August 2006 Satellites and Biological Impacts of Climate Change: A Case Study of the California...
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August 2006 Satellites and Biological Impacts of Climate Change: A Case Study of the California Mussel Christel Purvis 1 , Venkat Lakshmi 2 & Brian Helmuth 3 1,2 Department of Geological Sciences, University of South Carolina 3 Department of Biological Sciences, University of South Carolina 1 [email protected] Abstract The ecological effects of climate change are complicated and poorly understood despite decades of research in prime locations such as the thermally harsh coastlines of the Western United States. This study focuses on adding to 8 years of in situ logger data from a range of latitudes using land surface temperature (LST) from MODIS and ASTER. Remote sensing greatly reduces temporal and spatial limitations inherent with in situ methods while providing novel ‘outside-in’ information regarding the surrounding environment, thus addressing the larger ecosystem as well. The organism under study is the California mussel (Mytilus californianus), a common invertebrate along rocky coastlines. ASTER LST has an average variance from field-based measurements of mussel body temperature of 1.5°C ±4.9°C while that of MODIS is 2.1°C ±4.1°C (Terra) and 3.5°C ±5.5°C (Aqua). Such a wide range in standard deviations is predominantly a function of localized conditions such as wave splashing, fog banks and other variables too small to be accounted for by the sensors (spatial resolution of ASTER is 90m, MODIS is 1km). Despite a lower spatial resolution, MODIS is the more desirable sensor since it has a daily temporal repeat is on two satellites, thus having a total of four overpasses per day at any given site (two during the day and two at night). Therefore, MODIS is also used to assess daily variations in mussel body temperature. While the absolute temperature of a given mussel cannot be measured from space, satellite remote sensing does prove to be useful for tracking long-term variations in time and space of the intertidal population temperatures. Results and Discussion 1. Satellite-derived LST typically overestimates average mussel body temperature, yet is typically within the average daily maximum body temperature of the California mussel (Figure 2). During elevated tides, however (such as in southern California where they occur in the summer during MODIS overpasses) LST cannot account for the cooler temperatures experienced by submerged mussels. In such cases, additional inputs are necessary (Figure 3). 2. MODIS LST has proven to correlate with mussel body temperatures with similar accuracy to air temperature data from localized weather stations, yet is more readily available (Helmuth 1999). 3. The synergism of ASTER and MODIS data offers a hope for monitoring of intertidal organism health to observe effects of global change. In the absence of regular ASTER or MODIS data, we can use bio-engineering models for simulation of mussel body temperature on a meter- kilometer spatial scale. This would help blend NASA's Acknowledgements •Many thanks to Ujjwal Narayan for his continued assistance in programming. •Funding provided by NASA, Grant NNG04GE43G, Program Manager Woody Turner •Helmuth, B. “Thermal biology of rocky intertidal mussels: Quantifying body temperatures using climatological data.” Ecology 80 (1), pp. 15-34, 1999 Motivation and Methods Documented trends of global climate change have complicated implications for intra-habitat dynamics and bio-geographic distributions. The most common methods of investigating these ramifications involve time and labor intensive field studies, such as those being carried out along the rocky intertidal areas along the Pacific U.S. coast. Such studies have demonstrated that due to the thermally harsh conditions, those coastal sites can reveal a wealth of insights into direct and indirect consequences of varying climate conditions within a defined ecosystem. The main objective of this study is to assess the use of remote sensing to provide novel information regarding these environments in a more efficient manner compared to costly in situ methods. The two sensors investigated here are MODIS and ASTER. Both satellite platforms of MODIS (Terra and Aqua) were considered to take advantage of the twice-daily coverage. Data gathered by these sensors were compared to several years worth of in situ measurements at 9 different sites (Figure 1). The loggers were made of epoxy and were designed to mimic the size, shape and material properties of the Figure 3. This image