Image correlation and sampling study

The development of analytical approaches for solving image correlation and image sampling of multispectral data is discussed. Relevant multispectral image statistics which are applicable to image correlation and sampling are identified. The general image statistics include intensity mean, variance, amplitude histogram, power spectral density function, and autocorrelation function. The translation problem associated with digital image registration and the analytical means for comparing commonly used correlation techniques are considered. General expressions for determining the reconstruction error for specific image sampling strategies are developed

Dissolved iron transport pathways in the Ross Sea : influence of tides and horizontal resolution in a regional ocean model

© The Author(s), 2016. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Journal of Marine Systems 166 (2017): 73-86, doi:10.1016/j.jmarsys.2016.10.008.Phytoplankton production in the Ross Sea is regulated by the availability of dissolved iron (dFe), a limiting micro-nutrient, whose sources include Circumpolar Deep Water, sea ice melt, glacial melt, and benthic sources (sediment efflux and remineralization). We employ a passive tracer dye to model the benthic dFe sources and track pathways from deep areas of the continental shelf to the surface mixed layer in simulations with and without tidal forcing, and at 5 and 1.5km horizontal resolution. This, combined with dyes for each of the other dFe sources, provides an estimate of total dFe supply to surface waters. We find that tidal forcing increases the amount of benthic dye that covers the banks on the continental shelf. Calculations of mixed layer depth to define the surface ocean give similar average values over the shelf, but spatial patterns differ between simulations, particularly along the ice shelf front. Benthic dFe supply in simulations shows an increase with tidal forcing and a decrease with higher resolution. The changes in benthic dFe supply control the difference in total supply between simulations. Overall, the total dFe supply from simulations varies from 5.60 to 7.95 μmol m-2 yr-1, with benthic supply comprising 32-50%, comparing well with recent data and model synthesis. We suggest that including tides and using high horizontal resolution is important, especially when considering spatial variability of iron supply on the Ross Sea shelf.The authors acknowledge funding from NSF's Antarctic Research Program 496 (ODU: ANT-0944174; WHOI: ANT-0094165)

Estimating the Benthic Efflux of Dissolved Iron on the Ross Sea Continental Shelf

Continental margin sediments provide a potentially large but poorly constrained source of dissolved iron (dFe) to the upper ocean. The Ross Sea continental shelf is one region where this benthic supply is thought to play a key role in regulating the magnitude of seasonal primary production. Here we present data collected during austral summer 2012 that reveal contrasting low surface (0.08 +/- 0.07 nM) and elevated near-seafloor (0.74 +/- 0.47 nM) dFe concentrations. Combining these observations with results from a high-resolution physical circulation model, we estimate dFe efflux of 5.8 x 10(7) mol yr(-1) from the deeper portions (\u3e400m) of the Ross Sea continental shelf; more than sufficient to account for the inferred winter reserve dFe inventory at the onset of the growing season. In addition, elevated dFe concentrations observed over shallower bathymetry suggest that such features provide additional inputs of dFe to the euphotic zone throughout the year

Sea-ice production and air/ice/ocean/biogeochemistry interactions in the Ross Sea during the PIPERS 2017 autumn field campaign

The Ross Sea is known for showing the greatest sea-ice increase, as observed globally, particularly from 1979 to 2015. However, corresponding changes in sea-ice thickness and production in the Ross Sea are not known, nor how these changes have impacted water masses, carbon fluxes, biogeochemical processes and availability of micronutrients. The PIPERS project sought to address these questions during an autumn ship campaign in 2017 and two spring airborne campaigns in 2016 and 2017. PIPERS used a multidisciplinary approach of manned and autonomous platforms to study the coupled air/ice/ocean/biogeochemical interactions during autumn and related those to spring conditions. Unexpectedly, the Ross Sea experienced record low sea ice in spring 2016 and autumn 2017. The delayed ice advance in 2017 contributed to (1) increased ice production and export in coastal polynyas, (2) thinner snow and ice cover in the central pack, (3) lower sea-ice Chl-a burdens and differences in sympagic communities, (4) sustained ocean heat flux delaying ice thickening and (5) a melting, anomalously southward ice edge persisting into winter. Despite these impacts, airborne observations in spring 2017 suggest that winter ice production over the continental shelf was likely not anomalous

