Article
Multidisciplinary Sciences
M. Hoerhold, T. Muench, S. Weissbach, S. Kipfstuhl, J. Freitag, I. Sasgen, G. Lohmann, B. Vinther, T. Laepple
Summary: By redrilling ice cores, we reconstructed the temperatures in central and north Greenland from ad 1000 to 2011. Our findings show that the recent warming exceeds the historical temperature variability of the past millennium and is on average 1.5 +/- 0.4 degrees Celsius warmer than the twentieth century. This disproportionate warming is a result of natural variability and a long-term warming trend since ad 1800. The increased melting of Greenland's ice implies that anthropogenic influence has reached central and north Greenland, potentially accelerating overall mass loss.
Article
Meteorology & Atmospheric Sciences
Sieu-Cuong San, Yu-heng Tseng
Summary: Analysis of observational data shows the existence of a decadal subsurface spiciness mode in the North Pacific, involving ocean-atmosphere coupling. The Aleutian Low drives a pattern of positive and negative spiciness anomalies, which propagate equatorward along a deflected route. Equatorial sea surface temperature variability is strongly connected to extratropical spiciness anomalies, potentially leading to a decadal climate oscillation in the North Pacific. The dominant physical processes responsible for subsurface spiciness variability differ between the eastern midlatitude and subtropical North Pacific.
Article
Multidisciplinary Sciences
Taryn Lopez, Tobias P. Fischer, Terry Plank, Alberto Malinverno, Andrea L. Rizzo, Daniel J. Rasmussen, Elizabeth Cottrell, Cynthia Werner, Christoph Kern, Deborah Bergfeld, Tehnuka Ilanko, Janine L. Andrys, Katherine A. Kelley
Summary: Subduction plays a crucial role in transporting volatiles and creating a habitable Earth. This study uses isotopes to track the movement of carbon from subduction to volcanic outgassing along the Aleutian-Alaska Arc. The findings reveal significant variations in the isotopic composition of volcanic gases due to different recycling efficiencies and subduction characteristics. Fast and cool subduction releases a higher percentage of sediment-derived organic carbon to the atmosphere through degassing, while slow and warm subduction favors the recycling of altered oceanic crust carbon. These results challenge previous assumptions about carbon recycling in subduction zones and highlight the limitations of subducting organic carbon as an atmospheric carbon sink over long time scales.
Article
Multidisciplinary Sciences
Tianyi Huang, Simone B. Moos, Edward A. Boyle
Summary: Research findings in the eastern tropical North Pacific (ETNP) oxygen-deficient zone (ODZ) support theoretical and experimental studies predicting that lighter chromium is preferentially reduced in low-oxygen environments and residual dissolved chromium becomes heavier due to removal of particl-reactive Cr(III) on sinking particles. Microbial activity, dependent on sinking organic matter flux, may be the dominant mechanism for chromium transformation, rather than a simple inorganic chemical conversion.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2021)
Article
Geosciences, Multidisciplinary
T. Kukla, J. K. C. Rugenstein, D. E. Ibarra, M. J. Winnick, C. A. E. Stromberg, C. P. Chamberlain
Summary: The expansion of open habitats in the forests of west-central North America may be linked to a decrease in winter precipitation, rather than solely to changes in temperature or drier summers.
Article
Environmental Sciences
Colette L. Kelly, Nicole M. Travis, Pascale A. Baya, Karen L. Casciotti
Summary: By analyzing N2O concentration and isotopologues in the eastern tropical North Pacific (ETNP), it was found that high N2O levels observed at some stations may be due to unique conditions supporting high rates of N2O production. Additionally, the study revealed different sources and potential mechanisms contributing to N2O cycling in oxygen deficient zones.
