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Creators/Authors contains: "Heeter, Karen J."

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  1. Abstract

    Extreme summer temperatures are increasingly common across the Northern Hemisphere and inflict severe socioeconomic and biological consequences. In summer 2021, the Pacific Northwest region of North America (PNW) experienced a 2-week-long extreme heatwave, which contributed to record-breaking summer temperatures. Here, we use tree-ring records to show that summer temperatures in 2021, as well as the rate of summertime warming during the last several decades, are unprecedented within the context of the last millennium for the PNW. In the absence of committed efforts to curtail anthropogenic emissions below intermediate levels (SSP2–4.5), climate model projections indicate a rapidly increasing risk of the PNW regularly experiencing 2021-like extreme summer temperatures, with a 50% chance of yearly occurrence by 2050. The 2021 summer temperatures experienced across the PNW provide a benchmark and impetus for communities in historically temperate climates to account for extreme heat-related impacts in climate change adaptation strategies.

     
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  2. Abstract

    Understanding the response of tropical cyclone precipitation to ongoing climate change is essential to determine associated flood risk. However, instrumental records are short-term and fail to capture the full range of variability in seasonal totals of precipitation from tropical cyclones. Here we present a 473-year-long tree-ring proxy record comprised of longleaf pine from excavated coffins, a historical house, remnant stumps, and living trees in southern Mississippi, USA. We use cross-dating dendrochronological analyses calibrated with instrumental records to reconstruct tropical cyclone precipitation stretching back to 1540 CE. We compare this record to potential climatic controls of interannual and multidecadal tropical cyclone precipitation variability along the Gulf Coast. We find that tropical cyclone precipitation declined significantly in the two years following large Northern Hemisphere volcanic eruptions and is influenced by the behavior of the North Atlantic subtropical high-pressure system. Additionally, we suggest that tropical cyclone precipitation variability is significantly, albeit weakly, related to Atlantic multidecadal variability. Finally, we suggest that we need to establish a network for reconstructing precipitation from tropical cyclones in the Southeast USA if we want to capture regional tropical cyclone behavior and associated flood risks.

     
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  3. Abstract

    Projected warming of global surface air temperatures will further exacerbate droughts, wildfires, and other agents of ecosystem stress. We use latewood blue intensity from high‐elevationPicea engelmanniito reconstruct late‐summer maximum air temperature for the Greater Yellowstone Ecoregion (GYE) spanning 770–2019 CE. Using a robust regression model (r2 = 0.60), the 1,250‐year reconstruction reveals 2016 as the single‐warmest year and the warming trend since ca. 2000 as the most intense. The Medieval Climate Anomaly contained the highest‐ranking warm event (1050–1070 CE) and was characterized by substantial multidecadal variability rather than a period of prolonged, homogeneous warming. We document regional expression of past warm and cool events, such as an anomalously warm period spanning the fifteenth to sixteenth centuries, and the Maunder and Dalton minima of the Little Ice Age. Summer temperature variability across the GYE shows multicentennial agreement with trends in solar irradiance, volcanic activity, snowpack, and other regional‐to‐hemispheric temperature records.

     
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  4. Abstract

    Summer temperatures across eastern North America (hereafter East) will soon reach a level consistently above any observation experienced during the instrumental period. Increasing temperatures will have negative impacts on natural (e.g., water, plant and animal communities) and human (e.g., health, infrastructure, economies) systems upon which the large and growing centres of human population across the region depend. Within the network of Northern Hemisphere tree‐ring temperature proxy records, one of the most obvious geographic holes is the East, where few temperature‐sensitive proxies exist. Here we present the first steps towards building a network of temperature‐sensitive proxy records across the East using blue light intensity (BI) methods applied to the tree rings of multiple temperature sensitive tree species situated from North Carolina to Maine, USA. Our overall objective is to report on the most viable species for BI analysis across different regions of the East (e.g., Southeast US, Midwest US, Northeast US/Canadian Maritimes) by exploring temporal (e.g., since ca. 1900) and spatial relationships between instrumental temperatures and BI metrics. We found BI to be a strong predictor of March–October mean air temperature (R2= 0.61) across the Northeast US/eastern Canada, and Sep‐Oct maximum air temperature (R2= 0.42) across the Southeast US. Of all species tested,Tsuga canadensisandPicea rubenscontained the strongest BI temperature signal. Adding more BI sites from these and potentially other species, as well as inclusion of other temperature proxies (e.g., ring widths) will allow for the development of a skilful broad‐scale and long‐term temperature field reconstruction across the East.

     
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