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Abstract. High-resolution, well-dated climate archives provide anopportunity to investigate the dynamic interactions of climate patternsrelevant for future projections. Here, we present data from a new, annuallydated ice core record from the eastern Ross Sea, named the Roosevelt IslandClimate Evolution (RICE) ice core. Comparison of this record with climatereanalysis data for the 1979–2012 interval shows that RICE reliably capturestemperature and snow precipitation variability in the region. Trends over thepast 2700 years in RICE are shown to be distinct from those in WestAntarctica and the western Ross Sea captured by other ice cores. For most ofthis interval, the eastern Ross Sea was warming (or showing isotopicenrichment for other reasons), with increased snow accumulation and perhapsdecreased sea ice concentration. However, West Antarctica cooled and thewestern Ross Sea showed no significant isotope temperature trend. Thispattern here is referred to as the Ross Sea Dipole. Notably, during theLittle Ice Age, West Antarctica and the western Ross Sea experienced colderthan average temperatures, while the eastern Ross Sea underwent a period ofwarming or increased isotopic enrichment. From the 17th century onwards, thisdipole relationship changed. All three regions show current warming, withsnow accumulation declining in West Antarctica and the eastern Ross Sea butincreasing in the western Ross Sea. We interpret this pattern as reflectingan increase in sea ice in the eastern Ross Sea with perhaps the establishmentof a modern Roosevelt Island polynya as a local moisture source for RICE.

Abstract. High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually-dated ice core record from the eastern Ross Sea. Comparison of the Roosevelt Island Climate Evolution (RICE) ice core records with climate reanalysis data for the 1979–2012 calibration period shows that RICE records reliably capture temperature and snow precipitation variability of the region. RICE is compared with data from West Antarctica (West Antarctic Ice Sheet Divide Ice Core) and the western (Talos Dome) and eastern (Siple Dome) Ross Sea. For most of the past 2,700 years, the eastern Ross Sea was warming with perhaps increased snow accumulation and decreased sea ice extent. However, West Antarctica cooled whereas the western Ross Sea showed no significant temperature trend. From the 17th Century onwards, this relationship changes. All three regions now show signs of warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea, but increasing in the western Ross Sea. Analysis of decadal to centennial-scale climate variability superimposed on the longer term trend reveal that periods characterised by opposing temperature trends between the Eastern and Western Ross Sea have occurred since the 3rd Century but are masked by longer-term trends. This pattern here is referred to as the Ross Sea Dipole, caused by a sensitive response of the region to dynamic interactions of the Southern Annual Mode and tropical forcings.

High-resolution analysis of the ice core from Colle Gnifetti, Switzerland, allows yearly and sub-annual measurement of pollution for the period of highest lead production in the European Middle Ages, c. AD 1170-1220. Here, the authors use atmospheric circulation analysis and other geoarchaeological records to establish that Britain was the principal source of that lead pollution. The comparison of annual lead deposition at Colle Gnifetti displays a strong similarity to trends in lead production documented in the English historical accounts. This research provides unique new insight into the yearly political economy and environmental impact of the Angevin Empire of Kings Henry II, Richard the Lionheart and John. Keywords: Colle Gnifetti, Britain, Angevin, ice core, geoarchaeology, lead, silver, Pipe rolls, Introduction Twenty years ago, Brannvall et al. (1999) published the first high-resolution evidence demonstrating that the largest-scale lead pollution in Northern Europe prior to the modern era occurred between c. [...]

The seventh-century AD switch from gold to silver currencies transformed the socioeconomic landscape of North-west Europe. The source of silver, however, has proven elusive. Recent research, integrating ice-core data from the Colle Gnifetti drill site in the Swiss Alps, geoarchaeological records and numismatic and historical data, has provided new evidence for this transformation. Annual ice-core resolution data are combined with lead pollution analysis to demonstrate that significant new silver mining facilitated the change to silver coinage, and dates the introduction of such coinage to c. AD 660. Archaeological evidence and atmospheric modelling of lead pollution locates the probable source of the silver to mines at Melle, in France.Keywords: Europe, Colle Gnifetti, early medieval, ice core, lead pollution, silver coinage, IntroductionDuring the second half of the seventh century AD, the coin-using regions of North-west Europe switched from gold to silver currencies. This change was a key element in the social [...]

