Climatic Cycles Research Articles

An extended kinematic hardening constitutive model to include unsaturated behaviour for the prediction of soil deterioration

Linear geotechnical infrastructure undergoes seasonal volumetric changes due to climatic and hydrological cycles, leading to progressive failure of the soil mass and performance deterioration. The magnitude of the seasonal cycles of pore water pressure is expected to be increased by more extreme and frequent wet and dry events, leading to an accelerated deterioration process. Advanced constitutive models for unsaturated soils able to reproduce the observed behaviour are therefore required. A new advanced constitutive model for the hydro-mechanical behaviour of unsaturated soils is formulated and implemented within the framework of elasto-plasticity with internal variables. The effect of recent suction history is incorporated using a kinematic hardening constitutive model augmented by elements of bounding surface plasticity, initially developed for saturated soils, which is further extended to the unsaturated range through the inclusion of a loading collapse curve. The model permits the retention of information on recent stress history, allows prediction of irrecoverable stiffness and strength loss, and replicates the hysteretic response during cyclic loading. The model has been implemented in a constitutive driver using an implicit numerical scheme and its predictive capabilities are demonstrated by performing numerical simulations of a series of laboratory experiments involving complex sequences of isotropic loading, wetting, drying and shearing stages.

Opposed east-west climate response of the Arctic Ocean during the present interglacial

The role of the Arctic Ocean in the global climate system during the last climatic cycles remains conjectural, but radiocarbon-based chronologies and proxy data provide reliable information about the present interglacial. In the western Arctic, paleoceanographic data demonstrate a linkage between increasing Pacific water fluxes, resulting from the postglacial submergence of the Bering Strait, and the progressive warming, until climate conditions stabilized when sea level reached its present-day limit during the late Holocene. Meanwhile, the southeastern Arctic Ocean evolved from optimal conditions toward a perennial sea ice cover with cooling. We hypothesize that sea level, which determines the depth of Bering Strait and the submergence of the Arctic shelves, has led to enhanced production of seasonal sea ice and an increased freshwater export to the North Atlantic Ocean, since the onset of the present interglacial until preindustrial time.

Spatio-temporal changes in atmospheric aridity over the arid region of Central Asia during 1979–2019

The arid region of Central Asia (CA) is the largest non-zonal arid region in the world. It has experienced significant changes in climate and hydrological cycle systems owing to global warming, which has posed serious impacts on the water resources and ecological environment in this region. Although the atmospheric water vapor pressure deficit (VPD) can directly reflect the atmospheric moisture condition, studies on the change of atmospheric moisture deficit in CA are scarce. Thus, we investigated the changes in VPD in the arid region of CA from the perspective of atmospheric aridity based on the CRU TS4.04 and ERA5 data. Our results showed that the VPD in more than 95 % of grids in the arid region had a significantly increasing trend during 1979–2019. Seasonally, VPD trends were increasing in spring, summer, and autumn but decreasing in winter. The changes in saturated water vapor pressure and actual water vapor pressure determined the VPD changes. The saturated water vapor pressure showed a clearly upward trend, whereas the actual water vapor pressure did not increase at the same rate, resulting in the increase of VPD. The first four leading modes revealed by empirical orthogonal function (EOF) analysis represented the patterns by explaining 81.4 % of the total variance. The positive phase of EOF1 was characterized by a monopole pattern, and this mode continued to increase. Contrastingly, EOF2 (and EOF3) showed dipole patterns over east–west CA (and north–south CA), with a mainly interannual variability. Due to the combined effect of increasing temperatures and decreasing relative humidity, the VPD has been intensifying since the mid-to-late 1990 s in CA, and the atmosphere has become significantly drier. These research results can deepen the scientific understanding of global warming impacts on atmospheric moisture and provides a reference for revealing the VPD changes and their impacts on the climate system and ecosystem in arid regions. Our results highlight that the impacts of VPD change should be adequately considered in environmental management and policy-making processes in Central Asia.

