Precipitation is the largest freshwater flux that enables life on land. However, climate change is projected to increase the frequency and intensity of extreme precipitation events, which often culminate in droughts and floods with devastating impacts on humanity and the environment. To better understand the dynamics of precipitation in a changing climate, recent studies aimed to unravel the interaction between evaporation and precipitation. To do so, atmospheric moisture tracking models have often been employed to determine the origins of precipitation and establish source–sink relationships. However, due to the lack of sufficient and accurate observations to evaluate these models, their estimated source regions of precipitation often remain unvalidated. Nonetheless, the number of studies using such models is increasing, even if only a few have addressed associated uncertainties and even fewer employed multiple models.

Here, we advocate the need for moisture tracking model intercomparisons to advance this field of study. Therefore, we provide an overview of models and methods that track moisture through the atmosphere and determine the origins of precipitation. Further, we highlight conceptual differences between these models and demystify assumptions hidden in the analysis of source regions. Using selected case studies, we illustrate the uncertainty associated with the origin of precipitation and highlight the need for coordinated model comparisons using multiple models. Finally, we present our plans to engage with the entire moisture tracking community to collaborate on prospective model intercomparison studies. Through these efforts, we wish to raise awareness about the uncertainties inherent in moisture tracking approaches and achieve a better understanding of the drivers of precipitation in a changing climate.

How to cite: Keune, J., Benedict, I., Weijenborg, C., Schumacher, D. L., Koppa, A., and Miralles, D. G.: Estimating the origin of precipitation: uncertainties associated with atmospheric moisture tracking models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3606, https://doi.org/10.5194/egusphere-egu23-3606, 2023.

Moisture transport within atmospheric rivers (ARs) is a complex combination of processes, with convergence of moisture with different origin and its changes over the life cycle of an AR. The water vapour budget in an AR enables us to understand the contribution of the different moisture sources and sinks (horizontal transport, local evaporation and precipitation). Here, we focus on how these contributed to the formation and development of the exceptional AR associated with storm Denis that occurred in February 2020 leading to the 3rd highest UK average daily rainfall since 1891¹.

We use the WRF-ARW numerical limited-area atmospheric model to simulate the life-cycle of the AR in the North Atlantic basin. We use a resolution of 0.09º, and a domain covering both the AR’s formation region close to the Gulf of Mexico to the landfall region in northern and central Europe. Moreover, we performed two sets of sensitivity experiments by reducing the tropical moisture transport, and the sensible heat flux in specific areas of the oceanic basin to assess how these two main components affect the water vapour balance within the AR. We also defined a threshold to map the AR and used a centroid-based method to track its path in order to measure the shift of its location and intensity through time in the different experiments.  

Our findings reveal significant relationships between the reduction of tropical moisture and a change of the location of the AR. The analysis also detected regional and temporal changes in the water vapour budget due to the perturbations done in the sensitivity experiments. In addition, relative importance of moisture sources are assessed. As such, our work provides a new case study to unravel feedback processes and the influence to the AR characteristics when perturbing the water vapour balance.

How to cite: Lopez-Marti, F., Wu, L., Messori, G., and Rutgersson, A.: Sources of Moisture to Extreme Atmospheric Rivers: a storm Denis case study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1553, https://doi.org/10.5194/egusphere-egu23-1553, 2023.

Atmospheric rivers (ARs) are filaments of extensive water vapor transport in the lower troposphere. They play a crucial role in the global water cycle and are a main source of fresh water for the mid-latitudes. However, very intense and persistent ARs are important triggers of heavy rainfall events and have been associated with natural and economical damage. Further motivated by their high impacts, in the last decade occurrences of ARs have been intensively studied, detection algorithms have been developed, and multiple AR catalogs have been produced. As a common approach, the detection of ARs is based on localizing anomalous atmospheric transport of moisture, usually by setting an absolute threshold on vertically integrated vapor transport (IVT) and/or vertically integrated water vapor (IWV) fields. Behind this methodology, there is the implicit assumption of stationary atmospheric moisture levels, which is not necessarily true for long periods under the context of a warming atmosphere. Also, these thresholds have proven to vary regionally which results in often excluded low-level ARs.