Shallow firn cores, in addition to a near-basal ice core, were recovered in 2018 from the Quelccaya ice cap (5470 m a.s.l) in the Cordillera Vilcanota, Peru, and in 2017 from the Nevado Illimani glacier (6350 m a.s.l) in the Cordillera Real, Bolivia. The two sites are ~450 km apart. Despite meltwater percolation resulting from warming, particle-based trace element records (e.g. Fe, Mg, K) in the Quelccaya and Illimani shallow cores retain well-preserved signals. The firn core chronologies, established independently by annual layer counting, show a convincing overlap indicating the two records contain comparable signals and therefore capture similar regional scale climatology. Trace element records at a ~1–4 cm resolution provide past records of anthropogenic emissions, dust sources, volcanic emissions, evaporite salts and marine-sourced air masses. Using novel ultra-high-resolution (120 μm) laser technology, we identify annual layer thicknesses ranging from 0.3 to 0.8 cm in a section of 2000-year-old radiocarbon-dated near-basal ice which compared to the previous annual layer estimates suggests that Quelccaya ice cores drilled to bedrock may be older than previously suggested by depth-age models. With the information collected from this study in combination with past studies, we emphasize the importance of collecting new surface-to-bedrock ice cores from at least the Quelccaya ice cap, in particular, due to its projected disappearance as soon as the 2050s. [ABSTRACT FROM AUTHOR]

Knowledge of microparticle geometry is essential for accurate calculation of ice core volume-related dust metrics (mass, flux, and particle size distributions) and subsequent paleoclimate interpretations, yet particle shape data remain sparse in Antarctica. Here we present 41 discrete particle shape measurements, volume calculations, and calibrated continuous particle time series spanning 50–16 ka from the South Pole Ice Core (SPC14) to assess particle shape characteristics and variability. We used FlowCAM, a dynamic particle imaging instrument, to measure aspect ratios (width divided by length) of microparticles. We then compared those results to Coulter counter measurements on the same set of samples as well as high-resolution laser-based (Abakus) data collected from SPC14 during continuous flow analysis. The 41 discrete samples were collected during three periods of millennial-scale climate variability: Heinrich Stadial 1 (18–16 ka , n=6 ; ∼250 years per sample), the Last Glacial Maximum (LGM) (27–18 ka , n=19 ; ∼460 years per sample), and during both Heinrich Stadial 4 (42–36 ka , n=8 ; ∼620 years per sample) and Heinrich Stadial 5 (50–46 ka , n=8 ; ∼440 years per sample). Using FlowCAM measurements, we calculated different particle size distributions (PSDs) for spherical and ellipsoidal volume estimates. Our calculated volumes were then compared to published Abakus calibration techniques. We found that Abakus-derived PSDs calculated assuming ellipsoidal, rather than spherical, particle shapes provide a more accurate representation of PSDs measured by Coulter counter, reducing Abakus to Coulter counter flux and mass ratios from 1.82 (spherical assumption) to 0.79 and 1.20 (ellipsoidal assumptions; 1 being a perfect match). Coarser particles (>5.0 µm diameter) show greater variation in measured aspect ratios than finer particles (<5.0 µm). While fine particle volumes can be accurately estimated using the spherical assumption, applying the same assumption to coarse particles has a large effect on inferred particle volumes. Temporally, coarse and fine particle aspect ratios do not significantly change within or among the three time periods (p value >0.05), suggesting that long-range transport of dust is likely dominated by clay minerals and other elongated minerals. [ABSTRACT FROM AUTHOR]

Knowledge of microparticle geometry is essential for accurate calculation of ice core volume-related dust metrics (mass, flux, and particle size distributions) and subsequent paleoclimate interpretations, yet particle shape data remain sparse in Antarctica. Here we present 41 discrete particle shape measurements, volume calculations, 35 and calibrated continuous particle timeseries spanning 50 - 10 ka from the South Pole Ice Core (SPC14) to assess particle shape characteristics and variability. We used FlowCAM, a dynamic particle imaging instrument, to measure aspect ratios (width divided by length) of microparticles. We then compared those results to Coulter Counter measurements on the same set of samples as well as high-resolution laser-based (Abakus) data collected from the SPC14 core during continuous flow analysis. The 41 discrete samples (~490 years per sample in the Last Glacial Maximum; LGM) were collected during three periods of rapid global climate reorganization: Heinrich Stadial 1 (18 - 16 ka, n = 6), the LGM (27 - 18 ka, n = 19), and during Heinrich Stadial 4 (42 - 36 ka) and Heinrich Stadial 5 (50 - 46 ka, n = 16). Using FlowCAM measurements, we calculated different particle size distributions (PSDs) for spherical and ellipsoidal volume estimates. Our calculated volumes were then compared to published Abakus calibration techniques. We found that Abakus-derived PSDs calculated assuming ellipsoidal, rather than spherical, particle shapes provide a more accurate representation of PSDs measured by Coulter Counter, reducing Abakusto-Coulter Counter flux and mass ratios from 1.82 (spherical assumption) to 0.79 and 1.20 (ellipsoidal assumptions; 1 being a perfect match). Coarser particles (>5.0 µm diameter) show greater variation in measured aspect ratios than finer particles (<5.0 µm). While fine particle volumes can be accurately estimated using the spherical assumption, applying the same assumption to coarse particles has a large effect on inferred particle volumes. Temporally, coarse and fine particle aspect ratios do not significantly change within or among the three time periods (p-value > 0.05), suggesting that long range transport of dust is likely dominated by clay minerals and other elongated minerals. [ABSTRACT FROM AUTHOR]