Oceanic islands act as drivers for the genetic diversity of marine species: Cardita calyculata (Linnaeus, 1758) in the NE Atlantic as a case-study

Geographic distribution, as well as evolutionary and biogeographic processes and patterns of marine invertebrate benthic species are strongly shaped by dispersal ability during the life cycle. Remote oceanic islands lie at the brink of complex biotic and abiotic interactions which have significantly influenced the biodiversity patterns we see today. The interaction between geological environmental change and taxon-specific dispersal modes can influence species evolutionary patterns, eventually delimiting species-specific biogeographic regions. In this study, we compare the population genetic patterns of the marine bivalve Cardita calyculata in the northeast Atlantic, discussing the role of Macaronesian islands during past climatic cycles. The genetic structure and diversity patterns were outlined based on SSR-GBAS loci of 165 individuals and on the mitochondrial COI marker of 22 individuals from the Canary Islands, Madeira, Azores and the Mediterranean. The highly structured genetic pattern found among regions and within archipelagos suggests the central role of oceanic islands in promoting the divergence of the species in both the NE Atlantic and the Mediterranean. The high degree of divergence in the COI dataset (> 7%) suggests the existence of potential cryptic speciation that needs to be further explored with a more comprehensive sampling. Such patterns are only congruent with a scenario where C. calyculata populations were maintained during glacial/interglacial cycles, supporting the role of the studied archipelagos as drivers of diversity for marine biota. We stress the importance of developing studies for species with various life history and dispersal modes. In such a way, a more profound understanding of the biogeographic and evolutionary significance of oceanic islands can catalyse directed conservation efforts, especially in the context of the ongoing climate crisis.

Advances in giant clam (Tridacnidae spp.) sclerochronology and sclerochemistry

Understanding past environmental change through high-resolution palaeoenvironmental proxy reconstructions provides crucial baselines for understanding global environmental changes, particularly during the Quaternary Period. Such data are crucial for testing and refining climate models to enable better adaptations to current and future climate changes. Giant clams (Tridacnidae spp.), the largest bivalve mollusc in the Indo-Pacific region, possess distinctive features such as long lifespan, rapid growth, high-resolution growth patterns, wide distribution habitat, and stable shell geochemical composition. These attributes make giant clams a promising and dependable novel palaeoenvironmental archive, offering numerous available geochemical proxies. In this review, we examined preview studies on giant clams conducted for sclerochronology research, spanning publications from 1986 to 2023. The previous studies have proven that isotopic and trace elements proxies of the giant clam, including δ18O, δ13C, Sr/Ca, Mg/Ca, Ba/Ca, and Fe/Ca, can faithfully reconstruct palaeoclimate records including sea surface temperature, dissolved inorganic carbon, insolation, extreme weather events and primary productivity at ultra-high resolution. These proxies have been successfully employed for palaeoclimatic and palaeoenvironmental reconstructions from the Miocene to the present across a range of locations from South Japan to Northern Australia to the Red Sea. These studies have illuminated changes in interannual climate cycles, climate variation, and human migrations over thousands to millions of years. They have generated quantitative records that are valuable for testing and refining numerical climate models, understanding the relationship between past climate cycles and future climate variability, and providing insights into human-environment interactions over time. In the end, the review also addresses the challenges and provided recommendations for future research, highlighting persisting gaps in understanding the influence of microstructure on the shell, age dating of fossil samples, uncertainty in proxies, the need for tank experiments, and access to ultra-high resolution palaeoenvironmental records.

