The Coral Reef Temperature Anomaly Database (CoRTAD) Version 3 - Global, 4 km Sea Surface Temperature and Related Thermal Stress Metrics for 1982-2009 (NODC Accession 0068999)

[Text below adapted from: Selig, Elizabeth R., Kenneth S. Casey, and John F. Bruno (2009), New insights into global patterns of ocean temperature anomalies: implications for coral reef health and management, Global Ecology and Biogeography, in press. Hereafter referred to as "SCB2009".] The CoRTAD was developed using data from the Pathfinder Version 5 collection produced by the National Oceanic and Atmospheric Administration's (NOAA) National Oceanographic Data Center (NODC) and the University of Miami's Rosenstiel School of Marine and Atmospheric Science (http://pathfinder.nodc.noaa.gov). These sea surface temperature data are derived from the Advanced Very High Resolution Radiometer (AVHRR) sensor and are processed to a resolution of approximately 4.6 km at the equator. These data have the highest resolution covering the longest time period of any satellite-based ocean temperature dataset (see Figure 1 of SCB2009). Weekly averages of day and night data with a quality flag of 4 or better were used, which is a commonly accepted cutoff for "good" data (Kilpatrick et al., 2001, Casey and Cornillon, 1999). By using a day-night average, the number of missing pixels was reduced by 25% with virtually no loss in accuracy (see Table 2 of SCB2009).The Pathfinder algorithm eliminates any observation with a Sea Surface Temperature (SST) more than 2 degrees C different from a relatively coarse resolution SST value based on the Reynolds Optimum Interpolation Sea Surface Temperature (OISST version 2.0)* value, a long-term, in situ-based data set (Kilpatrick et al., 2001, Reynolds et al., 2002). Observations were added back into the analysis if the SST was greater than the OISST-5 degrees C, but less than the OISST+5 degrees C. The 5 degrees C threshold is a reasonable selection that allows diurnal warming events (Kawai and Wada, 2007) or other spatially limited warm spots back into the dataset without including unrealistic and erroneously warm values. Values less than the OISST were not included because they may have been biased by cloud contamination and other satellite errors, which tend to result in cooler SST estimates. These processes resulted in a dataset with only 21.2 percent missing data. To create a gap-free dataset for analysis, 3 x 3 pixel median spatial fill was used. A temporal fill was performed using the Piecewise Cubic Hermite Interpolating Polynomial (PCHIP) function in Matlab (The Mathworks Inc., 2006) to fill the remaining gaps. This conservative approach was chosen because it provided interpolated SSTs that are bounded by the nearest available values in time. It also used data from only a very limited spatial domain, which is an important consideration given the variability of coral reef environments.[*NOTE: The higher resolution Reynolds 25km Daily Optimum Interpolation Sea Surface Temperature (DOISST version 2.0) dataset was used in place of the OISST version 2.0 for the Pathfinder data from 1982-1984. The primary effect of this change is to retain more data in the high gradient regions and in regions where meandering or feature advection is present; effect on the retrieved SST is minimal. Two problems with the original Pathfinder data from 1982-1984 have been identified. An error was discovered in the processing of the reference SST fields, which created a "halo" of cold pixels around coastlines in the reference field. As a result, several anomalously cool Pathfinder SST pixels have passed the reference test during processing and been assigned quality flag values that are too high. The second problem arises from the fact that the reference SST field used for 1982-1984 data lacks inland SST observations. As a result, the gap-filling routine employed by the CoRTAD fails for inland pixels for the entire 1982-1984 period. In order to avoid contamination of climatology-based thermal metrics and statistics calculated in the CoRTAD, all data from 1982-1984 were omitted from the climatology. Thus, the CoRTAD Version 3 climatology was calculated using only 1985-2009 data. All CoRTAD fields have been calculated for the entire time series (1982-2009) based on this climatology. For an image demonstrating these problems in Pathfinder