Assessing Phytoplankton Nutritional Status and Potential Impact of Wet Deposition in Seasonally Oligotrophic Waters of the Mid-Atlantic Bight

To assess phytoplankton nutritional status in seasonally oligotrophic waters of the southern Mid-Atlantic Bight, and the potential for rain to stimulate primary production in this region during summer, shipboard bioassay experiments were performed using natural seawater and phytoplankton collected north and south of the Gulf Stream. Bioassay treatments comprised iron, nitrate, iron + nitrate, iron + nitrate + phosphate, and rainwater. Phytoplankton growth was inferred from changes in chlorophyll a, inorganic nitrogen, and carbon-13 uptake, relative to unamended control treatments. Results indicated the greatest growth stimulation by iron + nitrate + phosphate, intermediate growth stimulation by rainwater, modest growth stimulation by nitrate and iron + nitrate, and no growth stimulation by iron. Based on these data and analysis of seawater and atmospheric samples, nitrogen was the proximate limiting nutrient, with a secondary limitation imposed by phosphorus. Our results imply that summer rain events increase new production in these waters by contributing nitrogen and phosphorus, with the availability of the latter setting the upper limit on rain-stimulated new production. Plain Language Summary Human activities have substantially increased the atmospheric loading and deposition of biologically available nitrogen, an essential nutrient, to the surface ocean. Such atmospheric inputs to the ocean will likely impact on oceanic primary production by phytoplankton, and thus the marine ecosystem and ocean carbon cycling, although the scale and spatial distribution of such impacts are not well known. In this study, we used shipboard experiments, observations, and laboratory measurements to assess the potential impacts of atmospheric nitrogen deposition in rainfall on oceanic waters of the Mid-Atlantic Bight, off the U.S. eastern seaboard, during the summer. We find that the growth of phytoplankton in these waters is limited by the availability of nitrogen during summer, such that nitrogen added to the ocean by summer rain events can considerably stimulate phytoplankton primary production. However, the biological impact of these rainwater nitrogen inputs appears to be limited by the availability of another essential nutrient, phosphorus, which is present at relatively low concentrations in rainwater. This is the first study to directly examine the nutritional status of phytoplankton in relation to the impacts of rainwater nitrogen addition on primary production in oceanic waters off the U.S. East Coast

Atmospheric Input and Seasonal Inventory of Dissolved Iron in the Sargasso Sea: Implications for Iron Dynamics in Surface Waters of the Subtropical Ocean

Constraining the role of dust deposition in regulating the concentration of the essential micronutrient iron in surface ocean waters requires knowledge of the flux of seawater-soluble iron in aerosols and the replacement time of dissolved iron (DFe) in the euphotic zone. Here we estimate these quantities using seasonally resolved DFe data from the Bermuda Atlantic Time-series Study region and weekly-scale measurements of iron in aerosols and rain from Bermuda during 2019. In response to seasonal changes in vertical mixing, primary production and dust deposition, surface DFe concentrations vary from ∼0.2 nM in early spring to \u3e1 nM in late summer, with DFe inventories ranging from ∼30 to ∼80 μmol/m2, respectively, over the upper 200 m. Assuming the upper ocean approximates steady state for DFe on an annual basis, our aerosol and rainwater data require a mean euphotic-zone residence time of ∼0.8–1.9 years for DFe with respect to aeolian input

Iron Supply and Demand in Antarctic Shelf Ecosystem

The Ross Sea sustains a rich ecosystem and is the most productive sector of the Southern Ocean. Most of this production occurs within a polynya during the November-February period, when the availability of dissolved iron (dFe) is thought to exert the major control on phytoplankton growth. Here we combine new data on the distribution of dFe, high-resolution model simulations of ice melt and regional circulation, and satellite-based estimates of primary production to quantify iron supply and demand over the Ross Sea continental shelf. Our analysis suggests that the largest sources of dFe to the euphotic zone are wintertime mixing and melting sea ice, with a lesser input from intrusions of Circumpolar Deep Water and a small amount from melting glacial ice. Together these sources are in approximate balance with the annual biological dFe demand inferred from satellite-based productivity algorithms, although both the supply and demand estimates have large uncertainties

Basin-scale transport of hydrothermal dissolved metals across the South Pacific Ocean