Utilizing Paleoclimate Data to Analyze the Relationship Between Climate Change and Human Activities

Our research aims at finding the relationship between climatic cycle-changes and the human activities in ancient China. Most climatic changes show shifts in the precipitation volume and alternations between warm and cold periods. Through other research findings, we find the precipitation volume is closely connected with alternations of warm and cold periods. This report presents a linear comparison between the population of ancient China and the east Asia climate variables and chooses tree rings as the main indicator of the paleo-climate. Through the literature review and the data analysis, we find that (1) The dominant climate pattern in East Asia is East Asia Summer Monsoon system, causing centennial scaled climate periodicities, affecting the ecosystem and the society. (2) There are certain cycles of climate change, in which the warm period and the cold period have a certain influence on the population change. (3) The precipitation has a certain correlation with the population change. However, single temperature and precipitation cannot directly affect the population change, but also need to be combined with social and historical factors specific analysis.

A 650-Myr history of Earth's axial precession frequency and the evolution of the Earth-Moon system derived from cyclostratigraphy.

The preservation of Milankovitch cycles in the stratigraphic record provides independent geological information to study our ancient solar system and can be leveraged to constrain existing theoretical models. Here, we identify 34 high-quality cyclostratigraphic records spanning the past 650 million years and use them to infer the evolution of the Earth-Moon system through a Bayesian inversion method. We reconstruct the time evolution of Earth's axial precession frequency, lunar distance, length of day, and the periods of obliquity and climatic precession cycles. The results indicate an interval of high tidal energy dissipation in the Earth-Moon system at ~300 to 200 million years ago, and are broadly consistent with an independently calculated tidal evolution model. Our results provide an improved determination of the past periods of obliquity and climatic precession for astrochronology applications and yield important constraints on the history of tidal energy dissipation during the Phanerozoic Eon.

Snow leopard phylogeography and population structure supports two global populations with single refugial origin

AbstractSnow leopards (Panthera uncia) inhabit the mountainous regions of High Asia, which experienced serial glacial contraction and expansion during climatic cycles of the Pleistocene. The corresponding impacts of glacial vicariance may have alternately promoted or constrained genetic differentiation to shape the distribution of genetic lineages and population structure. We studied snow leopard phylogeography across High Asia by examining range-wide historical and contemporary genetic structure with mitochondrial DNA and microsatellite markers. We genotyped 182 individuals from across snow leopard range and sequenced portions of the mitogenome in a spatially stratified subset of 80 individuals to infer historical biogeographic and contemporary patterns of genetic diversity. We observed a lack of phylogeographic structure, and analyses suggested a single refugial origin for all sampled populations. Molecular data provided tentative evidence of a hypothesized glacial refugia in the Tian Shan-Pamir-Hindu Kush-Karakoram mountain ranges, and detected mixed signatures of population expansion. Concordant assessments of microsatellite data indicated two global genetic populations, though we detected geographic differences between historical and contemporary population structure and connectivity inferred from mitochondrial and microsatellite data, respectively. Using the largest sample size and geographic coverage to date, we demonstrate novel information on the phylogeographic history of snow leopards, and corroborate existing interpretations of snow leopard connectivity and genetic structure. We recommend that conservation efforts incorporate genetic data to define and protect meaningful conservation units and their underlying genetic diversity, and to maintain the snow leopard’s adaptive potential and continued resilience to environmental changes.

HYDROLOGICAL REGIME AND WATER RESOURCES OF RIVERS OF THE ZERAFSHAN BASIN UNDER CLIMATE CHANGE

The work assessed the impact of climate change on the hydrological regime - long-term fluctuations, intra-annual distributions, maximum flow rates and, in general, on the water resources of the rivers of the Zeravshan basin. Calculations to assess changes in meteorological parameters were performed for two climatic periods. Some changes in the regime of air temperature and precipitation were revealed. Their influence on the hydrological regime of rivers is assessed. Particular attention is paid to the issues of quantitative assessment of water resources of the rivers of the studied basin.

