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.

[1] Dominant storm tracks to two ice core sites on the western margin of the Ross Sea, Antarctica (Skinner Saddle (SKS) and Evans Piedmont Glacier), are investigated to establish key synoptic controls on snow accumulation. This is critical in terms of understanding the seasonality, source regions, and transport pathways of precipitation delivered to these sites. In situ snow depth and meteorological observations are used to identify major accumulation events in [2007][2008], which differ considerably between sites in terms of their magnitude and seasonal distribution. While snowfall at Evans Piedmont Glacier occurs almost exclusively during summer and spring, Skinner Saddle receives precipitation year round with a lull during the months of April and May. Cluster analysis of daily back trajectories reveals that the highest-accumulation days at both sites result from fast-moving air masses, associated with synoptic-scale low-pressure systems. There is evidence that short-duration pulses of snowfall at SKS also originate from mesocyclone development over the Ross Ice Shelf and local moisture sources. Changes in the frequency and seasonal distribution of these mechanisms of precipitation delivery will have a marked impact on annual accumulation over time and will therefore need careful consideration during the interpretation of stable isotope and geochemical records from these ice cores.

We present the first proxy record of sea-ice area (SIA) in the Ross Sea, Antarctica, from a 130 year coastal ice-core record. High-resolution deuterium excess data show prevailing stable SIA from the 1880s until the 1950s, a 2-5% reduction from the mid-1950s to the early-1990s, and a 5% increase after 1993. Additional support for this reconstruction is derived from ice-core methanesulphonic acid concentrations and whaling records. While SIA has continued to decline around much of the West Antarctic coastline since the 1950s, concurrent with increasing air and ocean temperatures, the underlying trend is masked in the Ross Sea by a switch to positive SIA anomalies since the early-1990s. This increase is associated with a strengthening of southerly winds and the enhanced northward advection of sea ice.

Synoptic variability in the Ross Sea region, Antarctica over the last thirty years is investigated using back‐trajectory modeling and cluster analysis. We identify two dominant air‐mass trajectory clusters: oceanic/West Antarctic and continental/East Antarctic. Our analysis shows that the oceanic/West Antarctic trajectories have an annual cycle similar to the Semiannual Oscillation and on average peak in frequency during April, while continental/East Antarctic trajectories reach their annual maximum during December. We demonstrate a causal association between the El Niño Southern Oscillation (ENSO) and the frequency of oceanic/West Antarctic trajectories originating from the Ross Sea and Amundsen Sea regions. In contrast, we find that the Southern Annular Mode (SAM) has little influence on the trajectory cluster frequencies. We then develop proxy records for synoptic variability using a shallow firn core from Gawn Ice Piedmont in Southern Victoria Land. Continental/East Antarctic trajectory frequency correlates with concentrations of nitrate (NO3), which is sourced from stratospheric air‐masses descending over the Antarctic interior. At seasonal to inter‐annual scales, the frequency of oceanic/West Antarctic trajectory clusters strongly correlate with deuterium excess, which is sensitive to changes in relative humidity and sea surface temperature in the Ross and Amundsen Seas. Inter‐annual variability in the frequency of oceanic/West Antarctic trajectories is discussed with respect to ENSO and changes in SST and sea ice extent.

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