is a composite of MODIS LST images taken on June 27, 2004 and emphasizes the variation in temperature with increasing latitude. Temperatures in Alegria, CA Figure 4. This two week time series from Jalama, CA shows the relationship between LST and mussel temperatures. Figure 5. MODIS LST correlation with mussel temperatures is strongly dependent upon the tidal cycle. Sea surface temperature data (shown here based on the National Data Buoy Center) provides pertinent information on the body temperatures of immersed mussels. Table 1. Various comparisons were performed based on available MODIS and ASTER LST, in situ loggers and tide heights. Columns C and D describe the average number of loggers present at a particular site as well as the variation in temperature among those loggers. Columns E through G summarize the difference between the satellite sensors and the in situ measurements (displayed as absolute values). H through J show the change in temperatures and tidal heights from the time of the morning Terra overpass to the afternoon Aqua overpass. Finally, column K compares the average of all ASTER LST pixels which lie within the MODIS pixel of interest with the value of that MODIS pixel itself. The * symbol denotes a lack of available images/data. σ indicates standard deviation. Times based on Pacific Standard Time. MODIS LST vs. In Situ Mussel Temp Based on all 9 Sites MODIS/Terra MODIS/Aqua Figures 6 and 7. The scatter plots above illustrate the correlation between MODIS LST (left) and ASTER LST (right) with the in situ measurements. Figures 1 and 2. In situ loggers were situated among dense mussel beds (left). Study sites are rocky shore communities of California mussels (right). Avgerage Maximum Mussel Temp Average Mussel Temperatur e Average MODIS Temperatu re Temperatures in Jalama, CA ASTER LST vs. In Situ Mussel Temp Study Sites Bamfiel d Lompoc Jalam a Alegr ia Coal Oil Point Piedras Blancas Bodega Boiler Bay Montere y <0°C <5°C <10°C 15°C 20°C 25°C 30°C 35°C 40°C 45°C >48°C Land Surface Temperatures
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Transcript of August 2006 Satellites and Biological Impacts of Climate Change: A Case Study of the California...
August 2006
Satellites and Biological Impacts of Climate Change:A Case Study of the California Mussel
Christel Purvis1, Venkat Lakshmi2 & Brian Helmuth3
1,2Department of Geological Sciences, University of South Carolina3Department of Biological Sciences, University of South Carolina
Abstract The ecological effects of climate change are complicated and poorly understood despite decades of research in prime locations such as the thermally harsh coastlines of the Western United States. This study focuses on adding to 8 years of in situ logger data from a range of latitudes using land surface temperature (LST) from MODIS and ASTER. Remote sensing greatly reduces temporal and spatial limitations inherent with in situ methods while providing novel ‘outside-in’ information regarding the surrounding environment, thus addressing the larger ecosystem as well. The organism under study is the California mussel (Mytilus californianus), a common invertebrate along rocky coastlines. ASTER LST has an average variance from field-based measurements of mussel body temperature of 1.5°C ±4.9°C while that of MODIS is 2.1°C ±4.1°C (Terra) and 3.5°C ±5.5°C (Aqua). Such a wide range in standard deviations is predominantly a function of localized conditions such as wave splashing, fog banks and other variables too small to be accounted for by the sensors (spatial resolution of ASTER is 90m, MODIS is 1km). Despite a lower spatial resolution, MODIS is the more desirable sensor since it has a daily temporal repeat is on two satellites, thus having a total of four overpasses per day at any given site (two during the day and two at night). Therefore, MODIS is also used to assess daily variations in mussel body temperature. While the absolute temperature of a given mussel cannot be measured from space, satellite remote sensing does prove to be useful for tracking long-term variations in time and space of the intertidal population temperatures.
Results and Discussion1. Satellite-derived LST typically overestimates average mussel body
temperature, yet is typically within the average daily maximum body temperature of the California mussel (Figure 2). During elevated tides, however (such as in southern California where they occur in the summer during MODIS overpasses) LST cannot account for the cooler temperatures experienced by submerged mussels. In such cases, additional inputs are necessary (Figure 3).