Climate-driven peatlands development and vegetation dynamics in Northeastern China since the mid-Holocene: New evidence from Huanan peatlands

Studying peatland evolution and vegetation patterns in response to climate change provides valuable insights into future ecosystem trends. This study focuses on the Huanan peatland located in Changbai Mountain regions in Northeast China, utilizing phytolith analysis and stable carbon isotope composition (δ13C) to reconstruct late Holocene vegetation dynamics. Additionally, grain size, total organic carbon (TOC), and total nitrogen (TN) analyses were conducted to understand peatland development and paleoclimate since the late Holocene. The research identifies three distinct climate periods since 5500 cal yr BP: an initial warm, humid phase (5500–4000 cal yr BP) characterized by high river levels that formed lacustrine sediments; a subsequent transition to cold, dry conditions (4000–1500 cal yr BP) that initiated peat formation; and continued dry, cold conditions (1500 cal yr BP to the present) with sustained peat growth. Phytolith data reveal a dominant forest vegetation type since 2000 cal yr BP, further divided into three periods: 2000–1300 cal yr BP, marked by diverse and dense vegetation; 1300–750 cal yr BP, with declining plant cover; and 750 cal yr BP to the present, characterized by an increase in woody plants but a reduction in local grass cover.

Ash deposits link Oceanic Anoxic Event 2 to High Arctic volcanism

Oceanic Anoxic Event 2 (OAE 2) was a major environmental perturbation that occurred ∼94 million years ago. It is associated with profound changes in global climate and carbon cycling, which are commonly attributed to large-scale carbon release from large igneous province (LIP) volcanism. However, the specific LIP(s) involved and the mechanisms of carbon release remain poorly understood, as indicated by discrepancies between carbon release rates suggested by numerical models and LIP degassing estimates. Our study refines the eruptive history of the High Arctic large igneous province (HALIP) by dating ashfall deposits in marine sediments from the Canadian High Arctic using an integrated stratigraphic approach. Our results show that silicic HALIP volcanism began tens of thousands of years before OAE 2, suggesting a strong causal link. Volcanic activity coincides with a marked shift in carbon isotope values, linked to the degassing of HALIP magmas and/or thermogenic gas release. We propose that the concurrent activity of two LIPs—the HALIP and the Kerguelen Plateau—could account for the high rates of carbon release inferred for OAE 2, providing a hypothesis for its pervasive environmental impact.

Contact zone of European (Meles meles Linnaeus, 1758) and Asian (M. leucurus Hodgson, 1847) badgers (Mustelidae, Mammalia) in the rightand left-bank districts of the Saratov region

DNA studies of badgers (Meles sp.) from the right-bank and left-bank areas of the Volga river in the Saratov region are described. Asian badgers (Meles leucurus Hodgson, 1847) inhabit the Left Volga Bank of the Saratov region, while European badgers (M. meles Linnaeus, 1758) inhabit the Right Volga Bank districts of the region, but Asian badgers were found in Khvalynsky district of the Saratov region, besides the European badger. Despite a sufficient number of publications devoted to the Asiatic badger distribution in the Vyatka–Kama region and the Volga region, and studies devoted to the development of systematics of the genus Meles in Russia, the question of the boundaries of the ranges of European and Asiatic badgers and the zones of their sympatry (parapatry) in the Volga–Kama region has not been fully investigated to date. Our work is devoted to the study of this question. As a result of analyzing the biological material collected by us, it was found that all five studied individuals of badgers from the Saratov Volga region phenotypically looked like Asian badgers, but our DNA analysis showed that only two of them were M. leucurus, whilst three ones were heterozygous individuals carrying genes from both species and were identified as hybrids. The remaining 29 individuals were captured in the right-bank areas of the region. Badgers were sampled from individuals from the northern to southern borders of the region in areas located along the Volga river on the Volga upland and in the Oka–Don plain. Of these, one individual from Khvalynsky district turned out to be an Asian badger, one individual from Krasnoarmeysky district was a hybrid of the two named species, and three individuals, one from Tatishchevsky, the second from Volsky and the third from Khvalynsky districts showed introgression of Asian badger genes into the genotype of the European badger. Thus, we have managed to find out that at this stage of development of the phase of the climatic cycle in the Lower Volga region, characterized by warming winters, the Volga river, with its two reservoirs within the Saratov region, is not an absolute zoogeographical boundary, and badgers, whose species are characterized by winter sleep, can in certain conditions overcome, most likely on ice, both the river itself and the lake parts of the Volgograd and Saratov reservoirs. According to the revealed introgression in some individuals from different areas on the Volga upland of the right bank of the Saratov region, it can be assumed that such traveling across the Volga river took place earlier, possibly before its flow was regulated by dams.