Here, we introduce AR-tracks, a global, high-resolution catalog of atmospheric rivers that we have developed based on the Image-Processing-based Atmospheric River Tracking (IPART) algorithm, using IVT estimates of the ERA5 reanalysis data set. As opposed to conventional detection methods, IPART calculates anomalies of the IVT field at the synoptical spatiotemporal scale of ARs and is, therefore, free from magnitude thresholds and stationarity assumptions. The resulting catalog displays a list of AR events, with a spatial resolution of 0.75° x 0.75° and a temporal resolution of 6 hours, covering the period between 1979 and 2019. For each AR, we provide common parameters such as the time and location of the landfall, the respective IVT value, the area, the width, and the length of the AR. Moreover, we also track the contour and the axis of each AR, the position of the centroid, and the proportion of the AR that is located over ocean and land, and over the different continents.

To show the potential of this new catalog, we study the spatiotemporal variability of European ARs between 1979-2019, analyzing the robustness of our results for distinct parameter choices in the definition of AR-tracks. We also use a novel power spectral measure to identify periodic cycles in the occurrence of European ARs, revealing spatially heterogeneous seasonal and multi-annual periodicities. Finally, we discuss the role of land-falling ARs as a trigger of heavy precipitation events in the regional domain.

With the extensive data we provide in this new catalog, we aim at contributing to the further understanding of the role of ARs in global climate dynamics, as long-lived ARs having cross-continent tracks can be reliably traced through their tropical/subtropical origins to high-latitude landfall, and novel topics such as inland penetration of ARs can be studied.

How to cite: Vallejo-Bernal, S. M., Braun, T., Marwan, N., and Kurths, J.: AR-tracks: A new comprehensive global catalog of atmospheric rivers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9251, https://doi.org/10.5194/egusphere-egu23-9251, 2023.

Global warming has resulted in frequent occurrences of hydrological extremes, especially floods, across the globe. Flooding may lead to significant loss of life and economic damage. The increase in these flood events is due to the short intense rainfall events. Finding the geographical sources of the moisture that causes these short intense rainfall events is an important step toward predicting extreme events. The present research intends to investigate moisture sources for precipitation events over the flood-prone Indian Basin. Using the lagrangian moisture diagnostic, the research will look at moisture sources below the boundary layer as well as variations above the boundary layer from 1980 to 2018 during the Indian Summer Monsoon season. The study will also look at how the contribution from various sources varies over the course of the Indian Summer Monsoon Rainfall season. This work will enhance our understanding of the hydrological cycle and assist with a variety of related issues, including water resource planning, weather forecasting, land and water management, and more.

How to cite: Choudhary, R., Dhanya, C. T., and Gosain, A. K.: Unravelling the sources of moisture for precipitation events in a flood-prone Indian basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9436, https://doi.org/10.5194/egusphere-egu23-9436, 2023.

How to cite: Muller, C., Roca, R., and De Meyer, V.: Precipitating Fraction, Not Intensity, Explains Extreme Coarse-Grained Precipitation Clausius-Clapeyron Scaling With Sea Surface Temperature Over Tropical Oceans, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16367, https://doi.org/10.5194/egusphere-egu23-16367, 2023.

Understanding rainfall and its extremes is essential for quantifying weather and climate related risks, and the management of water resources. However, climate projections of rainfall have large uncertainties because of differing sensitivities to changes in dynamic, thermodynamic and microphysical factors. Emergent statistical constraints derived from observations and high resolution simulations can be used to reduce these uncertainties, but must be based on process understanding to be robust.

Our recent work shows that clustering rainfall data into regions of similar wet day frequency, regardless of geographical separation, uncovers a strong correlation between wet day occurrence and daily rainfall accumulation distributions. This relationship is robust across a range of observational datasets with differing spatial resolutions.

We hypothesise that this relationship shows that the presence or absence of precipitation generating weather systems (atmospheric rivers, cyclones, fronts and mesoscale convective storms) rather than their individual intensities is critical for daily rainfall totals. In this presentation, we will first examine whether the probability of specific dynamic, thermodynamic and microphysical states drives wet day occurrence. We will also use feature analysis and tracking schemes to identify how the distribution of each of these dynamic, thermodynamic and microphysical states varies for each precipitation generating weather system. This potentially allows a quantification of the importance of different precipitation generating systems for different wet day occurrences and how each contributes to daily accumulation distributions. This expands on previous work which has shown that atmospheric rivers, cyclones, fronts and mesoscale convective storms have varying relationships to rainfall and their extremes. In particular, it allows us to identify their relative importance and explains their relative efficacy for precipitation generation.

How to cite: McDonald, A.: Understanding the relative importance of different precipitation generating weather systems and quantifying their efficiencies, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10922, https://doi.org/10.5194/egusphere-egu23-10922, 2023.