2. MODIS LST has proven to correlate with mussel body temperatures with similar accuracy to air temperature data from localized weather stations, yet is more readily available (Helmuth 1999).
3. The synergism of ASTER and MODIS data offers a hope for monitoring of intertidal organism health to observe effects of global change. In the absence of regular ASTER or MODIS data, we can use bio-engineering models for simulation of mussel body temperature on a meter-kilometer spatial scale. This would help blend NASA's observational capabilities with in situ monitoring and modeling to achieve the best results.
Acknowledgements•Many thanks to Ujjwal Narayan for his continued assistance in programming.•Funding provided by NASA, Grant NNG04GE43G, Program Manager Woody Turner•Helmuth, B. “Thermal biology of rocky intertidal mussels: Quantifying body temperatures using climatological data.” Ecology 80 (1), pp. 15-34, 1999
Motivation and Methods Documented trends of global climate change have complicated implications for intra-habitat dynamics and bio-geographic distributions. The most common methods of investigating these ramifications involve time and labor intensive field studies, such as those being carried out along the rocky intertidal areas along the Pacific U.S. coast. Such studies have demonstrated that due to the thermally harsh conditions, those coastal sites can reveal a wealth of insights into direct and indirect consequences of varying climate conditions within a defined ecosystem. The main objective of this study is to assess the use of remote sensing to provide novel information regarding these environments in a more efficient manner compared to costly in situ methods. The two sensors investigated here are MODIS and ASTER. Both satellite platforms of MODIS (Terra and Aqua) were considered to take advantage of the twice-daily coverage. Data gathered by these sensors were compared to several years worth of in situ measurements at 9 different sites (Figure 1). The loggers were made of epoxy and were designed to mimic the size, shape and material properties of the California mussel (Mytilius californianus).
Figure 3. This image is a composite of MODIS LST images taken on June 27, 2004 and emphasizes the variation in temperature with increasing latitude.
Temperatures in Alegria, CA
Figure 4. This two week time series from Jalama, CA shows the relationship between LST and mussel temperatures.
Figure 5. MODIS LST correlation with mussel temperatures is strongly dependent upon the tidal cycle. Sea surface temperature data (shown here based on the National Data Buoy Center) provides pertinent information on the body temperatures of immersed mussels.
Table 1. Various comparisons were performed based on available MODIS and ASTER LST, in situ loggers and tide heights. Columns C and D describe the average number of loggers present at a particular site as well as the variation in temperature among those loggers. Columns E through G summarize the difference between the satellite sensors and the in situ measurements (displayed as absolute values). H through J show the change in temperatures and tidal heights from the time of the morning Terra overpass to the afternoon Aqua overpass. Finally, column K compares the average of all ASTER LST pixels which lie within the MODIS pixel of interest with the value of that MODIS pixel itself. The * symbol denotes a lack of available images/data. σ indicates standard deviation. Times based on Pacific Standard Time.
MODIS LST vs. In Situ Mussel Temp
Based on all 9 SitesMODIS/TerraMODIS/Aqua
Figures 6 and 7. The scatter plots above illustrate the correlation between MODIS LST (left) and ASTER LST (right) with the in situ measurements.
Figures 1 and 2. In situ loggers were situated among dense mussel beds (left). Study sites are rocky shore communities of California mussels (right).
Avgerage Maximum
Mussel Temp
Average Mussel
Temperature
Average MODIS
Temperature
Temperatures in Jalama, CA
ASTER LST vs. In Situ Mussel Temp
Study Sites
Bamfield
Lompoc
Jalama
Alegria
Coal Oil Point
Piedras Blancas
Bodega
Boiler Bay
Monterey
<0°C<5°C<10°C15°C20°C25°C30°C35°C40°C45°C>48°C
Land SurfaceTemperatures
