Abstract Recent Inland Water Temperature Trends European Geosciences Union General Assembly 2016 – Abstract EGU – X4.27 Simon J. Hook 1, Nathan C. Healey 1, John Lenters 2, Catherine O’Reilly 3 1.NASA Jet Propulsion Laboratory, California Institute of Technology, 2. LimnoTech, Inc. 3. Illinois State University We are using thermal infrared satellite data in conjunction with in situ measurements to produce water temperatures for all the large inland water bodies in North America and the rest of the world for potential use as climate indicator. Recent studies have revealed significant warming of inland waters throughout the world. The observed rate of warming is – in many cases – greater than that of the ambient air temperature. These rapid, unprecedented changes in inland water temperatures have profound implications for lake hydrodynamics, productivity, and biotic communities. Scientists are just beginning to understand the global extent, regional patterns, physical mechanisms, and ecological consequences of lake warming. As part of our work we have collected thermal infrared satellite data from those satellite sensors that provide long-term and frequent spaceborne thermal infrared measurements of inland waters including ATSR, AVHRR, and MODIS and used these to examine trends in water surface temperature for approximately 169 of the largest inland water bodies in the world. We are now extending this work to generate temperature time-series of all North American inland water bodies that are sufficiently large to be studied using 1km resolution satellite data for the last 3 decades, approximately 268 lakes. These data are then being related to changes in the surface air temperature and compared with regional trends in water surface temperature derived from CMIP5/IPCC model simulations/projections to better predict future temperature changes. We will discuss the available datasets and processing methodologies together with the patterns they reveal based on recent changes in the global warming, with a particular focus on the inland waters of the southwestern USA. GISTEMP Team (2015), GISS Surface Temperature Analysis (GISTEMP). NASA Goddard Institute for Space Studies. Retrieved from the internet on June 10, 2015 at Hulley, G. C., S. J. Hook, and P. Schneider (2011), Optimized split-window coefficients for deriving surface temperatures from inland water bodies, Remote Sens. Environ., 115, O'Reilly, C. M., S. Sharma, D. K. Gray, S. E. Hampton, J. S. Read, R. J. Rowley, P. Schneider, J. D. Lenters, P. B. McIntyre, B. M. Kraemer, et al. (2015), Rapid and highly variable warming of lake surface waters around the globe, Geophys. Res. Lett., 42, 10773– The research described on this poster was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The authors would also like to acknowledge the National Climate Assessment. © 2015 California Institute of Technology. Government sponsorship acknowledged. - air2water tested considering two future scenarios: CMIP5-CCSM4 RCP 4.5 and RCP 8.5 to evaluate the effectiveness as a predictive tool for climate change scenarios for the period The water temperature/air temperature relationship is approximately linear. References and Acknowledgements Materials and Methods Study Sites Results Satellite data: approximately 169 worldwide, and 268 in North America. In situ data: approximately 118 water bodies worldwide. Summertime analysis: July-September (JAS) for North America, January-March (JFM) for Southern Hemisphere and at least 13 years of data. - In situ data are a point measurement, while the selected area of satellite data analysis (9 km 2 ) is assumed to be representative of the entire water body with respect to long-term trends. Model Predictions Under Future Climate Change at Lake Tahoe Factors Influencing Inland Water Temperature Trends Consolidating Sensors for Long-term Temperature Analysis Figure 4. Summertime (July-August) temperature retrievals for all available sensors at Lake Tahoe in California/Nevada (USA). Figure 2. Summertime surface temperature trends ( ) for inland water bodies across the world [O’Reilly et al., 2015]. Figure 5. Temperature retrievals for all available sensors at Lake Tahoe in California/Nevada (USA) with LOWESS smoothing and outliers removed. Black points indicate the summertime (July-August) averages. The trend shown is for the summertime values. Global Trends of Inland Water Temperatures Conclusions Lake NameSlopeInterceptR2R2 p valueStandard Error Clear Lake Lake Almanor Lake Tahoe Mono Lake Pyramid Lake Walker Lake Temperature Trends for Six Inland Water Bodies in CA/NV Lake Tahoe Salton Sea Figure 1. Photos of the Lake Tahoe and Salton Sea Calibration/Validation Instrumentation. Table 2. Summertime (July-August) surface water temperature trends (AVHRR NOAA-18, ATSR-1, ATSR-2, AATSR, MODIS aqua, MODIS terra, VIIRS) for the six largest inland water bodies in California/Nevada (USA): Note: Clear Lake and Lake Almanor represent a single pixel rather than the 3x3 array for all other lakes. - Global mean inland water trend: 0.34 o C decade -1, range: -0.7 – 1.3 o C decade Global mean air trend: 0.25 o C decade Inland water bodies are warming worldwide although there is a high level of spatial heterogeneity in warming rates. - Important to consider interconnectivity of geomorphic and climatic factors when determining driving factors of warming. - Rapid warming emphasizes the urgent need for incorporation of climate impacts on inland water bodies in future management efforts due to potentially detrimental ecological effects on aquatic ecosystems. Location 3 x 3 pixel window (1 km pixels) Minimum points in JAS Range 20 Smoothing LOWESS interpolation Image Time Night Range from Target Coordinates < 1 km Standard Deviation in 3 x 3 < 0.5 K Sensor Zenith Angle < 45° Cirrus Cloud Test Cloud Masking High Cloud Test Thermal Test Temperature Range = K Table 1. Processing criteria for satellite temperature analysis (example: MODIS). a RCP 4.5 Air Temperature [ o C] Water Temperature [ o C] b RCP 8.5 Air Temperature [ o C] Water Temperature [ o C] Figure 7. Relationships between reconstructed air temperature and modeled lake surface temperature in the four seasons for two climate change scenarios using CMIP5-CCSM4 climate projections: (a) RCP 4.5, and (b) RCP 8.5, and (c) estimation of future dissolved oxygen content. c Inland Waterbody Surface Temperature v1.0 Algorithm Figure 3. Proximal similarity (i.e.‘hotspot’ analysis) was determined using Getis-Ord Gi* z-scores for all lakes. [O’Reilly et al., 2015]. -Inland water bodies that are warming at similar rates due to shared climatic and geomorphic characteristics are widely distributed across the globe. Figure 6. Groups of lakes sharing similar factors influencing trends are not regionally clustered. (a) Regression tree of key climatic (air ( o C decade −1 ), cloud cover (CC) (change in % coverage decade −1 ), shortwave radiation (SW) (Wm −2 decade −1 )), and geomorphometric characteristics influencing lake summer surface water temperature trends; (b) spatial representation of lakes within each regression tree leaf [O’Reilly et al., 2015]; (c) summertime air temperature trends with surface water temperature trends overlaid for ; (d) summertime air temperature trends [GISTEMP Team, 2015] with surface water temperature trends overlaid for c d a b (Courtesy of Geoff Schladow, University of California, Davis) NASA UC Davis SNOTEL CRUCMIP5-CCSM4 Air temperature datasets: