Alan E. Strong

Remote sensing of sea surface temperatures during 2002 Barrier Reef coral bleaching

Early in 2002, satellites of the U.S. National Oceanic and Atmospheric Administration (NOAA) detected anomalously high sea surface temperatures (SST) developing in the western Coral Sea, midway along Australias Great Barrier Reef (GBR). This was the beginning of what was to become the most significant GBR coral bleaching event on record [Wilkinson, 2002]. During this time, NOAAs National Environmental Satellite, Data, and Information Service (NESDIS) provided satellite data as part of ongoing collaborative work on coral reef health with the Australian Institute of Marine Science (AIMS) and the Great Barrier Reef Marine Park Authority (GBRMPA). These data proved invaluable to AIMS and GBRMPA as they monitored and assessed the development and evolution of SSTs throughout the austral summer, enabling them to keep stakeholders, government, and the general public informed and up to date.

Crisis on coral reefs linked to climate change

Since 1982, coral reefs worldwide have been subjected to an increased frequency of the phenomenon known as coral bleaching. Bleaching involves the dramatic loss of pigmented, single-celled endosymbiotic algae that live within the gastrodermal cells of a coral host that depends on this relationship for survival. Prior to the 1980s, and as early as the 1920s when coral reef research intensified, localized bleaching events were reported and attributed to factors such as extremely low tides, hurricane damage, torrential rainstorms, freshwater runoff near reefs, or toxic algal blooms [Glynn, 1993]. However, these early occurrences have recently been overshadowed by geographically larger and more frequent bleaching events whose impact has expanded to regional and global proportions.

Sea surface temperature signals from satellites—An update

Polar satellite-derived observations of sea surface temperatures (SSTs) have been used routinely since 1982 to provide a complete monitoring of our planet, covering all comers of the oceans (unless covered by clouds) twice each day. In 1992, an initial glimpse was published (Strong, 1992) of some tendencies that had been observed during the 1980s. Now that seven additional years of NOAA satellite SST data have become available, the earlier time-series (Strong, 1992) has been up-dated, hi this analysis of the global nighttime SSTs, care was taken to avoid the anomalous conditions found during the 1982–83 El Chichon aerosols, 1991–92 Mt. Pinatubo aerosols, and the strong El Nino of 1997-98. Evidence of warming is found to be present throughout much of the Tropics and in the mid-latitude Northern Hemisphere. Estimates from the Southern Hemisphere, while strongly indicative of compensatory cooling in the region, are found to be not as reliable.

Comment on “Coral reef calcification and climate change: The effect of ocean warming”

McNeil et al. [2004] attempt to address an important question about the interactions of temperature and carbonate chemistry on calcification, but their projected values of reef calcification are based on assumptions that ignore critical observational and experimental literature. Certainly, more research is needed to better understand how changing temperatures and carbonate chemistry will affect not only coral reef calcification, but coral survival. As discussed above, the McNeil et al. [2004] analysis is based on assumptions that exclude potentially important factors and therefore needs to be viewed with caution. Copyright 2005 by the American Geophysical Union.

Upwelled spectral radiance distribution in relation to particulate matter in sea water

Spectral analysis of water color and concurrent measurements of the relative concentration of various particulate and dissolved constituents within a broad range of water types are necessary to quantify ocean color observations and successfully relate them to various biological and physical processes that can be monitored by remote sensing. Some of the results of a Nimbus-G prelaunch cruise in connection with the Coastal Zone Color Scanner (CZCS) experiment, which was carried out in the Gulf of Mexico in October 1977, are presented and discussed. Based upon a small but diverse sample of near-surface measurements, it appears possible to estimate total suspended particulate matter (SPM) to useful accuracies by forming ratios of the spectral radiances measured at wavelengths falling near the centers of certain CZCS bands, viz., 440 nm: 550 nm and 440 nm : 520 nm. Furthermore, the analysis suggests a very high degree of covariation between SPM and phytoplankton pigments except for certain well-defined special cases.