Among all greenhouse gases (GHGs), atmospheric water vapour is the most abundant and has huge influence on the Earth’s radiation budget, and plays decisive role in regional weather processes. Unlike other GHGs, which are controlled by emissions, atmospheric water vapour is influenced by the surface temperature. Here, we examine the long-term changes in global and regional water vapour using satellite and reanalysis datasets. The annual mean water vapour shows very high values in tropics and low values in the polar and high terrain regions. A clear seasonal cycle is observed in the water vapour, with high values in summer (25–65 kg/m²) and small values in winter (5–20 kg/m²), except in the tropics. The high values in summer is maily due to the enhanced evapotranpiration driven by surface air temperature, and water vapour transport by winds. There is a significant rise in annual mean global water vapour, driven by global warming, about 0.025–0.1 kg/m²/yr for the period 1980–2020. Furthermore, higher positive trends in water vapour is also observed in arid regions (Sahara, Arabian and Thar desert), Indian subcontinent and the Arctic. The higher values of water vapour trends in the Arctic is due to the significant rise in temperature there. Similarly, the increase in water vapour in desert regions is due to water vapour transport from nearby oceans. The associated radiative effects on short-wave at the surface varies from -5 to -70 W/m² over the tropical radiosonde stations, and the smallest of about -5– -10 W/m² in the polar regions. This study, therefore,  shows that there is significant rise in water vapour across the latitudes, which could further increase the global temperature through positive feedback mechamism and thus, change global and regional climate.

Keywords: Water Vapour, Evapotranspiration, Global Warming, Arctic, Desert; Radiative Effects

How to cite: Patel, V. K. and Kuttippurath, J.: Global warming triggers the notable rise in water vapour: implications for global climate change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3551, https://doi.org/10.5194/egusphere-egu23-3551, 2023.

Abstract

Summer (June to August) precipitation over the Three-River Headwaters’ (TRH) region has experienced a significant dry-to-wet transition during 1979-2020. The transition could have been caused by changed atmospheric circulations, which was modulated by oceanic forcings. This study intends to improve our understanding of the summer precipitation variability over the TRH region under the influence of oceanic modes. The combined effect of three interdecadal oceanic modes [Pacific decadal oscillation (PDO), Atlantic multidecadal oscillation (AMO), and Indian Ocean Basin mode (IOBM)] on the interdecadal dry-to-wet transition was examined, using composite analysis on HadISST and the fifth generation ECMWF reanalysis (ERA5) datasets. The results show that in positive AMO and negative PDO phases, a zonally oriented teleconnection wave train is generated across the Eurasian mid-to-high latitudes, propagating from the North Atlantic to northern East Asia along the westerly jet. This results in a weakened and northward-shifted westerly jet. Furthermore, the enhanced and northward-shifted Western Pacific Subtropical High (WPSH) brings water vapor from the Pacific Ocean, and cyclonic circulation over the Arabian Sea increases the amount of water vapor entering the TRH region. In positive IBOM phases, the warm Indian Ocean induces an anomalous anticyclone over the Bay of Bengal, and anomalous southwesterly delivers abundant water vapor from the Indian Ocean to the TRH region, which overlaps with the vapor transport caused by a positive AMO and PDO. As the Atlantic and Northern Pacific Oceans warm, the enhanced Walker circulation suppresses the ascending motion in the central Pacific and enhances the equatorial easterly, which in turn strengthens the anomalous anticyclone over the Bay of Bengal. As a result, the summer precipitation over the TRH is further increased. The analysis shows that the combined effect of the three oceanic modes played an important role in the dry-to-wet transition.

How to cite: Liu, X., Yang, M., Chen, D., and Wang, H.: The dry-to-wet transition of summer precipitation over the Three-River Headwaters’ region: the role played by three interdecadal oceanic modes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3316, https://doi.org/10.5194/egusphere-egu23-3316, 2023.