Hydrothermal venting along mid-ocean ridges exerts an important control on the chemical composition of sea water by serving as a major source or sink for a number of trace elements in the ocean(1-3). Of these, iron has received considerable attention because of its role as an essential and often limiting nutrient for primary production in regions of the ocean that are of critical importance for the global carbon cycle(4). It has been thought that most of the dissolved iron discharged by hydrothermal vents is lost from solution close to ridge-axis sources(2,5) and is thus of limited importance for ocean biogeochemistry(6). This long-standing view is challenged by recent studies which suggest that stabilization of hydrothermal dissolved iron may facilitate its longrange oceanic transport(7-10). Such transport has been subsequently inferred from spatially limited oceanographic observations(11-13). Here we report data from the US GEOTRACES Eastern Pacific Zonal Transect (EPZT) that demonstrate lateral transport of hydrothermal dissolved iron, manganese, and aluminium from the southern East Pacific Rise (SEPR) several thousand kilometres westward across the South Pacific Ocean. Dissolved iron exhibits nearly conservative (that is, no loss from solution during transport and mixing) behaviour in this hydrothermal plume, implying a greater longevity in the deep ocean than previously assumed(6,14). Based on our observations, we estimate a global hydrothermal dissolved iron input of three to four gigamoles per year to the ocean interior, which is more than fourfold higher than previous estimates(7,11,14). Complementary simulations with a global-scale ocean biogeochemical model suggest that the observed transport of hydrothermal dissolved iron requires some means of physicochemical stabilization and indicate that hydrothermally derived iron sustains a large fraction of Southern Ocean export productio

Iron, silicate, and light co-limitation of three Southern Ocean diatom species

The effect of combined iron, silicate, and light co-limitation was investigated in the three diatom species Actinocyclus sp. Ehrenberg, Chaetoceros dichaeta Ehrenberg, and Chaetoceros debilis Cleve, isolated from the Southern Ocean (SO). Growth of all species was co-limited by iron and silicate, reflected in a significant increase in the number of cell divisions compared to the control. Lowest relative Si uptake and drastic frustule malformation was found under iron and silicate co-limitation in C. dichaeta, while Si limitation in general caused cell elongation in both Chaetoceros species. Higher light intensities similar to SO surface conditions showed a negative impact on growth of C. dichaeta and Actinocyclus sp. and no effect on C. debilis. This is in contrast to the assumed light limitation of SO diatoms due to deep wind driven mixing. Our results suggest that growth and species composition of Southern Ocean diatoms is influenced by a sensitive interaction of the abiotic factors, iron, silicate, and light

Particle dynamics in the rising plume at Piccard Hydrothermal Field, Mid-Cayman Rise

Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 16 (2015): 2762–2774, doi:10.1002/2015GC005831.Processes active in rising hydrothermal plumes, such as precipitation, particle aggregation, and biological growth, affect particle size distributions and can exert important influences on the biogeochemical impact of submarine venting of iron to the oceans and their sediments. However, observations to date of particle size distribution within these systems are both limited and conflicting. In a novel buoyant hydrothermal plume study at the recently discovered high-temperature (398°C) Piccard Hydrothermal Field, Mid-Cayman Rise, we report optical measurements of particle size distributions (PSDs). We describe the plume PSD in terms of a simple, power-law model commonly used in studies of upper and coastal ocean particle dynamics. Observed PSD slopes, derived from spectral beam attenuation and laser diffraction measurements, are among the highest found to date anywhere in the ocean and ranged from 2.9 to 8.5. Beam attenuation at 650 nm ranged from near zero to a rarely observed maximum of 192 m−1 at 3.5 m above the vent. We did not find large (>100 μm) particles that would settle rapidly to the sediments. Instead, beam attenuation was well-correlated to total iron, suggesting the first-order importance of particle dilution, rather than precipitation or dissolution, in the rising plume at Piccard. Our observations at Piccard caution against the assumption of rapid deposition of hydrothermal, particulate metal fluxes, and illustrate the need for more particle size and composition measurements across a broader range of sites, globally.This work was funded by the National Science Foundation (OCE-1029223; OCE-1061863), NASA (NNX09AB75G) and Woods Hole Oceanographic Institution's Deep Ocean Exploration Institute and Ocean Ridge Initiative. Ship time (R/V Falkor cruise FK008) was funded by the Schmidt Ocean Institute and M.L.E. was supported by a WHOI Postdoctoral Scholar fellowship.2016-02-2