Coral reef habitat maps derived from a high-spatial-resolution multi-spectral satellite image using object based image analysis

Coral reef maps at various spatial scales and extents are needed for mapping, monitoring, modelling, and management of these environments. High spatial resolution satellite imagery, pixel <10 m, integrated with field survey data and processed with various mapping approaches, can provide these maps. These approaches have been accurately applied to single reefs (10-100 km**2), covering one high spatial resolution scene from which a single thematic layer (e.g. benthic community) is mapped. This article demonstrates how a hierarchical mapping approach can be applied to coral reefs from individual reef to reef-system scales (10-1000 km**2) using object-based image classification of high spatial resolution images guided by ecological and geomorphological principles. The approach is demonstrated for three individual reefs (10-35 km**2) in Australia, Fiji, and Palau; and for three complex reef systems (300-600 km**2) one in the Solomon Islands and two in Fiji. Archived high spatial resolution images were pre-processed and mosaics were created for the reef systems. Georeferenced benthic photo transect surveys were used to acquire cover information. Field and image data were integrated using an object-based image analysis approach that resulted in a hierarchically structured classification. Objects were assigned class labels based on the dominant benthic cover type, or location-relevant ecological and geomorphological principles, or a combination thereof. This generated a hierarchical sequence of reef maps with an increasing complexity in benthic thematic information that included: 'reef', 'reef type', 'geomorphic zone', and 'benthic community'. The overall accuracy of the 'geomorphic zone' classification for each of the six study sites was 76-82% using 6-10 mapping categories. For 'benthic community' classification, the overall accuracy was 52-75% with individual reefs having 14-17 categories and reef systems 20-30 categories. We show that an object-based classification of high spatial resolution imagery, guided by field data and ecological and geomorphological principles, can produce consistent, accurate benthic maps at four hierarchical spatial scales for coral reefs of various sizes and complexities.

Habitat map of Danajon Bank, Philippines, derived from a high-spatial-resolution multi-spectral satellite image and georeferenced point intercept transect and spot-check survey field data, using an object-based image classification method

A mosaic of two WorldView-2 high resolution multispectral images (Acquisition dates: October 2010 and April 2012), in conjunction with field survey data, was used to create a habitat map of the Danajon Bank, Philippines (10°15'0'' N, 124°08'0'' E) using an object-based approach. To create the habitat map, we conducted benthic cover (seafloor) field surveys using two methods. Firstly, we undertook georeferenced point intercept transects (English et al., 1997). For ten sites we recorded habitat cover types at 1 m intervals on 10 m long transects (n= 2,070 points). Second, we conducted geo-referenced spot check surveys, by placing a viewing bucket in the water to estimate the percent cover benthic cover types (n = 2,357 points). Survey locations were chosen to cover a diverse and representative subset of habitats found in the Danajon Bank. The combination of methods was a compromise between the higher accuracy of point intercept transects and the larger sample area achievable through spot check surveys (Roelfsema and Phinn, 2008, doi:10.1117/12.804806). Object-based image analysis, using the field data as calibration data, was used to classify the image mosaic at each of the reef, geomorphic and benthic community levels. The benthic community level segregated the image into a total of 17 pure and mixed benthic classes.

Snow and ice surfaces on King George Island (Antarctic Peninsula) with high-resolution TerraSAR-X time series, with links to shapfiles and GeoTIFFs

Changes of glaciers and snow cover in polar regions affect a wide range of physical and ecosystem processes on land and in the adjacent marine environment. In this study, we investigate the potential of 11-day repeat high-resolution satellite image time series from the TerraSAR-X mission to derive glaciological and hydrological parameters on King George Island, Antarctica during the period Oct/25/2010 to Apr/19/2011. The spatial pattern and temporal evolution of snow cover extent on ice-free areas can be monitored using multi-temporal coherence images. SAR coherence is used to map glacier extent of land terminating glaciers with an average accuracy of 25 m. Multi-temporal SAR color composites identify the position of the late summer snow line at about 220 m above sea level. Glacier surface velocities are obtained from intensity feature-tracking. Surface velocities near the calving front of Fourcade Glacier were up to 1.8 ± 0.01 m/d. Using an intercept theorem based on fundamental geometric principles together with differential GPS field measurements, the ice discharge of Fourcade Glacier was estimated to 20700 ± 5500 m**3/d (corresponding to ~19 ± 5 kt/d). The rapidly changing surface conditions on King George Island and the lack of high-resolution digital elevation models for the region remain restrictions for the applicability of SAR data and the precision of derived products.

EOT11a - Global Empirical Ocean Tide model from multi-mission satellite altimetry, with links to model results

EOT11a is a global (E)mpirical (O)cean (T)ide model derived in 2011 by residual analysis of multi-mission satellite (a)ltimeter data. EOT11a includes amplitudes and phases of the main astronomical tides M2, S2, N2, K2, 2N2, O1, K1, P2, and Q1, the non-linear constituent M4, the long period tides Mm and Mf, and the radiational tide S1. Ocean tides as well as loading tides are provided. EOT11a was computed by means of residual tidal analysis of multi-mission altimeter data from TOPEX/Poseidon, ERS-2, ENVISAT, and Jason-1/2, as far as acquired between September 1992 and April 2010. The resolution of 7.5'x7.5' is identical with FES2004 which was used as reference model for the residual tide analysis. The development of EOT11a was funded by the Deutsche Forschungsgemeinschaft (DFG) under grant BO1228/6-2.

A multi-proxy investigation of sediment core GeoB7165-1 and AMS 14C dating points from sediment cores off Conceptión (~ 36°S)

A high-resolution sea surface temperature and paleoproductivity reconstruction on a sedimentary record collected at 36°S off central-south Chile (GeoB 7165-1, 36°33'S, 73°40'W, 797 m water depth, core length 750 cm) indicates that paleoceanographic conditions changed abruptly between 18 and 17 ka. Comparative analysis of several cores along the Chilean continental margin (30°-41°S) suggests that the onset and the pattern of deglacial warming was not uniform off central-south Chile due to the progressive southward migration of the Southern Westerlies and local variations in upwelling. Marine productivity augmented rather abruptly at 13-14 ka, well after the oceanographic changes.We suggest that the late deglacial increase in paleoproductivity off central-south Chile reflects the onset of an active upwelling system bringing nutrient-rich, oxygen-poor Equatorial SubsurfaceWater to the euphotic zone, and a relatively higher nutrient load of the Antarctic Circumpolar Current. During the Last Glacial Maximum, when the Southern Westerlies were located further north, productivity off central-south Chile, in contrast to off northern Chile, was reduced due to direct onshore-blowing winds that prevented coastal upwelling and export production.

A database of multi-year (2004-2010) quality-assured surface solar hourly irradiation measurements for the Egyptian territory

A database containing the global and diffuse components of the surface solar hourly irradiation measured from 1 January 2004 to 31 December 2010 at eight stations of the Egyptian Meteorological Authority is presented. For three of these sites (Cairo, Aswan, and El-Farafra), the direct component is also available. In addition, a series of meteorological variables including surface pressure, relative humidity, temperature, wind speed and direction is provided at the same hourly resolution at all stations. The details of the experimental sites and instruments used for the acquisition are given. Special attention is paid to the quality of the data and the procedure applied to flag suspicious or erroneous measurements is described in details. Between 88 and 99% of the daytime measurements are validated by this quality control. Except at Barrani where the number is lower (13500), between 20000 and 29000 measurements of global and diffuse hourly irradiation are available at all sites for the 7-year period. Similarly, from 9000 to 13000 measurements of direct hourly irradiation values are provided for the three sites where this component is measured. With its high temporal resolution this consistent irradiation and meteorological database constitutes a reliable source to estimate the potential of solar energy in Egypt. It is also adapted to the study of high-frequency atmospheric processes such as the impact of aerosols on atmospheric radiative transfer. In the next future, it is planned to complete regularly the present 2004-2010 database.

High-resolution planktic stable isotope and trace element record of ODP Hole 161-976