In 2019, a record-breaking drought happened in the middle reaches of the Lancang-Mekong River Basin (M-LMRB), which brings about 650 million dollars in economic loss and affected 17 million residences. As climate change evolute, the LMRB is suffering from increasingly frequent and intensive drought with the mechanisms remaining unclear. This study analyzed the water vapor circulation of the drought event in 2019 based on the land-atmosphere water budget and backward trajectory model. Results show that the precipitation of the M-LMRB from May to October 2019 was 71.9% of the climatological mean (1959-2021). The moisture transported from the Indian Ocean, Bay of Bengal, and Pacific Ocean, which are the main moisture sources of the region, was found to decrease through the backward trajectory model. From the comparison of the atmospheric circulation of 2019 and the climatology, the anomalous anticyclone in the BOB, the anomalous westerlies in the Northeast Indian Ocean, and the anomalous cyclone in the Western Pacific Ocean were found to facilitate the stronger export of water vapor jointly. Therefore, the dynamic processes should be more responsible for the extreme drought event of the LMRB in 2019 than the thermodynamics processes. The findings of this study provide new insights into understanding mechanisms of climate change affecting extreme drought events through the atmospheric circulation and are helpful to the risk management of droughts under climate change.

How to cite: Gong, G., Zhang, S., and Liu, J.: The anomalous water vapor circulation in an extreme drought event in the middle reaches of the Lancang-Mekong River Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6262, https://doi.org/10.5194/egusphere-egu23-6262, 2023.

Isotope ratios in water vapor record evaporation (E) and precipitation (P) along moisture transport paths. At low latitudes, the path-integrated E-P signal is dominated by local E and P, providing an indicator of tropical water balance. In contrast, at high latitudes, E and P patterns upstream overwhelm local signals, reflecting the dependence on remote moisture sources. This dependence defines the length scales of moisture transport.

In the zonal mean, moisture transport length scales can be represented visually in two dimensions by moist isentropic surfaces, along which poleward moisture transport occurs. These surfaces explain why Rayleigh distillation reasonably approximates meridional variations in high-latitude isotope ratios while also providing a physical basis for why polar isotope-temperature relationships are distinct in space and time. 

Isotopically enabled GCM simulations and short-duration Antarctic ground-based observations both lend support for the isentropic view of moisture transport. They also suggest that this framework provides a simple means to predict changes in length scale in a warmer climate, assuming zonal-mean humidity changes follow Clausius-Clapeyron scaling. However, isotopic observations with the vertical resolution and temporal coverage necessary to easily evaluate recent and expected future variations in moist isentropic transport are lacking.

Here, we consider two possible alternative methods for testing predictions about long-term moisture length-scale changes with isotopic observations. Using the two-decade-long AIRS satellite record, we consider the extent to which mid-free tropospheric hydrogen isotope ratios, normalized by humidity, can provide a measure of length scale in a total-column sense. Second, we ask to what extent moist isentropic transport is set by episodic events, such as warm conveyor belts, that can be observed by infrequent but high-vertical-resolution airborne isotopic measurements. We discuss the implications of enhanced transport efficiency, expected in a warmer future, for increasing length scales and strengthening hydrological dependencies between remote locations.

How to cite: Bailey, A., Singh, H., Nusbaumer, J., Casado, M., Cauquoin, A., Heyblom, K., and Worden, J.: Changing length scales of moisture transport — their isotopic imprint and implications for remote moisture dependence, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4543, https://doi.org/10.5194/egusphere-egu23-4543, 2023.

Validation of gas exchange fluxes in models has been challenging due to the lack of ecosystem scale exchange fluxes partitioned into soil, plant and atmospheric components. One promising method to partition turbulent fluxes uses the exchange process dependent fractionation of molecules like CO2 and H2O. When applying this method to short spatiotemporal scales, an isotope flux (δ-flux) needs to be resolved. Few have attempted to measure this δ-flux as the required instrumentation only became available in recent years. In our presentation we will discuss observations made during the LIAISE 2021 field campaign using an EC system, Picarro L-2130i H2O isotope analyser, and Aerodyne TILDAS-CS CO2 isotope analyser. This campaign took place in the summer of 2021 in the heavily irrigated Ebro River basin near Lleida, Spain embedded in a semi-arid region.

We will present procedures to estimate and scrutinize the central δ-flux variable. To this end we calculated co-spectra of the relevant signals and compared their frequency dependent contributions. One relevant finding is that mole fractions and isotope ratios measured with the same instrument can be offset in time by more than a minute, thereby impacting the resulting δ-fluxes. Additionally, we found asymmetric signal loss between net ecosystem fluxes and δ-fluxes. We will show that such effects impact flux partitioning severely and indicate how they can be tackled using physically sound corrections. Only when such corrections and verifications are made, ecosystem flux partitioning can be applied to validate conceptual land-atmosphere exchange models. Such models will calculate the diurnal variability of CO2 and H2O isotopologue concentrations, and link local to regional scales, all with the purpose of better constraining current and future exchange fluxes. 