Remote sensing of algal blooms by aircraft and satellite in Lake Erie and Utah Lake

Abstract During late summer, when the surface waters of Lake Erie reach their maximum temperature, an algal bloom is likely to develop. Such phenomena, which characterize eutrophic conditions, have been noticed on other shallow lakes using the Earth Resources Technology Satellite (ERTS-1). The concentration of the algae into long streamers provides additional information on surface circulations. To augment the ERTS Multispectral Scanner Subsystem (MSS) data of Lake Erie an aircraft was used to obtain correlative thermal-IR and additional multiband photographs. The algal bloom is highly absorptive in the visible wavelengths but reverses contrast with the surrounding water in the near-IR bands. The absorption of shortwave energy heats the dark brown algal mass, providing a hot surface target for the thermal-IR scanner. A large bloom of Aphanizomenon flos-aquae observed in Utah Lake together with recent bloom history in Lake Erie is used to verify the Great Lakes bloom.

Sea-surface temperature and thermal stress in the Coral Triangle over the past two decades

Increasing ocean temperature has become one of the major concerns in recent times with reports of various related ecological impacts becoming commonplace. One of the more notable is the increased frequency of mass coral bleaching worldwide. This study focuses on the Coral Triangle region and utilizes the National Oceanic and Atmospheric Administration-Coral Reef Watch (NOAA-CRW) satellite-derived sea surface temperature (SST) and Degree Heating Weeks (DHW) products to investigate changes in the thermal regime of the Coral Triangle waters between 1985 and 2006. Results show an upward trend in SST during this period with an average rate of 0.2°C/decade. However, warming within this region is not uniform, and the waters of the northern and eastern parts of the Coral Triangle are warming fastest. Areas in the eastern part have experienced more thermal stress events, and these stress events appear to be more likely during a La Niña.

Reef-Scale Thermal Stress Monitoring of Coral Ecosystems: New 5-km Global Products from NOAA Coral Reef Watch

The U.S. National Oceanic and Atmospheric Administration (NOAA) Coral Reef Watch (CRW) program has developed a daily global 5-km product suite based on satellite observations to monitor thermal stress on coral reefs. These products fulfill requests from coral reef managers and researchers for higher resolution products by taking advantage of new satellites, sensors and algorithms. Improvements of the 5-km products over CRW’s heritage global 50-km products are derived from: (1) the higher resolution and greater data density of NOAA’s next-generation operational daily global 5-km geo-polar blended sea surface temperature (SST) analysis; and (2) implementation of a new SST climatology derived from the Pathfinder SST climate data record. The new products increase near-shore coverage and now allow direct monitoring of 95% of coral reefs and significantly reduce data gaps caused by cloud cover. The 5-km product suite includes SST Anomaly, Coral Bleaching HotSpots, Degree Heating Weeks and Bleaching Alert Area, matching existing CRW products. When compared with the 50-km products and in situ bleaching observations for 2013–2014, the 5-km products identified known thermal stress events and matched bleaching observations. These near reef-scale products significantly advance the ability of coral reef researchers and managers to monitor coral thermal stress in near-real-time.

Coral bleaching threatens oceans, life

People around the world depend on the resources provided by the ocean to support life. But global-scale damage to the coral reefs, a large and integral part of the ocean environment that supports a variety of sea life, is a frightening prospect that may unfold in the coming years. Recently, a phenomenon called coral bleaching has raised concerns about the deteriorating conditions in the worlds oceans and the implications for life on our planet. Coral bleaching occurs as coral tissue expels zooxanthellae, a symbiotic algae that resides in the structure of the coral and is essential to its survival. The widespread nature of the bleaching threatens the state of the environment.

Comparing stratospheric aerosols from El Chichón and Mount Pinatubo using AVHRR data

One of the key factors in assessing the climatic impact of the Mount Pinatubo eruption of June 15, 1991, is the relative size of this eruption as it compares with other eruptions. As a first approximation, the climatic changes observed after those earlier eruptions can be used to predict the changes to be expected from the more recent eruption. Ideally this intercomparison should be done with a common measurement system. Data from the advanced very high resolution radiometer (AVHRR) onboard the NOAA polar orbiting environmental satellite can be used to compare the optical properties of the aerosol layer produced by the two most recent major volcanic eruptions, El Chichon, early-April 1982, and Mount Pinatubo, mid-June 1991. In this paper, we use the error introduced into the multi-channel sea surface temperature (MCSST) fields by the volcanically-produced stratospheric aerosol layer to make a relative comparison of the size of the two eruptions. We also use aerosol optical thickness (AOT) estimates from the visible reflectance channel of the AVHRR to verify that the MCSST errors are indeed related to aerosol particle concentration in the stratosphere. During the first three months following both eruptions, these comparisons reveal that Mount Pinatubo introduced slightly less than twice (1.6 to 1.9) the amount of aerosol into the stratosphere as El Chichon.