Tropical cyclone landfalls in the Northwest Pacific under global warming

AbstractThis study projects the changes in tropical cyclone (TC) landfalls in the western North Pacific under shared socioeconomic pathway (SSPs) scenarios during the TC peak season by using low‐resolution global climate models participating in the Coupled Model Intercomparison Project phase 6 (CMIP6). Projections are based on the relationship between mid‐ and lower‐level atmospheric circulation and TC landfall frequency during the historical period from 1985 to 2014 and the future climate period from 2015 to 2100. The landfall areas for TCs are divided into northern East Asia (NEA), middle East Asia (MEA) and southern East Asia (SEA); the TC peak seasons are July–September for NEA and MEA, and July–November for SEA. To evaluate reproducibility, both ensemble and individual model outputs for mid‐ and lower‐level atmospheric circulations associated with TC landfall in each East Asian subregion are compared to the reanalysis. An ensemble of seven models with stable results for all three regions is more reasonable in simulating atmospheric circulation patterns than an ensemble of all CMIP6 models. The findings suggest that TC landfall is projected to increase by about 12% and 32% in NEA and MEA, respectively, in the late 21st century under the SSP5‐8.5 scenario compared to the historical period, while decreasing by 13% in SEA. These changes are consistent under both warming scenarios, and are more pronounced in the SSP5‐8.5 scenario compared to SSP1‐2.6, particularly in the later period of this century. An analysis of future atmospheric circulations suggests that global warming will weaken the western North Pacific subtropical high and cause its boundary to retreat eastward. This will lead to changes in the steering flow, which is closely related to TC tracks, resulting in TC landfalls to increase or decrease depending on the East Asian subregion.

Comparative Study of Potential Habitats for Two Endemic Grassland Caterpillars on the Qinghai-Tibet Plateau Based on BIOMOD2 and Land Use Data.

This study has systematically investigated and compared the geographical distribution patterns and population density of G. menyuanensis (Gm) and G. qinghaiensis (Gq), which are endemic to the QTP region and inflict severe damage. Using a method combining the BIOMOD2 integration model (incorporating nine ecological niche models) and current species distribution data, this study has compared changes in potential habitats and distribution centers of these two species during ancient, present, and future climate periods and conducted a correlation test on the prediction results with land use types. The study results indicate that there are differences in geographical distribution patterns, distribution elevations, and population density of these two species. Compared with single models, the integration model exhibits prominent accuracy and stability with higher KAPPA, TSS, and AUC values. The distribution of suitable habitats for these two species is significantly affected by climatic temperature and precipitation. There is a significant difference between the potential habitats of these two species. Gm and Gq are distributed in the northeastern boundary area and the central and eastern areas of the QTP, respectively. The areas of their suitable habitats are significantly and positively correlated with the area of grassland among all land use types of QTP, with no correlations with the areas of other land use types of QTP. The potential habitats of both species during the paleoclimate period were located in the eastern and southeastern boundary areas of the QTP. During the paleoclimate period, their potential habitats expanded towards the Hengduan Mountains (low-latitude regions) in the south compared with their current suitable habitats. With the subsequent temperature rising, their distribution centers shifted towards the northeast (high-latitude) regions, which could validate the hypothesis that the Hengduan Mountains were refuges for these species during the glacial period. In the future, there will be more potential suitable habitats for these two species in the QTP. This study elucidates the ecological factors affecting the current distribution of these grass caterpillars, provides an important reference for designating the prevention and control areas for Gm and Gq, and helps protect the alpine meadow ecosystem in the region.