How to cite: Moonen, R., Adnew, G., Hartogensis, O., Vila-Guerau de Arellano, J., and Röckmann, T.: Investigating diurnal ecosystem scale H2O and CO2 isotope fluxes in an irrigated semi-arid environment during the LIAISE 2021 field campaign, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13348, https://doi.org/10.5194/egusphere-egu23-13348, 2023.

Changes in ice sheet size and configuration impact global moisture and heat transport, but few proxy records examine these impacts. High-latitude precipitation-isotope proxy records are often interpreted to reflect temperature change, but can also reflect changes in moisture source. We present independent sub-centennial-scale records of summer temperature and summer precipitation δ²H from the same lake sediment archive on northeastern Baffin Island. We also examine published TraCE-21k transient model simulation results. These records span from 12 to 7 ka, when the Laurentide Ice Sheet underwent major retreat. The correlation structure between summer temperature and precipitation δ²H on northeastern Baffin Island changed from negative to positive around 10 ka. We interpret this change in correlation structure to indicate a shift in moisture sources to northeastern Baffin Island. TraCE-21k results suggest that moisture sources in this region are controlled by the relative strength of the high pressure systems and associated anticyclonic circulation over the Greenland and Laurentide ice sheets. We therefore interpret the proxy records as follows: when the Laurentide high dominated prior to 10 ka, northerly winds brought cold, dry Arctic air to the region, allowing ²H-enriched local sea breezes to provide most of the moisture to Baffin Island. After 10 ka, the Greenland high dominated, causing southerly flow to carry warm, moist, ²H-depleted air masses to northeastern Baffin Island. Regional centennial-scale cooling events caused by periodic freshwater inputs to the Labrador Sea throughout the Early Holocene were also associated with intervals of ²H-enriched summer precipitation. This study provides evidence that atmospheric circulation was influenced by the waning continental ice sheets. Similar ice-sheet influences are critical to consider when interpreting precipitation isotope proxy records spanning periods of dramatic ice-sheet change. These results demonstrate that precipitation isotopes can reflect changes in atmospheric circulation in the geologic record.

How to cite: Thomas, E., Cluett, A., Erb, M., McKay, N., Briner, J., Castañeda, I., Corcoran, M., Cowling, O., Gorbey, D., Lindberg, K., and Salacup, J.: Early Holocene Laurentide Ice Sheet retreat influenced summer atmospheric circulation in the North American Arctic: Evidence from precipitation isotope and temperature proxy records and a climate model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12634, https://doi.org/10.5194/egusphere-egu23-12634, 2023.

Stable isotope ratios of oxygen (δ¹⁸O_p) and hydrogen (δD_p) record information about the hydrological cycle. These signals are preserved in natural archives, such as speleothems, stalagmites, ice cores, and pedogenic carbonates. Recent studies have used these proxy records of water isotopologues to reconstruct the evolution of paleoclimates, paleoenvironments, and even tectonic-related changes in surface elevations. However, such reconstructions require information about the atmospheric dynamics that drive the spatial variability of isotopic ratios. δ¹⁸O_p and δD_p are known to reflect the history of air masses, surface temperature, precipitation, and synoptic-scale atmospheric teleconnection patterns like the North Atlantic Oscillation (NAO). Climate-driven variations in these data can complicate their interpretation of geologic processes. The NAO is the predominant mode of inter-annual and seasonal variability that controls the weather and climate system across the North Atlantic region and continental Europe. The influence of the NAO on the Global Network of Isotopes in Precipitation (GNIP) stations records of δ¹⁸O_p and δD_p across Europe was previously studied in the winter season when the NAO impacts are well defined. 

Here we build upon previous work by (1) investigating the present-day NAO-δ¹⁸O_p and -δD_p relationships and their associated atmospheric dynamics and causal mechanism in all seasons, and (2) studying the NAO’s influence on the δ¹⁸O and δD in precipitation in the late Cenozoic. We focus on the latter since many δ¹⁸O_p- and δD_p-based studies tackle problems in the Late Cenozoic. In addition, important characteristics of such pressure systems (e.g., the location of the centers of maximum and minimum pressures and axis of polarity) may change over longer (centennial to geological) time scales in response to different forcings such as atmospheric CO₂, paleogeography, orbital changes, and land-surface cover. To achieve the study’s first goal, we explore the NAO-δ¹⁸O_p and -δD_p link by tracking the NAO in the ERA5 reanalysis data and relating its variability with GNIP observational data across Europe. For the second goal, we use the isotope-enabled Atmospheric General Circulation Model ECHAM5-wiso to perform time-specific, high spatial resolution (paleo)climate simulations with (paleo)environmental conditions of the middle Miocene (~14 Ma), the mid-Pliocene (~3 Ma), the Last Glacial Maximum (~21 ka), the mid-Holocene (~6.5 ka), the pre-industrial (the reference year 1850) and the present-day (1979-2000). We then transfer the analyses from the first step to our paleoclimate simulation output, using the present-day simulation for calibration. Our results help reconstruct the NAO from proxy archives and provide context for more refined interpretations of the isotopic ratios of rainwater in proxy archives.