processing, please see the "Known Problems" section of the Pathfinder Version 5 User Guide at http://pathfinder.nodc.noaa.gov/userguide.html.]Using these gap-filled data, we then created site-specific climatologies for each reef grid cell to describe long-term temperature patterns over the 21-year dataset (Eqn. 1). The climatology was generated using a harmonic analysis procedure that fits annual and semi-annual signals to the time series of weekly SSTs at each grid cell: climSST(t) = A*cos(2pi*t + B) + C*cos(4pi*t + D) + E (1)where t is time, A and B are coefficients representing the annual phase and amplitude, C and D are the semi-annual phase and amplitude, and E is the long-term temperature mean. Similar approaches have been used for generating climatologies because they are more robust than simple averaging techniques, which can be more susceptible to data gaps from periods of cloudiness (Podesta et al., 1991, Mesias et al., 2007). Sea surface temperatures from AVHRR quantify only the temperature of the 'skin' of the ocean, roughly the first 10 micrometers of the ocean surface (Donlon et al., 2007). Most field surveys of coral cover occur between 1 and 15 m depth. To be useful for coupling with coral reef biological data, these temperature data must be relatively accurate beyond the 'skin' of the ocean. Linear regression was used to examine how data from in situ reef temperature loggers compared with data from the CoRTAD to demonstrate the good accuracy of the CoRTAD temperature data compared to in situ data at a variety of depths and locations around the world (see Table 2 of SCB2009 for details). Temperature anomaly metrics: Several metrics could be used to link coral reef ecosystem health with temperature including trophic structure, diversity or percent coral cover (Newman et al., 2006, Roberts et al., 2002, Bruno and Selig, 2007). However, this analysis focused on coral bleaching and disease because they are key drivers of coral decline and their relationships with temperature patterns are better understood (Aronson and Precht, 2001, Bruno et al., 2007, Glynn, 1993). Analyses were performed on two metrics (see Table 1 of SCB2009): one that is commonly known to lead to bleaching (Liu et al., 2003, Strong et al., 2004, Glynn, 1993), and one that is correlated with increased disease severity (Selig et al., 2006, Bruno et al., 2007. Coral bleaching results when corals lose their symbiotic zooxanthellae (Glynn, 1993, Glynn, 1996). Bleaching is a natural stress response not only to warm temperatures, but also to cool temperatures (Hoegh-Guldberg and Fine, 2004) as well as light and salinity values different from the normal range (Glynn, 1993). Corals can recover from bleaching, but their ability to do so is dependent on the magnitude and duration of the anomaly event (Glynn, 1993). The temperature thresholds that result in coral bleaching vary by location and species (Berkelmans and Willis, 1999). Bleaching is often connected to Thermal Stress Anomalies (TSAs), which are defined as areas where temperatures exceed by 1 degree C or more the climatologically warmest week of the year (Table 2, Glynn, 1993). The temperature anomaly thresholds relevant to disease have been studied in only one pathogen-host system (Selig et al., 2006, Bruno et al., 2007). In that system, changes in disease cases were correlated with Weekly Sea Surface Temperature Anomalies (WSSTAs), temperatures that were 1 degree C greater than the weekly average for that location. The best metric for predicting bleaching or disease may vary according to location, species, and pathogen (Selig et al., 2006, Bruno et al., 2007, Berkelmans, 2002). For example, bleaching on the Great Barrier Reef was best predicted by the maximum anomaly over a 3 day period (Berkelmans et al., 2004), rather than an anomaly metric like the TSA. Although the 7-day averaging approach in the CoRTAD may be too temporally coarse to capture all bleaching events, it is necessary to maintain consistency and minimize gaps in the dataset across broad spatial scales. In addition, the data are less likely to yield false positives for TSAs and will likely capture most WSSTA events, which have a lower temperature threshold. References: Aronson R.B. and W.F. Precht (2001). White-band disease and the changing face of Caribbean coral reefs. Hydrobiologia, 460, 25-38. Berkelmans