Ocean sunfish rewarm at the surface after deep excursions to forage for siphonophores.

PubMed

Nakamura, Itsumi; Goto, Yusuke; Sato, Katsufumi

2015-05-01

Ocean sunfish (Mola mola) were believed to be inactive jellyfish feeders because they are often observed lying motionless at the sea surface. Recent tracking studies revealed that they are actually deep divers, but there has been no evidence of foraging in deep water. Furthermore, the surfacing behaviour of ocean sunfish was thought to be related to behavioural thermoregulation, but there was no record of sunfish body temperature. Evidence of ocean sunfish feeding in deep water was obtained using a combination of an animal-borne accelerometer and camera with a light source. Siphonophores were the most abundant prey items captured by ocean sunfish and were typically located at a depth of 50-200 m where the water temperature was <12 °C. Ocean sunfish were diurnally active, made frequently deep excursions and foraged mainly at 100-200 m depths during the day. Ocean sunfish body temperatures were measured under natural conditions. The body temperatures decreased during deep excursions and recovered during subsequent surfacing periods. Heat-budget models indicated that the whole-body heat-transfer coefficient between sunfish and the surrounding water during warming was 3-7 times greater than that during cooling. These results suggest that the main function of surfacing is the recovery of body temperature, and the fish might be able to increase heat gain from the warm surface water by physiological regulation. The thermal environment of ocean sunfish foraging depths was lower than their thermal preference (c. 16-17 °C). The behavioural and physiological thermoregulation enables the fish to increase foraging time in deep, cold water. Feeding rate during deep excursions was not related to duration or depth of the deep excursions. Cycles of deep foraging and surface warming were explained by a foraging strategy, to maximize foraging time with maintaining body temperature by vertical temperature environment. © 2015 The Authors. Journal of Animal Ecology © 2015 British Ecological Society.

Geology and biology of North Pacific cold seep communities

NASA Astrophysics Data System (ADS)

Robison, Bruce H.; Greene, H. Gary

Because of crushing pressure, low temperature, and stygian darkness, the floor of the deep sea is one of the most hostile habitats on Earth. Until recently it was widely believed that the base of the food chain for all deep-sea communities was plant life in the ocean's sunlit upper layer. With the discovery of hydrothermal vent and cold-seep communities, which are based on chemical rather than solar energy, those beliefs were overturned. New studies focused on the animals that inhabit cold seep regions have begun to throw light on the geological basis of chemosynthetic communities. The initial results suggest a strong relationship between geologically determined fluid flux, and the diversity and abundance of animals at the seeps.

Deepwater Program: Exploration and Research of Northern Gulf of Mexico Deepwater Natural and Artificial Hard Bottom Habitats with Emphasis on Coral Communities: Reefs, Rigs and Wrecks

DTIC Science & Technology

2010-01-01

Ocean Acidification on Coral Reefs and Other Marine Calcifiers: A Guide for...Roberts, J.M. & Guinotte, J.J. (2007) Corals in deep water: Will the unseen hand of ocean acidification destroy cold water ecosystems? Coral Reefs ...scleractinians from the NE Atlantic Ocean . Coral Reefs , 24(3), 514-522. Wang JL, Whitlock MC (2003) Estimating effective population size and migration rates

Biotechnological uses of enzymes from psychrophiles

PubMed Central

Cavicchioli, R.; Charlton, T.; Ertan, H.; Omar, S. Mohd; Siddiqui, K. S.; Williams, T. J.

2011-01-01

Summary The bulk of the Earth's biosphere is cold (e.g. 90% of the ocean's waters are ≤ 5°C), sustaining a broad diversity of microbial life. The permanently cold environments vary from the deep ocean to alpine reaches and to polar regions. Commensurate with the extent and diversity of the ecosystems that harbour psychrophilic life, the functional capacity of the microorganisms that inhabitat the cold biosphere are equally diverse. As a result, indigenous psychrophilic microorganisms provide an enormous natural resource of enzymes that function effectively in the cold, and these cold‐adapted enzymes have been targeted for their biotechnological potential. In this review we describe the main properties of enzymes from psychrophiles and describe some of their known biotechnological applications and ways to potentially improve their value for biotechnology. The review also covers the use of metagenomics for enzyme screening, the development of psychrophilic gene expression systems and the use of enzymes for cleaning. PMID:21733127

Gyre-scale deep convection in the subpolar North Atlantic Ocean during winter 2014-2015

NASA Astrophysics Data System (ADS)

Piron, A.; Thierry, V.; Mercier, H.; Caniaux, G.

2017-02-01

Using Argo floats, we show that a major deep convective activity occurred simultaneously in the Labrador Sea (LAB), south of Cape Farewell (SCF), and the Irminger Sea (IRM) during winter 2014-2015. Convection was driven by exceptional heat loss to the atmosphere (up to 50% higher than the climatological mean). This is the first observation of deep convection over such a widespread area. Mixed layer depths exceptionally reached 1700 m in SCF and 1400 m in IRM. The deep thermocline density gradient limited the mixed layer deepening in the Labrador Sea to 1800 m. Potential densities of deep waters were similar in the three basins (27.73-27.74 kg m-3) but warmer by 0.3°C and saltier by 0.04 in IRM than in LAB and SCF, meaning that each basin formed locally its own deep water. The cold anomaly that developed recently in the North Atlantic Ocean favored and was enhanced by this exceptional convection.

Deserts on the sea floor: Edward Forbes and his azoic hypothesis for a lifeless deep ocean.

PubMed

Anderson, Thomas R; Rice, Tony

2006-12-01

While dredging in the Aegean Sea during the mid-19th century, Manxman Edward Forbes noticed that plants and animals became progressively more impoverished the greater the depth they were from the surface of the water. By extrapolation Forbes proposed his now infamous azoic hypothesis, namely that life would be extinguished altogether in the murky depths of the deep ocean. The whole idea seemed so entirely logical given the enormous pressure, cold and eternal darkness of this apparently uninhabitable environment. Yet we now know that the sea floor is teeming with life. Curiously, it took 25 years for the azoic hypothesis to fall from grace. This was despite the presence of ample contrary evidence, including starfishes, worms and other organisms that seemingly originated from the deep seabed. This is a tale of scientists ignoring observations that ran counter to their deep-seated, yet entirely erroneous, beliefs.

Calcification rates and the effect of ocean acidification on Mediterranean cold-water corals

PubMed Central

Maier, C.; Watremez, P.; Taviani, M.; Weinbauer, M. G.; Gattuso, J. P.

2012-01-01

Global environmental changes, including ocean acidification, have been identified as a major threat to scleractinian corals. General predictions are that ocean acidification will be detrimental to reef growth and that 40 to more than 80 per cent of present-day reefs will decline during the next 50 years. Cold-water corals (CWCs) are thought to be strongly affected by changes in ocean acidification owing to their distribution in deep and/or cold waters, which naturally exhibit a CaCO3 saturation state lower than in shallow/warm waters. Calcification was measured in three species of Mediterranean cold-water scleractinian corals (Lophelia pertusa, Madrepora oculata and Desmophyllum dianthus) on-board research vessels and soon after collection. Incubations were performed in ambient sea water. The species M. oculata was additionally incubated in sea water reduced or enriched in CO2. At ambient conditions, calcification rates ranged between −0.01 and 0.23% d−1. Calcification rates of M. oculata under variable partial pressure of CO2 (pCO2) were the same for ambient and elevated pCO2 (404 and 867 µatm) with 0.06 ± 0.06% d−1, while calcification was 0.12 ± 0.06% d−1 when pCO2 was reduced to its pre-industrial level (285 µatm). This suggests that present-day CWC calcification in the Mediterranean Sea has already drastically declined (by 50%) as a consequence of anthropogenic-induced ocean acidification. PMID:22130603

The relationships between precipitation, convective cloud and tropical cyclone intensity change

NASA Astrophysics Data System (ADS)

Ruan, Z.; Wu, Q.

2017-12-01

Using 16 years precipitation, brightness temperature (IR BT) data and tropical cyclone (TC) information, this study explores the relationship between precipitation, convective cloud and tropical cyclone (TC) intensity change in the Western North Pacific Ocean. It is found that TC intensity has positive relation with TC precipitation. TC precipitation increases with increased TC intensity. Based on the different phase of diurnal cycle, convective TC clouds were divided into very cold deep convective clouds (IR BTs<208K) and cold high clouds (208K

Ecosystem engineering creates a direct nutritional link between 600-m deep cold-water coral mounds and surface productivity.

PubMed

Soetaert, Karline; Mohn, Christian; Rengstorf, Anna; Grehan, Anthony; van Oevelen, Dick

2016-10-11

Cold-water corals (CWCs) form large mounds on the seafloor that are hotspots of biodiversity in the deep sea, but it remains enigmatic how CWCs can thrive in this food-limited environment. Here, we infer from model simulations that the interaction between tidal currents and CWC-formed mounds induces downwelling events of surface water that brings organic matter to 600-m deep CWCs. This positive feedback between CWC growth on carbonate mounds and enhanced food supply is essential for their sustenance in the deep sea and represents an example of ecosystem engineering of unparalleled magnitude. This 'topographically-enhanced carbon pump' leaks organic matter that settles at greater depths. The ubiquitous presence of biogenic and geological topographies along ocean margins suggests that carbon sequestration through this pump is of global importance. These results indicate that enhanced stratification and lower surface productivity, both expected consequences of climate change, may negatively impact the energy balance of CWCs.

Ecosystem engineering creates a direct nutritional link between 600-m deep cold-water coral mounds and surface productivity

NASA Astrophysics Data System (ADS)

Soetaert, Karline; Mohn, Christian; Rengstorf, Anna; Grehan, Anthony; van Oevelen, Dick

2016-10-01

Cold-water corals (CWCs) form large mounds on the seafloor that are hotspots of biodiversity in the deep sea, but it remains enigmatic how CWCs can thrive in this food-limited environment. Here, we infer from model simulations that the interaction between tidal currents and CWC-formed mounds induces downwelling events of surface water that brings organic matter to 600-m deep CWCs. This positive feedback between CWC growth on carbonate mounds and enhanced food supply is essential for their sustenance in the deep sea and represents an example of ecosystem engineering of unparalleled magnitude. This ’topographically-enhanced carbon pump’ leaks organic matter that settles at greater depths. The ubiquitous presence of biogenic and geological topographies along ocean margins suggests that carbon sequestration through this pump is of global importance. These results indicate that enhanced stratification and lower surface productivity, both expected consequences of climate change, may negatively impact the energy balance of CWCs.

Gulf of Mexico Deep-Sea Coral Ecosystem Studies, 2008-2011

USGS Publications Warehouse

Kellogg, Christina A.

2009-01-01

Most people are familiar with tropical coral reefs, located in warm, well-illuminated, shallow waters. However, corals also exist hundreds and even thousands of meters below the ocean surface, where it is cold and completely dark. These deep-sea corals, also known as cold-water corals, have become a topic of interest due to conservation concerns over the impacts of trawling, exploration for oil and gas, and climate change. Although the existence of these corals has been known since the 1800s, our understanding of their distribution, ecology, and biology is limited due to the technical difficulties of conducting deep-sea research. DISCOVRE (DIversity, Systematics, and COnnectivity of Vulnerable Reef Ecosystems) is a new U.S. Geological Survey (USGS) program focused on deep-water coral ecosystems in the Gulf of Mexico. This integrated, multidisciplinary, international effort investigates a variety of topics related to unique and fragile deep-sea coral ecosystems from the microscopic level to the ecosystem level, including components of microbiology, population genetics, paleoecology, food webs, taxonomy, community ecology, physical oceanography, and mapping.

Deep ocean ventilation in the Central Fram Strait during the past 35 kyr

NASA Astrophysics Data System (ADS)

Ezat, M.; Rasmussen, T. L.; Skinner, L.; Zamelczyk, K.

2017-12-01

Ocean ventilation in the Arctic Mediterranean via transformation of northward inflowing warm Atlantic surface water into cold deep water affects regional climate, large-scale atmospheric circulation and carbon storage in the deep ocean. Radiocarbon dating of benthic foraminifera has been used to suggest a near-cessation of Arctic Ocean ventilation during the Last Glacial Maximum. During the last deglaciation episodic surges of this Arctic `aged' glacial deep water into the Nordic Seas and the subpolar North Atlantic Ocean may have occurred (Thornalley et al., 2011, 2015; Science). A recent study from the SE Norwegian Sea and the Iceland Basin has revealed large radiocarbon age differences between different benthic foraminiferal species during the last deglaciation (Ezat et al., 2017; Paleoceanography), which arguments for a re-evaluation of previous bottom-water radiocarbon ventilation age reconstructions from the region. Here, we present new species-specific benthic and planktic foraminiferal radiocarbon dates from the central Fram Strait and the SE Norwegian Sea for the past 35 kyr. Several lines of evidence in this new dataset demonstrate that the previously suggested `extreme aging' of >6000 14C years in the Arctic Mediterranean is most likely erroneous. In addition, benthic-planktic age offsets in the deep central Fram Strait display a remarkable decrease from 1300-2300 14C years in late Marine Isotope Stage (MIS) 3 to 0-500 14C year in MIS 2, which correlates with a decrease in benthic d13C and reduction in the benthic-planktic d18O gradient. We are in the process of compiling/screening published ventilation age reconstructions from the Arctic Mediterranean and the subpolar North Atlantic in the light of our new results in order to establish a basin-scale evolution of ocean ventilation since late MIS 3 in this region.

Imaging a Hydrate-Related Cold Vent Offshore Vancouver Island From Deep-Towed Multichannel Seismic Data

DTIC Science & Technology

2009-02-20

vent). 2500 2600 2700 Distance (m) 2800 2900 3000 1.791 Figure 11. Southeast-northwest seismic section, showing hydrate cap details from DTI 6. The...line DT16 Line DTI 6 continues as a long transit line extending to the north- west. The 1999 COAMS (Canadian Ocean Acoustic Measurement System) grid...inline IN26 is coincident with DTI 6 (Figure 1). A com- bination of the surface-towed seismic data and the deep-towed DTAGS data is needed to provide

Episodic Southern Ocean Heat Loss and Its Mixed Layer Impacts Revealed by the Farthest South Multiyear Surface Flux Mooring

NASA Astrophysics Data System (ADS)

Ogle, S. E.; Tamsitt, V.; Josey, S. A.; Gille, S. T.; Cerovečki, I.; Talley, L. D.; Weller, R. A.

2018-05-01

The Ocean Observatories Initiative air-sea flux mooring deployed at 54.08°S, 89.67°W, in the southeast Pacific sector of the Southern Ocean, is the farthest south long-term open ocean flux mooring ever deployed. Mooring observations (February 2015 to August 2017) provide the first in situ quantification of annual net air-sea heat exchange from one of the prime Subantarctic Mode Water formation regions. Episodic turbulent heat loss events (reaching a daily mean net flux of -294 W/m2) generally occur when northeastward winds bring relatively cold, dry air to the mooring location, leading to large air-sea temperature and humidity differences. Wintertime heat loss events promote deep mixed layer formation that lead to Subantarctic Mode Water formation. However, these processes have strong interannual variability; a higher frequency of 2 σ and 3 σ turbulent heat loss events in winter 2015 led to deep mixed layers (>300 m), which were nonexistent in winter 2016.

A picture on the wall: innovative mapping reveals cold-water coral refuge in submarine canyon.

PubMed

Huvenne, Veerle A I; Tyler, Paul A; Masson, Doug G; Fisher, Elizabeth H; Hauton, Chris; Hühnerbach, Veit; Le Bas, Timothy P; Wolff, George A

2011-01-01

Cold-water corals are azooxanthellate species found throughout the ocean at water depths down to 5000 m. They occur in patches, reefs or large mound structures up to 380 m high, and as ecosystem engineers create important habitats for a diverse fauna. However, the majority of these habitats are now within reach of deep-sea bottom trawling. Many have been severely damaged or are under threat, despite recent protection initiatives. Here we present a cold-water coral habitat type that so far has been overlooked--quite literally--and that has received minimal impact from human activities. Vertical and overhanging cliffs in deep-sea canyons, revealed using an innovative approach to marine habitat mapping, are shown to provide the perfect substratum for extensive cold-water coral-based communities. Typical canyon-related processes, including locally enhanced internal tides and focussed downslope organic carbon transport, provide favourable environmental conditions (current regime, food input) to sustain the communities, even outside the optimal depth and density envelopes reported elsewhere in the NE Atlantic. Our findings show that deep-sea canyons can form natural refuges for faunal communities sensitive to anthropogenic disturbance, and have the potential to fulfil the crucial role of larval sources for the recolonisation of damaged sites elsewhere on the margin.

A Picture on the Wall: Innovative Mapping Reveals Cold-Water Coral Refuge in Submarine Canyon

PubMed Central

Huvenne, Veerle A. I.; Tyler, Paul A.; Masson, Doug G.; Fisher, Elizabeth H.; Hauton, Chris; Hühnerbach, Veit; Le Bas, Timothy P.; Wolff, George A.

2011-01-01

Cold-water corals are azooxanthellate species found throughout the ocean at water depths down to 5000 m. They occur in patches, reefs or large mound structures up to 380 m high, and as ecosystem engineers create important habitats for a diverse fauna. However, the majority of these habitats are now within reach of deep-sea bottom trawling. Many have been severely damaged or are under threat, despite recent protection initiatives. Here we present a cold-water coral habitat type that so far has been overlooked – quite literally – and that has received minimal impact from human activities. Vertical and overhanging cliffs in deep-sea canyons, revealed using an innovative approach to marine habitat mapping, are shown to provide the perfect substratum for extensive cold-water coral-based communities. Typical canyon-related processes, including locally enhanced internal tides and focussed downslope organic carbon transport, provide favourable environmental conditions (current regime, food input) to sustain the communities, even outside the optimal depth and density envelopes reported elsewhere in the NE Atlantic. Our findings show that deep-sea canyons can form natural refuges for faunal communities sensitive to anthropogenic disturbance, and have the potential to fulfil the crucial role of larval sources for the recolonisation of damaged sites elsewhere on the margin. PMID:22194903

Countermeasures to Microbiofouling in Simulated Ocean Thermal Energy Conversion Heat Exchangers with Surface and Deep Ocean Waters in Hawaii

PubMed Central

Berger, Leslie Ralph; Berger, Joyce A.

