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1. Temperature and hydroclimate variability in mid-latitude arid Central Asia during the past 13,600 years: a multi-proxy investigation of Issyk-Kul (Kyrgyzstan)

   Castañeda, Isla S; Sun, Heeyeon; Salacup, Jeff (March 2024, Geological Society of America)

   Arid Central Asia (ACA) will be among the places on Earth most strongly affected by future changes in water supply. Rising temperatures and projected increases in inter-annual precipitation variability are expected to bring economic and environmental stress to a region characterized by high population growth. To date, mid-latitude continental locations have received relatively less research attention in comparison to the high-latitude or tropical locations and therefore represent a gap in our understanding of past climate dynamics. Issyk–Kul (Kyrgyzstan), one of the largest lakes in the world, is a unique site to examine mid-latitude climate variability in ACA due to its location in a mountainous region of the Asian continental interior that today is situated outside of the influence of the monsoons to the south or southeast. Here we use previously collected sediment cores from Issyk-Kul to generate new temperature, hydroclimate and vegetation records spanning from 13,600 to 2,000 years ago. We evaluate the use of several organic geochemical temperature proxies including lacustrine alkenones (UK′37 Index), TEX86, and proxies based on hydroxylated isoprenoid glycerol dialkyl glycerol tetraethers (OH-GDGTs). We also examine the distributions and isotopic composition of plant waxes (n-alkanes) to examine changes in the vegetation surrounding Issyk-Kul. Plant wax deuterium isotopes are used to investigate changes in precipitation amount and shifts in the dominant moisture source to ACA, while carbon isotopes are used to examine past shifts in C3 vs C4 vegetation. Our results thus far reveal that multiple proxies indicate a strong response of Issyk-Kul to climate variability during the Bølling–Allerød and Younger Dryas. Improved knowledge of past mid-latitude climate dynamics is needed to predict future conditions in ACA more accurately. 

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2. Climate and environmental reconstruction from Lake Junin sediments using terrestrial and aquatic biomarkers

   Lopera_Congote, L; Werne, J; Abbott, M; Woods, A; Rodbell, D (December 2023, American Geophysical Union)

   Climate variability at glacial-interglacial timescales is not well characterized in the tropical Andes, and paleoclimate records are lacking in this region. Lake Junin, in the Peruvian Andes, offers a unique and continuous paleoclimate archive that spans the last 700,000 years. Here, we use organic compounds to characterize climate variability in the region since the Last Glacial Maximum. First, we determined the preservation of organic matter in the sediments using the Carbon Preference Index (CPI), which suggests that n-alkanes have not been altered, and their H isotope composition can be used as paleo precipitation proxies. To reconstruct the isotopic composition of lake water, biomarkers from Eustigmatophyte algae (long chain diols) and diatoms (loliolide/isololiolide) have been identified. This will allow us to better understand aridity and evaporation as well as lake water inputs through time. Additionally, we will use the changes in n-alkane chain length distributions to constrain changes in terrestrial plants (long chain n-alkanes) and aquatic macrophytes (mid-chain n-alkanes) as a potential proxy for changes in lake level as a response to climate. Finally, temperature will be reconstructed using the distributions of br-GDGTs (branched glycerol dialkyl glycerol tetraethers). Using these set of proxies, we aim to characterize climate variability during the Holocene and the end of the LGM in the context of teleconnections between the South American Summer Monsoon and global climate patterns 

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3. RECONSTRUCTING CLIMATE AND ENVIRONMENTAL CHANGE FROM LAKE JUNIN SEDIMENTS USING TERRESTRIAL AND AQUATIC BIOMARKERS

   https://doi.org/10.1130/abs/2023AM-390283  

   Lopera_Congote, Laura; Woods, Arielle; Rodbell, Donald; Werne, Josef; Abbott, Mark (January 2023, Geologic Society of America)

   Paleoclimate records from the tropical Andes are scarce, and the variability of glacial-interglacial cycles is still not well characterized. Lake Junin, in the Peruvian Andes, offers a unique and continuous paleoclimate archive that spans the last 700,000 years. Here, we explore the potential of organic compounds in reconstructing Andean paleoclimate over the last 20,000 years. To address this, we first evaluated the preservation of organic matter in the lake’s sediments. The Carbon Preference Index (CPI) suggests that n-alkanes have not been altered, and their H isotope composition can be used as paleo precipitation proxies. Furthermore, biomarkers from Eustigmatophyte algae (long chain diols) and diatoms (loliolide/isololiolide) have been identified, and can be used to reconstruct the hydrogen isotopic composition of lake water. The contrast between rainfall and lake water will be a good tool for understanding lake water inputs through time as well as evaporation and aridity. Changes in n-alkane chain length will be used to identity the terrestrial plant (long chain n-alkanes) and aquatic macrophyte inputs (mid-chain n-alkanes), with potential implications for interpreting past lake level change as a function of climate. Finally, distributions of br-GDGTs (branched glycerol dialkyl glycerol tetraethers) will be used to reconstruct past temperature changes. With these proxies, we aim to characterize climate variability at the end of the Last Glacial Maximum (LGM) and the Holocene, with a focus on characterizing climate variability in the light of teleconnections between the South American Summer Monsoon and global climate patterns and their relationship with hydroclimate in the Amazon Basin. 

