About

Isla S. Castañeda is an Associate Professor with a joint appointment between the Department of Geosciences and Commonwealth Honors College at the University of Massachusetts Amherst. She holds a PhD from the University of Minnesota, obtained in 2007. Her main research interests involve utilizing organic geochemical and isotopic proxies to examine past climates and environments. Her work encompasses paleoclimate, paleoceanography, organic biogeochemistry, paleolimnology and limnology, stable isotope geochemistry, biogeochemical cycles, anthropogenic impacts on the environment, climate variability, and hominin evolution. She is also dedicated to developing and improving proxies for reconstructing past environmental conditions, contributing to the understanding of Earth's historical climate and environmental changes.

Research topics

• Geology
• Oceanography
• Paleontology
• Climatology
• Environmental science
• Soil science
• Earth science
• Geomorphology
• Chemistry
• Environmental chemistry
• Geography
• Engineering
• Physical geography

Selected publications

• Sharp turnovers in Pliocene hydroclimate variability in the Levantine Corridor, East Mediterranean

  2026-03-14

  articleOpen access

  The Pliocene (5.33-2.58 Ma) was comparatively warmer (+ 1.8-3.6 0C) than today and was characterized by elevated CO2 concentrations (400 ppmv). Thus, studying sedimentary sequences dated to this interval can serve as excellent analogues for comparing present conditions and provide tools for better modeling future trends. Yet, while most studies rely on marine archives, continental data dating back to this interval are scarce, particularly from boundary regions such as the Levantine Corridor. Sediments from the Erk-el-Ahmar Fm. (lacustrine, 3.9 Ma, Jordan Valley, Israel) and Bnot Lot member of the Sedom Fm. (lagoonal/lacustrine, 3.2-4.0 Ma, Dead Sea, Israel) highlight as one of the few well-exposed continental archives in the region that date back to that time.In the present contribution, we explore these two sedimentary archives and integrate in a multi-proxy fashion the physical, chemical, and biological properties of both outcrop and core sections (with the latter only retrieved from the Erk-el-Ahmar sequence). This study aims to reconstruct the paleoenvironmental setting and changing hydroclimatic conditions in the Levantine Corridor during these time intervals. By amalgamating the datasets, we show that while the region is characterized by increased warmth and augmentation in precipitation patterns, occasional cooling phases coupled with drought punctuate the Pliocene climatic history in the Levantine region.By synthesizing these diverse datasets into a consistent narrative, the project illuminates how precipitation, evaporation, and ecosystem processes interact under high-CO2 and high-temperature conditions. The outcomes provide the first robust benchmark of Pliocene hydroclimate evolution in the Levantine Corridor, offering critical insight into thresholds of lake resilience, feedback mechanisms, and the persistence of aquatic systems under sustained global warmth.

  PublisherDOI

• GaDGeT: An open-source R-workflow for fast and flexible GDGT index calculations

  SoftwareX · 2025-10-21

  articleOpen accessSenior author

  Understanding recent rapid environmental and climatic changes requires placing them in a long-term context derived from reconstructions from natural archives. Membrane lipids such as glycerol dialkyl glycerol tetraethers (GDGTs) are increasingly recognized as vital proxies for paleoenvironmental and climatic reconstructions. While this field is rapidly evolving, with frequent publications introducing new calibrations, indices, and ratios derived from a growing range of compounds, there remains a notable lack of automated workflows for subsequent data processing. In response, we introduce <em>GaDGeT</em>, a comprehensive software designed to streamline GDGT data analyses, including the calculation of concentrations, fractional abundances, and published GDGT-indices and ratios. Users input raw HPLC peak area datasets, and <em>GaDGeT</em> automatically processes and organizes the results into structured output directories as CSV files. Implemented in the open-source language R, it ensures reproducibility and transparency. <em>GaDGeT</em>’s platform-independent, modular design makes it accessible and adaptable for researchers of varying expertise levels and enables the software to evolve alongside advancements in the field. <em>GaDGeT</em> currently focuses on data processing and output generation rather than visualization. The software is continuously updated with additional calibrations, and its open framework allows users to extend the tool with their own functions and indices. We encourage users to consult the original publications for appropriate interpretation and to share their HPLC peak area files to promote transparency, support peer review, and enhance the scientific utility of GDGT datasets.