1986-01-01

Countermeasures to biofouling in simulated ocean thermal energy conversion heat exchangers have been studied in single-pass flow systems, using cold deep and warm surface ocean waters off the island of Hawaii. Manual brushing of the loops after free fouling periods removed most of the biofouling material. However, over a 2-year period a tenacious film formed. Daily free passage of sponge rubber balls through the tubing only removed the loose surface biofouling layer and was inadequate as a countermeasure in both titanium and aluminum alloy tubes. Chlorination at 0.05, 0.07, and 0.10 mg liter-1 for 1 h day-1 lowered biofouling rates. Only at 0.10 mg liter-1 was chlorine adequate over a 1-year period to keep film formation and heat transfer resistance from rising above the maximum tolerated values. Lower chlorination regimens led to the buildup of uneven or patchy films which produced increased flow turbulence. The result was lower heat transfer resistance values which did not correlate with the amount of biofouling. Surfaces which were let foul and then treated with intermittent or continuous chlorination at 0.10 mg of chlorine or less per liter were only partially or unevenly cleaned, although heat transfer measurements did not indicate that fact. It took continuous chlorination at 0.25 mg liter-1 to bring the heat transfer resistance to zero and eliminate the fouling layer. Biofouling in deep cold seawater was much slower than in the warm surface waters. Tubing in one stainless-steel loop had a barely detectable fouling layer after 1 year in flow. With aluminum alloys sufficient corrosion and biofouling material accumulated to require that some fouling coutermeasure be used in long-term operation of an ocean thermal energy conversion plant. Images PMID:16347076

Bringing OTEC Environmental Assessments of the 1980s Up To 21st Century Oceanographic Standards (Invited)

NASA Astrophysics Data System (ADS)

Sansone, F. J.; Comfort, C. M.; Weng, K. C.

2010-12-01

Although the potential environmental effects of OTEC plant construction and operation were evaluated in the 1980s as part of earlier OTEC development, recent OTEC efforts have led to the re-examination of the issues involved. During the intervening years we have significantly increased our understanding of the oceans, and our ability to observe and model the marine environment has improved markedly. For example, OTEC environmental assessments have traditionally included the effects of discharging deep seawater, with its elevated levels of dissolved inorganic nutrients and dissolved inorganic carbon, and depleted levels of dissolved oxygen, into the upper water column. However, the role of trace elements in controlling marine primary production rates is now widely accepted, and their natural vertical distribution in the ocean needs to be considered. Our expanded understanding of ocean biogeochemistry also makes environmental assessment more complicated. For example, discharges of deep seawater within the photic zone of the ocean, but below the surface mixed layer, should result in photosynthetic production that would remove both dissolved nutrients and dissolved carbon dioxide at approximately the same stoichiometric ratio as they are elevated in deep seawater; thus, the only large-scale related environmental impact would involve the fate of the resulting photosynthetically produced organic matter. Similarly, our improved knowledge of marine physical chemistry allows a better understanding of OTEC’s potential impact on the ocean’s inorganic carbon chemistry. For example, the reduction in pressure of deep seawater as it is brought to the surface, and the increase in temperature due to OTEC heat exchange, will both lead to an increase in the deep water’s pH; opposite effects will occur in the shallow seawater used by OTEC. Determination of the net effect will require modeling using predicted pumping rates for warm and cold seawater, the planned intake and discharge depths and temperatures, the inorganic carbon chemistry at the specific site, and recently refined inorganic carbon equilibria data. Ecological data (e.g., primary productivity, the biomass of various trophic levels, biota attraction to floating objects, etc.) should also be updated with the results from more contemporary studies. Additional factors that should be examined include electromagnetic effects of cabling, alterations in the bio-physical coupling of water column as a result of the discharge plume, potential harmful algal bloom development, and low-frequency noise production. Moreover, new ocean observation techniques such as gliders and AUVs allow large areas of the ocean to be monitored in 3-D for extended periods of time. Similarly, new marine modeling techniques, such as regional ocean modeling systems (ROMS), allow OTEC plumes to be studied in the context of a 3-D dynamic ocean, including such features as internal tides and mesoscales eddies, and allow assimilation of 3-D data to improve model performance. As an early step in these efforts, we have used HOT time-series data to determine patterns of seasonal variability in the upper ocean (warm water intake and discharge zone) and in the deep ocean (cold water uptake) near the site for the proposed Kahe Point, Oahu OTEC demonstration plant.

Intraseasonal variability in the summer South China Sea: Wind jet, cold filament, and recirculations

NASA Astrophysics Data System (ADS)

Xie, Shang-Ping; Chang, Chueh-Hsin; Xie, Qiang; Wang, Dongxiao

2007-10-01

A recent study shows that the blockage of the southwest monsoon by the mountain range on the east coast of Indochina triggers a chain of ocean-atmospheric response, including a wind jet and cold filament in the South China Sea (SCS). We extend this climatological analysis by using higher temporal resolution (weekly) to study intraseasonal variability in summer. Our analysis shows that the development of the wind jet and cold filament is not a smooth seasonal process but consists of several intraseasonal events each year at about 45-day intervals. In a typical intraseasonal event, the wind jet intensifies to above 12 m/s, followed in a week by the development of a cold filament advected by an offshore jet east of South Vietnam on the boundary of a double gyre circulation in the ocean. The double gyre circulation itself also strengthens in response to the intraseasonal wind event via Rossby wave adjustment, reaching the maximum strength in 2 to 3 weeks. The intraseasonal cold filaments appear to influence the surface wind, reducing the local wind speed because of the increased static stability in the near-surface atmosphere. To first order, the above sequence of events may be viewed as the SCS response to atmospheric intraseasonal wind pulses, which are part of the planetary-scale boreal summer intraseasonal oscillation characterized by the northeastward propagation of atmospheric deep convection. The intraseasonal anomalies of sea surface temperature and precipitation are in phase over the SCS, suggesting an oceanic feedback onto the atmosphere. As wind variations are now being routinely monitored by satellite, the lags of 1-3 weeks in oceanic response offer useful predictability that may be exploited.

Characteristics of Mesoscale Organization in WRF Simulations of Convection during TWP-ICE

NASA Technical Reports Server (NTRS)

Del Genio, Anthony D.; Wu, Jingbo; Chen, Yonghua

2013-01-01

Compared to satellite-derived heating profiles, the Goddard Institute for Space Studies general circulation model (GCM) convective heating is too deep and its stratiform upper-level heating is too weak. This deficiency highlights the need for GCMs to parameterize the mesoscale organization of convection. Cloud-resolving model simulations of convection near Darwin, Australia, in weak wind shear environments of different humidities are used to characterize mesoscale organization processes and to provide parameterization guidance. Downdraft cold pools appear to stimulate further deep convection both through their effect on eddy size and vertical velocity. Anomalously humid air surrounds updrafts, reducing the efficacy of entrainment. Recovery of cold pool properties to ambient conditions over 5-6 h proceeds differently over land and ocean. Over ocean increased surface fluxes restore the cold pool to prestorm conditions. Over land surface fluxes are suppressed in the cold pool region; temperature decreases and humidity increases, and both then remain nearly constant, while the undisturbed environment cools diurnally. The upper-troposphere stratiform rain region area lags convection by 5-6 h under humid active monsoon conditions but by only 1-2 h during drier break periods, suggesting that mesoscale organization is more readily sustained in a humid environment. Stratiform region hydrometeor mixing ratio lags convection by 0-2 h, suggesting that it is strongly influenced by detrainment from convective updrafts. Small stratiform region temperature anomalies suggest that a mesoscale updraft parameterization initialized with properties of buoyant detrained air and evolving to a balance between diabatic heating and adiabatic cooling might be a plausible approach for GCMs.

Global habitat suitability for framework-forming cold-water corals.

PubMed

Davies, Andrew J; Guinotte, John M

2011-04-15

Predictive habitat models are increasingly being used by conservationists, researchers and governmental bodies to identify vulnerable ecosystems and species' distributions in areas that have not been sampled. However, in the deep sea, several limitations have restricted the widespread utilisation of this approach. These range from issues with the accuracy of species presences, the lack of reliable absence data and the limited spatial resolution of environmental factors known or thought to control deep-sea species' distributions. To address these problems, global habitat suitability models have been generated for five species of framework-forming scleractinian corals by taking the best available data and using a novel approach to generate high resolution maps of seafloor conditions. High-resolution global bathymetry was used to resample gridded data from sources such as World Ocean Atlas to produce continuous 30-arc second (∼1 km(2)) global grids for environmental, chemical and physical data of the world's oceans. The increased area and resolution of the environmental variables resulted in a greater number of coral presence records being incorporated into habitat models and higher accuracy of model predictions. The most important factors in determining cold-water coral habitat suitability were depth, temperature, aragonite saturation state and salinity. Model outputs indicated the majority of suitable coral habitat is likely to occur on the continental shelves and slopes of the Atlantic, South Pacific and Indian Oceans. The North Pacific has very little suitable scleractinian coral habitat. Numerous small scale features (i.e., seamounts), which have not been sampled or identified as having a high probability of supporting cold-water coral habitat were identified in all ocean basins. Field validation of newly identified areas is needed to determine the accuracy of model results, assess the utility of modelling efforts to identify vulnerable marine ecosystems for inclusion in future marine protected areas and reduce coral bycatch by commercial fisheries.

Oxygen uptake and vertical transport during deep convection events

NASA Astrophysics Data System (ADS)

Sun, D.; Ito, T.; Bracco, A.

2016-02-01

Dissolved oxygen (O2) is essential for the chemistry and living organisms of the oceans. O2 is consumed in the interior ocean due to the respiration of organic matter, and must be replenished by physical ventilation with the O2-rich surface waters. The O2 supply to the deep waters happens only through the subduction and deep convection during cold seasons at high latitude oceans. The Labrador Sea is one of the few regions where deep ventilation occurs. According to observational and modeling studies, the intensity, duration and timing of deep convection events have varied significantly on the interannual and decadal timescales. In this study we develop a theoretical framework to understand the air-sea transfer of O2 during open-ocean deep convection events. The theory is tested against a suite of numerical integrations using MITgcm in non-hydrostatic configuration including the parameterization of diffusive and bubble mediated gas transfer. Forced with realistic air-sea buoyancy fluxes, the model can reproduce the evolution of temperature, salinity and dissolved O2 observed by ARGO floats in the Labrador Sea. Idealized sensitivity experiments are performed changing the intensity and duration of the buoyancy forcing as well as the wind speed for the gas exchange parameterizations. The downward transport of O2 results from the combination of vertical homogenization of existing O2 and the uptake from the air-sea flux. The intensity of the buoyancy forcing controls the vertical extent of convective mixing which brings O2 to the deep ocean. Integrated O2 uptake increases with the duration of convection even when the total buoyancy loss is held constant. The air-sea fluxes are highly sensitive to the wind speed especially for the bubble injection flux, which is a major addition to the diffusive flux under strong winds. However, the bubble injection flux can be partially compensated by the diffusive outgassing in response to the elevated saturation state. Under strong buoyancy forcing, this compensation is suppressed by the entrainment of relatively O2-poor deep waters. These results imply and allow to quantify the direct link between variability of deep convection and the supply of O2 in the North Atlantic.

Glacial-interglacial atmospheric CO2 change: a possible "standing volume" effect on deep-ocean carbon sequestration

NASA Astrophysics Data System (ADS)

Skinner, L. C.

2009-09-01

So far, the exploration of possible mechanisms for glacial atmospheric CO2 drawdown and marine carbon sequestration has tended to focus on dynamic or kinetic processes (i.e. variable mixing-, equilibration- or export rates). Here an attempt is made to underline instead the possible importance of changes in the standing volumes of intra-oceanic carbon reservoirs (i.e. different water-masses) in influencing the total marine carbon inventory. By way of illustration, a simple mechanism is proposed for enhancing the marine carbon inventory via an increase in the volume of relatively cold and carbon-enriched deep water, analogous to modern Lower Circumpolar Deep Water (LCDW), filling the ocean basins. A set of simple box-model experiments confirm the expectation that a deep sea dominated by an expanded LCDW-like watermass holds more CO2, without any pre-imposed changes in ocean overturning rate, biological export or ocean-atmosphere exchange. The magnitude of this "standing volume effect" (which operates by boosting the solubility- and biological pumps) might be as large as the contributions that have previously been attributed to carbonate compensation, terrestrial biosphere reduction or ocean fertilisation for example. By providing a means of not only enhancing but also driving changes in the efficiency of the biological- and solubility pumps, this standing volume mechanism may help to reduce the amount of glacial-interglacial CO2 change that remains to be explained by other mechanisms that are difficult to assess in the geological archive, such as reduced mass transport or mixing rates in particular. This in turn could help narrow the search for forcing conditions capable of pushing the global carbon cycle between glacial and interglacial modes.

Modelling deep-water formation in the north-west Mediterranean Sea with a new air-sea coupled model: sensitivity to turbulent flux parameterizations

NASA Astrophysics Data System (ADS)

Seyfried, Léo; Marsaleix, Patrick; Richard, Evelyne; Estournel, Claude

2017-12-01

In the north-western Mediterranean, the strong, dry, cold winds, the Tramontane and Mistral, produce intense heat and moisture exchange at the interface between the ocean and the atmosphere leading to the formation of deep dense waters, a process that occurs only in certain regions of the world. The purpose of this study is to demonstrate the ability of a new coupled ocean-atmosphere modelling system based on MESONH-SURFEX-SYMPHONIE to simulate a deep-water formation event in real conditions. The study focuses on summer 2012 to spring 2013, a favourable period that is well documented by previous studies and for which many observations are available. Model results are assessed through detailed comparisons with different observation data sets, including measurements from buoys, moorings and floats. The good overall agreement between observations and model results shows that the new coupled system satisfactorily simulates the formation of deep dense water and can be used with confidence to study ocean-atmosphere coupling in the north-western Mediterranean. In addition, to evaluate the uncertainty associated with the representation of turbulent fluxes in strong wind conditions, several simulations were carried out based on different parameterizations of the flux bulk formulas. The results point out that the choice of turbulent flux parameterization strongly influences the simulation of the deep-water convection and can modify the volume of the newly formed deep water by a factor of 2.

The Presence and Characterization of Antarctic Bottom Water Located Between the Mid-Atlantic Ridge and the Rio Grande Rise

NASA Astrophysics Data System (ADS)

Miller, R. H.; Reece, R.; Estep, J.; Christeson, G. L.; Acquisto, T. M.

2016-12-01

Circumpolar waters of widely varying properties enter South Atlantic Ocean circulation, interleaving their properties. Antarctic bottom water (ABW) flows northward into the South Atlantic at the eastern edge of the South American continent and around the Rio Grande Rise (RGR), a large aseismic ocean ridge in the deep water off the coast of Brazil. The majority of ABW transport occurs below depths of 3500 m, so very little is lost at the top of the RGR. In early 2016, the CREST (Crustal Reflectivity Experiment Southern Transect) expedition acquired multichannel seismic (MCS) and ocean bottom seismometer (OBS) datasets along a crustal segment in the South Atlantic, stretching from the Mid Atlantic Ridge (MAR) west to the RGR. During OBS recovery, a communications problem occurred in which the OBS received the transducer pulse from the ship, but the ship did not receive the OBS return pulse. The nine shallowest instruments, closest to the MAR, did not experience this problem, but all remaining instruments did. All instruments were extensively tested in the water column and in the lab and exhibited no malfunctions. We hypothesize that a deepwater layer of differing physical properties, located nearer the OBS than the boat, dispersed the return pulse resulting in the break in communications. ABW is a good candidate for a potential cold deepwater body in this region. We will examine multi-beam bathymetry returns and seismic reflection data for indications of reflections in the deepwater column. If observations support the presence of cold deepwater, we will fully characterize its properties and boundaries and determine if the characteristics match that of ABW. This study will characterize the behavior and nature of potential cold deepwater currents east of the Rio Grande Rise in an attempt to verify the presence of ABW. Information regarding the effects of differential water layering on acoustic communication with seafloor instruments could benefit future deployments to affected regions. Additionally, more insight into deep water ocean circulation could provide critical information for modeling with implications for chemical and heat exchange as well as ocean-climate interaction.

NOAA Office of Ocean Exploration and Research'sOkeanos Explorer Program 2014 Discoveries - U.S. Atlantic Continental Margin and Gulf of Mexico

NASA Astrophysics Data System (ADS)

Lobecker, E.; McKenna, L.; Sowers, D.; Elliott, K.; Kennedy, B.

2014-12-01

NOAA ShipOkeanos Explorer, the only U.S. federal vessel dedicated to global ocean exploration, made several important discoveries in U.S. waters of the North Atlantic Ocean and Gulf of Mexico during the 2014 field season. Based on input received from a broad group ofmarine scientists and resource managers, over 100,000 square kilometers of seafloor and associated water column were systematically explored using advanced mapping sonars. 39 ROV diveswere conducted, leading to new discoveries that will further ourunderstanding of biologic, geologic, and underwater-cultural heritage secrets hidden withinthe oceans. In the Atlantic, season highlights include completion of a multi-year submarine canyons mapping effort of the continental shelf break from North Carolina to the U.S.-Canada maritime border;new information on the ephemerality of recently discovered and geographically extensive cold water seeps; and continued exploration of the New England Seamount chain; and mapping of two potential historically significant World War II wreck sites. In the Gulf of Mexico, season highlights includecompletion of a multi-year mapping effort of the West Florida Escarpment providing new insight into submarine landslides and detachment zones;the discovery of at least two asphalt volcanoes, or 'tar lilies'; range extensions of deep-sea corals; discovery of two potential new species of crinoids; identification of at least 300 potential cold water seeps; and ROV exploration of three historically significant19th century shipwrecks. In both regions, high-resolution mapping led to new insight into the geological context in which deep sea corals develop,while ROV dives provided valuable observations of deep sea coral habitats and their associated organisms, and chemosynthetic habitats. All mapping and ROV data is freely available to the public in usable data formats and maintained in national geophysical and oceanographic data archives.

Quaternary paleoceanography of the deep Arctic Ocean based on quantitative analysis of Ostracoda

USGS Publications Warehouse

Cronin, T. M.; Holtz, T.R.; Whatley, R.C.

