Coming Soon - In review
Spoth-Ascencao, M.M., Hall, B.L., Gill. J, Diefendorf, A.F., Lowell, T.V., Russell, J., Corcoran, M.C. and Brickle, P., in review. A 13,000-year record of the Southern Hemisphere Westerlies inferred from pollen and plant wax isotopes from the South Atlantic. Paleoceanography Paleoclimatology
Spoth-Ascencao, M.M., Diefendorf, A., Gill, J., Hall, B., Putnam, A., Corcoran, M. and Mensing, S., in review. Tracking Holocene Hydrology in High Sierra Nevada, California. Quaternary Science Reviews
Hall, B., Putnam, A., Lowell, A., Denton, G., Russell, J., Soteres, R., Spoth-Ascencao, M.M., Miles, M., Thomas, S., Moreno, P., Schaefer, J., and Schwartz, R., 2026. Rapid thinning of the Cordillera Darwin icefield at the onset of Termination I. Geology
"Despite more than a century of research, the cause of the last ice-age termination remains uncertain. Here, we reconstruct the thinning history of the Cordillera Darwin Icefield, southernmost Chile, to track relative summer temperature change at the end of the ice age and to explore potential drivers of the warming. Eighteen 10Be exposure ages of erratics perched on glacially scoured bedrock indicate rapid surface lowering of at least 500 m elevation in the heart of the former icefield at some time between 18.8 and 16.9 ka at the onset of the termination. We infer that this drop in ice level reflects an increase in summer temperatures, which led to extensive glacier melt. We attribute the underlying cause to a poleward shift of the southern westerly winds, which placed the Cordillera Darwin Icefield in warmer air masses with temperatures incompatible with its LGM extent."
Azevedo-Schmidt, L., Landrum, M., Spoth, M.M., Brocchini N., Hamley K., Mereghetti, A., Tirrell, A.J., and Gill, J.L., 2025. Advancing terrestrial ecology by improving cross-temporal research and collaboration. Bioscience.
"Ecology spans spatial and temporal scales and is inclusive of the history of life on Earth. However, research that occurs at millennial timescales or longer has historically been defined as paleoecology and has not always been well integrated with modern (neo-) ecology. This bifurcation has been previously highlighted, with calls for improved engagement among the subdisciplines, but their priority research areas have not been directly compared. To characterize the research agendas for terrestrial ecological research across different temporal scales, we compared two previous studies, Sutherland and colleagues (2013; neoecology) and Seddon and colleagues (2014; paleoecology), that outlined priority research questions. We identified several themes with potential for temporal integration and explored case studies that highlight cross-temporal collaboration. Finally, a path forward is outlined, focusing on education and training, research infrastructure, and collaboration. Our aim is to improve our understanding of biodiversity patterns and processes by promoting an inclusive and integrative approach that treats time as a foundational concept in ecology."
Spoth, M.M., Hall, B.L., Lowell, T.V., Diefendorf, A.F., Corcoran, M.C. and Brickle, P., 2023. Tracking the southern hemisphere westerlies during and since the last glacial maximum with multiproxy lake records from the Falkland Islands (52° S). Quaternary Science Reviews
"The Southern Hemisphere Westerlies (SHW) and their linkages with key ocean and atmospheric processes have the potential to drive abrupt climate change. The westerlies migrate seasonally and are thought to have shifted during past climate events, such as the last glacial termination. However, the timing, magnitude, direction, and mechanisms behind such shifts remain a topic of ongoing study. Here, we contribute to the understanding of past temporal and spatial changes in the SHW by mapping their fluctuations in the South Atlantic region from the last glacial maximum (LGM) to present. We use lake sediment proxies, including plant wax isotopes extracted from two tarns on Mt. Usborne, East Falkland (51.7 °S) to infer changes in paleoclimate and in the mean annual position of the SHW over the last ∼23,000 years. Together, the proxies indicate that the position of the SHW during the LGM lay north of the Falkland Islands. We interpret our plant wax isotopic record as showing a southward migration of the mean annual position of the wind belt beginning just before ∼21 ka, accompanied by warming at Mt. Usborne at ∼16.5 ka. The late-glacial climate was variable at the field site, and the mean annual position of the SHW may have fluctuated around the latitude of the Falkland Islands. The early Holocene was characterized by relatively warm, dry conditions with high evaporation rates, and the SHW may have lain south of the islands. A brief southern excursion at 7–6 ka was followed by gradual northward migration of the SHW for the remainder of the Holocene to the pre-industrial position. This northward migration was paired with increasingly wet, cool conditions in the Falkland Islands, and the islands appear to be experiencing some of the wettest conditions of the last 23,000 years during the late Holocene."