Major tunnel valleys and sedimentation changes document extensive Early Pleistocene glaciations of the Barents Sea

Sedimentary records of Early Pleistocene (~2.6–0.8 Ma) glaciations are sparse on shelves, yet trough mouth fans on adjacent continental slopes provide a continuous record of ice-sheet and climate development throughout the Quaternary. Here, we interpret high-quality 3D seismic reflection data combined with borehole and chronostratigraphic information from a shelf-slope setting in the southwestern Barents Sea to study meltwater and sediment inputs to the deep ocean, focusing on the onset of Pleistocene glaciations. Sandy deposits were brought to the slopes of the high-latitude Bear Island Fan by a preglacial contourite-turbidite system from ⁓2.6–2.4 Ma. Muddy glacigenic debris flows document the first shelf-edge glaciation at ⁓2.4 Ma. From 1.78–0.78 Ma, muddy turbidity-current- and debris-flow-derived sediments were delivered from shelf to slope via six tunnel valleys measuring up to 12 km in width and 200 m in depth. These tunnel valleys and associated downslope deposits formed during the 41-kyr climate cycles of the Early Pleistocene, and evidence abundant channelized, meltwater discharges from these glaciations. Following the mid-Pleistocene transition to 100-kyr cycles, a change in the style of glaciation is suggested by a change in landform and facies associations consistent with a reduced meltwater contribution. This study shows that the Norwegian-Barents shelf was extensively glaciated in the Early Pleistocene, with a first shelf-edge glaciation from ~2.4 Ma.

Role of Climatic Cycles on the Duality of Chemical and Physical Modes of Sulfate Attack in Concrete

Role of Climatic Cycles on the Duality of Chemical and Physical Modes of Sulfate Attack in Concrete

The ammonite faunas of the upper Hypselocyclum to Divisum zones (Lower Kimmeridgian, Upper Jurassic) at Małogoszcz, Holy Cross Mts., central Poland: their stratigraphical interpretation and evolutionary development

AbstractThe transgressive succession of deposits of the upper Lower Kimmeridgian at Małogoszcz in the south-western margin of the Holy Cross Mts. in central Poland yielded diversified faunas of ammonites. The commonly represented Submediterranean ataxioceratid ammonites include the last members of Ataxioceras in the Hypselocyclum Zone and the assemblage of various Crussoliceras, Garnierisphinctes and Progeronia, mostly developed in the Divisum Zone, and associated upwards (Uhlandi Subzone) with aspidoceratids (Pseudhimalayites). A few typical Mediterranean ammonites (Nebrodites, Presimoceras, Idoceras, Taramelliceras) are indicative of the Herbichi Zone. The Subboreal ammonites include mostly Eurasenia and Involuticeras in addition to some Rasenia and Rasenioides of the uppermost Cymodoce Zone, corresponding to the Askepta Subzone. The changes in composition of ammonite faunas and comparison with the coeval faunas of other areas of Europe give indications on the evolutionary development of some Ataxioceratidae and Aulacostephanidae at the end of Early Kimmeridgian. The development of the Crussoliceras, Garnierisphinctes and Progeronia, having possibly their roots in the Mediterranean areas, was strictly correlated with the overall transgression and oscillations of sea-level controlled possibly by climatic eccentricity cycles of the northern Tethyan shelf. This resulted also in the decline of older Ataxioceras and its nearby allies. The indigenous lineage of Aulacostephanidae includes the transition from Eurasenia to “Pararasenia”. The development from Rasenioides to Aulacostephanoides occurred mostly in the Subboreal areas – although some late representatives of Rasenioides like R. moeschi reached the area of study. The existence of an independent lineage leading from Rasenia involuta to heavily-ribbed Aulacostephanoides/Aulacostephanus is also suggested.