1994-01-01

Ostracodes were studied from deep Arctic Ocean cores obtained during the Arctic 91 expedition of the Polarstern to the Nansen, Amundsen and Makarov Basins, the Lomonosov Ridge, Morris Jesup Rise and Yermak Plateau, in order to investigate their distribution in Arctic Ocean deep water (AODW) and apply these data to paleoceanographic reconstruction of bottom water masses during the Quaternary. Analyses of coretop assemblages from Arctic 91 boxcores indicate the following: ostracodes are common at all depths between 1000 and 4500 m, and species distribution is strongly influenced by water mass characteristics and bathymetry; quantitative analyses comparing Eurasian and Canada Basin assemblages indicate that distinct assemblages inhabit regions east and west of the Lomonosov Ridge, a barrier especially important to species living in lower AODW; deep Eurasian Basin assemblages are more similar to those living in Greenland Sea deep water (GSDW) than those in Canada Basin deep water; two upper AODW assemblages were recognized throughout the Arctic Ocean, one living between 1000 and 1500 m, and the other, having high species diversity, at 1500-3000 m. Downcore quantitative analyses of species' abundances and the squared chord distance coefficient of similarity reveals a distinct series of abundance peaks in key indicator taxa interpreted to signify the following late Quaternary deep water history of the Eurasian Basin. During the Last Glacial Maximum (LGM), a GSDW/AODW assemblage, characteristic of cold, well oxygenated deep water > 3000 m today, inhabited the Lomonosov Ridge to depths as shallow as 1000 m, perhaps indicating the influence of GSDW at mid-depths in the central Arctic Ocean. During Termination 1, a period of high organic productivity associated with a strong inflowing warm North Atlantic layer occurred. During the mid-Holocene, several key faunal events indicate a period of warming and/or enhanced flow between the Canada and Eurasian Basins. A long-term record of ostracode assemblages from kastenlot core PS2200-5 (1073 m water depth) from the Morris Jesup Rise indicates a quasi-cyclic pattern of water mass changes during the last 300 kyr. Interglacial ostracode assemblages corresponding to oxygen isotope stages 1, 5, and 7 indicate rapid changes in dissolved oxygen and productivity during glacial-interglacial transitions. ?? 1994.

A Reconstruction of Sea Surface Temperature Gradients and an Assessment of the Suspected Presence of Continental Ice During the Cold Mid-Paleocene (61-57 Ma)

NASA Astrophysics Data System (ADS)

Bijl, P.; Cramwinckel, M.; Frieling, J.; Peterse, F.

2016-12-01

The early Eocene `hothouse' climate experienced paratropical vegetation on high latitudes and high (>1100 ppmv) atmospheric CO2 concentrations. It is generally considered as analogous to the endmember climate state should we use up all available fossil fuels. However, we do not know exactly through which processes this long-term warm episode came to be nor do we understand what the initial climate state was at the onset of this long-term climate. Deep-sea warming towards early Eocene hothouse conditions started in the mid-Paleocene, ending a 2 Myr time interval of relatively cold deep ocean temperatures. Reconstructed pCO2 concentrations of the mid-Paleocene seem to have been close to those of present-day, although data is scarce. The mid-Paleocene is notoriously sparsely represented in shelf sedimentary records, as most records show a conspicuous hiatus between 58 and 60 Mys. This gives the suggestion of a major global low in sea level, which is inconsistent with estimates of global ocean spreading rates, which suggest a relatively high sea level on long time scales for the Cretaceous-early Paleogene. The cold deep-sea temperatures, the conspicuously low sea level and low atmospheric CO2 during the mid-Paleocene have stimulated suggestions of the presence of major ice sheets on the poles, yet the absence of any trace for continental ice, either direct ice-proximal evidence or from benthic foraminiferal oxygen isotope records, calls the presence of such ice sheets into question. I will present a number of high resolution sea surface temperature records (based mostly on organic geochemical biomarker proxies) which start to reveal a latitudinal temperature gradient for the mid-Paleocene. Reconstructions come from shelf sediments from Tasmania, Australia, Tanzania, Tropical Atlantic Ocean, New Jersey). With these new records, I put Paleogene climate evolution into context. I will further present a review of shelf sedimentary records across the mid-paleocene to assess the sea level variability in this time, to verifiy the suspected presence of continental ice, and speculate on possible alternative mechanisms for sea level change.

Meridional overturning circulation conveys fast acidification to the deep Atlantic Ocean.

PubMed

Perez, Fiz F; Fontela, Marcos; García-Ibáñez, Maribel I; Mercier, Herlé; Velo, Anton; Lherminier, Pascale; Zunino, Patricia; de la Paz, Mercedes; Alonso-Pérez, Fernando; Guallart, Elisa F; Padin, Xose A

2018-02-22

Since the Industrial Revolution, the North Atlantic Ocean has been accumulating anthropogenic carbon dioxide (CO 2 ) and experiencing ocean acidification, that is, an increase in the concentration of hydrogen ions (a reduction in pH) and a reduction in the concentration of carbonate ions. The latter causes the 'aragonite saturation horizon'-below which waters are undersaturated with respect to a particular calcium carbonate, aragonite-to move to shallower depths (to shoal), exposing corals to corrosive waters. Here we use a database analysis to show that the present rate of supply of acidified waters to the deep Atlantic could cause the aragonite saturation horizon to shoal by 1,000-1,700 metres in the subpolar North Atlantic within the next three decades. We find that, during 1991-2016, a decrease in the concentration of carbonate ions in the Irminger Sea caused the aragonite saturation horizon to shoal by about 10-15 metres per year, and the volume of aragonite-saturated waters to reduce concomitantly. Our determination of the transport of the excess of carbonate over aragonite saturation ( xc [CO 3 2- ])-an indicator of the availability of aragonite to organisms-by the Atlantic meridional overturning circulation shows that the present-day transport of carbonate ions towards the deep ocean is about 44 per cent lower than it was in preindustrial times. We infer that a doubling of atmospheric anthropogenic CO 2 levels-which could occur within three decades according to a 'business-as-usual scenario' for climate change-could reduce the transport of xc [CO 3 2- ] by 64-79 per cent of that in preindustrial times, which could severely endanger cold-water coral habitats. The Atlantic meridional overturning circulation would also export this acidified deep water southwards, spreading corrosive waters to the world ocean.

Meridional overturning circulation conveys fast acidification to the deep Atlantic Ocean

NASA Astrophysics Data System (ADS)

Perez, Fiz F.; Fontela, Marcos; García-Ibáñez, Maribel I.; Mercier, Herlé; Velo, Anton; Lherminier, Pascale; Zunino, Patricia; de La Paz, Mercedes; Alonso-Pérez, Fernando; Guallart, Elisa F.; Padin, Xose A.

2018-02-01

Since the Industrial Revolution, the North Atlantic Ocean has been accumulating anthropogenic carbon dioxide (CO2) and experiencing ocean acidification, that is, an increase in the concentration of hydrogen ions (a reduction in pH) and a reduction in the concentration of carbonate ions. The latter causes the ‘aragonite saturation horizon’—below which waters are undersaturated with respect to a particular calcium carbonate, aragonite—to move to shallower depths (to shoal), exposing corals to corrosive waters. Here we use a database analysis to show that the present rate of supply of acidified waters to the deep Atlantic could cause the aragonite saturation horizon to shoal by 1,000-1,700 metres in the subpolar North Atlantic within the next three decades. We find that, during 1991-2016, a decrease in the concentration of carbonate ions in the Irminger Sea caused the aragonite saturation horizon to shoal by about 10-15 metres per year, and the volume of aragonite-saturated waters to reduce concomitantly. Our determination of the transport of the excess of carbonate over aragonite saturation (xc[CO32-])—an indicator of the availability of aragonite to organisms—by the Atlantic meridional overturning circulation shows that the present-day transport of carbonate ions towards the deep ocean is about 44 per cent lower than it was in preindustrial times. We infer that a doubling of atmospheric anthropogenic CO2 levels—which could occur within three decades according to a ‘business-as-usual scenario’ for climate change—could reduce the transport of xc[CO32-] by 64-79 per cent of that in preindustrial times, which could severely endanger cold-water coral habitats. The Atlantic meridional overturning circulation would also export this acidified deep water southwards, spreading corrosive waters to the world ocean.

Deconstructing the conveyor belt.

PubMed

Lozier, M Susan

2010-06-18

For the past several decades, oceanographers have embraced the dominant paradigm that the ocean's meridional overturning circulation operates like a conveyor belt, transporting cold waters equatorward at depth and warm waters poleward at the surface. Within this paradigm, the conveyor, driven by changes in deepwater production at high latitudes, moves deep waters and their attendant properties continuously along western boundary currents and returns surface waters unimpeded to deepwater formation sites. A number of studies conducted over the past few years have challenged this paradigm by revealing the vital role of the ocean's eddy and wind fields in establishing the structure and variability of the ocean's overturning. Here, we review those studies and discuss how they have collectively changed our view of the simple conveyor-belt model.

Mesoscale observational analysis of lifting mechanism of a warm-sector convective system producing the maximal daily precipitation in China mainland during pre-summer rainy season of 2015

NASA Astrophysics Data System (ADS)

Wu, Mengwen; Luo, Yali

2016-08-01

A long-lived, quasi-stationary mesoscale convective system (MCS) producing extreme rainfall (maximum of 542 mm) over the eastern coastal area of Guangdong Province on 20 May 2015 is analyzed by using high-resolution surface observations, sounding data, and radar measurements. New convective cells are continuously initiated along a mesoscale boundary at the surface, leading to formation and maintenance of the quasi-linear-shaped MCS from about 2000 BT 19 to 1200 BT 20 May. The boundary is originally formed between a cold dome generated by previous convection and southwesterly flow from the ocean carrying higher equivalent potential temperature ( θ e) air. The boundary is subsequently maintained and reinforced by the contrast between the MCS-generated cold outflow and the oceanic higher- θ e air. The cold outflow is weak (wind speed ≤ 5 m s -1), which is attributable to the characteristic environmental conditions, i.e., high humidity in the lower troposphere and weak horizontal winds in the middle and lower troposphere. The low speed of the cold outflow is comparable to that of the near surface southerly flow from the ocean, resulting in very slow southward movement of the boundary. The boundary features temperature contrasts of 2-3°C and is roughly 500-m deep. Despite its shallowness, the boundary appears to exert a profound influence on continuous convection initiation because of the very low level of free convection and small convection inhibition of the near surface oceanic air, building several parallel rainbands (of about 50-km length) that move slowly eastward along the MCS and produce about 80% of the total rainfall. Another MCS moves into the area from the northwest and merges with the local MCS at about 1200 BT. The cold outflow subsequently strengthens and the boundary moves more rapidly toward the southeast, leading to end of the event in 3 h.

Bending-related faulting and mantle serpentinization at the Middle America trench.

PubMed

Ranero, C R; Morgan, J Phipps; McIntosh, K; Reichert, C

2003-09-25

The dehydration of subducting oceanic crust and upper mantle has been inferred both to promote the partial melting leading to arc magmatism and to induce intraslab intermediate-depth earthquakes, at depths of 50-300 km. Yet there is still no consensus about how slab hydration occurs or where and how much chemically bound water is stored within the crust and mantle of the incoming plate. Here we document that bending-related faulting of the incoming plate at the Middle America trench creates a pervasive tectonic fabric that cuts across the crust, penetrating deep into the mantle. Faulting is active across the entire ocean trench slope, promoting hydration of the cold crust and upper mantle surrounding these deep active faults. The along-strike length and depth of penetration of these faults are also similar to the dimensions of the rupture area of intermediate-depth earthquakes.

Extrapolar climate reversal during the last deglaciation.

PubMed

Asmerom, Yemane; Polyak, Victor J; Lachniet, Matthew S

2017-08-02

Large ocean-atmosphere and hydroclimate changes occurred during the last deglaciation, although the interplay between these changes remains ambiguous. Here, we present a speleothem-based high resolution record of Northern Hemisphere atmospheric temperature driven polar jet variability, which matches the Greenland ice core records for the most of the last glacial period, except during the last deglaciation. Our data, combined with data from across the globe, show a dramatic climate reversal during the last deglaciation, which we refer to as the Extrapolar Climate Reversal (ECR). This is the most prominent feature in most tropical and subtropical hydroclimate proxies. The initiation of the ECR coincides with the rapid rise in CO 2 , in part attributed to upwelling in the Southern Ocean and the near collapse of the Atlantic Meridional Overturning Circulation. We attribute the ECR to upwelling of cold deep waters from the Southern Ocean. This is supported by a variety of proxies showing the incursion of deep Southern Ocean waters into the tropics and subtropics. Regional climate variability across the extropolar regions during the interval previously referred to as the "Mystery Interval" can now be explained in the context of the ECR event.

Astronomically paced changes in deep-water circulation in the western North Atlantic during the middle Eocene

NASA Astrophysics Data System (ADS)

Vahlenkamp, Maximilian; Niezgodzki, Igor; De Vleeschouwer, David; Bickert, Torsten; Harper, Dustin; Kirtland Turner, Sandra; Lohmann, Gerrit; Sexton, Philip; Zachos, James; Pälike, Heiko

2018-02-01

North Atlantic Deep Water (NADW) currently redistributes heat and salt between Earth's ocean basins, and plays a vital role in the ocean-atmosphere CO2 exchange. Despite its crucial role in today's climate system, vigorous debate remains as to when deep-water formation in the North Atlantic started. Here, we present datasets from carbonate-rich middle Eocene sediments from the Newfoundland Ridge, revealing a unique archive of paleoceanographic change from the progressively cooling climate of the middle Eocene. Well-defined lithologic alternations between calcareous ooze and clay-rich intervals occur at the ∼41-kyr beat of axial obliquity. Hence, we identify obliquity as the driver of middle Eocene (43.5-46 Ma) Northern Component Water (NCW, the predecessor of modern NADW) variability. High-resolution benthic foraminiferal δ18O and δ13C suggest that obliquity minima correspond to cold, nutrient-depleted, western North Atlantic deep waters. We thus link stronger NCW formation with obliquity minima. In contrast, during obliquity maxima, Deep Western Boundary Currents were weaker and warmer, while abyssal nutrients were more abundant. These aspects reflect a more sluggish NCW formation. This obliquity-paced paleoceanographic regime is in excellent agreement with results from an Earth system model, in which obliquity minima configurations enhance NCW formation.

Ocean Drilling Program Records of the Last Five Million Years: A View of the Ocean and Climate System During a Warm Period and a Major Climate Transition

NASA Astrophysics Data System (ADS)

Ravelo, A. C.

2003-12-01

The warm Pliocene (4.7 to 3.0 Ma), the most recent period in Earth's history when global equilibrium climate was warmer than today, provides the opportunity to understand what role the components of the climate system that have a long timescale of response (cryosphere and ocean) play in determining globally warm conditions, and in forcing the major global climate cooling after 3.0 Ma. Because sediments of this age are well preserved in many locations in the world's oceans, we can potentially study this warm period in detail. One major accomplishment of the Ocean Drilling Program is the recovery of long continuous sediment sequences from all ocean basins that span the last 5.0 Ma. Dozens of paleoceanographers have generated climate records from these sediments. I will present a synthesis of these data to provide a global picture of the Pliocene warm period, the transition to the cold Pleistocene period, and changes in climate sensitivity related to this transition. In the Pliocene warm period, tropical sea surface temperature (SST) and global climate patterns suggest average conditions that resemble modern El Ni¤os, and deep ocean reconstructions indicate enhanced thermohaline overturning and reduced density and nutrient stratification. The data indicate that the warm conditions were not related to tectonic changes in ocean basin shape compared to today, rather they reflect the long term adjustment of the climate system to stronger than modern radiative forcing. The warm Pliocene to cold Pleistocene transition provides an opportunity to study the feedbacks of various components of the climate system. The marked onset of significant Northern hemisphere glaciation (NHG) at 2.75 Ma occurred in concert with a reduction in deep ocean ventilation, but cooling in subtropical and tropical regions was more gradual until Walker circulation was established in a major step at 2.0 Ma. Thus, regional high latitude ice albedo feedbacks, rather than low latitude processes, must have been primarily responsible for NHG at 2.75 Ma. And, regional air-sea feedbacks in the tropics, rather than ice sheet expansion, must have been primarily responsible for the marked increase in Walker circulation at 2.0 Ma. Finally, the detailed timing of events from different regions suggests that a tectonic `threshold' cannot explain the warm to cold climate transition. Studies of the last 5.0 Ma can also be used to understand how climate responds to changes in the Earth's radiative budget because seasonal and latitudinal variations in solar forcing are extremely well known, and many of the records that have been generated have the resolution and age control appropriate for the study of the climate response to these variations (Milankovitch cycles). In particular, how feedbacks operate when the mean climate state is warm versus cold can be studied. There is clear evidence that the amplitude of the climate response to solar forcing depends on the background mean state. In other words, the sensitivity of the climate to small perturbations in solar forcing has changed with time, and the balance of evidence indicates that tropical conditions, not high latitude conditions (such as ice sheet size) control this sensitivity. In sum, the Ocean Drilling Program has provided scientists with a window into the Pliocene warm period, and an opportunity to understand the workings of the ocean-climate system

Noble gases recycled into the mantle through cold subduction zones

NASA Astrophysics Data System (ADS)

Smye, Andrew J.; Jackson, Colin R. M.; Konrad-Schmolke, Matthias; Hesse, Marc A.; Parman, Steve W.; Shuster, David L.; Ballentine, Chris J.

2017-08-01

Subduction of hydrous and carbonated oceanic lithosphere replenishes the mantle volatile inventory. Substantial uncertainties exist on the magnitudes of the recycled volatile fluxes and it is unclear whether Earth surface reservoirs are undergoing net-loss or net-gain of H2O and CO2. Here, we use noble gases as tracers for deep volatile cycling. Specifically, we construct and apply a kinetic model to estimate the effect of subduction zone metamorphism on the elemental composition of noble gases in amphibole - a common constituent of altered oceanic crust. We show that progressive dehydration of the slab leads to the extraction of noble gases, linking noble gas recycling to H2O. Noble gases are strongly fractionated within hot subduction zones, whereas minimal fractionation occurs along colder subduction geotherms. In the context of our modelling, this implies that the mantle heavy noble gas inventory is dominated by the injection of noble gases through cold subduction zones. For cold subduction zones, we estimate a present-day bulk recycling efficiency, past the depth of amphibole breakdown, of 5-35% and 60-80% for 36Ar and H2O bound within oceanic crust, respectively. Given that hotter subduction dominates over geologic history, this result highlights the importance of cooler subduction zones in regassing the mantle and in affecting the modern volatile budget of Earth's interior.

Insolation-induced mid-Brunhes transition in Southern Ocean ventilation and deep-ocean temperature.

PubMed

Yin, Qiuzhen

2013-02-14

Glacial-interglacial cycles characterized by long cold periods interrupted by short periods of warmth are the dominant feature of Pleistocene climate, with the relative intensity and duration of past and future interglacials being of particular interest for civilization. The interglacials after 430,000 years ago were characterized by warmer climates and higher atmospheric concentrations of carbon dioxide than the interglacials before, but the cause of this climatic transition (the so-called mid-Brunhes event (MBE)) is unknown. Here I show, on the basis of model simulations, that in response to insolation changes only, feedbacks between sea ice, temperature, evaporation and salinity caused vigorous pre-MBE Antarctic bottom water formation and Southern Ocean ventilation. My results also show that strong westerlies increased the pre-MBE overturning in the Southern Ocean via an increased latitudinal insolation gradient created by changes in eccentricity during austral winter and by changes in obliquity during austral summer. The stronger bottom water formation led to a cooler deep ocean during the older interglacials. These insolation-induced differences in the deep-sea temperature and in the Southern Ocean ventilation between the more recent interglacials and the older ones were not expected, because there is no straightforward systematic difference in the astronomical parameters between the interglacials before and after 430,000 years ago. Rather than being a real 'event', the apparent MBE seems to have resulted from a series of individual interglacial responses--including notable exceptions to the general pattern--to various combinations of insolation conditions. Consequently, assuming no anthropogenic interference, future interglacials may have pre- or post-MBE characteristics without there being a systematic change in forcings. These findings are a first step towards understanding the magnitude change of the interglacial carbon dioxide concentration around 430,000 years ago.