  PublisherDOI

• Holocene temperatures in southwestern Greenland controlled by topography, ice sheet proximity and oceanic conditions

  2025-07-31

  preprintOpen accessCorresponding

  Abstract. The Holocene thermal maximum (HTM), a period during the early and middle-Holocene when Greenland likely experienced warmer than pre-industrial climate, provides an ideal opportunity to test the sensitivity of the Greenland Ice Sheet to prolonged warmer-than-preindustrial conditions. However, available climate reconstructions from the region provide a controversial picture of the HTM—several reconstructions show an earlier HTM between the early- to middle-Holocene, while others show a delayed HTM between the middle to late Holocene. This discrepancy may be due to either the seasonal sensitivity of the proxies or to spatio-temporal climate variations. Here we generate five new Holocene branched glycerol dialkyl glycerol tetraether (brGDGT)-inferred ice-free season lake water temperature timeseries from lakes along a latitudinal transect in southwestern Greenland, yielding a total of seven Holocene brGDGT timeseries in this region. Lake model simulations suggest minimal intra-lake variation in both the seasonal production window of brGDGTs and the sensitivity of studied lakes to air temperature changes, suggesting regional climate as a primary mechanism influencing these timeseries. Five of the brGDGT timeseries suggest a thermal maximum between approx. 7 and 5 ka, following the peak summer solar insolation and in agreement with many regional reconstructions. A coastal site that is influenced by ocean-atmosphere heat exchange experienced a thermal maximum between approx. 5 to 3 ka, coinciding with nearby sea surface temperature reconstructions. A site far from both the coast and the Greenland Ice Sheet suggests peak warmth in the early Holocene. This suggests that local variations in temperature, influenced by the proximity to the ice sheet and ocean, caused the discrepancies in the Holocene temperature reconstructions in proxy timeseries in southwestern Greenland. Further investigations quantifying seasonal sensitivity and local effects (e.g., site-specific systematics, and proximity to ice sheet and ocean) may reveal similarities among proxy timeseries.

  PublisherOA PDFDOI

• Spatial-temporal Patterns of the Holocene Climate over Arid Central Asia: Insights from the Lacustrine Records of Eastern Lake Issyk-Kul

  Abstracts with programs - Geological Society of America · 2025-01-01

  article
  PublisherDOI

• chromatoPy: An Open‐Source Tool for Chromatographic Peak Deconvolution and Integration Applied to Glycerol Dialkyl Glycerol Tetraethers

  Paleoceanography and Paleoclimatology · 2025-12-01

  articleOpen access

  Abstract Glycerol dialkyl glycerol tetraethers (GDGTs) are valuable proxies for reconstructing past environmental conditions but sources of analytical uncertainty remain unresolved, as highlighted by a recent inter‐laboratory comparison project. Analytical uncertainties owe in part to subjective solutions to manual peak integration, including baseline corrections, peak deconvolution, and signal smoothing. Here, we present chromatoPy, an open‐source Python package implementing a multi‐Gaussian fitting algorithm that automatically models peak co‐elution while requiring user approval of the fitted results, thereby improving peak area integration accuracy, enhancing reproducibility, and reducing the time required for peak processing. We evaluate chromatoPy through inter‐user comparisons and against manual integration using a global data set of GDGTs from marine, lacustrine, and loess sediments, demonstrating high concordance in peak areas and fractional abundances for both branched and isoprenoid GDGTs. Subtle but systematic differences are observed primarily for branched GDGTs prone to co‐elution, which is consistent with the deconvolution approach employed. By reducing analyst subjectivity and providing uncertainty estimates, chromatoPy facilitates more comparable GDGT measurements across laboratories and data sets, thereby strengthening the foundations of GDGT‐based paleoclimate and biogeochemical reconstructions. The package significantly decreases processing time while providing quantitative uncertainty estimates using Monte Carlo error propagation, enabling rapid replicate analyses. chromatoPy thus offers a robust, user‐friendly tool that enhances reproducibility and will ultimately yield more reliable paleoclimate reconstructions.

