More Like this

1. On the spatial and temporal shift in the archetypal seasonal temperature cycle as driven by annual and semi‐annual harmonics

   https://doi.org/10.1002/env.2665  

   North, Joshua S.; Schliep, Erin M.; Wikle, Christopher K. (December 2020, Environmetrics)

   Abstract Statistical methods are required to evaluate and quantify the uncertainty in environmental processes, such as land and sea surface temperature, in a changing climate. Typically, annual harmonics are used to characterize the variation in the seasonal temperature cycle. However, an often overlooked feature of the climate seasonal cycle is the semi‐annual harmonic, which can account for a significant portion of the variance of the seasonal cycle and varies in amplitude and phase across space. Together, the spatial variation in the annual and semi‐annual harmonics can play an important role in driving processes that are tied to seasonality (e.g., ecological and agricultural processes). We propose a multivariate spatiotemporal model to quantify the spatial and temporal change in minimum and maximum temperature seasonal cycles as a function of the annual and semi‐annual harmonics. Our approach captures spatial dependence, temporal dynamics, and multivariate dependence of these harmonics through spatially and temporally varying coefficients. We apply the model to minimum and maximum temperature over North American for the years 1979–2018. Formal model inference within the Bayesian paradigm enables the identification of regions experiencing significant changes in minimum and maximum temperature seasonal cycles due to the relative effects of changes in the two harmonics. 

   more » « less
2. Remote Sensing of Water Quantity and Quality in Geospatial Education: Lake Sidney Lanier, Georgia, USA

   Brookins-Jackson, C.D.; Boyd, Z.L.; Freeland, A.C.; Mann, B.L.; Perry, M.K.; Ignatius, A.R. (January 2022, Apalachicola-Chattahoochee-Flint Waters Conference: Shared Resources in Changing Times. Albany, GA)

   To increase geospatial awareness about local water resources, our team developed learning resources for the 150 km² Lake Sidney Lanier reservoir located in North Georgia, USA. The reservoir is vital for hydroelectric power generation, recreation, tourism, and consumptive uses. Using geospatial analysis in Google Earth Engine (GEE), we analyzed precipitation trends in the watershed using Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) data. We also quantified expansion and contraction of reservoir surface area using Landsat-derived Global Surface Water data. As Lake Sidney Lanier is a managed reservoir, surface water extent fluctuations are related to climatic variables, consumptive use, and hydropower generation. Water temperature varies based on seasonality, water depth, water clarity, and lake stratification. Changing temperature dynamics affect ecosystem health and determine other important water quality parameters such as dissolved oxygen concentrations. Landsat 8 Thermal Infrared Sensor (TIRS) data were used to examine temperature trends over multiple years and investigate the timing of lake stratification and mixing. Highly turbid waters are associated with pollutants and lower water quality and can affect ecosystem productivity by minimizing sunlight penetration into the water column. Sentinel 2 MSI data were processed using a turbidity algorithm to analyze temporal trends and spatial correlations with reservoir inflows. Finally, high concentrations of chlorophyll a were used as a proxy to identify harmful algal blooms. The spatial differences in headwaters and near-dam locations were examined and near real-time satellite data were explored for potential development of early-warning systems to protect ecosystem and human health. 

   more » « less
3. Differential Responses of Maximum Versus Median Chlorophyll‐ a to Air Temperature and Nutrient Loads in an Oligotrophic Lake Over 31 Years

   https://doi.org/10.1029/2020WR027296  

   Ward, Nicole K.; Steele, Bethel G.; Weathers, Kathleen C.; Cottingham, Kathryn L.; Ewing, Holly A.; Hanson, Paul C.; Carey, Cayelan C. (June 2020, Water Resources Research)

   Abstract Globally, phytoplankton abundance is increasing in lakes as a result of climate change and land‐use change. The relative importance of climate and land‐use drivers has been examined primarily for mesotrophic and eutrophic lakes. However, oligotrophic lakes show different sensitivity to climate and land‐use drivers than mesotrophic and eutrophic lakes, necessitating further exploration of the relative contribution of the two drivers of change to increased phytoplankton abundance. Here, we investigated how air temperature (a driver related to climate change) and nutrient load (a driver related to land‐use and climate change) interact to alter water quality in oligotrophic Lake Sunapee, New Hampshire, USA. We used long‐term data and the one‐dimensional hydrodynamic General Lake Model (GLM) coupled with Aquatic EcoDyanmics (AED) modules to simulate water quality. Over the 31‐year simulation, summer median chlorophyll‐aconcentration was positively associated with summer air temperature, whereas annual maximum chlorophyll‐aconcentration was positively associated with the previous 3 years of external phosphorus load. Scenario testing demonstrated a 2°C increase in air temperature significantly increased summer median chlorophyll‐aconcentration, but not annual maximum chlorophyll‐aconcentration. For both maximum and median chlorophyll‐aconcentration, doubling external nutrient loads of total nitrogen and total phosphorus at the same time, or doubling phosphorus alone, resulted in a significant increase. This study highlights the importance of aligning lake measurements with the ecosystem metrics of interest, as maximum chlorophyll‐aconcentration may be more uniquely sensitive to nutrient load and that typical summer chlorophyll‐aconcentration may increase due to warming alone. 