A weak AMOC in a cold climate: Causes and remedies for a bias in the low-resolution version of the UK Earth System Model

NASA Astrophysics Data System (ADS)

Kuhlbrodt, T.; Jones, C.

2016-02-01

The UK Earth System Model (UKESM) is currently being developed by the UK Met Office and the academic community in the UK. The low-resolution version of UKESM has got a nominal grid cell size of 150 km in the atmosphere (Unified Model [UM], N96) and 1° in the ocean (NEMO, ORCA1). In several preliminary test configurations of UKESM-N96-ORCA1, we find a significant cold bias in the northern hemisphere in comparison with HadGEM2 (N96-ORCA025, i.e. 0.25° resolution in the ocean). The sea surface is too cold by more than 2 K, and up to 6 K, in large parts of the North Atlantic and the northwest Pacific. In addition to the cold bias, the maximum AMOC transport (diagnosed below 500 m depth) decreases in all the configurations, displaying values between 11 and 14 Sv after 50 years run length. Transport at 26°N is even smaller and hence too weak in relation to observed values (approx. 18 Sv). The mixed layer is too deep within the North Atlantic Current and the Kuroshio, but too shallow north of these currents. The cold bias extends to a depth of several hundred metres. In the North Atlantic, it is accompanied by a freshening of up to 1.5 psu, compared to present-day climatology, along the path of the North Atlantic Current. A core problem appears to be the cessation of deep-water formation in the Labrador Sea. Remarkably, using earlier versions of NEMO and the UM, the AMOC is stable at around 16 or 17 Sv in the N96-ORCA1 configuration. We report on various strategies to reduce the cold bias and enhance the AMOC transport. Changing various parameters that affect the vertical mixing in NEMO has no significant effect. Modifying the bathymetry to deepen and widen the channels across the Greenland-Iceland-Scotland sill leads to a short-term improvement in AMOC transport, but only for about ten years. Strikingly, in a configuration with longer time steps for the atmosphere model we find a climate that is even colder, but has got a more vigorous maximum AMOC transport (14 Sv instead of 12 Sv). Conversely, if the isopycnal diffusivity is augmented by a factor of 1.5, we find a warming and an even weaker AMOC transport. This brings us to further strategies to modify the atmosphere-ocean fluxes of heat and freshwater.

Energy flow and trophic partitioning of contrasting Cold Water Coral ecosystems of the NE Atlantic.

NASA Astrophysics Data System (ADS)

Kiriakoulakis, K.; Smith, E. L.; Dempster, N. M.; Roberts, M.; Hennige, S. J.; Wolff, G. A.

2016-02-01

This study investigates the energy flow, trophic positioning and nutritional quality of suspended particulate organic matter (sPOM) that reaches cold-water coral (CWC) ecosystems from two contrasting oceanographic settings of the N. E. Atlantic using molecular (lipid) and stable isotopic analysis. Study sites are the shallow ( 150m) Mingulay Reef on the NW Scotland shelf vs the deeper ( 700m) Logachev Mounds on the eastern slope of the Rockall Bank. Cold water corals are now being realised as abundant, cosmopolitan and biodiverse hotspots of the global ocean. Recent research has shown links between high levels of surface primary productivity and sPOM flux; which when combined with hydrodynamic processes facilitates an almost continuous supply of nutrient rich sPOM to these deep-ocean ecosystems. However, little is understood regarding the exact nutritional requirements of these ecosystems. Fresh marine sPOM is usually rich in proteins and lipids; however during transport into the ocean interior its chemical composition is influenced by a variety of complex transformation, remineralisation and repackaging processes; thus altering its `freshness' and nutritional quality. The study of the bioavailable and nutritional fractions of sPOM in relation to specific oceanographic transport regimes can help further understand the processes, nutritional requirements and energy flow of these ecosystems. Isotopic ratios of carbon and nitrogen were analysed using EA-IR-MS and lipids via GC-MS. Initial results show significant differences in δ15N and δ13C values of sPOM between the two areas, indicating differences in trophic dynamics and sPOM re-working between locations. In addition lipid results highlight differences in trophic contributions to the energy flows of the two locations, yet similarities in molecular nutritional component contributions; thus supporting previous studies regarding the importance of certain lipid classes in the development of these deep and fragile ecosystems. This multi-disciplinary approach to biogeochemical analysis may also be used to detect chemosynthetic energy pathway contributions to sPOM.

Southern Ocean Convection and tropical telleconnections

NASA Astrophysics Data System (ADS)

Marinov, I.; Cabre, A.; Gnanadesikan, A.

2014-12-01

We show that Southern Ocean (SO) temperatures in the latest generation of Earth System Models exhibit two major modes of variation, one driven by deep convection, the other by tropical variability. We perform a CMIP5 model intercomparison to understand why different climate models represent SO variability so differently in long, control simulations. We show that multiyear variability in Southern Ocean sea surface temperatures (SSTs) can in turn influence oceanic and atmospheric conditions in the tropics on short (atmospheric) time-scales. We argue that the strength and pattern of SO-tropical teleconnections depends on the intensity of SO deep convection. Periodic convection in the SO is a feature of most CMIP5 models under preindustrial forcing (deLavergne et al., 2014). Models show a wide distribution in the spatial extent, periodicity and intensity of their SO convection, with some models convecting most of the time, and some showing very little convection. In a highly convective coupled model, we find that multidecadal variability in SO and global SSTs, as well as SO heat storage are driven by Weddell Sea convective variability, with convective decades relatively warm due to the heat released from the deep southern ocean and non-convective decades cold due to the subsurface storage of heat. Furthermore, pulses of SO convection drive SST and sea ice variations, influencing absorbed shortwave and emitted longwave radiation, wind, cloud and precipitation patterns, with climatic implications for the low latitudes via fast atmospheric teleconnections. We suggest that these high-low latitude teleconnection mechanisms are relevant for understanding hiatus decades. Additionally, Southern Ocean deep convection varied significantly during past, natural climate changes such as during the last deglaciation. Weddell Sea open convection was recently weakened, likely as a consequence of anthropogenic forcing and the resulting surface freshening. Our study opens up the tantalizing possibility that such large-scale changes in SO deep convection might have tropical and indeed global implications via atmospheric teleconnections. We advocate the collection of both paleo and modern proxies that can verify these model-derived mechanisms and global teleconnections.

Ocean climate and seal condition.

PubMed

Le Boeuf, Burney J; Crocker, Daniel E

2005-03-28

The condition of many marine mammals varies with fluctuations in productivity and food supply in the ocean basin where they forage. Prey is impacted by physical environmental variables such as cyclic warming trends. The weaning weight of northern elephant seal pups, Mirounga angustirostris, being closely linked to maternal condition, indirectly reflects prey availability and foraging success of pregnant females in deep waters of the northeastern Pacific. The aim of this study was to examine the effect of ocean climate on foraging success in this deep-diving marine mammal over the course of three decades, using cohort weaning weight as the principal metric of successful resource accrual. The mean annual weaning weight of pups declined from 1975 to the late 1990s, a period characterized by a large-scale, basin-wide warm decadal regime that included multiple strong or long-duration El Niños; and increased with a return to a cool decadal regime from about 1999 to 2004. Increased foraging effort and decreased mass gain of adult females, indicative of reduced foraging success and nutritional stress, were associated with high ocean temperatures. Despite ranging widely and foraging deeply in cold waters beyond coastal thermoclines in the northeastern Pacific, elephant seals are impacted significantly by ocean thermal dynamics. Ocean warming redistributes prey decreasing foraging success of females, which in turn leads to lower weaning mass of pups. Annual fluctuations in weaning mass, in turn, reflect the foraging success of females during the year prior to giving birth and signals changes in ocean temperature cycles.

Radar attenuation in Europa's ice shell: Obstacles and opportunities for constraining the shell thickness and its thermal structure

NASA Astrophysics Data System (ADS)

Kalousová, Klára; Schroeder, Dustin M.; Soderlund, Krista M.

2017-03-01

Young surface and possible recent endogenic activity make Europa one of the most exciting solar system bodies and a primary target for spacecraft exploration. Future Europa missions are expected to carry ice-penetrating radar instruments designed to investigate its subsurface thermophysical structure. Several authors have addressed the radar sounders' performance at icy moons, often ignoring the complex structure of a realistic ice shell. Here we explore the variation in two-way radar attenuation for a variety of potential thermal structures of Europa's shell (determined by reference viscosity, activation energy, tidal heating, surface temperature, and shell thickness) as well as for low and high loss temperature-dependent attenuation model. We found that (i) for all investigated ice shell thicknesses (5-30 km), the radar sounder will penetrate between 15% and 100% of the total thickness, (ii) the maximum penetration depth varies laterally, with deepest penetration possible through cold downwellings, (iii) direct ocean detection might be possible for shells of up to 15 km thick if the signal travels through cold downwelling ice or the shell is conductive, (iv) even if the ice/ocean interface is not directly detected, penetration through most of the shell could constrain the deep shell structure through returns from deep non-ocean interfaces or the loss of signal itself, and (v) for all plausible ice shells, the two-way attenuation to the eutectic point is ≲30 dB which shows a robust potential for longitudinal investigation of the ice shell's shallow thermophysical structure.

More losers than winners in a century of future Southern Ocean seafloor warming

NASA Astrophysics Data System (ADS)

Griffiths, Huw J.; Meijers, Andrew J. S.; Bracegirdle, Thomas J.

2017-10-01

The waters of the Southern Ocean are projected to warm over the coming century, with potential adverse consequences for native cold-adapted organisms. Warming waters have caused temperate marine species to shift their ranges poleward. The seafloor animals of the Southern Ocean shelf have long been isolated by the deep ocean surrounding Antarctica and the Antarctic Circumpolar Current, with little scope for southward migration. How these largely endemic species will react to future projected warming is unknown. By considering 963 invertebrate species, we show that within the current century, warming temperatures alone are unlikely to result in wholesale extinction or invasion affecting Antarctic seafloor life. However, 79% of Antarctica's endemic species do face a significant reduction in suitable temperature habitat (an average 12% reduction). Our findings highlight the species and regions most likely to respond significantly (negatively and positively) to warming and have important implications for future management of the region.

The crabs that live where hot and cold collide.

PubMed

Thurber, Andrew R

2015-07-01

The distribution of Kiwa tyleri with the large male individual in the high-temperature flow (right hand side - fluid flow indicated by shimmering water) and the mixed sex assemblage (left). Note the heavy coat of epibiotic bacteria (grey colouring) on the individual in the hottest section of the vent, as expected from being closest to the sulphide needed to sustain the epibiotic bacteria that this species harvests for its food. Image courtesy of Dr. L. Marsh (Credit: NERC ChEsSo Consortium). In Focus: Marsh, L., Copley, J.T., Tyler, P.A. & Thatje, S. (2015) In hot and cold water: differential life-history traits are key to success in contrasting thermal deep-sea environments. Journal of Animal Ecology, 84, 898-913. Southern Ocean hydrothermal vents juxtapose two extremes - intense food-poor cold and scalding food-rich oases. At these vents, Marsh et al. (2015) found a community of Kiwa (Yeti) crabs that separated themselves along this gradient with the largest males sitting in hot, food-rich waters, while smaller males and females co-occur in an intermediate zone of warmth. However, as their eggs start to develop, females embark away from the vent to the food-poor yet stable cold of the Southern Ocean. This species has found an intriguing way to balance foraging risk and population persistence at the interface of hot and cold. © 2015 The Author. Journal of Animal Ecology © 2015 British Ecological Society.

FEASIBILITY OF LARGE-SCALE OCEAN CO2 SEQUESTRATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dr. Peter Brewer; Dr. James Barry

2002-09-30

We have continued to carry out creative small-scale experiments in the deep ocean to investigate the science underlying questions of possible future large-scale deep-ocean CO{sub 2} sequestration as a means of ameliorating greenhouse gas growth rates in the atmosphere. This project is closely linked to additional research funded by the DoE Office of Science, and to support from the Monterey Bay Aquarium Research Institute. The listing of project achievements here over the past year reflects these combined resources. Within the last project year we have: (1) Published a significant workshop report (58 pages) entitled ''Direct Ocean Sequestration Expert's Workshop'', basedmore » upon a meeting held at MBARI in 2001. The report is available both in hard copy, and on the NETL web site. (2) Carried out three major, deep ocean, (3600m) cruises to examine the physical chemistry, and biological consequences, of several liter quantities released on the ocean floor. (3) Carried out two successful short cruises in collaboration with Dr. Izuo Aya and colleagues (NMRI, Osaka, Japan) to examine the fate of cold (-55 C) CO{sub 2} released at relatively shallow ocean depth. (4) Carried out two short cruises in collaboration with Dr. Costas Tsouris, ORNL, to field test an injection nozzle designed to transform liquid CO{sub 2} into a hydrate slurry at {approx}1000m depth. (5) In collaboration with Prof. Jill Pasteris (Washington University) we have successfully accomplished the first field test of a deep ocean laser Raman spectrometer for probing in situ the physical chemistry of the CO{sub 2} system. (6) Submitted the first major paper on biological impacts as determined from our field studies. (7) Submitted a paper on our measurements of the fate of a rising stream of liquid CO{sub 2} droplets to Environmental Science & Technology. (8) Have had accepted for publication in Eos the first brief account of the laser Raman spectrometer success. (9) Have had two papers submitted for the Greenhouse Gas Technology--6 Conference (Kyoto) accepted. (10) Been nominated by the U.S. Dept. of State to attend the Nov. 2002 IPCC Workshop on Carbon Capture and Storage. (11) Given presentations at national meetings, including the AGU Ocean Sciences Meeting, the American Chemical Society, the Minerals, Materials, and Metals Society, the National Academy of Engineering, and given numerous invited lectures.« less

Deployment, release and recovery of ocean riser pipes

DOEpatents

Person, Abraham; Wetmore, Sherman B.; McNary, James F.

1980-11-18

An ocean thermal energy conversion facility includes a long pipe assembly which is supported at its upper end by the hull of the floating facility. Cold water flows to the facility from deep in the ocean. The pipe assembly comprises an elongate pipe construction and a weight connected to the lower end of the construction by a line of selected length. A floatation collar is connected to the construction at its upper end to cause the construction to have positive buoyancy and a center of buoyancy closer to the upper end of the construction than its center of mass. The weight renders the entire pipe assembly negatively buoyant. In the event that support of the pipe assembly should be lost, as by release of the assembly from the facility hull in an emergency, the assembly sinks to the ocean floor where it is moored by the weight. The pipe construction floats submerged above the ocean floor in a substantially vertical attitude which facilitates recovery of the assembly.

Ocean circulation and properties in Petermann Fjord, Greenland

NASA Astrophysics Data System (ADS)

Johnson, H. L.; Münchow, A.; Falkner, K. K.; Melling, H.

2011-01-01

The floating ice shelf of Petermann glacier interacts directly with the ocean and is thought to lose at least 80% of its mass through basal melting. Based on three opportunistic ocean surveys in Petermann Fjord we describe the basic oceanography: the circulation at the fjord mouth, the hydrographic structure beneath the ice shelf, the oceanic heat delivered to the under-ice cavity, and the fate of the resulting melt water. The 1100 m deep fjord is separated from neighboring Hall Basin by a sill between 350 and 450 m deep. Fjord bottom waters are renewed by episodic spillover at the sill of Atlantic water from the Arctic. Glacial melt water appears on the northeast side of the fjord at depths between 200 m and that of the glacier's grounding line (about 500 m). The fjord circulation is fundamentally three-dimensional; satellite imagery and geostrophic calculations suggest a cyclonic gyre within the fjord mouth, with outflow on the northeast side. Tidal flows are similar in magnitude to the geostrophic flow. The oceanic heat flux into the fjord appears more than sufficient to account for the observed rate of basal melting. Cold, low-salinity water originating in the surface layer of Nares Strait in winter intrudes far under the ice. This may limit basal melting to the inland half of the shelf. The melt rate and long-term stability of Petermann ice shelf may depend on regional sea ice cover and fjord geometry, in addition to the supply of oceanic heat entering the fjord.

Response of a comprehensive climate model to a broad range of external forcings: relevance for deep ocean ventilation and the development of late Cenozoic ice ages

NASA Astrophysics Data System (ADS)

Galbraith, Eric; de Lavergne, Casimir

2018-03-01

Over the past few million years, the Earth descended from the relatively warm and stable climate of the Pliocene into the increasingly dramatic ice age cycles of the Pleistocene. The influences of orbital forcing and atmospheric CO2 on land-based ice sheets have long been considered as the key drivers of the ice ages, but less attention has been paid to their direct influences on the circulation of the deep ocean. Here we provide a broad view on the influences of CO2, orbital forcing and ice sheet size according to a comprehensive Earth system model, by integrating the model to equilibrium under 40 different combinations of the three external forcings. We find that the volume contribution of Antarctic (AABW) vs. North Atlantic (NADW) waters to the deep ocean varies widely among the simulations, and can be predicted from the difference between the surface densities at AABW and NADW deep water formation sites. Minima of both the AABW-NADW density difference and the AABW volume occur near interglacial CO2 (270-400 ppm). At low CO2, abundant formation and northward export of sea ice in the Southern Ocean contributes to very salty and dense Antarctic waters that dominate the global deep ocean. Furthermore, when the Earth is cold, low obliquity (i.e. a reduced tilt of Earth's rotational axis) enhances the Antarctic water volume by expanding sea ice further. At high CO2, AABW dominance is favoured due to relatively warm subpolar North Atlantic waters, with more dependence on precession. Meanwhile, a large Laurentide ice sheet steers atmospheric circulation as to strengthen the Atlantic Meridional Overturning Circulation, but cools the Southern Ocean remotely, enhancing Antarctic sea ice export and leading to very salty and expanded AABW. Together, these results suggest that a `sweet spot' of low CO2, low obliquity and relatively small ice sheets would have poised the AMOC for interruption, promoting Dansgaard-Oeschger-type abrupt change. The deep ocean temperature and salinity simulated under the most representative `glacial' state agree very well with reconstructions from the Last Glacial Maximum (LGM), which lends confidence in the ability of the model to estimate large-scale changes in water-mass geometry. The model also simulates a circulation-driven increase of preformed radiocarbon reservoir age, which could explain most of the reconstructed LGM-preindustrial ocean radiocarbon change. However, the radiocarbon content of the simulated glacial ocean is still higher than reconstructed for the LGM, and the model does not reproduce reconstructed LGM deep ocean oxygen depletions. These ventilation-related disagreements probably reflect unresolved physical aspects of ventilation and ecosystem processes, but also raise the possibility that the LGM ocean circulation was not in equilibrium. Finally, the simulations display an increased sensitivity of both surface air temperature and AABW volume to orbital forcing under low CO2. We suggest that this enhanced orbital sensitivity contributed to the development of the ice age cycles by amplifying the responses of climate and the carbon cycle to orbital forcing, following a gradual downward trend of CO2.