Modeling Climate and Tectonic Controls on Bias in Measured River Incision Rates

AbstractRates of land surface processes provide insights into climatic and tectonic influences on topography. Bedrock incision rates are estimated by dating perched landforms such as strath terraces, assuming a constant bedrock incision rate from terrace abandonment to the next terrace level or present river level. These estimates express biases from the stochastic nature of sediment and water discharge in controlling river incision as well as from using a mobile channel elevation as a reference frame, leading to different incision rates when calculated over different timeframes. We introduce a 1‐D model incorporating fluvial mechanics, tectonics, sediment, and climate variability to predict these biases and assess their sensitivity to climate and tectonics. Findings suggest biases intensify under highly variable climates and slow rock uplift, with climate periodicity being a primary control for our modeled scenarios. Our model provides a mechanism to improve river incision measurement uncertainty, impacting paleoclimate and tectonic geomorphology reconstructions.

Distinct seasonal changes and precession forcing of surface and subsurface temperatures in the mid-latitudinal North Atlantic during the onset of the Late Pliocene

Abstract. The Late Pliocene marks the intensification of Northern Hemisphere glaciation (iNHG), offering a unique opportunity to study climate evolution and ice-sheet-related feedback mechanisms. In this study, we present high-resolution Mg / Ca-based sea surface temperatures (SSTs) and subsurface temperatures (SubTs) derived from the foraminiferal species Globigerinoides ruber and Globorotalia hirsuta, respectively, at the Integrated Ocean Drilling Program (IODP) Expedition 306 Site U1313 in the mid-latitudinal North Atlantic during the early Late Pliocene, 3.65–3.37 million years ago (Ma). We find distinct differences between our new G. ruber Mg / Ca-based SST record and previously published alkenone-based SST records from the same location. These discrepancies in both absolute values and variations highlight distinctly different seasonal influences on the proxies. The G. ruber Mg / Ca-based SST data were primarily influenced by local summer insolation, showing a dominant precession cycle. Conversely, the variations in alkenone-based SST, dominated by the obliquity and lacking the precession cycle, are found to be more indicative of cold-season changes, despite previous interpretations of these records as reflecting annual mean temperatures. A simultaneous decline in Mg / Ca-based SST and SubT records from 3.65 to 3.5 Ma suggests a diminished poleward oceanic heat transport, implying a weakening of the North Atlantic Current (NAC). A comparison with Early Pleistocene G. ruber Mg / Ca-based SST records shows a shift in the dominant climatic cycle from precession to obliquity, alongside a marked increase in amplitude, indicating an enhanced influence of obliquity cycles correlated with the expansion of Northern Hemisphere ice sheets.

Predicting particle catchment areas of deep-ocean sediment traps using machine learning

Abstract. The ocean's biological carbon pump plays a major role in climate and biogeochemical cycles. Photosynthesis at the surface produces particles that are exported to the deep ocean by gravity. Sediment traps, which measure deep-carbon fluxes, help to quantify the carbon stored by this process. However, it is challenging to precisely identify the surface origin of particles trapped thousands of meters deep due to the influence of ocean circulation on the sinking path of carbon. In this study, we conducted a series of numerical Lagrangian experiments in the Porcupine Abyssal Plain region of the North Atlantic and developed a machine learning approach to predict the surface origin of particles trapped in a deep-ocean sediment trap. Our numerical experiments support the predictive performance of the machine learning approach, and surface conditions appear to provide valuable information for accurately predicting the source area, suggesting a potential application with satellite data. We also identify factors that potentially affect prediction efficiency, and we show that the best predictions are associated with low kinetic energy and the presence of mesoscale eddies above the trap. This new tool could provide a better link between satellite-derived sea surface observations and deep-ocean sediment trap measurements, ultimately improving our understanding of the biological-carbon-pump mechanism.