Rashit M. Hantemirov

Shrubs are expanding rapidly in response to climate warming, yet their dendroclimatic responses remain poorly characterised in the Russian Arctic compared to other circumpolar regions. We analysed the radial growth responses of green alder (Alnus alnobetula subsp. fruticosa Raus) to climate variables across two adjacent Arctic regions: the southern Yamal Peninsula and Polar Urals. Tree-ring width chronologies were developed from 68 individual shrubs sampled between 1997 and 2024, yielding the longest continuous global alder chronology (154 years, 1869–2023). Correlation analysis revealed that June-July temperatures were the primary driver of radial growth across all sites (p < 0.01), consistent with temperature-limited growth in high-latitude ecosystems. However, climate-growth relationships exhibited significant temporal and spatial heterogeneity. Precipitation signals were spatially heterogeneous, with April snowpack and July moisture limiting growth at specific sites. Daily response analysis revealed a critical 11–19-day advancement in peak growth correlation in the modern period (1974–2023) compared to earlier intervals, providing robust dendrochronological evidence of recent phenological shifts. These phenological shifts have significant implications for the trophic mismatch between vegetation productivity and reindeer calving timing, potentially threatening food security for indigenous herding communities. Our findings underscore the necessity of integrating shrub dendrochronology into Arctic climate reconstructions and highlight the complex nature of climate-vegetation relationships under rapid warming.

Tree rings are crucial for reconstructing past climates, with maximum latewood density (MXD) as a key metric. However, wood integrity is critical for accurate MXD‐based reconstructions, raising concerns when using potentially degraded relict wood. Quantitative wood anatomy (QWA) provides a morphometric alternative. We compared X‐ray and QWA‐derived density measurements from recent and five‐millennia‐old relict wood from Siberia's Yamal region. We measured bulk density and holo‐cellulose‐to‐wood ratio and employed spectroscopic analyses to identify chemical factors affecting density loss. The findings indicate likely abiotic degradation in relict wood, evidenced by significantly lower bulk density, holo‐cellulose content, and MXD than recent samples, while anatomical density and maximum radial cell wall thickness appeared unchanged. MXD‐based estimates suggested 1.7°C colder June‐August (JJA) temperatures 4,700 years ago, while QWA‐based estimates indicated 0.4°C warmer JJA temperatures than the 20th‐century mean. For relict wood with potential mass loss due to degradation, QWA is recommended over traditional MXD methods.

Extreme solar energetic particle events, known as Miyake events, are rare phenomena observed by cosmogenic isotopes, with only six documented. The timing of the ca. 660 BCE Miyake event remains undefined until now. Here, we assign its occurrence to 664–663 BCE through new radiocarbon measurements in gymnosperm larch tree rings from arctic-alpine biomes (Yamal and Altai). Using a 22-box carbon cycle model and Bayesian statistics, we calculate the radiocarbon production rate during the event that is 3.2–4.8 times higher than the average solar modulation, and comparable to the 774–775 CE solar-proton event. The prolonged radiocarbon signature manifests a 12‰ rise over two years. The non-uniform signal in the tree rings is likely driven by the low rate of CO₂ gas exchange between the trees and the ambient atmosphere, and the high residence time of radiocarbon in the post-event stratosphere. We caution about using the event’s pronounced signature for precise single-year-dating.

Based on the analysis of the frequency of anomalous anatomical structures in the wood of Siberian larch and Siberian spruce (frost rings, light rings, and false rings, as well as missing and narrow rings), we reconstructed a timeline of climatic extremes (summer frosts, sharp multiday decreases in air temperature during the growing season, and low average summer temperatures) in Yamal (Western Siberia) over the last 4500 years. In total, 229 years were determined to have experienced extreme events. The most significant temperature extremes were recorded in 2053, 1935, 1647, 1626, 1553, 1538, 1410, 1401, 982, 919, 883 BCE, 143, 404, 543, 640, 1209, 1440, 1453, 1466, 1481, 1601 and 1818 CE. These dates with extrema observed in Yamal corrobarated with tree ring data from other regions and revealed several coincidences. That is, in these years, the observed extremes appeared to have been on a global rather than a regional scale. Moreover, these dates coincided with traces of large volcanic eruptions found in ice cores from Greenland and Antarctica, dated to approximately the same years. Therefore, the cause of the extreme summer cooling on a global scale, in most cases, can be linked to large volcanic eruptions.

The Arctic is warming faster than any other region on Earth. Putting this rapid warming into perspective is challenging because instrumental records are often short or incomplete in polar regions and precisely-dated temperature proxies with high temporal resolution are largely lacking. Here, we provide this long-term perspective by reconstructing past summer temperature variability at Yamal Peninsula – a hotspot of recent warming – over the past 7638 years using annually resolved tree-ring records. We demonstrate that the recent anthropogenic warming interrupted a multi-millennial cooling trend. We find the industrial-era warming to be unprecedented in rate and to have elevated the summer temperature to levels above those reconstructed for the past seven millennia (in both 30-year mean and the frequency of extreme summers). This is undoubtedly of concern for the natural and human systems that are being impacted by climatic changes that lie outside the envelope of natural climatic variations for this region.

The Sun sporadically produces eruptive events leading to intense fluxes of solar energetic particles (SEPs) that dramatically disrupt the near-Earth radiation environment. Such events have been directly studied for the last decades but little is known about the occurrence and magnitude of rare, extreme SEP events. Presently, a few events that produced measurable signals in cosmogenic radionuclides such as ¹⁴C, ¹⁰Be and ³⁶Cl have been found. Analyzing annual ¹⁴C concentrations in tree-rings from Switzerland, Germany, Ireland, Russia, and the USA we discovered two spikes in atmospheric ¹⁴C occurring in 7176 and 5259 BCE. The ~2% increases of atmospheric ¹⁴C recorded for both events exceed all previously known ¹⁴C peaks but after correction for the geomagnetic field, they are comparable to the largest event of this type discovered so far at 775 CE. These strong events serve as accurate time markers for the synchronization with floating tree-ring and ice core records and provide critical information on the previous occurrence of extreme solar events which may threaten modern infrastructure.

—In recent years, the supra-long Yamal tree-ring chronology has been significantly extended and became much more reliable. This article characterizes the sample wood used to build the longest absolutely dated Siberian Larch tree-ring chronology of the Subarctic area, i.e. from 6748 BC to 2019 AD, for a total continuous period of 8768 years. The ecological value of the temporal and spatial distribution of the dated trees are presented, and their potential use for application in various field of natural sciences and humanities are discussed.