Multi-decadal to centennial planktic d18O and Mg/Ca records were generated at ODP976 in the Alboran Sea. The site is in the flow path of Atlantic inflow waters entering the Mediterranean and captured North Atlantic signals through the surface inflow and the atmosphere. The records reveal similar climatic oscillations during the last two glacial-to-interglacial transitions, albeit with a different temporal pacing. Glacial termination 1 (T1) was marked by Heinrich event 1 (H1), post-H1 Bolling/Allerod (B/A) warming and Younger Dryas (YD) cooling. During T2 the H11 d18O anomaly was twice as high and lasted 30% longer than during H1. The post-H11 warming marked the start of MIS5e while the subsequent YD-style cooling occurred during early MIS5e. The post-H11 temperature increase at ODP976 matched the sudden Asian Monsoon Termination II at 129 ka BP. Extending the 230Th-dated speleothem timescale to ODP976 suggests glacial conditions in the Northeast Atlantic region were terminated abruptly and interglacial warmth was reached in less than a millennium. The early-MIS5e cooling and freshening at ODP976 coincided with similar changes at North Atlantic sites suggesting this was a basin-wide event. By analogy with T1 we argue that this was a YD-type event that was shifted into the early stages of the last interglacial period. This scenario is consistent with evidence from northern North Atlantic and Nordic Sea sites that the continuing disintegration of the large Saalian Stage (MIS6) ice sheet in Eurasia delayed the advection of warm North Atlantic waters and full-strength convective overturn until later stages of MIS5e.

Major components and major and trace elements from ODP Site 175-1085

We have analyzed 33 Pliocene bulk sediment samples from Ocean Drilling Program Site 1085 in the Cape Basin, located offshore of western Africa in the Angola-Benguela Current system, for 17 major and trace elements, and interpreted their associations and temporal variations in the context of an allied data set of CaCO3, opal, and Corg. We base our interpretations on elemental ratios, accumulation rates, inter-element correlations, and several multi-element statistical techniques. On the basis of qualitative assessment of downhole changes in the distributions of P and Ba, utilized as proxies of export production, we conclude that highs in bulk and biogenic accumulation that occur at 3.2 Ma, 3.0 Ma, 2.4 Ma, and 2.25 Ma were caused by increases in export production as well as terrigenous flux, and record a greater sequestering of organic matter during these time periods. Studies of refractory elements and other indicator proxies (SiO2, Al2O3, TiO2, Fe2O3, MgO, V, Cr, Sr, and Zr) strongly suggest that the terrigenous component of the bulk sediment is composed of two compositional end-members, one being 'basaltic' in composition and the other similar to an 'average shale'. The basaltic end-member comprises approximately 10-15% of the total bulk sediment and its presence is consistent with the local geology of source material in the drainage basin of the nearby Orange River. The increase in bulk accumulation at 2.4 Ma appears to reflect a greater relative increase in basaltic input than the relative increase in shale-type input. Although studies such as this cannot precisely identify the transport mechanisms of the different terrigenous components, these results are most consistent with variations in sea level (and associated changes in shelf geometry and fluvial input) being responsible for the changing depositional conditions along the Angolan Margin during this time period.

Natural remanent magnetization (NRM) from ODP Site 1263 covering magnetochron C20r and C21n and high-resolution bulk carbon isotope (d13C) records from Sites 702 and 1263

To explore cause and consequences of past climate change, very accurate age models such as those provided by the astronomical timescale (ATS) are needed. Beyond 40 million years the accuracy of the ATS critically depends on the correctness of orbital models and radioisotopic dating techniques. Discrepancies in the age dating of sedimentary successions and the lack of suitable records spanning the middle Eocene have prevented development of a continuous astronomically calibrated geological timescale for the entire Cenozoic Era. We now solve this problem by constructing an independent astrochronological stratigraphy based on Earth's stable 405 kyr eccentricity cycle between 41 and 48 million years ago (Ma) with new data from deep-sea sedimentary sequences in the South Atlantic Ocean. This new link completes the Paleogene astronomical timescale and confirms the intercalibration of radioisotopic and astronomical dating methods back through the Paleocene-Eocene Thermal Maximum (PETM, 55.930 Ma) and the Cretaceous-Paleogene boundary (66.022 Ma). Coupling of the Paleogene 405 kyr cyclostratigraphic frameworks across the middle Eocene further paves the way for extending the ATS into the Mesozoic.

Multi-temporal mapping of seagrass cover, species and biomass of the Eastern Banks, Moreton Bay, Australia, with links to shapefiles

