Real-time data assimilative modeling on Georges bank

Real-time oceanic forecasts were constructed at sea on Georges Bank during Spring 1999. Ship- and shore-based computations were combined to deliver daily 3-day forecasts to shipboard scientists for interpreting observations and planning operations. Data assimilated included acoustic Doppler current profiler velocities, drifter trajectories, and taxa-specific plankton observations from a Video Plankton Recorder (VPR) system. Services provided included basic 3-D circulation forecasts, forecast positions of drifters, dye and zoo-plankton, and the advective adjustment of observations to produce synoptic maps. The results indicate that real-time, at-sea data assimilative modeling can provide valuable information services and can be deployed routinely, provided that networking among ships, instruments, and shore continues to improve. This paper summarizes the real-time modeling experience. Results of the larger effort including scientific data interpretation are being reported separately

The interaction of phytoplankton, zooplankton and currents from 15 months of continuous data in the Mid-Atlantic Bight

Fifteen months of data from an acoustic Doppler current profiler (ADCP) and three fluorometers obtained during the SEEP-II program in the southern Mid-Atlantic Bight provide a unique view of the seasonal progression of zooplankton and phytoplankton biomass and their responses to physical forcing. Phytoplankton and zooplankton biomass records were highly variable with a continuum of energy at all frequencies and substantial interannual variation. The zooplankton and phytoplankton spring blooms were coincident; that is, the spring increase in zooplankton biomass did not lag behind that of phytoplankton. The spring bloms were not the dominant events of the records, however; the largest fluctuations were linked to current fluctuations, although not always in the same manner. The seasonal succession of zooplankton and phytoplankton species, together with changes in stratification, led to significant differences in the vertical distribution of biomass and its response to physical forcing. There was about a factor of two difference in the maximum zooplankton biomass between two successive springs, while there was no difference in the phytoplankton blooms. Coherence between the phytoplankton, zooplankton and currents were all low. While individual events usually could be ascribed to along- or cross-shelf advective processes, the apparent extreme variability in horizontal biological gradients makes generalizations, aside from those on seasonal time scales, impossible from a single location. Examination of spring bloom data from two successive springs shows a fairly typical relation between primary and secondary production. Thus, the net daily chlorophyll increases ranged from 2.5 to 7.5%, and zooplankton daily ingestion was estimated at 30–55% of primary production, while 38–67% of the daily production was lost to micro-zooplankton, bacteria and the benthos. Zooplankton daily lossed were estimated to be between 25 and 33%. Time-scale estimates for phytoplankton increases agree with incubation values; however, those for zooplankton were much shorter than their reproduction rate, indicating active aggregation behavior

Cold anticyclonic eddies formed from cold pool water in the southern Middle Atlantic Bight

AVHRR satellite imagery of the southern Mid-Atlantic Bight during May 1993 revealed a large area of cold water over the shelf break and slope that appeared to spin up into a series of southward propagating anticyclonic eddies. The eddies had diameters of 35–45 km at the surface and moved southward at about 20 cm/sec. A radial TOYO CTD (to 50m) and ADCP velocity (to 400m) transect was conducted across the southern-most of these eddies. The upper 50 meters had minimum temperatures of less than 7°C and salinities of about 33 pss, characteristics similar to cold pool waters usually found over the continental shelf. ADCP velocity data from one of the eddies revealed anticyclonic flow extending to a depth of about 250m. The transport of cold pool water by the eddies was estimated to be 0.1 to 0.2 Sv which is of the same order as the annual mean alongshore transport of shelf water in this region. The origin of the deeper water within the eddy is unlikely to be the continental shelf because the shelf break is less than 100 m. The depth and velocity profiles along the TOYO transect were consistent with the constant potential vorticity eddy model of Flierl (1979) although the source of the eddy kinetic energy is uncertain. The cause for the exodus of cold pool water from the shelf, which extended northward to at least 38°N, is unclear but must involve the establishment of an alongshore baroclinic pressure gradient against the usual southwestward shelf flow. It is possible that the intrusion of Gulf Stream waters onto the shelf near Cape Hatteras was a precursor of this off shelf transport. The southern-most eddy was marked by high biological productivity and very high oxygen supersaturation. The phytoplankton bloom detected within the exported cold pool water, located over the continental slope, suggests a mechanism whereby production fueled by nutrients derived from the shelf can be locally exported into deep wate

Acoustic Doppler current profiling from the JGOFS Arabian sea cruises aboard the RV T.G. Thompson

Acoustic Doppler current profiler (ADCP) data is part of the core data for the U.S. JGOFS Arabian Sea project, along with hydrographic and nutrient data. Seventeen cruises are scheduled to take place between September 1994 and January 1996 on the R/V T.G. Thompson. They are numbered consecutively from the ship`s commissioning with the first JGOFS cruise designated TN039. Table 1 lists start and end dates of each cruise with its mission. All but the first cruise have been or will be staged from Muscat, Oman. Each cruise is scheduled for a duration of between two weeks and one month. Seven of the cruises, referred to as process cruises, follow a standard cruise track, taking hydrographic, chemical and biological measurements. The rest of the cruises, which take place generally within the standard cruise region defined by a set track, are for the deployment and recovery of moored equipments and towing of a SeaSoar. ADCP data are collected using an autonomous data acquisition system developed for ship-of-opportunity cruises, named the AutoADCP system. The system is an extension of RD instrument`s DAS version 2.48 using enhancements made possible with {open_quotes}user-exit{close_quotes} programs. It makes it possible to collect ADCP data without the constant monitoring usually necessary and insures constant data coverage and uniform data quality