Bathymetry data reveal glaciers vulnerable to ice-ocean interaction in Uummannaq and Vaigat glacial fjords, west Greenland

NASA Astrophysics Data System (ADS)

Rignot, E.; Fenty, I.; Xu, Y.; Cai, C.; Velicogna, I.; Cofaigh, C. Ó.; Dowdeswell, J. A.; Weinrebe, W.; Catania, G.; Duncan, D.

2016-03-01

Marine-terminating glaciers play a critical role in controlling Greenland's ice sheet mass balance. Their frontal margins interact vigorously with the ocean, but our understanding of this interaction is limited, in part, by a lack of bathymetry data. Here we present a multibeam echo sounding survey of 14 glacial fjords in the Uummannaq and Vaigat fjords, west Greenland, which extends from the continental shelf to the glacier fronts. The data reveal valleys with shallow sills, overdeepenings (>1300 m) from glacial erosion, and seafloor depths 100-1000 m deeper than in existing charts. Where fjords are deep enough, we detect the pervasive presence of warm, salty Atlantic Water (AW) (>2.5°C) with high melt potential, but we also find numerous glaciers grounded on shallow (<200 m) sills, standing in cold (<1°C) waters in otherwise deep fjords, i.e., with reduced melt potential. Bathymetric observations extending to the glacier fronts are critical to understand the glacier evolution.

Pulling boat hands: a unique dermatosis from coastal New England.

PubMed

Toback, A C; Korson, R; Krusinski, P A

1985-04-01

We report a previously unrecognized hand dermatosis, pulling boat hands (PBH), occurring in thirteen participants at the Outward Bound School on Hurricane Island, Maine. Painful and pruritic macules, plaques, and vesicles developed exclusively while subjects lived aboard a pulling boat, the school's open rowing/sailing craft. Nine of those affected were women and eight had Raynaud's phenomenon or vasospasm. These subjects experienced thirty episodes of PBH during May through October, 1978 to 1982. Histopathology revealed a superficial and deep lymphohistiocytic perivascular infiltrate, subepidermal blister formation, red blood cell extravasation, and dermal capillary thrombosis compatible with cold injury to the skin. All patients experienced prolonged percussion to their hands while rowing as well as a continuous environmental exposure to cold air, wind, humidity, ocean spume, and precipitation. These clinical, histopathologic, and environmental findings suggest a unique syndrome that combines the vascular effects of mechanical trauma from rowing with those of nonfreezing cold injury.

Three modes of interdecadal trends in sea surface temperature and sea surface height

NASA Astrophysics Data System (ADS)

Gnanadesikan, A.; Pradal, M.

2013-12-01

It might be thought that sea surface height and sea surface temperature would be tightly related. We show that this is not necessarily the case on a global scale. We analysed this relationship in a suite of coupled climate models run under 1860 forcing conditions. The models are low-resolution variants of the GFDL Earth System Model, reported in Galbraith et al. (J. Clim. 2011). 1. Correlated changes in global sea surface height and global sea surface temperature. This mode corresponds to opening and closing of convective chimneys in the Southern Ocean. As the Southern Ocean destratifies, sea ice formation is suppressed during the winter and more heat is taken up during the summer. This mode of variability is highly correlated with changes in the top of the atmosphere radiative budget and weakly correlated with changes in the deep ocean circulation. 2. Uncorrelated changes in global sea surface height and global sea surface temperature. This mode of variability is associated with interdecadal variabliity in tropical winds. Changes in the advective flux of heat to the surface ocean play a critical role in driving these changes, which also result in significant local changes in sea level. Changes sea ice over the Southern Ocean still result in changes in solar absorption, but these are now largely cancelled by changes in outgoing longwave radiation. 3. Anticorrelated changes in global sea surface height and global sea surface temperatures. By varying the lateral diffusion coefficient in the ocean model, we are able to enhance and suppress convection in the Southern and Northern Pacific Oceans. Increasing the lateral diffusion coefficients shifts the balance sources of deep water away from the warm salty deep water of the North Atlantic and towards cold fresh deep water from the other two regions. As a result, even though the planet as a whole warms, the deep ocean cools and sea level falls, with changes of order 30 cm over 500 years. The increase in solar absorption in polar regions is more than compensated by an increase in outgoing longwave radiation. Relationship between global SSH trend over a decade and (A) local SSH change over a decade (m/m). (B) Global SST change over a decade (m/K) (C) Portion of decadal SST change correlated with net radiation at the top of the atmosphere (m/K) (D) Portion of decadal SST change not correlated with net radiation at the top of the atmosphere.

Dueling Deglacial Depth Transects: A Synthesis of Isotope Records from the South Atlantic and Pacific Oceans Provides Insight into Deglacial Ocean Circulation

NASA Astrophysics Data System (ADS)

Sikes, E. L.; Allen, K. A.; Lund, D. C.

2016-12-01

The end of the last ice age was marked by rapid increases in atmospheric CO2 and changes in ocean circulation and seawater δ13C and Δ14C, suggesting that enhanced ventilation of the deep ocean may have released sequestered CO2 to the atmosphere. Here we compare depth transects of Δ14C and high-resolution Cibicidoides sp. δ13C and δ18O records from the Southwest Pacific and the Southwest Atlantic to gain insight into the changing extent and composition of water masses in the Southern Hemisphere. Our vertical transects document that during the Last Glacial Maximum (LGM), water mass properties and boundaries in the Southwest Atlantic and Pacific were very different from one another and from their respective modern profiles. The shallow to deep δ13C difference (Δδ13C, 660- 2500 m) in the Pacific was 1.7‰, more than double the Holocene value ( 0.7‰) and a deep watermass boundary was situated above 1600m. LGM Δδ13C in the Atlantic was similar to the Pacific, but the deep geochemical front was situated at 2500 m (as observed previously; e.g. Hoffman and Lund, 2012). At the onset of Heinrich Stadial 1 (HS1; 18 - 14.5 ka), changes in the shallow isotope records (< 1500 m) from the two basins differed, indicating independent controls on intermediate water composition/formation in these two ocean basins. During HS1 in the Pacific, rapid δ13C and Δ14C enrichment above 1600 m coincided with δ13C depletion in Atlantic waters between 1500 m and 2500 m. Benthic δ13C below 2500 m in both basins and D14C in the Pacific remained depleted until the Antarctic Cold Reversal (ACR; 14.7 to 12.7 ka). During the ACR, Pacific Δ14C below 1600 m increased while both the Atlantic and Pacific experienced a rapid increase in δ13C and decrease in δ18O below 2500 m. These simultaneous isotopic shifts in the Pacific and Atlantic support the idea of a widespread pulse of deep-water ventilation driven by the resumption of North Atlantic Deep Water formation during the ACR. Overall, early shallow to intermediate ventilation differed between the two basins and simultaneous deep ventilation occurred later in the deglaciation, coincident with the reinitiation of deep overturning circulation during the Bølling-Allerød.

Oceanographic, Air-sea Interaction, and Environmental Aspects of Artificial Upwelling Produced by Wave-Inertia Pumps for Potential Hurricane Intensity Mitigation

NASA Astrophysics Data System (ADS)

Soloviev, A.; Dean, C.

2017-12-01

The artificial upwelling system consisting of the wave-inertia pumps driven by surface waves can produce flow of cold deep water to the surface. One of the recently proposed potential applications of the artificial upwelling system is the hurricane intensity mitigation. Even relatively small reduction of intensity may provide significant benefits. The ocean heat content (OHC) is the "fuel" for hurricanes. The OHC can be reduced by mixing of the surface layer with the cold water produced by wave-inertia pumps. Implementation of this system for hurricane mitigation has several oceanographic and air-sea interaction aspects. The cold water brought to the surface from a deeper layer has higher density than the surface water and, therefore, tends to sink back down. The mixing of the cold water produced by artificial upwelling depends on environmental conditions such as stratification, regional ocean circulation, and vertical shear. Another aspect is that as the sea surface temperature drops below the air temperature, the stable stratification develops in the atmospheric boundary layer. The stable atmospheric stratification suppresses sensible and latent heat air-sea fluxes and reduces the net longwave irradiance from the sea surface. As a result, the artificial upwelling may start increasing the OHC (though still reducing the sea surface temperature). In this work, the fate of the cold water in the stratified environment with vertical shear has been studied using computational fluid dynamics (CFD) tools. A 3D large eddy simulation model is initialized with observational temperature, salinity, and current velocity data from a sample location in the Straits of Florida. A periodic boundary condition is set along the direction of the current, which allows us to simulate infinite fetch. The model results indicate that the cold water brought to the sea surface by a wave-inertia pump forms a convective jet. This jet plunges into the upper ocean mixed layer and penetrates the thermocline. On the way down, the jet partially mixes with the surrounding water reducing the temperature of the upper ocean. The OHC thus can either reduce or increase, depending on the wave-inertia pump parameters. Based on the model results, we discuss feasibility of the implementation of the artificial upwelling system for hurricane intensity mitigation.

A new classification scheme of European cold-water coral habitats: Implications for ecosystem-based management of the deep sea

NASA Astrophysics Data System (ADS)

Davies, J. S.; Guillaumont, B.; Tempera, F.; Vertino, A.; Beuck, L.; Ólafsdóttir, S. H.; Smith, C. J.; Fosså, J. H.; van den Beld, I. M. J.; Savini, A.; Rengstorf, A.; Bayle, C.; Bourillet, J.-F.; Arnaud-Haond, S.; Grehan, A.

2017-11-01

Cold-water corals (CWC) can form complex structures which provide refuge, nursery grounds and physical support for a diversity of other living organisms. However, irrespectively from such ecological significance, CWCs are still vulnerable to human pressures such as fishing, pollution, ocean acidification and global warming Providing coherent and representative conservation of vulnerable marine ecosystems including CWCs is one of the aims of the Marine Protected Areas networks being implemented across European seas and oceans under the EC Habitats Directive, the Marine Strategy Framework Directive and the OSPAR Convention. In order to adequately represent ecosystem diversity, these initiatives require a standardised habitat classification that organises the variety of biological assemblages and provides consistent and functional criteria to map them across European Seas. One such classification system, EUNIS, enables a broad level classification of the deep sea based on abiotic and geomorphological features. More detailed lower biotope-related levels are currently under-developed, particularly with regards to deep-water habitats (>200 m depth). This paper proposes a hierarchical CWC biotope classification scheme that could be incorporated by existing classification schemes such as EUNIS. The scheme was developed within the EU FP7 project CoralFISH to capture the variability of CWC habitats identified using a wealth of seafloor imagery datasets from across the Northeast Atlantic and Mediterranean. Depending on the resolution of the imagery being interpreted, this hierarchical scheme allows data to be recorded from broad CWC biotope categories down to detailed taxonomy-based levels, thereby providing a flexible yet valuable information level for management. The CWC biotope classification scheme identifies 81 biotopes and highlights the limitations of the classification framework and guidance provided by EUNIS, the EC Habitats Directive, OSPAR and FAO; which largely underrepresent CWC habitats.

Project NEPTUNE: an innovative, powered, fibre-optic cabled deep ocean observatory spanning the Juan de Fuca plate, NE Pacific

NASA Astrophysics Data System (ADS)

Barnes, C.; Delaney, J.

2003-04-01

NEPTUNE is an innovative facility, a deep-water cabled observatory, that will transform marine science. MARS and VENUS are deep and shallow-water test bed facilities for NEPTUNE located in Monterey Canyon, California and in southern British Columbia, respectively; both were funded in 2002. NEPTUNE will be a network of over 30 subsea observatories covering the 200,000 sq. km Juan de Fuca tectonic plate, Northeast Pacific. It will draw power via two shore stations and receive and exchange data with scientists through 3000 km of submarine fiber-optic cables. Each observatory, and cabled extensions, will host and power many scientific instruments on the surrounding seafloor, in seafloor boreholes and buoyed through the water column. Remotely operated and autonomous vehicles will reside at depth, recharge at observatories, and respond to distant labs. Continuous near-real-time multidisciplinary measurement series will extend over 30 years. Free from the limitations of battery life, ship schedules/ accommodations, bad weather and delayed access to data, scientists will monitor remotely their deep-sea experiments in real time on the Internet, and routinely command instruments to respond to storms, plankton blooms, earthquakes, eruptions, slope slides and other events. Scientists will be able to pose entirely new sets of questions and experiments to understand complex, interacting Earth System processes such as the structure and seismic behavior of the ocean crust; dynamics of hot and cold fluids and gas hydrates in the upper ocean crust and overlying sediments; ocean climate change and its effect on the ocean biota at all depths; and the barely known deep-sea ecosystem dynamics and biodiversity. NEPTUNE is a US/Canada (70/30) partnership to design, test, build and operate the network on behalf of a wide scientific community. The total cost of the project is estimated at about U.S. 250 million from concept to operation. Over U.S. 50 million has already been funded for design, development, and the test beds. NEPTUNE will be among the first of many such cabled ocean observatories. Much is to be gained by being among the scientific and industrial pioneers. The multidisciplinary data archive will be an amazing, expanding resource for scientists and students. The public will share in the research discoveries of one of the last unexplored places on earth through an extensive education/outreach program.

Kinetic bottlenecks to chemical exchange rates for deep-sea animals - Part 1: Oxygen

NASA Astrophysics Data System (ADS)

Hofmann, A. F.; Peltzer, E. T.; Brewer, P. G.

2012-10-01

Ocean warming will reduce dissolved oxygen concentrations which can pose challenges to marine life. Oxygen limits are traditionally reported simply as a static concentration thresholds with no temperature, pressure or flow rate dependency. Here we treat the oceanic oxygen supply potential for heterotrophic consumption as a dynamic molecular exchange problem analogous to familiar gas exchange processes at the sea surface. A combination of the purely physico-chemical oceanic properties temperature, hydrostatic pressure, and oxygen concentration defines the ability of the ocean to supply oxygen to any given animal. This general oceanic oxygen supply potential is modulated by animal specific properties such as the diffusive boundary layer thickness to define and limit maximal oxygen supply rates. Here we combine all these properties into formal, mechanistic equations defining novel oceanic properties that subsume various relevant classical oceanographic parameters to better visualize, map, comprehend, and predict the impact of ocean deoxygenation on aerobic life. By explicitly including temperature and hydrostatic pressure into our quantities, various ocean regions ranging from the cold deep-sea to warm, coastal seas can be compared. We define purely physico-chemical quantities to describe the oceanic oxygen supply potential, but also quantities that contain organism-specific properties which in a most generalized way describe general concepts and dependencies. We apply these novel quantities to example oceanic profiles around the world and find that temperature and pressure dependencies of diffusion and partial pressure create zones of greatest physical constriction on oxygen supply typically at around 1000 m depth, which coincides with oxygen concentration minimum zones. In these zones, which comprise the bulk of the world ocean, ocean warming and deoxygenation have a clear negative effect for aerobic life. In some shallow and warm waters the enhanced diffusion and higher partial pressure due to higher temperatures might slightly overcompensate for oxygen concentration decreases due to decreases in solubility.

The source and distribution of thermogenic dissolved organic matter in the ocean

NASA Astrophysics Data System (ADS)

Dittmar, T.; Suryaputra, I. G. N. A.; Paeng, J.

2009-04-01

Thermogenic organic matter (ThOM) is abundant in the environment. ThOM is produced at elevated temperature and pressure in deep sediments and earth's crust, and it is also a residue of fossil fuel and biomass burning ("black carbon"). Because of its refractory character, it accumulates in soils and sediments and, therefore, may sequester carbon from active cycles. It was hypothesized that a significant component of marine dissolved organic matter (DOM) might be thermogenic. Here we present a detailed data set on the distribution of thermogenic DOM in major water masses of the deep and surface ocean. In addition, several potential sources of thermogenic DOM to the ocean were investigated: active seeps of brine fluids in the deep Gulf of Mexico, rivers, estuaries and submarine groundwaters. Studies on deep-sea hydrothermal vents and aerosol deposition are ongoing. All DOM samples were isolated from seawater via solid phase extraction (SPE-DOM). ThOM was quantified in the extracts as benzene-polycarboxylic acids (BPCAs) after nitric acid oxidation via high-performance liquid chromatography and diode array detection (HPLC-DAD). BPCAs are produced exclusively from fused ring systems and are therefore unambiguous molecular tracers for ThOM. In addition to BPCA determination, the molecular composition and structure of ThOM was characterized in detail via ultrahigh resolution mass spectrometry (FT-ICR-MS). All marine and river DOM samples yielded significant amounts of BPCAs. The cold seep system in the deep Gulf of Mexico, but also black water rivers (like the Suwannee River) were particularly rich in ThOM. Up to 10% of total dissolved organic carbon was thermogenic in both systems. The most abundant BPCA was benzene-pentacarboxylic acid (B5CA). The molecular composition of BPCAs and the FT-ICR-MS data indicate a relatively small number (5-8) of fused aromatic rings per molecule. Overall, the molecular BPCA patterns were very similar independent of the source of ThOM. Petroleum-derived ThOM in the deep Gulf of Mexico had very similar structures than fused ring systems in asphaltenes, but also ThOM in the rivers and groundwaters was similar. First data on aerosols, on the other had, show a clear difference between particulate and dissolved samples. ThOM from aerosols and most soils was characterized by an abundance of benzene-hexacarboxylic acid (B6CA), different from thermogenic DOM. Dissolution processes may cause partial breakdown of larger fused ring systems and thus cause similar structural units in all DOM samples. In the deep ocean, the distribution of thermogenic DOM was relatively homogeneous throughout the water column. The concentration of carbon that resides in thermogenic polycyclic aromatic hydrocarbon varied between 610 and 800 nM (1.5-2% of total dissolved organic carbon). The total amount of thermogenic DOM in the deep ocean is approx. one Peta mole carbon globally. The relatively homogenous distribution of thermogenic DOM in the abyssal ocean indicates that thermogenic DOM behaves virtually inert in the abyssal environment. One of the most striking features is that the oldest water masses, which are not enriched in industrial products (such as the Freon CFC-12) showed highest concentrations of thermogenic DOM. The younger water masses such as Antarctic bottom and intermediate waters are not particularly enriched in thermogenic DOM. This distribution suggests a preindustrial origin of ThOM in the deep ocean. Rivers and deep-sea seep systems were both identified as potential sources of ThOM to the deep ocean. Radiocarbon dating on BPCAs will provide further evidence for the origin of BC in the deep ocean.