R. (2002). Time-integrated thermal bleaching thresholds of reefs and their variation on the Great Barrier Reef. Marine Ecology Progress Series, 229, 73-82. Berkelmans R., G. De'ath, S. Kininmonth and W.J. Skirving (2004). A comparison of the 1998 and 2002 coral bleaching events on the Great Barrier Reef: spatial correlation, patterns, and predictions. Coral Reefs, 23, 74-83. Berkelmans R. and B.L. Willis (1999). Seasonal and local spatial patterns in the upper thermal limits of corals on the inshore central Great Barrier Reef. Coral Reefs, 18, 219-228. Bruno J.F. and E.R. Selig (2007). Regional decline of coral cover in the Indo-Pacific: timing, extent, and subregional comparisons. Public Library of Science One, 2, e711. Bruno, J.F., E.R. Selig, K.S. Casey, C.A. Page, B.L. Willis, C.D. Harvell, H. Sweatman, and A. Melendy (2007). Thermal stress and coral cover as drivers of coral disease outbreaks, Public Library of Science Biology, Vol. 5, No. 6, e124.(DOI:10.1371/journal.pbio.0050124) Casey K.S. and P. Cornillon (1999). A comparison of satellite and in situ-based sea surface temperature climatologies. Journal of Climate, 12, 1848-1863. Donlon C., Robinson I., Casey K.S., Vazquez-Cuervo J., Armstrong E., Arino O., Gentemann C., May D., LeBorgne P., Piolle J., Barton I., Beggs H., Poulter D.J.S., Merchant C.J., Bingham A., Heinz S., Harris A., Wick G., Emery B., Minnett P., Evans R., Llewellyn-Jones D., Mutlow C., Reynolds R.W., Kawamura H. and Rayner N. (2007). The global ocean data assimilation experiment high-resolution sea surface temperature pilot project. Bulletin of the American Meteorological Society, 88, 1197-1213.Glynn P.W. (1993). Coral reef bleaching - ecological perspectives. Coral Reefs, 12, 1-17. Glynn P.W. (1996). Coral reef bleaching: facts, hypotheses and implications. Global Change Biology, 2, 495-509. Hoegh-Guldberg O. and Fine M.(2004). Low temperatures cause coral bleaching. Coral Reefs, 23, 444-444. Kawai Y. and Wada A. (2007). Diurnal sea surface temperature variation and its impact on the atmosphere and ocean: A review. Journal of Oceanography, 63, 721-744. Kilpatrick K.A., Podesta G.P. and Evans R.(2001). Overview of the NOAA/NASA advanced very high resolution radiometer Pathfinder algorithm for sea surface temperature and associated matchup database. Journal of Geophysical Research-Oceans, 106, 9179-9197. Liu G., Skirving W. and Strong A.E. (2003). Remote sensing of sea surface temperatures during 2002 Barrier Reef coral bleaching. EOS, 84, 137-144. Mesias J.M., Bisagni J.J. and Brunner A. (2007). A high-resolution satellite-derived sea surface temperature climatology for the western North Atlantic Ocean. Continental Shelf Research, 27, 191-207. Newman M.J.H., Paredes G.A., Sala E. and Jackson J.B.C. (2006). Structure of Caribbean coral reef communities across a large gradient of fish biomass. Ecology Letters, 9, 1216-1227. Podesta G.P., Brown O.B. and Evans R.H. (1991). The annual cycle of satellite-derived sea-surface temperature in the southwestern Atlantic Ocean. Journal of Climate, 4, 457-467. Reynolds R.W., Rayner N.A., Smith T.M., Stokes D.C. and Wang W.Q. (2002). An improved in situ and satellite SST analysis for climate. Journal of Climate, 15, 1609-1625. Roberts C.M., McClean C.J., Veron J.E.N., Hawkins J.P., Allen G.R., McAllister D.E., Mittermeier C.G., Schueler F.W., Spalding M., Wells F., Vynne C. and Werner T.B. (2002). Marine biodiversity hotspots and conservation priorities for tropical reefs. Science, 295, 1280-1284. Selig, E.R., C.D. Harvell, J.F. Bruno, B.L. Willis, C.A. Page, K.S. Casey and H. Sweatman (2006). Analyzing the relationship between ocean temperature anomalies and coral disease outbreaks at broad spatial scales. In; J.T. Phinney, O. Hoegh-Guldberg, J. Kleypas, W. Skirving, and A. Strong (eds.). Coral reefs and climate change: science and management. American Geophysical Union, Washington, DC, Pages 111-128. Selig, E.R., K.S. Casey, and J. Bruno (2008). Global patterns of variability in coral reef temperature anomalies: the importance of fine scale spatial and temporal heterogeneity. Global Change Biology, submitted. Strong A.E., Liu G., Meyer J., Hendee J.C. and Sasko D. (2004). Coral Reef Watch 2002. Bulletin of Marine Science, 75, 259-268.The Mathworks Inc. (2006) Matlab. In. The Mathworks Inc., Natick, MA.

Resource Description: NODC Accession Number 0054501