GLOBAL BIOGEOCHEMICAL CYCLES
(2021)
Article
Multidisciplinary Sciences
Daniel B. Nelson, David Basler, Ansgar Kahmen
Summary: A framework using machine learning has been developed to calculate isotope time series at monthly resolution for precipitation, improving the accuracy of precipitation isotope model predictions.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2021)
Article
Meteorology & Atmospheric Sciences
Shangfeng Chen, Wen Chen, Renguang Wu, Bin Yu, Jun Ying
Summary: This study investigates the combined impacts of the winter North Pacific Oscillation (NPO) and early spring Aleutian Low intensity (ALI) on the subsequent El Nino-Southern Oscillation (ENSO). Opposite-sign NPO-ALI years lead to pronounced sea surface temperature (SST) anomalies in the central and eastern Pacific in the following winter, while same-sign NPO-ALI years result in small SST anomalies. The constructive superposition of anomalies induced by NPO and ALI enhances the subtropical North Pacific SST and precipitation anomalies in late spring, which affects the tropical western central Pacific and subsequent winter ENSO occurrence. The observed joint impacts of NPO and ALI on ENSO are reproduced in most CMIP6 models.
Article
Multidisciplinary Sciences
Joshua H. Miller, Daniel C. Fisher, Brooke E. Crowley, Ross Secord, Bledar A. Konomi
Summary: Under harsh Pleistocene climates, migration and seasonally patterned landscape use were critical for reproductive success of mastodons and other megafauna. Using isotopic analysis of a mastodon tusk, researchers found that the geographic ranges and mobility of the mastodon changed as it matured, with an increase in movement and the development of seasonal landscape use. The mastodon's death in northeast Indiana suggests that this area may have been important for mating and had regional significance for late Pleistocene mastodons.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Multidisciplinary Sciences
Akash Ganguly, Harsh Oza, Virendra Padhya, Amit Pandey, Swagatika Chakra, R. D. Deshpande
Summary: This article investigates the process of moisture recycling in precipitation in Northeast India and finds that locally recycled moisture is the primary source of annual rainfall. The study highlights the crucial role of wetlands and forest-cover in governing the regional hydro-meteorology and water availability.
SCIENTIFIC REPORTS
(2023)
Article
Meteorology & Atmospheric Sciences
Phoebe G. Aron, Christopher J. Poulsen, Richard P. Fiorella, Naomi E. Levin, Rene P. Acosta, Brian J. Yanites, Elizabeth J. Cassel
Summary: The study presents a three-year record of isotopic variability in central Andean precipitation, highlighting the negative correlation between elevation and delta O-18(p) values. Results show that seasonal variations in delta O-18(p) are influenced by upstream rainout and local convection. Both eastern- and western-derived air masses contribute to precipitation in southern Peru, and seasonal d-excess(p) cycles record moisture recycling and relative humidity at remote moisture sources.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2021)
Article
Geochemistry & Geophysics
Carl Tape, Anthony Lomax
Summary: This study revisits five earthquakes along the Aleutian-Alaska subduction plate boundary through probabilistic relocation of mainshocks and aftershocks. Significant differences in aftershock regions were found, shedding light on the relationship between seismic events and geological structures.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2022)
Article
Oceanography
Boda Li, Huanting Hu, William M. Berelson, Jess F. Adkins, Laurence Y. Yeung
Summary: The isotopic composition of dissolved oxygen can be used as a tracer for respiration and transport in the subsurface ocean. However, uncertainties in transport parameters and isotopic fractionation factors limit its effectiveness. In this study, new data and a model were used to investigate the oxygen isotopologues in the subsurface Pacific. The results suggest that the traditional isotopic fingerprints associated with oxygen consumption in the Pacific Ocean may need to be reexamined.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2022)
Article
Geochemistry & Geophysics
Ziv Sade, Shahar Hegyi, Maximilian Hansen, Denis Scholz, Itay Halevy
Summary: The curvature and slope of speleothem surfaces affect reaction rates by altering the thickness of the CaCO3-precipitating solution; thinner and faster-flowing solutions have opposite effects on the isotopic composition of carbonate minerals.
GEOCHIMICA ET COSMOCHIMICA ACTA
(2022)
Article
Geochemistry & Geophysics
Chuanming Liu, Shane Zhang, Anne F. F. Sheehan, Michael H. H. Ritzwoller
Summary: Comprehensive observations of surface wave anisotropy are conducted across Alaska and the Aleutian subduction zone to improve understanding of its tectonics, mantle dynamics, and earthquake risk. Using data from various sources, including earthquakes and ambient noise, researchers create tomographic maps that provide insights into the crustal and uppermost mantle structure of the region.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2022)
Article
Geosciences, Multidisciplinary
Sonja Felder, Takuya Sagawa, Mervyn Greaves, Melanie J. Leng, Ken Ikehara, Katsunori Kimoto, Siro Hasegawa, Thomas Wagner, Andrew C. G. Henderson
Summary: This study highlights the importance of understanding the palaeoceanography of the Japan Sea (JS) in analyzing the mid-Pleistocene transition (MPT). Through the analysis of sediments from IODP Site U1427, the study reveals that the δO-18 values in the JS vary during different stages of the MPT, indicating changes in the connection between the JS and adjacent ocean.
PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY
(2022)
Article
Geography, Physical
Ellie Broadman, Darrell S. Kaufman, R. Scott Anderson, Sonya Bogle, Matthew Ford, David Fortin, Andrew C. G. Henderson, Jack H. Lacey, Melanie J. Leng, Nicholas P. McKay, Samuel E. Munoz
Summary: This study investigates the postglacial history of the Kenai Peninsula in Alaska, focusing on the deglaciation, vegetation development, and past hydroclimate of the region. By analyzing proxy datasets from Hidden and Kelly lakes, the researchers were able to understand the retreat of glacier ice, the importance of groundwater in lake hydrology, and the influence of climate change on lake water isotopes. The findings highlight the usefulness of mass balance modeling and the potential confounding effects of groundwater on interpreting paleolimnologic oxygen isotope data.
QUATERNARY RESEARCH
(2022)
Article
Geosciences, Multidisciplinary
Edward E. Berg, Darrell S. Kaufman, R. Scott Anderson, Gregory C. Wiles, Thomas V. Lowell, Edward A. D. Mitchell, Feng Sheng Hu, Alan Werner
Summary: Recent decades of warming climate in southern Alaska have led to drying wetlands and falling lake levels. This study examines the historical fluctuations in lake levels, including high and low stands, and the impact of these changes on vegetation succession. The research also highlights how data from peat records in satellite fens can be used to reconstruct paleo-lake levels.
Article
Forestry
Raphael Neukom, Nathan Steiger, Darrell Kaufman, Martin Grosjean
Summary: Buntgen et al. present a new reconstruction of extra-tropical summer temperatures based on updated versions of a large number of tree-ring width chronologies. The comparison between their reconstruction and the PAGES 2k reconstructions is flawed due to the different reconstruction targets. The study highlights the importance of careful interpretation and reliable assessment of scientific results.
Article
Ecology
Agata Buchwal, M. Syndonia Bret-Harte, Hannah Bailey, Jeffrey M. Welker
Summary: Tundra shrubs' growth-ring widths are mainly influenced by June air temperature. Tissue-specific ring-width chronologies show the strongest correlations with air temperature during the period from June 8th to 20th. Structural equation modeling indicates that shrub growth is indirectly linked to regional Arctic and Pacific Decadal Oscillation climate indices.
Article
Geography, Physical
Teena Chauhan, Hans Petter Sejrup, Berit Oline Hjelstuen, Darrell S. Kaufman, Irfan Baig, Benedict T. I. Reinardy
Summary: This study contributes to the chronology of Early to Mid-Pleistocene sediments in the North Sea through the use of amino acid racemization and strontium isotope analyses. The combined use of these methods helps to refine the chronology of North Sea sediments, particularly those related to glacial processes.
QUATERNARY GEOCHRONOLOGY
(2022)
Article
Geography, Physical
Emily Millman, Lucy Wheeler, Katharina Billups, Darrell Kaufman, Kirsty E. H. Penkman
Summary: The study assessed the impact of two oxidative pre-treatments on amino acid concentration and D/L values in benthic and planktic foraminifers, finding that hydrogen peroxide pre-treatment is sufficient for AAR applications in foraminifera.
QUATERNARY GEOCHRONOLOGY
(2022)
Article
Fisheries
Derek W. Chamberlin, Virginia R. Shervette, Darrell S. Kaufman, Jordon E. Bright, William F. Patterson III
Summary: We investigated the relationship between aspartic acid D:l ratios and otolith-derived age estimates in Gulf of Mexico red snapper and Caribbean yellowtail snapper. The results suggest that amino acid racemization may be an effective tool for direct age estimation and age validation in fishes.
CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES
(2023)
Article
Geography, Physical
Lorna Louise Thurston, Erik Schiefer, Nicholas P. McKay, Darrell S. Kaufman
Summary: Lake-based studies provide valuable records of sediment yield over different time scales, which can enhance our understanding of sediment transfer in catchments and complement fluvial-based studies. This particular study used fallout radionuclides and sediment density patterns to estimate sediment accumulation rates in Lake Peters, Alaska, and compared the results with fluvial-based sediment delivery.
EARTH SURFACE PROCESSES AND LANDFORMS
(2023)
Article
Geography, Physical
Emmy A. A. Wrobleski, Ellie Broadman, A. L. Werner, Donald T. T. Rodbell, Darrell S. S. Kaufman
Summary: Major shifts in hydroclimate have been observed in south-central Alaska during the last deglacial period and the Holocene. Rare freshwater calcium carbonate deposits in lakes on the Kenai Peninsula can be used to reconstruct past hydroclimate changes, including the influence of groundwater inflow. The sediment sequence from groundwater-fed Kelly Lake was analyzed, revealing changes in isotopes and proxies that indicate shifts in hydroclimate and the influence of meteoric water and groundwater on the lake's sedimentation.
JOURNAL OF QUATERNARY SCIENCE
(2023)
Review
Multidisciplinary Sciences
Darrell S. Kaufman, Ellie Broadman
Summary: This review examines evidence from indicators and drivers of global change to evaluate whether anthropogenic global warming was preceded by a long-term warming trend or by global cooling. It finds that multimillennial-scale cooling before industrialization requires extra climate forcing and major climate feedbacks, while global warming challenges proxy-based reconstructions of past climate. The resolution of this conundrum has implications for understanding climate sensitivity and advancing our understanding of slow-moving climate variability.
Article
Geology
Matias Do Nascimento Ritter, Fernando Erthal, Matthew A. Kosnik, Michal Kowalewski, Joao Carlos Coimbra, Felipe Caron, Darrell S. Kaufman
Summary: Surficial shell accumulations from shallow marine settings are typically dominated by recent specimens and exhibit strongly right-skewed age-frequency distributions. This study examines age-frequency distributions from offshore settings in southern Brazil and finds that deeper water environments have slightly longer time averaging and symmetrical to left-skewed distributions dominated by specimens from the Last Glacial Maximum. The observed changes in age-frequency distributions along the onshore-offshore gradient likely reflect sea-level changes and corresponding variations in biological productivity.
Article
Environmental Sciences
J. E. Hatton, H. C. Ng, L. Meire, E. M. S. Woodward, M. J. Leng, C. D. Coath, A. Stuart-Lee, T. Wang, A. L. Annett, K. R. Hendry
Summary: Glaciers and ice sheets are rapidly warming due to climate change, and research suggests that glacial meltwaters provide important nutrients to downstream ecosystems. However, the fate of these nutrients in fjord environments is still uncertain. A study in southwest Greenland used concentration data and isotopic compositions to investigate silicon cycling in two contrasting fjords. The results suggest that glacially derived amorphous silica may play a role in modifying coastal waters within fjords.
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
(2023)
Article
Geosciences, Multidisciplinary
Christopher L. Hancock, Nicholas P. McKay, Michael P. Erb, Darrell S. Kaufman, Cody R. Routson, Ruza F. Ivanovic, Lauren J. Gregoire, Paul Valdes
Summary: Substantial changes in terrestrial hydroclimate during the Holocene are recorded in geological archives and simulated by computer models. Proxy records and model simulations indicate wetter-than-modern conditions during the early and mid-Holocene in Northern Hemisphere monsoon regions, while Southern Hemisphere monsoon regions were drier. The pattern of change is less certain in the midlatitudes, with proxy composites showing a wetting trend and simulations indicating relatively low magnitude of change.
PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY
(2023)
Article
Environmental Sciences
Leah P. Marshall, Darrell S. Kaufman, R. Scott Anderson, Nicholas P. McKay, Edward A. G. Schuur
Summary: This study investigates the accumulation and degradation of organic matter in permafrost over the Holocene. The results show that the preservation of organic matter in upland areas is influenced by hillslope geomorphic processes, cryoturbation, and climatic variations. The findings provide insights into the carbon dynamics in permafrost environments and their potential feedback on climate change.
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
(2023)