Seasonal Variation of Barrier Layer in the Southern Ocean

NASA Astrophysics Data System (ADS)

Pan, Li; Zhong, Yisen; Liu, Hailong; Zhou, Lei; Zhang, Zhaoru; Zhou, Meng

2018-03-01

The seasonal variability of barrier layer (BL) and its formation mechanism in the Southern Ocean are investigated using the most recent Argo data. The results reveal that the BL is a persistent feature in the Southern Ocean with a strong seasonal cycle. The thickest BL appears in winter with the maximum amplitude exceeding 250 m while it dramatically decreases to less than 50 m in summer. The spatial distribution of BL is zonally oriented in the Pacific and Indian Ocean sectors, which is in agreement with that of the mixed layer depth (MLD) and the isothermal layer depth (ILD). Two areas with the most prominent BL are identified. One is located south of Australia and the other in the southeastern Pacific. The BL formation in both areas is generally attributed to a shallow mixed layer controlled by surface freshwater intrusion and a deep isothermal layer modulated by seasonal vertical convection. In the former region, the cold and fresh Antarctic Surface Water (ASW) is transported northward across the Subantarctic Front (SAF) by the Ekman effect and overlies the warm Subantarctic Mode Water (SAMW). The resulting inverse temperature structure facilitates the development of thick BLs. In the latter region, the BL emerges in the ventilation area where the shallow Surface Salinity Minimum Water (SSMW) coming from north leans against the deep vertical isotherms. In summer, positive surface heat flux into the ocean overwhelms other thermodynamic effects in the mixed layer heat budget. The MLD and ILD coincide and thus the BL is destroyed.

Availability of free oxygen in deep bottom water of some Archean-Early Paleoproterozoic ocean basins as derived from iron formation facies analyses

NASA Astrophysics Data System (ADS)

Beukes, N. J.; Smith, A.

2013-12-01

Archean to Early Paleoproterozoic ocean basins are commonly, although not exclusively, depicted as rather static systems; either permanently stratified with shallow mixed oxygenated water overlying anoxic deep water or with a totally anoxic water column. The anoxic water columns are considered enriched in dissolved ferrous iron derived from hydrothermal plume activity. These sourced deposition of iron formations through precipitation of mainly ferrihydrite via reaction with free oxygen in the stratified model or anaerobic iron oxidizing photoautotrophs in the anoxic model. However, both these models face a simple basic problem if detailed facies reconstructions of deepwater microbanded iron formations (MIFs) are considered. In such MIFs it is common that the deepest water and most distal facies is hematite rich followed shoreward by magnetite, iron silicate and siderite facies iron formation. Examples of such facies relations are known from jaspilitic iron formation of the ~3,2 Ga Fig Tree Group (Barberton Mountainland), ~ 2,95 Ga iron formations of the Witwatersrand-Mozaan basin and the ~2,5 Ga Kuruman Iron Formation, Transvaal Supergroup, South Africa. Facies relations of these MIFs with associated siliciclastics or carbonates also indicate that the upper water columns of the basins, down to below wave base, were depleted in iron favoring anoxic-oxic stratification rather than total anoxia. In the MIFs it can be shown that hematite in the distal facies represents the earliest formed diagenetic mineral; most likely crystallized from primary ferrihydrite. The problem is one of how ferrihydrite could have been preserved on the ocean floor if it was in direct contact with reducing ferrous deep bottom water. Rather dissolved ferrous iron would have reacted with ferrihydrite to form diagenetic magnetite. This dilemma is resolved if in the area of deepwater hematite MIF deposition, the anoxic ferrous iron enriched plume was detached from the basin floor due to buoyancy in slightly oxygenated cold deep ocean water. Ferrihydrite, precipitated along the oxic-anoxic interface along the bottom of the buoyant plume could then settle to the floor of the basin without interference of dissolved ferrous iron. This model requires that oxygen, derived from photosynthesis in shallow water, circulated down to deep water creating a slightly oxygenated ocean basin system invaded by buoyant anoxic ferrous plumes. In areas where these plumes came in contact with the basin floor, magnetite and/or carbonate facies iron formation formed; the latter in areas of highest organic carbon influx. Extensive glacial diamictites in the Witwatersrand-Mozaan basin argues for climatic zonation in the Mesoarchean driving deep ocean currents. This model may explain why the rise of oxygen in the atmosphere was so long delayed after development of oxygenic photosynthesis; simply because in the dynamic ocean system oxygen could come into contact with much larger volumes of reduced species in the water column and along the ocean floor than in a static stratified system. It also impacts on reconstruction of microbial communities in Archean oceans.

Coralline algal Barium as indicator for 20th century northwestern North Atlantic surface ocean freshwater variability

PubMed Central

Hetzinger, S.; Halfar, J.; Zack, T.; Mecking, J. V.; Kunz, B. E.; Jacob, D. E.; Adey, W. H.

2013-01-01

During the past decades climate and freshwater dynamics in the northwestern North Atlantic have undergone major changes. Large-scale freshening episodes, related to polar freshwater pulses, have had a strong influence on ocean variability in this climatically important region. However, little is known about variability before 1950, mainly due to the lack of long-term high-resolution marine proxy archives. Here we present the first multidecadal-length records of annually resolved Ba/Ca variations from Northwest Atlantic coralline algae. We observe positive relationships between algal Ba/Ca ratios from two Newfoundland sites and salinity observations back to 1950. Both records capture episodical multi-year freshening events during the 20th century. Variability in algal Ba/Ca is sensitive to freshwater-induced changes in upper ocean stratification, which affect the transport of cold, Ba-enriched deep waters onto the shelf (highly stratified equals less Ba/Ca). Algal Ba/Ca ratios therefore may serve as a new resource for reconstructing past surface ocean freshwater changes. PMID:23636135

Coralline algal barium as indicator for 20th century northwestern North Atlantic surface ocean freshwater variability.

PubMed

Hetzinger, S; Halfar, J; Zack, T; Mecking, J V; Kunz, B E; Jacob, D E; Adey, W H

2013-01-01

During the past decades climate and freshwater dynamics in the northwestern North Atlantic have undergone major changes. Large-scale freshening episodes, related to polar freshwater pulses, have had a strong influence on ocean variability in this climatically important region. However, little is known about variability before 1950, mainly due to the lack of long-term high-resolution marine proxy archives. Here we present the first multidecadal-length records of annually resolved Ba/Ca variations from Northwest Atlantic coralline algae. We observe positive relationships between algal Ba/Ca ratios from two Newfoundland sites and salinity observations back to 1950. Both records capture episodical multi-year freshening events during the 20th century. Variability in algal Ba/Ca is sensitive to freshwater-induced changes in upper ocean stratification, which affect the transport of cold, Ba-enriched deep waters onto the shelf (highly stratified equals less Ba/Ca). Algal Ba/Ca ratios therefore may serve as a new resource for reconstructing past surface ocean freshwater changes.

Collapse and rapid resumption of Atlantic meridional circulation linked to deglacial climate changes.

PubMed

McManus, J F; Francois, R; Gherardi, J-M; Keigwin, L D; Brown-Leger, S

2004-04-22

The Atlantic meridional overturning circulation is widely believed to affect climate. Changes in ocean circulation have been inferred from records of the deep water chemical composition derived from sedimentary nutrient proxies, but their impact on climate is difficult to assess because such reconstructions provide insufficient constraints on the rate of overturning. Here we report measurements of 231Pa/230Th, a kinematic proxy for the meridional overturning circulation, in a sediment core from the subtropical North Atlantic Ocean. We find that the meridional overturning was nearly, or completely, eliminated during the coldest deglacial interval in the North Atlantic region, beginning with the catastrophic iceberg discharge Heinrich event H1, 17,500 yr ago, and declined sharply but briefly into the Younger Dryas cold event, about 12,700 yr ago. Following these cold events, the 231Pa/230Th record indicates that rapid accelerations of the meridional overturning circulation were concurrent with the two strongest regional warming events during deglaciation. These results confirm the significance of variations in the rate of the Atlantic meridional overturning circulation for abrupt climate changes.

Technology development plan: Geotechnical survey systems for OTEC (Ocean Thermal Energy Conversion) cold water pipes

NASA Astrophysics Data System (ADS)

Valent, Philip J.; Riggins, Michael

1989-04-01

An overview is given of current and developing technologies and techniques for performing geotechnical investigations for siting and designing Cold Water Pipes (CWP) for shelf-resting Ocean Thermal Energy Conversion (OTEC) power plants. The geotechnical in situ tools used to measure the required parameters and the equipment/systems used to deploy these tools are identified. The capabilities of these geotechnical tools and deployment systems are compared to the data requirements for the CWP foundation/anchor design, and shortfalls are identified. For the last phase of geotechnical data gathering for design, a drillship will be required to perform soil boring work, to obtain required high quality sediment samples for laboratory dynamic testing, and to perform deep penetration in situ tests. To remedy shortfalls and to reduce the future OTEC CWP geotechnical survey costs, it is recommended that a seafloor resting machine be developed to advance the friction cone penetrometer, and also probably a pressuremeter, to provide geotechnical parameters to shallow subseafloor penetrations on slopes of 35 deg and in water depths to 1300 m.

Attenuation of sinking particulate organic carbon flux through the mesopelagic ocean

PubMed Central

Marsay, Chris M.; Sanders, Richard J.; Henson, Stephanie A.; Pabortsava, Katsiaryna; Achterberg, Eric P.; Lampitt, Richard S.

2015-01-01

The biological carbon pump, which transports particulate organic carbon (POC) from the surface to the deep ocean, plays an important role in regulating atmospheric carbon dioxide (CO2) concentrations. We know very little about geographical variability in the remineralization depth of this sinking material and less about what controls such variability. Here we present previously unpublished profiles of mesopelagic POC flux derived from neutrally buoyant sediment traps deployed in the North Atlantic, from which we calculate the remineralization length scale for each site. Combining these results with corresponding data from the North Pacific, we show that the observed variability in attenuation of vertical POC flux can largely be explained by temperature, with shallower remineralization occurring in warmer waters. This is seemingly inconsistent with conclusions drawn from earlier analyses of deep-sea sediment trap and export flux data, which suggest lowest transfer efficiency at high latitudes. However, the two patterns can be reconciled by considering relatively intense remineralization of a labile fraction of material in warm waters, followed by efficient downward transfer of the remaining refractory fraction, while in cold environments, a larger labile fraction undergoes slower remineralization that continues over a longer length scale. Based on the observed relationship, future increases in ocean temperature will likely lead to shallower remineralization of POC and hence reduced storage of CO2 by the ocean. PMID:25561526

Meltwater routing and the Younger Dryas.

PubMed

Condron, Alan; Winsor, Peter

2012-12-04

The Younger Dryas--the last major cold episode on Earth--is generally considered to have been triggered by a meltwater flood into the North Atlantic. The prevailing hypothesis, proposed by Broecker et al. [1989 Nature 341:318-321] more than two decades ago, suggests that an abrupt rerouting of Lake Agassiz overflow through the Great Lakes and St. Lawrence Valley inhibited deep water formation in the subpolar North Atlantic and weakened the strength of the Atlantic Meridional Overturning Circulation (AMOC). More recently, Tarasov and Peltier [2005 Nature 435:662-665] showed that meltwater could have discharged into the Arctic Ocean via the Mackenzie Valley ~4,000 km northwest of the St. Lawrence outlet. Here we use a sophisticated, high-resolution, ocean sea-ice model to study the delivery of meltwater from the two drainage outlets to the deep water formation regions in the North Atlantic. Unlike the hypothesis of Broecker et al., freshwater from the St. Lawrence Valley advects into the subtropical gyre ~3,000 km south of the North Atlantic deep water formation regions and weakens the AMOC by <15%. In contrast, narrow coastal boundary currents efficiently deliver meltwater from the Mackenzie Valley to the deep water formation regions of the subpolar North Atlantic and weaken the AMOC by >30%. We conclude that meltwater discharge from the Arctic, rather than the St. Lawrence Valley, was more likely to have triggered the Younger Dryas cooling.

Estimating the recharge properties of the deep ocean using noble gases and helium isotopes

NASA Astrophysics Data System (ADS)

Loose, Brice; Jenkins, William J.; Moriarty, Roisin; Brown, Peter; Jullion, Loic; Naveira Garabato, Alberto C.; Torres Valdes, Sinhue; Hoppema, Mario; Ballentine, Chris; Meredith, Michael P.

2016-08-01

The distribution of noble gases and helium isotopes in the dense shelf waters of Antarctica reflects the boundary conditions near the ocean surface: air-sea exchange, sea ice formation, and subsurface ice melt. We use a nonlinear least squares solution to determine the value of the recharge temperature and salinity, as well as the excess air injection and glacial meltwater content throughout the water column and in the precursor to Antarctic Bottom Water. The noble gas-derived recharge temperature and salinity in the Weddell Gyre are -1.95°C and 34.95 psu near 5500 m; these cold, salty recharge values are a result of surface cooling as well as brine rejection during sea ice formation in Antarctic polynyas. In comparison, the global value for deep water recharge temperature is -0.44°C at 5500 m, which is 1.5°C warmer than the southern hemisphere deep water recharge temperature, reflecting a distinct contribution from the north Atlantic. The contrast between northern and southern hemisphere recharge properties highlights the impact of sea ice formation on setting the gas properties in southern sourced deep water. Below 1000 m, glacial meltwater averages 3.5‰ by volume and represents greater than 50% of the excess neon and argon found in the water column. These results indicate glacial melt has a nonnegligible impact on the atmospheric gas content of Antarctic Bottom Water.

Barium isotopes in cold-water corals

NASA Astrophysics Data System (ADS)

Hemsing, Freya; Hsieh, Yu-Te; Bridgestock, Luke; Spooner, Peter T.; Robinson, Laura F.; Frank, Norbert; Henderson, Gideon M.

2018-06-01

Recent studies have introduced stable Ba isotopes (δ 138 / 134Ba) as a novel tracer for ocean processes. Ba isotopes could potentially provide insight into the oceanic Ba cycle, the ocean's biological pump, water-mass provenance in the deep ocean, changes in activity of hydrothermal vents, and land-sea interactions including tracing riverine inputs. Here, we show that aragonite skeletons of various colonial and solitary cold-water coral (CWC) taxa record the seawater (SW) Ba isotope composition. Thirty-six corals of eight different taxa from three oceanic regions were analysed and compared to δ 138 / 134Ba measurements of co-located seawater samples. Sites were chosen to cover a wide range of temperature, salinity, Ba concentrations and Ba isotope compositions. Seawater samples at the three sites exhibit the well-established anti-correlation between Ba concentration and δ 138 / 134Ba. Furthermore, our data set suggests that Ba/Ca values in CWCs are linearly correlated with dissolved [Ba] in ambient seawater, with an average partition coefficient of DCWC/SW = 1.8 ± 0.4 (2SD). The mean isotope fractionation of Ba between seawater and CWCs Δ138/134BaCWC-SW is -0.21 ± 0.08‰ (2SD), indicating that CWC aragonite preferentially incorporates the lighter isotopes. This fractionation likely does not depend on temperature or other environmental variables, suggesting that aragonite CWCs could be used to trace the Ba isotope composition in ambient seawater. Coupled [Ba] and δ 138 / 134Ba analysis on fossil CWCs has the potential to provide new information about past changes in the local and global relationship between [Ba] and δ 138 / 134Ba and hence about the operation of the past global oceanic Ba cycle in different climate regimes.

Ecohydrodynamics of cold-water coral reefs: a case study of the Mingulay Reef Complex (western Scotland).

PubMed

Moreno Navas, Juan; Miller, Peter I; Miller, Peter L; Henry, Lea-Anne; Hennige, Sebastian J; Roberts, J Murray

2014-01-01

Ecohydrodynamics investigates the hydrodynamic constraints on ecosystems across different temporal and spatial scales. Ecohydrodynamics play a pivotal role in the structure and functioning of marine ecosystems, however the lack of integrated complex flow models for deep-water ecosystems beyond the coastal zone prevents further synthesis in these settings. We present a hydrodynamic model for one of Earth's most biologically diverse deep-water ecosystems, cold-water coral reefs. The Mingulay Reef Complex (western Scotland) is an inshore seascape of cold-water coral reefs formed by the scleractinian coral Lophelia pertusa. We applied single-image edge detection and composite front maps using satellite remote sensing, to detect oceanographic fronts and peaks of chlorophyll a values that likely affect food supply to corals and other suspension-feeding fauna. We also present a high resolution 3D ocean model to incorporate salient aspects of the regional and local oceanography. Model validation using in situ current speed, direction and sea elevation data confirmed the model's realistic representation of spatial and temporal aspects of circulation at the reef complex including a tidally driven current regime, eddies, and downwelling phenomena. This novel combination of 3D hydrodynamic modelling and remote sensing in deep-water ecosystems improves our understanding of the temporal and spatial scales of ecological processes occurring in marine systems. The modelled information has been integrated into a 3D GIS, providing a user interface for visualization and interrogation of results that allows wider ecological application of the model and that can provide valuable input for marine biodiversity and conservation applications.

Ecohydrodynamics of Cold-Water Coral Reefs: A Case Study of the Mingulay Reef Complex (Western Scotland)

PubMed Central

Navas, Juan Moreno; Miller, Peter L.; Henry, Lea-Anne; Hennige, Sebastian J.; Roberts, J. Murray

2014-01-01

Ecohydrodynamics investigates the hydrodynamic constraints on ecosystems across different temporal and spatial scales. Ecohydrodynamics play a pivotal role in the structure and functioning of marine ecosystems, however the lack of integrated complex flow models for deep-water ecosystems beyond the coastal zone prevents further synthesis in these settings. We present a hydrodynamic model for one of Earth's most biologically diverse deep-water ecosystems, cold-water coral reefs. The Mingulay Reef Complex (western Scotland) is an inshore seascape of cold-water coral reefs formed by the scleractinian coral Lophelia pertusa. We applied single-image edge detection and composite front maps using satellite remote sensing, to detect oceanographic fronts and peaks of chlorophyll a values that likely affect food supply to corals and other suspension-feeding fauna. We also present a high resolution 3D ocean model to incorporate salient aspects of the regional and local oceanography. Model validation using in situ current speed, direction and sea elevation data confirmed the model's realistic representation of spatial and temporal aspects of circulation at the reef complex including a tidally driven current regime, eddies, and downwelling phenomena. This novel combination of 3D hydrodynamic modelling and remote sensing in deep-water ecosystems improves our understanding of the temporal and spatial scales of ecological processes occurring in marine systems. The modelled information has been integrated into a 3D GIS, providing a user interface for visualization and interrogation of results that allows wider ecological application of the model and that can provide valuable input for marine biodiversity and conservation applications. PMID:24873971

Microbial life in cold, hydrologically active oceanic crustal fluids

NASA Astrophysics Data System (ADS)

Meyer, J. L.; Jaekel, U.; Girguis, P. R.; Glazer, B. T.; Huber, J. A.