The spatial and temporal dynamics of seagrasses have been studied from the leaf to patch (100 m**2) scales. However, landscape scale (> 100 km**2) seagrass population dynamics are unresolved in seagrass ecology. Previous remote sensing approaches have lacked the temporal or spatial resolution, or ecologically appropriate mapping, to fully address this issue. This paper presents a robust, semi-automated object-based image analysis approach for mapping dominant seagrass species, percentage cover and above ground biomass using a time series of field data and coincident high spatial resolution satellite imagery. The study area was a 142 km**2 shallow, clear water seagrass habitat (the Eastern Banks, Moreton Bay, Australia). Nine data sets acquired between 2004 and 2013 were used to create seagrass species and percentage cover maps through the integration of seagrass photo transect field data, and atmospherically and geometrically corrected high spatial resolution satellite image data (WorldView-2, IKONOS and Quickbird-2) using an object based image analysis approach. Biomass maps were derived using empirical models trained with in-situ above ground biomass data per seagrass species. Maps and summary plots identified inter- and intra-annual variation of seagrass species composition, percentage cover level and above ground biomass. The methods provide a rigorous approach for field and image data collection and pre-processing, a semi-automated approach to extract seagrass species and cover maps and assess accuracy, and the subsequent empirical modelling of seagrass biomass. The resultant maps provide a fundamental data set for understanding landscape scale seagrass dynamics in a shallow water environment. Our findings provide proof of concept for the use of time-series analysis of remotely sensed seagrass products for use in seagrass ecology and management.

Global Ocean Colour for Carbon Cycle Research (full product set)

In 2005, the International Ocean Colour Coordinating Group (IOCCG) convened a working group to examine the state of the art in ocean colour data merging, which showed that the research techniques had matured sufficiently for creating long multi-sensor datasets (IOCCG, 2007). As a result, ESA initiated and funded the DUE GlobColour project (http://www.globcolour.info/) to develop a satellite based ocean colour data set to support global carbon-cycle research. It aims to satisfy the scientific requirement for a long (10+ year) time-series of consistently calibrated global ocean colour information with the best possible spatial coverage. This has been achieved by merging data from the three most capable sensors: SeaWiFS on GeoEye's Orbview-2 mission, MODIS on NASA's Aqua mission and MERIS on ESA's ENVISAT mission. In setting up the GlobColour project, three user organisations were invited to help. Their roles are to specify the detailed user requirements, act as a channel to the broader end user community and to provide feedback and assessment of the results. The International Ocean Carbon Coordination Project (IOCCP) based at UNESCO in Paris provides direct access to the carbon cycle modelling community's requirements and to the modellers themselves who will use the final products. The UK Met Office's National Centre for Ocean Forecasting (NCOF) in Exeter, UK, provides an understanding of the requirements of oceanography users, and the IOCCG bring their understanding of the global user needs and valuable advice on best practice within the ocean colour science community. The three year project kicked-off in November 2005 under the leadership of ACRI-ST (France). The first year was a feasibility demonstration phase that was successfully concluded at a user consultation workshop organised by the Laboratoire d'Océanographie de Villefranche, France, in December 2006. Error statistics and inter-sensor biases were quantified by comparison with insitu measurements from moored optical buoys and ship based campaigns, and used as an input to the merging. The second year was dedicated to the production of the time series. In total, more than 25 Tb of input (level 2) data have been ingested and 14 Tb of intermediate and output products created, with 4 Tb of data distributed to the user community. Quality control (QC) is provided through the Diagnostic Data Sets (DDS), which are extracted sub-areas covering locations of in-situ data collection or interesting oceanographic phenomena. This Full Product Set (FPS) covers global daily merged ocean colour products in the time period 1997-2006 and is also freely available for use by the worldwide science community at http://www.globcolour.info/data_access_full_prod_set.html. The GlobColour service distributes global daily, 8-day and monthly data sets at 4.6 km resolution for, chlorophyll-a concentration, normalised water-leaving radiances (412, 443, 490, 510, 531, 555 and 620 nm, 670, 681 and 709 nm), diffuse attenuation coefficient, coloured dissolved and detrital organic materials, total suspended matter or particulate backscattering coefficient, turbidity index, cloud fraction and quality indicators. Error statistics from the initial sensor characterisation are used as an input to the merging methods and propagate through the merging process to provide error estimates for the output merged products. These error estimates are a key component of GlobColour as they are invaluable to the users; particularly the modellers who need them in order to assimilate the ocean colour data into ocean simulations. An intensive phase of validation has been undertaken to assess the quality of the data set. In addition, inter-comparisons between the different merged datasets will help in further refining the techniques used. Both the final products and the quality assessment were presented at a second user consultation in Oslo on 20-22 November 2007 organised by the Norwegian Institute for Water Research (NIVA); presentations are available on the GlobColour WWW site. On request of the ESA Technical Officer for the GlobColour project, the FPS data set was mirrored in the PANGAEA data library.