How to cite: Boateng, D., G. Mutz, S., and A. Ehlers, T.: The influence of North Atlantic Oscillation on oxygen and hydrogen stable isotopes in precipitation of the Late Cenozoic: implications on paleoenvironment reconstructions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1752, https://doi.org/10.5194/egusphere-egu23-1752, 2023.

A continuous bi-weekly water isotope analysis (δ¹⁸O, δD, and d-excess) was done since 2015 from a subtropical reservoir (Feitsui Reservoir) in northern Taiwan. The Feitsui reservoir is an important national freshwater system, as it provides water for the large urban population of Taipei. The isotopic data reveals a multiyear pattern and it closely follows the rainfall isotopic composition. We made a simple mass-balance model using the rainfall isotopic composition, inflow and outflow volumes, and meteorological parameters that fit well (R² = 0.55; p-value < 0.05) with the observed isotopic composition of the reservoir. Based on this model, we estimated reservoir isotopic composition for the previous 20 years (2001-2021). The model also well reproduced a few years of historical data reported in the literature. In the model, we noted two conspicuous patterns: (1) multiyear cyclicity in δ¹⁸O and d-excess, and (2) a long-term enriching trend in δ¹⁸O. These patterns were not so obvious in rainfall because of the strong seasonality, which gets diluted in the reservoir because of the longer water residence time (~6 months). However, these patterns became visible in rainfall isotopes after removing the seasonal cycles. The observed multiyear patterns do not resemble with the known multiyear global processes, such as ENSO, PDO, and the East Asian Monsoon Index. However, the role of these global processes cannot be ruled out completely. We believe that because of the unique geographical location of the island, multiple moisture sources (South China Sea and central/northern China), dual monsoons (summer and winter monsoons), and complex hydrometeorological processes, the signals of these multiyear global processes get modulated and modified. The long-term enriching trend in δ¹⁸O seems to be a consequence of climate change. The enriching trend is more vivid during the winters than summers. This indicates the possible role of global warming and the expansion of the tropics because the Tropics of Cancer passes through central Taiwan. There also remains a significant knowledge gap in understanding the role of winter monsoons in East Asia. This study highlights the importance and the need for rigorous climatic research in Taiwan because of its unique location which makes it highly sensitive to climate change. This study may also have implications for paleoclimatic studies because it highlights the complex hydrometeorology of the region.

How to cite: Oza, H., Wang, C.-H., and Liang, M.-C.: Enigmatic Multi-Year Oscillations in Water Isotopic Composition of East Asia: Insights from a Subtropical Reservoir, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13842, https://doi.org/10.5194/egusphere-egu23-13842, 2023.

Stable water isotope signals in inland Antarctic ice cores have provided wealth of information about past climates. This study investigated atmospheric circulation processes that influence precipitation isotopes in inland Antarctica associated with atmospheric circulations in the southern mid-latitudes during the Last Glacial Maximum (LGM, ~21 000 year ago). A couple of probable climates during this climate period were simulated using the isotope-enabled atmospheric general circulation model MIROC5-iso. Our results showed a steepened meridional sea surface temperature gradient in the southern mid-latitudes associated with a strengthening of the southern westerlies. This change in the atmospheric circulation enhanced the intrusion of warm and humid air from low latitudes that contributes to precipitation events, inducing heavy water isotope precipitation inland East Antarctica. Our results suggest that past southern westerlies can be constrained using water isotopic signals in Antarctic ice cores.

How to cite: Kino, K., Cauquoin, A., Okazaki, A., Oki, T., and Yoshimura, K.: Heavy Water Isotope Precipitation in Inland East Antarctica Accompanied by Strong Southern Westerly Winds during the Last Glacial Maximum, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4775, https://doi.org/10.5194/egusphere-egu23-4775, 2023.