   more » « less
4. Time series of high-frequency profiles of depth, temperature, dissolved oxygen, conductivity, specific conductance, chlorophyll a, turbidity, pH, oxidation-reduction potential, photosynthetically active radiation, colored dissolved organic matter, phycocyanin, phycoerythrin, and descent rate for Beaverdam Reservoir, Carvins Cove Reservoir, Falling Creek Reservoir, Gatewood Reservoir, and Spring Hollow Reservoir in southwestern Virginia, USA 2013-2024

   https://doi.org/10.6073/pasta/75d1c9a57a49030c468ab19db3643c36  

   Carey, Cayelan C; Breef-Pilz, Adrienne; Lewis, Abigail S; Hoffman, Kathryn K (April 2025, Environmental Data Initiative)

   Depth profiles of water biogeochemical properties were collected with SeaBird Electronics (SBE) Conductivity, Temperature, and Depth (CTD) profilers from 2013-2024 at five drinking water reservoirs in southwestern Virginia, USA. The study reservoirs are: Beaverdam Reservoir (Vinton, Virginia), Carvins Cove Reservoir (Roanoke, Virginia), Falling Creek Reservoir (Vinton, Virginia), Gatewood Reservoir (Pulaski, Virginia), and Spring Hollow Reservoir (Salem, Virginia). Beaverdam, Carvins Cove, Falling Creek, and Spring Hollow Reservoirs are owned and operated by the Western Virginia Water Authority as primary or secondary drinking water sources for Roanoke, Virginia, and Gatewood Reservoir is a drinking water source for the town of Pulaski, Virginia. The dataset consists of CTD depth profiles measured at the deepest site of each reservoir adjacent to the dam as well as other upstream reservoir sites. The profiles were collected approximately fortnightly in the spring months, weekly in the summer and early autumn, and monthly in the late autumn and winter. Beaverdam Reservoir, Carvins Cove Reservoir, and Falling Creek Reservoir were sampled every year in the dataset (2013-2024); Spring Hollow Reservoir was only sampled 2013-2017 and 2019; and Gatewood Reservoir was only sampled in 2016. Data availability differs across years due to additional sensors that have been added or replaced over time. From 2013-2016, profiles were taken with a CTD equipped with an SBE 43 Dissolved Oxygen sensor and an ECO FLNTU sensor for turbidity and chlorophyll. From 2017-2024, profiles were taken with a CTD equipped with an SBE 43 Dissolved Oxygen sensor, an ECO FLNTU sensor for turbidity and chlorophyll, a PAR-LOG ICSW sensor for photosynthetically active radiation, and a SBE 27 pH and ORP (oxidation-reduction potential) sensor. In 2022 and 2023, profiles were also taken with an additional CTD equipped with an SBE 43 Dissolved Oxygen sensor; an ECO Triplet Scattering Fluorescence sensor for CDOM, phycocyanin, and phycoerythrin; an ECO FLNTU sensor for turbidity and chlorophyll; and PAR-LOG ICSW for photosynthetically active radiation. All variables were measured every 0.25 seconds, resulting in depth profiles at approximately ten centimeter resolution. Maximum cast depth is not necessarily equal to site depth; see methods for more information. 

   more » « less
5. Observations of biological production and light transmittance with warming and sea ice decline across the Pacific Arctic Distributed Biological Observatory

   Frey, Karen E (December 2024, American Geophysical Union 2024 Fall Meeting)

   Recent low sea ice extents across Distributed Biological Observatory (DBO) sites in the northern Bering, Chukchi, and Beaufort seas of the Pacific Arctic region have been due to both later fall/winter freeze-up and earlier spring breakup, which in turn have important cascading impacts on the physical, biological, and biogeochemical state of the overall marine environment throughout this region. Satellite observations of the DBO sites that span across a large latitudinal gradient (~62–72°N) include sea surface temperature (SST), sea ice concentration, annual sea ice persistence and the timing of sea ice breakup/formation, chlorophyll-a concentrations, and primary productivity. While we observe significant trends in SST, sea ice, and chlorophyll-a/primary productivity throughout the year, the most significant and synoptic trends for the DBO sites have been those during late summer and autumn (warming SST during October/November, later shifts in the timing of sea ice formation, and increases in chlorophyll-a/primary productivity during August/September). Measurements of the transmittance of solar radiation through the ocean water column is also one of the critical elements for understanding the potential implications of these recent shifts in sea ice, including impacts on primary production, damaging effects of UV radiation on phytoplankton, photodegradation of dissolved organic matter, and upper ocean heating. Field-based observations of downwelling irradiance and upwelling radiance profiles in the top ~30-50 meters of ocean waters are also presented, collected at discrete stations across DBO sites 1–5 in the northern Bering and Chukchi Seas. Profiles were collected during July 2018, 2019, 2021, 2022, and 2023 as part of the DBO program onboard the Canadian Coast Guard Ship (CCGS) Sir Wilfrid Laurier, and represent a first time series of optical measurements across these DBO sites. Continued monitoring of the transmittance of solar radiation through the water column at these DBO sites will be crucial for understanding changes in the underwater light field as the duration of the open water season continues to lengthen with declining seasonal sea ice cover. 

   more » « less