2012-12-01

It is estimated that at least half of Earth's microbial biomass is found in the deep subsurface, yet very little is known about the diversity and functional roles of these microbial communities due to the limited accessibility of subseafloor samples. Ocean crustal fluids, which may have a profound impact on global nutrient cycles given the large volumes of water moving through the crustal aquifer, are particularly difficult to sample. Access to uncontaminated ocean crustal fluids is possible with CORK (Circulation Obviation Retrofit Kit) observatories, installed through the Integrated Ocean Drilling Program (IODP). Here we present the first microbiological characterization of the formation fluids from cold, oxygenated igneous crust at North Pond on the western flank of the Mid Atlantic Ridge. Fluids were collected from two CORKs installed at IODP boreholes 1382A and 1383C and include fluids from three different depth horizons within oceanic crust. Collection of borehole fluids was monitored in situ using an oxygen optode and solid-state voltammetric electrodes. In addition, discrete samples were analyzed on deck using a comparable lab-based system as well as a membrane-inlet mass spectrometer to quantify all dissolved volatiles up to 200 daltons. The instruments were operated in parallel and both in situ and shipboard geochemical measurements point to a highly oxidized fluid, revealing an apparent slight depletion of oxygen in subsurface fluids (~215μM) relative to bottom seawater (~245μM). We were unable to detect reduced hydrocarbons, e.g. methane. Cell counts indicated the presence of roughly 2 x 10^4 cells per ml in all fluid samples, and DNA was extracted and amplified for the identification of both bacterial and archaeal community members. The utilization of ammonia, nitrate, dissolved inorganic carbon, and acetate was measured using stable isotopes, and oxygen consumption was monitored to provide an estimate of the rate of respiration per cell per day. These results provide the first dataset describing the diversity of microbes present in cold, oxygenated ocean crustal fluids and the biogeochemical processes they mediate in the subseafloor.

Deep, diverse and definitely different: unique attributes of the world's largest ecosystem

NASA Astrophysics Data System (ADS)

Ramirez-Llodra, E.; Brandt, A.; Danovaro, R.; Escobar, E.; German, C. R.; Levin, L. A.; Martinez Arbizu, P.; Menot, L.; Buhl-Mortensen, P.; Narayanaswamy, B. E.; Smith, C. R.; Tittensor, D. P.; Tyler, P. A.; Vanreusel, A.; Vecchione, M.

2010-04-01

The deep sea, the largest biome on Earth, has a series of characteristics that make this environment both distinct from other marine and land ecosystems and unique for the entire planet. This review describes these patterns and processes, from geological settings to biological processes, biodiversity and biogeographical patterns. It concludes with a brief discussion of current threats from anthropogenic activities to deep-sea habitats and their fauna. Investigations of deep-sea habitats and their fauna began in the late 19th Century. In the intervening years, technological developments and stimulating discoveries have promoted deep-sea research and changed our way of understanding life on the planet. Nevertheless, the deep sea is still mostly unknown and current discovery rates of both habitats and species remain high. The geological, physical and geochemical settings of the deep-sea floor and the water column form a series of different habitats with unique characteristics that support specific faunal communities. Since 1840, 27 new habitats/ecosystems have been discovered from the shelf break to the deep trenches and discoveries of new habitats are still happening in the early 21st Century. However, for most of these habitats, the global area covered is unknown or has been only very roughly estimated; an even smaller - indeed, minimal - proportion has actually been sampled and investigated. We currently perceive most of the deep-sea ecosystems as heterotrophic, depending ultimately on the flux on organic matter produced in the overlying surface ocean through photosynthesis. The resulting strong food limitation, thus, shapes deep-sea biota and communities, with exceptions only in reducing ecosystems such as inter alia hydrothermal vents or cold seeps, where chemoautolithotrophic bacteria play the role of primary producers fuelled by chemical energy sources rather than sunlight. Other ecosystems, such as seamounts, canyons or cold-water corals have an increased productivity through specific physical processes, such as topographic modification of currents and enhanced transport of particles and detrital matter. Because of its unique abiotic attributes, the deep sea hosts a specialized fauna. Although there are no phyla unique to deep waters, at lower taxonomic levels the composition of the fauna is distinct from that found in the upper ocean. Amongst other characteristic patterns, deep-sea species may exhibit either gigantism or dwarfism, related to the decrease in food availability with depth. Food limitation on the seafloor and water column is also reflected in the trophic structure of deep-sea communities, which are adapted to low energy availability. In most of the heterotrophic deep-sea settings, the dominant megafauna is composed of detritivores, while filter feeders are abundant in habitats with hard substrata (e.g. mid-ocean ridges, seamounts, canyon walls and coral reefs) and chemoautotrophy through symbiotic relationships is dominant in reducing habitats. Deep-sea biodiversity is among of the highest on the planet, mainly composed of macro and meiofauna, with high evenness. This is true for most of the continental margins and abyssal plains with hot spots of diversity such as seamounts or cold-water corals. However, in some ecosystems with particularly "extreme" physicochemical processes (e.g. hydrothermal vents), biodiversity is low but abundance and biomass are high and the communities are dominated by a few species. Two large-scale diversity patterns have been discussed for deep-sea benthic communities. First, a unimodal relationship between diversity and depth is observed, with a peak at intermediate depths (2000-3000 m), although this is not universal and particular abiotic processes can modify the trend. Secondly, a poleward trend of decreasing diversity has been discussed, but this remains controversial and studies with larger and more robust datasets are needed. Because of the paucity in our knowledge of habitat coverage and species composition, biogeographic studies are mostly based on regional data or on specific taxonomic groups. Recently, global biogeographic provinces for the pelagic and benthic deep ocean have been described, using environmental and, where data were available, taxonomic information. This classification described 30 pelagic provinces and 38 benthic provinces divided into 4 depth ranges, as well as 10 hydrothermal vent provinces. One of the major issues faced by deep-sea biodiversity and biogeographical studies is related to the high number of species new to science that are collected regularly, together with the slow description rates for these new species. Taxonomic coordination at the global scale is particularly difficult but is essential if we are to analyse large diversity and biogeographic trends. Because of their remoteness, anthropogenic impacts on deep-sea ecosystems have not been addressed very thoroughly until recently. The depletion of biological and mineral resources on land and in shallow waters, coupled with technological developments, is promoting the increased interest in services provided by deep-water resources. Although often largely unknown, evidence for the effects of human activities in deep-water ecosystems - such as deep-sea mining, hydrocarbon exploration and exploitation, fishing, dumping and littering - is already accumulating. Because of our limited knowledge of deep-sea biodiversity and ecosystem functioning and because of the specific life-history adaptations of many deep-sea species (e.g. slow growth and delayed maturity), it is essential that the scientific community works closely with industry, conservation organisations and policy makers to develop conservation and management options.

Salinity driven oceanographic upwelling

DOEpatents

Johnson, D.H.

1984-08-30

The salinity driven oceanographic upwelling is maintained in a mariculture device that includes a long main duct in the general shape of a cylinder having perforated cover plates at each end. The mariculture device is suspended vertically in the ocean such that one end of the main duct is in surface water and the other end in relatively deep water that is cold, nutrient rich and relatively fresh in comparison to the surface water which is relatively warm, relatively nutrient deficient and relatively saline. A plurality of elongated flow segregating tubes are disposed in the main duct and extend from the upper cover plate beyond the lower cover plate into a lower manifold plate. The lower manifold plate is spaced from the lower cover plate to define a deep water fluid flow path to the interior space of the main duct. Spacer tubes extend from the upper cover plate and communicate with the interior space of the main duct. The spacer tubes are received in an upper manifold plate spaced from the upper cover plate to define a surface water fluid flow path into the flow segregating tubes. A surface water-deep water counterflow is thus established with deep water flowing upwardly through the main duct interior for discharge beyond the upper manifold plate while surface water flows downwardly through the flow segregating tubes for discharge below the lower manifold plate. During such counterflow heat is transferred from the downflowing warm water to the upflowing cold water. The flow is maintained by the difference in density between the deep water and the surface water due to their differences in salinity. The upwelling of nutrient rich deep water is used for marifarming by fertilizing the nutrient deficient surface water. 1 fig.

Salinity driven oceanographic upwelling

DOEpatents

Johnson, David H.

1986-01-01

The salinity driven oceanographic upwelling is maintained in a mariculture device that includes a long main duct in the general shape of a cylinder having perforated cover plates at each end. The mariculture device is suspended vertically in the ocean such that one end of the main duct is in surface water and the other end in relatively deep water that is cold, nutrient rich and relatively fresh in comparison to the surface water which is relatively warm, relatively nutrient deficient and relatively saline. A plurality of elongated flow segregating tubes are disposed in the main duct and extend from the upper cover plate beyond the lower cover plate into a lower manifold plate. The lower manifold plate is spaced from the lower cover plate to define a deep water fluid flow path to the interior space of the main duct. Spacer tubes extend from the upper cover plate and communicate with the interior space of the main duct. The spacer tubes are received in an upper manifold plate spaced from the upper cover plate to define a surface water fluid flow path into the flow segregating tubes. A surface water-deep water counterflow is thus established with deep water flowing upwardly through the main duct interior for discharge beyond the upper manifold plate while surface water flows downwardly through the flow segregating tubes for discharge below the lower manifold plate. During such counterflow heat is transferred from the downflowing warm water to the upflowing cold water. The flow is maintained by the difference in density between the deep water and the surface water due to their differences in salinity. The upwelling of nutrient rich deep water is used for marifarming by fertilizing the nutrient deficient surface water.

Paleoceanographic Changes during the Past 95000 Years from the Indian Sector of the Southern Ocean

NASA Astrophysics Data System (ADS)

Manoj, M. C.; Meloth, T.; Mohan, R.

2012-12-01

High-resolution planktic/benthic foraminiferal stable isotope and mean sortable silt records in a sediment core (SK200/22a) from the sub-Antarctic regime of the Indian sector of Southern Ocean depict the variations in surface and deep water hydrography during the past 95,000 years. The δ18O records of shallow- and deep-dwelling planktonic foraminiferal species (Neogloboquadrina pachyderma, Globigerina bulloides and Globorotalia inflata), primarily reflects the changes in upper water column characteristics. The δ18O records revealed the presence of the Antarctic Cold Reversal and the timing of the variability in major surface warming events appears in phase with the Antarctic temperature variations at the millennial time scale. Comparison between the proxies of sea surface conditions like planktonic δ18O and productivity proxies like carbonate and biogenic opal content in the core indicate that millennial scale sea surface warming fluctuated with productivity. The marine isotopic stage (MIS) 1 and MIS2 are characterized by near constant variations in mean sortable silt values, negating any significant changes in the deep water flow during these periods. The MIS 3 - MIS 5 periods were characterized by a general increase in mean sortable silt value, suggesting a strengthening of bottom-current activity that triggered winnowing at these periods. This is supported by the low δ13C records of epibenthic Cibicidoides wuellerstorfi during the glacials and some parts of MIS3 and MIS 5, confirming older nutrient-rich and poorly ventilated southern sourced deep waters at these periods. The termination I is marked by decrease in flow speed and an increase in the C. wuellerstorfi δ13C values. Comparison of mean sortable silt and C. wuellerstorfi δ13C record with the Antarctic ice core records reveal that pulses of reduced bottom water flow of Circumpolar Deep Water/North Atlantic Deep Water are synchronous with the Antarctic warming events. The decreased flow speed during the Antarctic warm events may be due to the lower production rate of southern-sourced water or reduced density, leading to reduced geostrophic flow. During the cold phases of the Antarctic climate, enhanced southern westerly wind transport caused increased sea-ice export leading to increase in density of southern-sourced water.

The dynamics of biogeographic ranges in the deep sea.

PubMed

McClain, Craig R; Hardy, Sarah Mincks

2010-12-07

Anthropogenic disturbances such as fishing, mining, oil drilling, bioprospecting, warming, and acidification in the deep sea are increasing, yet generalities about deep-sea biogeography remain elusive. Owing to the lack of perceived environmental variability and geographical barriers, ranges of deep-sea species were traditionally assumed to be exceedingly large. In contrast, seamount and chemosynthetic habitats with reported high endemicity challenge the broad applicability of a single biogeographic paradigm for the deep sea. New research benefiting from higher resolution sampling, molecular methods and public databases can now more rigorously examine dispersal distances and species ranges on the vast ocean floor. Here, we explore the major outstanding questions in deep-sea biogeography. Based on current evidence, many taxa appear broadly distributed across the deep sea, a pattern replicated in both the abyssal plains and specialized environments such as hydrothermal vents. Cold waters may slow larval metabolism and development augmenting the great intrinsic ability for dispersal among many deep-sea species. Currents, environmental shifts, and topography can prove to be dispersal barriers but are often semipermeable. Evidence of historical events such as points of faunal origin and climatic fluctuations are also evident in contemporary biogeographic ranges. Continued synthetic analysis, database construction, theoretical advancement and field sampling will be required to further refine hypotheses regarding deep-sea biogeography.

The dynamics of biogeographic ranges in the deep sea

PubMed Central

McClain, Craig R.; Hardy, Sarah Mincks

2010-01-01

Anthropogenic disturbances such as fishing, mining, oil drilling, bioprospecting, warming, and acidification in the deep sea are increasing, yet generalities about deep-sea biogeography remain elusive. Owing to the lack of perceived environmental variability and geographical barriers, ranges of deep-sea species were traditionally assumed to be exceedingly large. In contrast, seamount and chemosynthetic habitats with reported high endemicity challenge the broad applicability of a single biogeographic paradigm for the deep sea. New research benefiting from higher resolution sampling, molecular methods and public databases can now more rigorously examine dispersal distances and species ranges on the vast ocean floor. Here, we explore the major outstanding questions in deep-sea biogeography. Based on current evidence, many taxa appear broadly distributed across the deep sea, a pattern replicated in both the abyssal plains and specialized environments such as hydrothermal vents. Cold waters may slow larval metabolism and development augmenting the great intrinsic ability for dispersal among many deep-sea species. Currents, environmental shifts, and topography can prove to be dispersal barriers but are often semipermeable. Evidence of historical events such as points of faunal origin and climatic fluctuations are also evident in contemporary biogeographic ranges. Continued synthetic analysis, database construction, theoretical advancement and field sampling will be required to further refine hypotheses regarding deep-sea biogeography. PMID:20667884

Deep, diverse and definitely different: unique attributes of the world's largest ecosystem

NASA Astrophysics Data System (ADS)

Ramirez-Llodra, E.; Brandt, A.; Danovaro, R.; de Mol, B.; Escobar, E.; German, C. R.; Levin, L. A.; Martinez Arbizu, P.; Menot, L.; Buhl-Mortensen, P.; Narayanaswamy, B. E.; Smith, C. R.; Tittensor, D. P.; Tyler, P. A.; Vanreusel, A.; Vecchione, M.

2010-09-01

The deep sea, the largest biome on Earth, has a series of characteristics that make this environment both distinct from other marine and land ecosystems and unique for the entire planet. This review describes these patterns and processes, from geological settings to biological processes, biodiversity and biogeographical patterns. It concludes with a brief discussion of current threats from anthropogenic activities to deep-sea habitats and their fauna. Investigations of deep-sea habitats and their fauna began in the late 19th century. In the intervening years, technological developments and stimulating discoveries have promoted deep-sea research and changed our way of understanding life on the planet. Nevertheless, the deep sea is still mostly unknown and current discovery rates of both habitats and species remain high. The geological, physical and geochemical settings of the deep-sea floor and the water column form a series of different habitats with unique characteristics that support specific faunal communities. Since 1840, 28 new habitats/ecosystems have been discovered from the shelf break to the deep trenches and discoveries of new habitats are still happening in the early 21st century. However, for most of these habitats the global area covered is unknown or has been only very roughly estimated; an even smaller - indeed, minimal - proportion has actually been sampled and investigated. We currently perceive most of the deep-sea ecosystems as heterotrophic, depending ultimately on the flux on organic matter produced in the overlying surface ocean through photosynthesis. The resulting strong food limitation thus shapes deep-sea biota and communities, with exceptions only in reducing ecosystems such as inter alia hydrothermal vents or cold seeps. Here, chemoautolithotrophic bacteria play the role of primary producers fuelled by chemical energy sources rather than sunlight. Other ecosystems, such as seamounts, canyons or cold-water corals have an increased productivity through specific physical processes, such as topographic modification of currents and enhanced transport of particles and detrital matter. Because of its unique abiotic attributes, the deep sea hosts a specialized fauna. Although there are no phyla unique to deep waters, at lower taxonomic levels the composition of the fauna is distinct from that found in the upper ocean. Amongst other characteristic patterns, deep-sea species may exhibit either gigantism or dwarfism, related to the decrease in food availability with depth. Food limitation on the seafloor and water column is also reflected in the trophic structure of heterotrophic deep-sea communities, which are adapted to low energy availability. In most of these heterotrophic habitats, the dominant megafauna is composed of detritivores, while filter feeders are abundant in habitats with hard substrata (e.g. mid-ocean ridges, seamounts, canyon walls and coral reefs). Chemoautotrophy through symbiotic relationships is dominant in reducing habitats. Deep-sea biodiversity is among of the highest on the planet, mainly composed of macro and meiofauna, with high evenness. This is true for most of the continental margins and abyssal plains with hot spots of diversity such as seamounts or cold-water corals. However, in some ecosystems with particularly "extreme" physicochemical processes (e.g. hydrothermal vents), biodiversity is low but abundance and biomass are high and the communities are dominated by a few species. Two large-scale diversity patterns have been discussed for deep-sea benthic communities. First, a unimodal relationship between diversity and depth is observed, with a peak at intermediate depths (2000-3000 m), although this is not universal and particular abiotic processes can modify the trend. Secondly, a poleward trend of decreasing diversity has been discussed, but this remains controversial and studies with larger and more robust data sets are needed. Because of the paucity in our knowledge of habitat coverage and species composition, biogeographic studies are mostly based on regional data or on specific taxonomic groups. Recently, global biogeographic provinces for the pelagic and benthic deep ocean have been described, using environmental and, where data were available, taxonomic information. This classification described 30 pelagic provinces and 38 benthic provinces divided into 4 depth ranges, as well as 10 hydrothermal vent provinces. One of the major issues faced by deep-sea biodiversity and biogeographical studies is related to the high number of species new to science that are collected regularly, together with the slow description rates for these new species. Taxonomic coordination at the global scale is particularly difficult, but is essential if we are to analyse large diversity and biogeographic trends.