Directly measured currents and estimated transport pathways of Atlantic Water between 59.5°N and the Iceland-Faroes-Scotland Ridge

Using vessel-mounted acoustic Doppler current profiler data from four different routes between Scotland, Iceland and Greenland, we map out the mean flow of water in the top 400 m of the northeastern North Atlantic. The poleward transport east of the Reykjanes Ridge (RR) decreases from ~8.5 to 10 Sv (1 Sverdrup=106 m3 s−1) at 59.5°N to 61°N to 6 Sv crossing the Iceland–Faroes–Scotland Ridge. The two longest ~1200 km transport integrals have 1.4–0.94 Sv uncertainty, respectively. The overall decrease in transport can in large measure be accounted for by a ~1.5 Sv flow across the RR into the Irminger Sea north of 59.5°N and by a ~0.5 Sv overflow of dense water along the Iceland–Faroes Ridge. A remaining 0.5 Sv flux divergence is at the edge of detectability, but if real could be accounted for through wintertime convection to >400 m and densification of upper ocean water. The topography of the Iceland Basin and the banks west of Scotland play a fundamental role in controlling flow pathways towards and past Iceland, the Faroes and Scotland. Most water flows north unimpeded through the Iceland Basin, some in the centre of the basin along the Maury Channel, and some along Hatton Bank, turning east along the northern slopes of George Bligh Bank, Lousy Bank and Bill Bailey’s Bank, whereupon the flow splits with ~3 Sv turning northwest towards the Iceland–Faroes Ridge and the remainder continuing east towards and north of the Wyville-Thomson Ridge (WTR) to the Scotland slope thereby increasing the Slope Current transport from ~1.5 Sv south of the WTR to 3.5 Sv in the Faroes–Shetland Channel

Modeling vertical oxygen and carbon flux during stratified spring and summer conditions on the continental shelf, Middle Atlantic Bight, eastern U.S.A

The Shelf Edge Exchange Processes II (SEEP-II) program was designed to examine the potential for export of organic carbon from the continental shelf to the deeper ocean. In the Middle Atlantic Bight of the east coast, U.S.A., a “cold pool” of relict winter water is isolated by the development of a strong seasonal thermocline on the shelf. Oxygen concentrations were monitored in and above the cold pool from March 1988 to May 1989, with electrodes moored at 19 and 38 m at a 42-m station off the Delmarva Peninsula, eastern U.S.A. An oxygen-flux simulation model was constructed to describe long-term changes in oxygen concentration and saturation. The model utilized biological rate and biomass measurements obtained at the mooring location during cruises. Vertical eddy diffusion was constrained by comparison with the redistribution of chlorofluorocarbons and heat after stratification, and by sensitivity analyses. Model predictions of the average daily change in oxygen concentration and saturation at 38 m were in good agreement with average changes recorded by moored oxygen sensors, when biological generation of oxygen was approximately equal to the thermotrophic consumption. Strong, but transient, fluctuations concentration and saturation were clearly associated with specific advective events, and had little lasting impact on the overall long-term trends. Consequently, model parameters derived from intermittent, cruise-based observations yielded satisfactory predictions of long-term trends. A carbon budget was constructed for the stratified summer period from data that largely overlapped with those used for the oxygen model. The continental shelf ecosystem operates in approximate balance during the summer, with a potential export of no more than 4% of primary production

Sustainable observations of the AMOC: methodology and technology

The Atlantic Meridional Overturning Circulation (AMOC) is a key mechanism of heat, freshwater, and carbon redistribution in the climate system. The precept that the AMOC has changed abruptly in the past, notably during and at the end of the last ice age, and that it is ‘very likely’ to weaken in the coming century due to anthropogenic climate change is a key motivation for sustained observations of the AMOC. This paper reviews the methodology and technology used to observe the AMOC and assesses these ideas and systems for accuracy, shortcomings, potential improvements and sustainability. We review hydrographic techniques and look at how these traditional techniques can meet modern requirements. Transport mooring arrays provide the ‘gold standard’ for sustained AMOC observing, utilizing dynamic height, current meter, and other instrumentation and techniques to produce continuous observations of the AMOC. We consider the principle of these systems and how they can be sustained and improved into the future. Techniques utilizing indirect measurements, such as satellite altimetry, coupled with in‐situ measurements, such as the Argo float array, are also discussed. Existing technologies that perhaps have not been fully exploited for estimating AMOC are reviewed and considered for this purpose. Technology is constantly evolving and we look to the future of technology and how it can be deployed for sustained and expanded AMOC measurements. Finally, all of these methodologies and technologies are considered with a view to a sustained and sustainable future for AMOC observation

A large genome-wide association study of age-related macular degeneration highlights contributions of rare and common variants

Advanced age-related macular degeneration (AMD) is the leading cause of blindness in the elderly, with limited therapeutic options. Here we report on a study of >12 million variants, including 163,714 directly genotyped, mostly rare, protein-altering variants. Analyzing 16,144 patients and 17,832 controls, we identify 52 independently associated common and rare variants (P < 5 × 10 -8) distributed across 34 loci. Although wet and dry AMD subtypes exhibit predominantly shared genetics, we identify the first genetic association signal specific to wet AMD, near MMP9 (difference P value = 4.1 × 10 -10). Very rare coding variants (frequency <0.1%) in CFH, CFI and TIMP3 suggest causal roles for these genes, as does a splice variant in SLC16A8. Our results support the hypothesis that rare coding variants can pinpoint causal genes within known genetic loci and illustrate that applying the approach systematically to detect new loci requires extremely large sample sizes. © 2016 Nature America, Inc