Corcoran, M.C., Diefendorf, A.F., Lowell, T.V., Hall, B.L., Spoth, M.M., Schartman, A. and Brickle, P., 2022. Hydrogen and carbon isotope fractionation in modern plant wax n-alkanes from the Falkland Islands. Organic Geochemistry
"The hydrogen isotopic composition of terrestrial plant waxes (δ2Hwax) is widely used to reconstruct past hydroclimate. δ2Hwax values reflect plant source water or precipitation δ2H (δ2Hprecip) values, and when extracted from sediment archives, records of past δ2Hprecip values can be generated. In order to better interpret these δ2Hwax records, modern calibrations between plant waxes and source water are required when vegetation and location diverge from plant calibrations in other regions. To date, no modern study has examined how δ2Hwax values and source water δ2H values relate in the southern mid- and high-latitude maritime climatic regions where the climate is affected by the Southern Hemisphere Westerly Wind Belt. We present the first modern calibration of δ2Hwax values on the Falkland Islands by analyzing n-alkane plant wax concentrations, δ2H and δ13C values from 11 of the most common plant species, one lichen species, and surface lake sediment samples from four sites on Mount Usborne on East Falkland. Based on plant wax concentrations, the most commonly observed plants on the landscape, Empetrum rubrum and Cortaderia pilosa, are contributing the most to the waxes in sediment archives. We calculate the fractionation between the n-C29 alkane δ2Hwax and δ2Hprecip values (ε2Hwax/precip) for all plant species to be –110 ± 17‰ (1σ, n = 22), which is similar to the global average ε2Hwax/precip. Observed and modelled monthly δ2Hprecip values indicate that δ2Hwax values can be interpreted as mean annual δ2Hprecip values, ultimately establishing the framework for utilizing plant wax-based paleoreconstructions from the mid-latitude maritime climatic regions."
Braddock, S., Hall, B.L., Johnson, J.S., Balco, G., Spoth, M.M., Whitehouse, P.L., Campbell, S., Goehring, B.M., Rood, D.H. and Woodward, J., 2022. Relative sea-level data preclude major late Holocene ice-mass change in Pine Island Bay. Nature Geoscience
"The rapidly retreating Thwaites and Pine Island glaciers together dominate present-day ice loss from the West Antarctic Ice Sheet and are implicated in runaway deglaciation scenarios. Knowledge of whether these glaciers were substantially smaller in the mid-Holocene and subsequently recovered to their present extents is important for assessing whether current ice recession is irreversible. Here we reconstruct relative sea-level change from radiocarbon-dated raised beaches at sites immediately seawards of these glaciers, allowing us to examine the response of the earth to loading and unloading of ice in the Amundsen Sea region. We find that relative sea level fell steadily over the past 5.5 kyr without rate changes that would characterize large-scale ice re-expansion. Moreover, current bedrock uplift rates are an order of magnitude greater than the rate of long-term relative sea-level fall, suggesting a change in regional crustal unloading and implying that the present deglaciation may be unprecedented in the past ~5.5 kyr. While we cannot preclude minor grounding-line fluctuations, our data are explained most easily by early Holocene deglaciation followed by relatively stable ice positions until recent times and imply that Thwaites and Pine Island glaciers have not been substantially smaller than present during the past 5.5 kyr."