numerous earthquakes, which are both recorded in lake sediments. In Lago Icalma (39°S), long piston and short gravity coring, as well as 3.5 kHz high-resolution seismic profiling, has been carried out in order to study the Holocene sedimentary infill of the lake, with a special focus on earthquake-triggered deposits.Macroscopic description of sediment cores and detailed grain-size analyses allow us to identify four types of seismically-induced deposits, or "seismites": slump deposits, chaotic deposits, turbidites s.s. and homogenites. Homogenites are characterized by the occurrence of three distinct units on grain-size profiles (coarse base, thick homogenous unit topped by a thin layer of very fine sediment) and by the typical distribution of the grain-size parameters in a skewness-sorting diagram, while turbidites s.s. are characterized by a continuous fining upward trend. Radiocarbon, 210Pb dating, and tephrochronology allow us to demonstrate that the regional seismotectonic activity was probably very high between 2200 and 3000 cal. yr. BP as well as between 7000 and 8000 cal. yr. BP and that none of the historically documented earthquakes have triggered any seismite in Lago Icalma. The most recent seismite recognized in the sediments of Lago Icalma is a slump deposit dated at 1100 ± 100 AD, i.e. older than the period covered by historical records. The remarkable record of seismites between 2200 and 3000 cal. yr. BP is probably influenced by a major eruption of Sollipulli volcano at 3000 cal.yr. BP, which has rejuvenated the stock of terrigenous particles available for erosion, by depositing a thick layer of pumices all over the watershed of Lago Icalma and by clearing the vegetation covering the volcanic ash soils. This paper demonstrates that the record of seismically-triggered deposits in lake sediments is not only controlled by the intensity of the triggering earthquake and the occurrence of unstable sediment along the lake slopes but also by the presence of particles available for erosion/remobilisation in the watershed.

No abstract

Short-term climate changes in Southern Chile are investigated by a multi-proxy analysis of a 53-cm-long sedimentary sequence selected among eight short cores retrieved in Lago

18The climate of Chilean Patagonia is strongly influenced by the southern westerlies, which 19 control the amount and latitudinal distribution of precipitation in the southern Andes. In 20 austral summer, the Southern Westerly Wind Belt (SWWB) is restricted to the high latitudes. 21It expands northward in winter, which results in a strong precipitation seasonality between 22 ~35 and 45°S. Here, we present a new precipitation seasonality proxy record from Quitralco 23 fjord (46°S), where relatively small latitudinal shifts in the SWWB result in large changes in 24 precipitation seasonality. Our 1400 yr record is based on sedimentological and geochemical 25 data obtained on a sediment core collected in front of a small river that drains the 26 2 Patagonian Andes, which makes this site particularly sensitive to changes in river discharge. 27Our results indicate Fe/Al and Ti/Al values that are low between 600 and 1200 CE, increasing 28 at 1200-1500 CE, and high between 1500 and 1950 CE. Increasing Fe/Al and Ti/Al values 29 reflect a decrease in mean sediment grain-size from 30 to 20 µm, which is interpreted as a 30 decrease in seasonal floods resulting from an equatorward shift of the SWWB. Our results 31 suggest that, compared to present-day conditions, the SWWB was located in a more 32 poleward position before 1200 CE. It gradually shifted towards the equator in 1200-1500 CE, 33where it remained in a sustained position until 1950 CE. This pattern is consistent with most 34 precipitation records from central and southern Chile. The comparison of our record with 35 published regional sea surface temperature (SST) reconstructions for the late Holocene 36shows that equatorward shifts in the SWWB are systematically coeval with decreasing SSTs 37 and vice versa, which resembles fluctuations over glacial-interglacial timescales. We argue 38 that the synchronicity between SST and SWWB changes during the last 1400 years 39 represents the response of the SWWB to temperature changes in the Southern Hemisphere. 40 41 Keywords 42Southern westerlies, inorganic geochemistry, paleohydrology, paleohydroclimatology, fjord 43 sediments, southern South America, Chilean Patagonia 44 45 Introduction 46The southern westerlies are the prevailing winds at the mid latitudes of the Southern 47Hemisphere, blowing between the subtropical anticyclone and the cyclonic subpolar air 48 masses. The Southern Westerly Wind Belt (SWWB) extends roughly between 30 and 60ºS, 49and it exhibits latitudinal variations at seasonal to glacial-interglacial timescales. Due to the 50 3 absence of continental barriers in the Southern Ocean, the SWWB directly controls the 51 strength of the Antarctic Circumpolar Current (ACC), which in turn affects the release of CO 2 52 from the deep ocean up to the atmosphere, particularly on glacial-interglacial timescales 53 (Anderson et al., 2009). In addition to modulating the strength of the ACC, the SWWB also 54 controls the amount of precipitation on the windward side of the mountain ranges located 55 along its ...

No abstract

No abstract