  PublisherOA PDFDOI

• Early Holocene Atmospheric Circulation Changes Over Northern Europe Based on Isotopic and Biomarker Evidence From Kola Peninsula

  Paleoceanography and Paleoclimatology · 2025-03-01 · 3 citations

  articleOpen access

  Abstract Rapid Arctic warming this century will likely cause major water cycle and atmospheric circulation changes, including weakening mid‐latitude westerly winds and more persistent summer high pressures over Fennoscandia. These conditions can cause drought in northern Europe and extreme rainfall in the Mediterranean region. Uncertainties in the spatiotemporal patterns of these predictions can be partially addressed with records of past climate response to rapid change. The early Holocene collapse of the Northern Hemisphere ice sheets provides a natural experiment to evaluate the climate response to rapid changes in boundary conditions. We analyzed lipid biomarker distributions and hydrogen isotope (δ 2 H) values from Lake Imandra, Kola Peninsula, to infer Holocene summer temperature and summer precipitation δ 2 H values. Sensitivity tests of a lake model suggest summer precipitation δ 2 H values are the main mechanism influencing Lake Imandra δ 2 H values. Summer precipitation isotope values exhibited a nearly 20‰ 2 H‐depletion between 8.6 and 8.0 ka, with 2 H ‐enriched values before 8.6 ka and 2 H ‐depleted values 8.0 ka to present. Maximum warmth occurred from 8.5 to 7.0 ka. Climate model experiments suggest that the early Holocene Laurentide Ice Sheet collapse caused a westward shift of the Fennoscandian summer high‐pressure center. This caused a decrease in the proportion of local, 2 H‐enriched precipitation falling throughout Fennoscandia and an increase in far‐traveled, 2 H‐depleted precipitation from the mid‐latitudes, circulation that persisted throughout the Holocene. These results illustrate the sensitivity of climate in Fennoscandia and show that circulation regime shifts can occur in response to changes in boundary conditions far upwind.

  PublisherOA PDFDOI

• Hot-spring inputs and climate drive dynamic shifts in archaeal communities in Lake Magadi, Kenya Rift Valley

  Biogeosciences · 2025-08-14 · 2 citations

  articleOpen access

  Abstract. The methane index (MI) is an organic geochemical index that uses isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) as a proxy for methane cycling. Here, we report results from sediments in core MAG14-2A that span almost 500 ka in Lake Magadi, Kenya. The deposits show abrupt shifts between high and low MI values through calcareous, tuffaceous and zeolitic silts. The MI switches “off” (MI &lt; 0.2) and “on” (MI &gt; 0.5) through the core with bulk organic matter enriched in 13C during “MI-off” periods (∼ −18 ‰) in the upper part of the core, whereas 13C is lower (−22 ‰ to −25 ‰) in lower parts of the sedimentary sequence. Sediments deposited when the MI switches “on” showed δ13COM values as low as −89.4 ‰, but most values were within the range of −28 ‰ to −30 ‰, which is consistent with contributions from methanogens rather than methanotrophs. Thus, the likely source of these high MI values in Lake Magadi is methanogenic archaea. Our results show that hydrothermal inputs of bicarbonate-rich waters into Lake Magadi combined with further evaporative concentration cause a shift in the dominant archaeal communities, alternating between two stable states.

  PublisherOA PDFDOI

• Supplementary material to "Holocene temperatures in southwestern Greenland controlled by topography, ice sheet proximity and oceanic conditions"

  2025-07-31

  preprintOpen access
  PublisherDOI

• Branched GMGTs Capture Mid- to Late-Pleistocene Temperature Change in the Lake Malawi Drill Core

  Abstracts with programs - Geological Society of America · 2025-01-01

  articleSenior author
  PublisherDOI

• 17,000 YEARS OF LEAF WAX N-ALKANOIC ACID DISTRIBUTIONS AND STABLE HYDROGEN ISOTOPES AT LAKE EMANDA (EASTERN SIBERIAN HIGHLANDS)

  Abstracts with programs - Geological Society of America · 2025-01-01

  article
  PublisherDOI

Frequent coauthors

• Stefan Schouten

  Utrecht University

  70 shared

• Jaap S. Sinninghe Damsté

  Royal Netherlands Institute for Sea Research

  52 shared

• Jeffrey M. Salacup

  University of Massachusetts Amherst

  46 shared

• David De Vleeschouwer

  University of Münster

  46 shared

• Gerald Auer

  University of Graz

  43 shared

• Beth A. Christensen

  Rowan University

  43 shared

• Jorijntje Henderiks

  43 shared

• Julie Brigham‐Grette

  41 shared

Labs

• Department of Earth, Geographic, and Climate SciencesPI