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4. Eastern Canadian Arctic Lake water Isotope Samples, 1992-2021

   https://doi.org/10.18739/A2S756N13  

   Gorbey, Devon; Thomas, Elizabeth K (April 2025, NSF Arctic Data Center)

   Lacustrine δ2H and δ18O isotope proxies are powerful tools for reconstructing past climate and precipitation changes in the Arctic. However, robust paleoclimate record interpretations depend on site-specific lake water isotope systematics, which are poorly described in the eastern Canadian Arctic due to insufficient modern lake water isotope data. We use modern lake water isotopes (δ18O and δ2H) collected between 1994-1997 and 2017–2021 from a transect of sites spanning a Québec-to-Ellesmere Island gradient to evaluate the effects of inflow seasonality and evaporative enrichment on the δ2H and δ18O composition of lake water. Four lakes near Iqaluit, Nunavut sampled biweekly through three ice-free seasons reflect mean annual precipitation isotopes with slight evaporative enrichment. In a 23° latitudinal transect of 181 lakes, through-flowing lake water δ2H and δ18O fall along local meteoric water lines. Despite variability within each region, we observe a latitudinal pattern: southern lakes reflect mean annual precipitation isotopes, whereas northern lakes reflect summer-biased precipitation isotopes. This pattern suggests that northern lakes are more fully flushed with summer precipitation, and we hypothesize that this occurs because the ratio of runoff to precipitation increases with latitude as vegetation cover decreases. Therefore, proxy records from through-flowing lakes in this region should reflect precipitation isotopes with minimal influence of evaporation, but vegetation changes in lake catchments across a latitudinal transect and through geologic time may influence the seasonality of lake water isotopic compositions. Thus, we recommend that future lake water isotope proxy records are considered in context with temperature and ecological proxy records. 

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5. Modern Eastern Canadian Arctic Lake Water Isotopes Exhibit Latitudinal Patterns in Inflow Seasonality and Minimal Evaporative Enrichment

   https://doi.org/10.1029/2021PA004384  

   Gorbey, D. B.; Thomas, E. K.; Sauer, P. E.; Raynolds, M. K.; Miller, G. H.; Corcoran, M. C.; Cowling, O. C.; Crump, S. E.; Lovell, K.; Raberg, J. H. (May 2022, Paleoceanography and Paleoclimatology)

   Abstract Lacustrine δ²H and δ¹⁸O isotope proxies are powerful tools for reconstructing past climate and precipitation changes in the Arctic. However, robust paleoclimate record interpretations depend on site‐specific lake water isotope systematics, which are poorly described in the eastern Canadian Arctic due to insufficient modern lake water isotope data. We use modern lake water isotopes (δ¹⁸O and δ²H) collected between 1994–1997 and 2017–2021 from a transect of sites spanning a Québec‐to‐Ellesmere Island gradient to evaluate the effects of inflow seasonality and evaporative enrichment on the δ²H and δ¹⁸O composition of lake water. Four lakes near Iqaluit, Nunavut sampled biweekly through three ice‐free seasons reflect mean annual precipitation isotopes with slight evaporative enrichment. In a 23° latitudinal transect of 181 lakes, through‐flowing lake water δ²H and δ¹⁸O fall along local meteoric water lines. Despite variability within each region, we observe a latitudinal pattern: southern lakes reflect mean annual precipitation isotopes, whereas northern lakes reflect summer‐biased precipitation isotopes. This pattern suggests that northern lakes are more fully flushed with summer precipitation, and we hypothesize that this occurs because the ratio of runoff to precipitation increases with latitude as vegetation cover decreases. Therefore, proxy records from through‐flowing lakes in this region should reflect precipitation isotopes with minimal influence of evaporation, but vegetation changes in lake catchments across a latitudinal transect and through geologic time may influence the seasonality of lake water isotopic compositions. Thus, we recommend that future lake water isotope proxy records are considered in context with temperature and ecological proxy records. 

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