Long precipitation records are needed to place recent droughts and wet periods in their historical context. This study combines documentary weather accounts, early rain-gauge measurements, atmospheric-circulation and temperature indices, and tree-ring isotope evidence to reconstruct precipitation for contrasting lowland and upland water-resource domains for the Greater Dublin Area (GDA). We develop and evaluate three reconstruction products: a monthly documentary-instrumental reconstruction extending to 1711 (the Jenkinson series); a monthly statistical ensemble, combining Lasso and Random Forest models, extending to 1748; and a tree-ring δ18O reconstruction of May-August precipitation extending to 1200 CE. Monthly reconstructions are evaluated against 1 km gridded observations over their common overlap period, 1865–1977. Both monthly reconstructions reproduce observed rainfall variability, but the documentary-instrumental Jenkinson reconstruction generally shows stronger agreement at monthly, seasonal, annual and event scales. The statistical ensemble provides an independent, circulation-informed estimate but produces smoother variability and underestimates some extremes. The tree-ring reconstruction shows weaker interannual agreement with Dublin rainfall but supplies a substantially longer perspective on summer hydroclimatic variability. However, superior performance against observations does not necessarily translate into greater reliability during the reconstructed period. The two monthly reconstructions diverge most strongly in winter and spring before the mid-nineteenth century, potentially reflecting snow- and sleet-related undercatch in early precipitation measurements which affects the Jenkinson series. This divergence has important consequences for inferred long-term trends. The Jenkinson series indicates large and frequently significant increases in winter and spring precipitation that are not evident in the statistical ensemble. In contrast, both reconstructions show substantial, persistent and often statistically significant decreases in summer precipitation, although these are generally larger in the Jenkinson series. Used together, the reconstructions extend the evidence available for evaluating historical droughts, pluvials and water-resource vulnerability in the Greater Dublin Area beyond the instrumental period.
Antarctic sea-ice cover reached historically low levels in 2023, consistent with the simulated decline in sea-ice extent in response to anthropogenic warming. As Antarctic sea ice is closely linked to multiple components of the Earth system, its demise could precipitate widespread, cascading changes across the cryosphere, atmosphere, and ocean. However, the nature and strength of these interconnections remain poorly understood and are often inadequately represented in models. In this review, we combine modern observations, models, and paleoclimate archives spanning the last glacial cycle to examine how reductions in sea ice may affect other components of the Earth system. We review how Antarctic sea ice interacts with ocean and atmosphere circulation, ice sheets and ice shelves, marine productivity, and the carbon cycle. We find evidence from theory and models that Antarctic sea ice exerts important influences on the Earth system. Paleo-proxy reconstructions provide examples in which changes in sea ice co-occur with changes in the carbon cycle, marine productivity, and ocean circulation. However, isolating the specific impact of sea ice remains challenging in such a highly interconnected system.
A recent study identified an east-west dipole pattern in Asian Summer Monsoon precipitation and in its oxygen-isotope composition variability in response to orbital forcing (Wen et al., 2024). The Korean Peninsula (KP) is situated near the nodal line of this dipole and should therefore exhibit muted precessional variability in both. So far, this conjecture has not been tested using paleoclimatic data. Here, we present speleothem oxygen isotope (δ18O) records from the KP, which support the notion of suppressed orbital-scale hydroclimate variability. Conducting a transient model simulation with the isotope-enabled Community Earth System Model (iCESM1.2) covering the past 130 000 years, along with tagging experiments for low and high insolation conditions, we show that, on precessional timescales, isotopic contributions from oceanic and continental moisture sources compensate each other over the KP, resulting in only a weak regional signal in precipitation δ18O. Based on iCESM1.2 simulations, we further demonstrate that deuterium excess (d-excess) variability over the KP would still capture the moisture source region's zonal seesaw response to precessional forcing. We propose that, given the region's strong sensitivity to changes in moisture sources, paleo-water d-excess reconstructions from East Asia speleothems could provide valuable additional constraints on the drivers of regional monsoon systems. This study offers new insights into the spatiotemporal variability of Pan-Asian hydroclimates and its links to changes in moisture source.
Iron (Fe) availability modulates phytoplankton blooms in High-Nutrient Low-Chlorophyll (HNLC) regions, i.e., ocean areas characterized by an abundance of major nutrients but low marine productivity. Fe can be delivered to the oceans through atmospheric dust deposition, making ice cores unique archives for reconstructing past changes in aeolian Fe deposition. However, while it is known that during dustier periods atmospheric Fe depositions increased, uncertainties remain regarding the fraction of Fe actually available to phytoplankton. Here, we present evidence from the EGRIP ice core (Greenland) during the Pleistocene-Holocene transition (10.3–13.0 ka), which provides insights into atmospheric aerosol deposition over the Fe-limited North Pacific Ocean. Results show that, in contrast to the 17-fold enhancement in total Fe determined by Inductively Coupled Plasma Mass Spectrometry, the iron fraction more likely available for phytoplankton (i.e., labile iron) increased only modestly (+29 %) during the Younger Dryas compared to the Early Holocene, likely due to prevailing alkaline aerosol conditions reducing its solubility. This finding supports the hypothesis that factors other than atmospheric Fe deposition (e.g., stronger water stratification, sea-ice extent, volcanic eruptions, iron remobilization from sediments), played a more relevant role in regulating marine net primary productivity in the HNLC North Pacific Ocean over the last glacial transition.
Hot European summers are often preceded by dry springs such as in 2022, but also in 1473 or 1540, two well-known summers of catastrophic heat. Spring precipitation deficits deplete soil moisture levels, which can amplify extreme summer temperature anomalies in Europe through land-atmosphere feedback mechanisms and altered atmospheric circulation. However, the link is not particularly strong, and hence long time series might help to better elucidate the mechanisms. Starting from documentary data and an atlas of temperature, precipitation, and atmospheric circulation over Europe for climate extremes in the last 600 years, we explore this relationship in more detail. We analyse the extreme heat summer of 1473, which followed dry spring conditions in Southeastern Europe related to a positive East Atlantic pattern. We then use the ModE-RA paleo-reanalysis and combine it with an analysis of 11 760 years of atmospheric model simulations as well as other reanalyses and reconstructions. Using a moving climatology approach with LOESS regressions to calculate anomalies, we identify significant negative correlations between winter-spring precipitation and summer temperatures in all data sets in the latitude band 36–48° N (strongest over southeastern Europe), corresponding to known moisture-limited regions. Moreover, apart from precipitation anomalies, hot summers are preceded by increased blocking over north-central Europe and a positive East Atlantic pattern. Conversely, dry winter-springs are followed by more frequent blocking over northern Europe and, in model simulations, an increase in frequency and intensity of summer heatwaves. A linear regression approach for temperature in the northern Mediterranean region shows that precipitation in April and May has a strong, direct influence that does not vanish when taking the detailed atmospheric circulation in winter, spring, and summer into account, and hence cannot be explained by the effect of circulation on both, spring precipitation and summer temperature.
