Glacially deformed pieces of wood, organic lake sediments and clasts of reworked peat have been collected in front of Alpine glaciers since AD 1990. The palaeoglaciological interpretation of these organic materials is related to earlier phases of glacier recession surpassing that of today's shrunken glaciers and to tree growth and peat accumulation in the valleys now occupied by the glaciers. Glacial transport of the material is indicated by wood anatomy, incorporated silt, sand and gravel particles, missing bark and deformed treerings. A total of 65 samples have been radiocarbon dated so far, and clusters of dates provide evidence of eight phases of glacier recession: 9910-9550, 9010-7980, 7250-6500. 6170-5950, 5290-3870, 3640-3360, 27407250-6500. 6170-5950, 5290-3870, 3640-3360, -26207250-6500. 6170-5950, 5290-3870, 3640-3360, and 15307250-6500. 6170-5950, 5290-3870, 3640-3360, -1170 Allowing for the timelag between climatic fluctuations, glacier response and vegetation colonization, these recession phases may lag behind climatic changes by 100-200 years.

The sediment sequence from Hässeldala port in southeastern Sweden provides a unique Lateglacial/early Holocene record that contains five different tephra layers. Three of these have been geochemically identified as the Borrobol Tephra, the Hässeldalen Tephra and the 10-ka Askja Tephra. Twenty-eight high-resolution 14 C measurements have been obtained and three different age models based on Bayesian statistics are employed to provide age estimates for the five different tephra layers. The chrono-and pollen stratigraphic framework supports the stratigraphic position of the Borrobol Tephra as found in Sweden at the very end of the Older Dryas pollen zone and provides the first age estimates for the Askja and Hässeldalen tephras. Our results, however, highlight the limitations that arise in attempting to establish a robust, chronologically independent lacustrine sequence that can be correlated in great detail to ice core or marine records. Radiocarbon samples are prone to error and sedimentation rates in lake basins may vary considerably due to a number of factors. Any type of valid and 'realistic' age model, therefore, has to take these limitations into account and needs to include this information in its prior assumptions. As a result, the age ranges for the specific horizons at Hässeldala port are large and calendar year estimates differ according to the assumptions of the age-model. Not only do these results provide a cautionary note for overdependence on one age-model for the derivation of age estimates for specific horizons, but they also demonstrate that precise correlations to other palaeoarchives to detect leads or lags is problematic. Given the uncertainties associated with establishing age-depth models for sedimentary sequences spanning the Lateglacial period, however, this exercise employing Bayesian probability methods represents the best possible approach and provides the most statistically significant age estimates for the pollen zone boundaries and tephra horizons.

Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850–2014. Global temperature composites show a remarkable degree of coherence between high- and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era, and is shared in the Linked Paleo Data (LiPD) format, including serializations in Matlab, R and Python.

Much renewed research interest in Arctic regions stems from the increasing concentration of atmospheric greenhouse gases and the alleged climatic sensitivity of high latitude areas. Glacier and permafrost changes are among a number of proxies used for monitoring past and present Arctic climate change. Here we present observations on frozen in situ soil and vegetation, found below cold-based glacier Longyearbreen (78813?N), 2 km upstream from the present glacier terminus. Dating of the relict vegetation indicates that the glacier has increased in length from about 3 km to its present size of about 5 km during the last c. 1100 years. The meteorological setting of non-surging Longyearbreen suggests this example of late-Holocene glacier growth represents a widespread phenomenon in Svalbard and in adjoining Arctic regions. In addition, we use the subglacial permafrozen soil system to evaluate microbial survival capacity over considerable time periods, and we present evidence for microbes having survived more than 1100 years in a subglacial, permafrozen state.

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