A global ocean climatological atlas of the Turner angle: implications for double-diffusion and water-mass structure

NASA Astrophysics Data System (ADS)

You, Yuzhu

2002-11-01

The 1994 Levitus climatological atlas is used to calculate the Turner angle (named after J. Stewart Turner) to examine which oceanic water masses are favorable for double-diffusion in the form of diffusive convection or salt-fingering and which are doubly stable. This atlas complements the Levitus climatology. It reveals the major double-diffusive signals associated with large-scale water-mass structure. In total, about 44% of the oceans display double-diffusion, of which 30% is salt-fingering and 14% is diffusive double-diffusion. Results show that various central and deep waters are favorable for salt-fingering. The former is due to positive evaporation minus precipitation, and the latter is due to thermohaline circulation, i.e. the southward spreading of relatively warm, salty North Atlantic Deep Water (NADW) overlying cold, fresh Antarctic Bottom Water. In the northern Indian Ocean and eastern North Atlantic, favorable conditions for salt-fingering are found throughout the water column. The Red Sea (including the Persian Gulf) and Mediterranean Sea are the sources of warm, salty water for the ocean. As consequence, temperature and salinity in these outflow regions both decrease from the sea surface to the bottom. On the other hand, ocean currents are in general sluggish in these regions. In the polar and subpolar regions of Arctic and Antarctic, Okhotsk Sea, Gulf of Alaska, the subpolar gyre of the North Pacific, the Labrador Sea, and the Norwegian Sea, the upper layer water is favorable for diffusive convection because of high latitude surface cooling and ice melting. Weak and shallow diffusive convection is also found throughout tropical regions and the Bay of Bengal. The former is due to excessive precipitation over evaporation and rain cooling, and the latter is due to both precipitation and river runoff. Diffusive convection in the ocean's interior is unique to the South Atlantic between Antarctic Intermediate Water and upper NADW (uNADW). It is the consequence of the intrusive equatorward flow of upper Circumpolar Deep Water, which carries with it the minimum temperature and very low salinity overlying warm, salty uNADW.

A phylogenetic perspective on diversity of Galatheoidea (Munida, Munidopsis) from cold-water coral and cold seep communities in the western North Atlantic Ocean

USGS Publications Warehouse

Coykendall, D. Katharine; Nizinski, Martha S.; Morrison, Cheryl L.

2016-01-01

Squat lobsters (Galatheoidea and Chirostyloidea), a diverse group of decapod crustaceans, are ubiquitous members of the deep-sea fauna. Within Galatheoidea, the genera Munida and Munidopsis are the most diverse, but accurate estimates of biodiversity are difficult due to morphological complexity and cryptic diversity. Four species of Munida and nine species of Munidopsis from cold-water coral (CWC) and cold seep communities in the northwestern Atlantic Ocean (NWA) and the Gulf of Mexico (GOM) were collected over eleven years and fifteen research cruises in order to assess faunal associations and estimate squat lobster biodiversity. Identification of the majority of specimens was determined morphologically. Mitochondrial COI sequence data, obtained from material collected during these research cruises, was supplemented with published sequences of congeners from other regions. The phylogenetic analysis of Munida supports three of the four NWA and GOM species (M. microphthalma, M. sanctipauli, and M. valida) as closely related taxa. The fourth species, Munida iris, is basal to most other species of Munida, and is closely related to M. rutllanti, a species found in the northeastern Atlantic Ocean (NEA). The majority of the nine species of Munidopsis included in our analyses were collected from chemosynthetic cold seep sites from the GOM. While seep taxa were scattered throughout the phylogenetic tree, four of these species (Munidopsis livida, M. similis, M. bermudezi, and M. species A) from the NWA and the GOM were part of a large eighteen-species clade that included species collected from Pacific Ocean chemosynthetic habitats, such as hydrothermal vents and whale falls. Shinkaia crosnieri was the sister taxon to the chemosynthetic clade, and M. livida was the most basal member of this clade. Munidopsis sp. B, an undescribed species with representative individuals collected from two GOM chemosynthetic sites, exhibited the largest genetic distance from other northern Atlantic species. Generally, intraspecific diversity was lower and patterns of haplotype diversity more simple in species of Munidopsis relative to Munida. This study puts two genera of NWA and GOM squat lobsters into a population genetic and phylogenetic context with regard to biogeography and habitat to enhance understanding of the history and evolutionary trajectories of these morphologically and ecologically diverse groups.

A phylogenetic perspective on diversity of Galatheoidea (Munida, Munidopsis) from cold-water coral and cold seep communities in the western North Atlantic Ocean

NASA Astrophysics Data System (ADS)

Katharine Coykendall, D.; Nizinski, Martha S.; Morrison, Cheryl L.

2017-03-01

Squat lobsters (Galatheoidea and Chirostyloidea), a diverse group of decapod crustaceans, are ubiquitous members of the deep-sea fauna. Within Galatheoidea, the genera Munida and Munidopsis are the most diverse, but accurate estimates of biodiversity are difficult due to morphological complexity and cryptic diversity. Four species of Munida and nine species of Munidopsis from cold-water coral (CWC) and cold seep communities in the northwestern Atlantic Ocean (NWA) and the Gulf of Mexico (GOM) were collected over eleven years and fifteen research cruises in order to assess faunal associations and estimate squat lobster biodiversity. Identification of the majority of specimens was determined morphologically. Mitochondrial COI sequence data, obtained from material collected during these research cruises, was supplemented with published sequences of congeners from other regions. The phylogenetic analysis of Munida supports three of the four NWA and GOM species (M. microphthalma, M. sanctipauli, and M. valida) as closely related taxa. The fourth species, Munida iris, is basal to most other species of Munida, and is closely related to M. rutllanti, a species found in the northeastern Atlantic Ocean (NEA). The majority of the nine species of Munidopsis included in our analyses were collected from chemosynthetic cold seep sites from the GOM. While seep taxa were scattered throughout the phylogenetic tree, four of these species (Munidopsis livida, M. similis, M. bermudezi, and M. species A) from the NWA and the GOM were part of a large eighteen-species clade that included species collected from Pacific Ocean chemosynthetic habitats, such as hydrothermal vents and whale falls. Shinkaia crosnieri was the sister taxon to the chemosynthetic clade, and M. livida was the most basal member of this clade. Munidopsis sp. B, an undescribed species with representative individuals collected from two GOM chemosynthetic sites, exhibited the largest genetic distance from other northern Atlantic species. Generally, intraspecific diversity was lower and patterns of haplotype diversity more simple in species of Munidopsis relative to Munida. This study puts two genera of NWA and GOM squat lobsters into a population genetic and phylogenetic context with regard to biogeography and habitat to enhance understanding of the history and evolutionary trajectories of these morphologically and ecologically diverse groups.

Interaction of sea water and lava during submarine eruptions at mid-ocean ridges

USGS Publications Warehouse

Perfit, M.R.; Cann, J.R.; Fornari, D.J.; Engels, J.; Smith, D.K.; Ridley, W.I.; Edwards, M.H.

2003-01-01

Lava erupts into cold sea water on the ocean floor at mid-ocean ridges (at depths of 2,500 m and greater), and the resulting flows make up the upper part of the global oceanic crust. Interactions between heated sea water and molten basaltic lava could exert significant control on the dynamics of lava flows and on their chemistry. But it has been thought that heating sea water at pressures of several hundred bars cannot produce significant amounts of vapour and that a thick crust of chilled glass on the exterior of lava flows minimizes the interaction of lava with sea water. Here we present evidence to the contrary, and show that bubbles of vaporized sea water often rise through the base of lava flows and collect beneath the chilled upper crust. These bubbles of steam at magmatic temperatures may interact both chemically and physically with flowing lava, which could influence our understanding of deep-sea volcanic processes and oceanic crustal construction more generally. We infer that vapour formation plays an important role in creating the collapse features that characterize much of the upper oceanic crust and may accordingly contribute to the measured low seismic velocities in this layer.

Glacial - interglacial changes of northwest Pacific stratification, inferred from deep and shallow living radiolarians

NASA Astrophysics Data System (ADS)

Hays, J. D.

2009-12-01

Shallow (0-200m) and deep (200 to1000m) living radiolarian flux is used to measure past production from within discrete intervals of the ocean’s water column. Deep-living faunas can also be used as proxies for export production, for they remineralize it and respond geographically and temporally to varying export. Few members of the mesopelagic community leave a fossil record, but of those that do, radiolarians are the most abundant and diverse group. In northwest Pacific late Pleistocene (glacial) sediments, deep-living radiolarian flux dominates over shallow-living flux, but the reverse is true in Holocene sediments, with the dramatic dominance change occurring across the Pleistocene-Holocene boundary. Changing primary productivity can’t cause these flux changes, for shallow-living faunas have access to the same carbon flux as do deep-living faunas, but rather they signal a major reorganization of the radiolarian fauna within the water column and suggest greater glacial than Holocene carbon export. In the Holocene world-ocean, the only region where deep-living radiolarian flux dominates over shallow-living flux is in the Sea of Okhotsk, suggesting environmental similarities between this sea and the northwest Pacific. In winter, cold Siberian air chills the upper hundred meters of the Sea of Okhotsk, promoting the spread of vast sea ice fields. High productivity in a thin (10-15m) summer mixed layer depletes nutrients Between 15 and about 150m exists a layer of cold (-1 to 0 degrees C.) intermediate water, within which radiolarian concentrations are low, but these concentrations increase between 200 and 500m in warmer intermediate water (Nimmergut and Abelmann, 2002). This radiolarian stratification results in greater deep- than shallow-living radiolarian flux to the sea floor. A similar water structure in the glacial northwest Pacific is the probable cause of similar flux patterns between the glacial northwest Pacific and Holocene Sea of Okhotsk. If so then cold glacial northwest Pacific intermediate water promoted the southward spread of sea ice. This inference is supported by the near coincidence of the southern limit of deep-living species dominated glacial sediments and extensive ice rafting. It also explains nutrient depleted glacial northwest Pacific surface waters inferred from isotopic data.

Temporal change in deep-sea benthic ecosystems: a review of the evidence from recent time-series studies.

PubMed

Glover, A G; Gooday, A J; Bailey, D M; Billett, D S M; Chevaldonné, P; Colaço, A; Copley, J; Cuvelier, D; Desbruyères, D; Kalogeropoulou, V; Klages, M; Lampadariou, N; Lejeusne, C; Mestre, N C; Paterson, G L J; Perez, T; Ruhl, H; Sarrazin, J; Soltwedel, T; Soto, E H; Thatje, S; Tselepides, A; Van Gaever, S; Vanreusel, A

2010-01-01

Societal concerns over the potential impacts of recent global change have prompted renewed interest in the long-term ecological monitoring of large ecosystems. The deep sea is the largest ecosystem on the planet, the least accessible, and perhaps the least understood. Nevertheless, deep-sea data collected over the last few decades are now being synthesised with a view to both measuring global change and predicting the future impacts of further rises in atmospheric carbon dioxide concentrations. For many years, it was assumed by many that the deep sea is a stable habitat, buffered from short-term changes in the atmosphere or upper ocean. However, recent studies suggest that deep-seafloor ecosystems may respond relatively quickly to seasonal, inter-annual and decadal-scale shifts in upper-ocean variables. In this review, we assess the evidence for these long-term (i.e. inter-annual to decadal-scale) changes both in biologically driven, sedimented, deep-sea ecosystems (e.g. abyssal plains) and in chemosynthetic ecosystems that are partially geologically driven, such as hydrothermal vents and cold seeps. We have identified 11 deep-sea sedimented ecosystems for which published analyses of long-term biological data exist. At three of these, we have found evidence for a progressive trend that could be potentially linked to recent climate change, although the evidence is not conclusive. At the other sites, we have concluded that the changes were either not significant, or were stochastically variable without being clearly linked to climate change or climate variability indices. For chemosynthetic ecosystems, we have identified 14 sites for which there are some published long-term data. Data for temporal changes at chemosynthetic ecosystems are scarce, with few sites being subjected to repeated visits. However, the limited evidence from hydrothermal vents suggests that at fast-spreading centres such as the East Pacific Rise, vent communities are impacted on decadal scales by stochastic events such as volcanic eruptions, with associated fauna showing complex patterns of community succession. For the slow-spreading centres such as the Mid-Atlantic Ridge, vent sites appear to be stable over the time periods measured, with no discernable long-term trend. At cold seeps, inferences based on spatial studies in the Gulf of Mexico, and data on organism longevity, suggest that these sites are stable over many hundreds of years. However, at the Haakon Mosby mud volcano, a large, well-studied seep in the Barents Sea, periodic mud slides associated with gas and fluid venting may disrupt benthic communities, leading to successional sequences over time. For chemosynthetic ecosystems of biogenic origin (e.g. whale-falls), it is likely that the longevity of the habitat depends mainly on the size of the carcass and the ecological setting, with large remains persisting as a distinct seafloor habitat for up to 100 years. Studies of shallow-water analogs of deep-sea ecosystems such as marine caves may also yield insights into temporal processes. Although it is obvious from the geological record that past climate change has impacted deep-sea faunas, the evidence that recent climate change or climate variability has altered deep-sea benthic communities is extremely limited. This mainly reflects the lack of remote sensing of this vast seafloor habitat. Current and future advances in deep-ocean benthic science involve new remote observing technologies that combine a high temporal resolution (e.g. cabled observatories) with spatial capabilities (e.g. autonomous vehicles undertaking image surveys of the seabed). Copyright © 2010 Elsevier Ltd. All rights reserved.

Circulation, Hydrography, and Transport over the Summit of Axial-the Destination Node of OOI's Cabled Array

NASA Astrophysics Data System (ADS)

Xu, G.; Lavelle, J. W.

2016-12-01

A numerical model of ocean flow and transport is used to extrapolate observations of currents and hydrography and infer patterns of material flux in the deep ocean around Axial Volcano--the destination node of the Ocean Observatories Initiative (OOI)'s Cabled Array. Using an inverse method, the model is made to approximate measured deep ocean flow around this site during a 35-day time period in 2002. The model is then used to extract month-long mean patterns and examine smaller-scale spatial and temporal variability around Axial. Like prior observations, model month-long mean currents flow anti-cyclonically (clockwise) around the volcano's summit in toroidal form at speeds of up to 7 cm/s. The mean vertical circulation has a net effect of pumping water out of the caldera. Temperature and salinity iso-surfaces sweep upward and downward on opposite sides of the volcano with vertical excursions of up to 70 m. As a time mean, the temperature (salinity) anomaly takes the form of a cold (briny) dome above the summit. Passive tracer material released at the location of the ASHES vent field exits the caldera through its southern open end and over the western bounding wall driven by vertical flow. Once outside the caldera, the tracer circles the summit in clockwise fashion, while gradually bleeding southwestward into the ambient ocean. Another tracer release experiment using a source of 2-day duration inside and near the northern end of the caldera suggests a residence time of the fluid at that locale of 5-6 days.

Meridional Transect of Atlantic Overturning Circulation across the Mid-Pleistocene Transition

NASA Astrophysics Data System (ADS)

Goldstein, S. L.; Pena, L. D.; Seguí, M. J.; Kim, J.; Yehudai, M.; Farmer, J. R.; Ford, H. L.; Haynes, L.; Hoenisch, B.; Raymo, M. E.; Ferretti, P.; Bickert, T.

2016-12-01

The Mid-Pleistocene Transition (MPT) marked a major transition in glacial-interglacial periodicity from dominantly 41 kyr to 100 kyr cycles between 1.3-0.7 Ma. From Nd isotope records in the South Atlantic, Pena and Goldstein (Science, 2014) concluded that the Atlantic overturning circulation circulation experienced major weakening between 950-850 ka (MIS 25-21), which generated the climatic conditions that intensified cold periods, prolonged their duration, and stabilized 100 kyr cycles. Such weakening would provide a mechanism for decreased atmospheric CO2 (Hönisch et al., Science, 2009) by allowing for additional atmospheric CO2 to be stored in the deep ocean. We present a summary of work in-progress to generate two dimensional representations of the Atlantic meridional overturning circulation, from the north Atlantic to the Southern Ocean, at different time slices over the past 2Ma, including the MPT, based on Nd isotope ratios measured on Fe-Mn-oxide encrusted foraminifera and fish debris. Thus far we are analyzing samples from DSDP/ODP Sites 607, 1063 from the North Atlantic, 926 from the Equatorial Atlantic, 1264, 1267, 1088, 1090 in the South Atlantic, and 1094 from the Southern Ocean. Our data generated thus far support important changes in the overturning circulation during the MPT, and greater glacial-interglacial variability in the 100 kyr world compared with the 40 kyr world. In addition, the data indicate a North Atlantic-sourced origin for the ocean circulation disruption during the MPT. Comparison with ɛNd records in different ocean basins and with benthic foraminiferal δ13C and B/Ca ratios will also allow us to understand the links between deep ocean circulation changes and the global carbon cycle.

Investigations of a novel fauna from hydrothermal vents along the Arctic Mid-Ocean Ridge (AMOR) (Invited)

NASA Astrophysics Data System (ADS)

Rapp, H.; Schander, C.; Halanych, K. M.; Levin, L. A.; Sweetman, A.; Tverberg, J.; Hoem, S.; Steen, I.; Thorseth, I. H.; Pedersen, R.

2010-12-01

The Arctic deep ocean hosts a variety of habitats ranging from fairly uniform sedimentary abyssal plains to highly variable hard bottoms on mid ocean ridges, including biodiversity hotspots like seamounts and hydrothermal vents. Deep-sea hydrothermal vents are usually associated with a highly specialized fauna, and since their discovery in 1977 more than 400 species of animals have been described. This fauna includes various animal groups of which the most conspicuous and well known are annelids, mollusks and crustaceans. The newly discovered deep sea hydrothermal vents on the Mohns-Knipovich ridge north of Iceland harbour unique biodiversity. The Jan Mayen field consists of two main areas with high-temperature white smoker venting and wide areas with low-temperature seepage, located at 5-700 m, while the deeper Loki Castle vent field at 2400 m depth consists of a large area with high temperature black smokers surrounded by a sedimentary area with more diffuse low-temperature venting and barite chimneys. The Jan Mayen sites show low abundance of specialized hydrothermal vent fauna. Single groups have a few specialized representatives but groups otherwise common in hydrothermal vent areas are absent. Slightly more than 200 macrofaunal species have been identified from this vent area, comprising mainly an assortment of bathyal species known from the surrounding area. Analysis of stable isotope data also indicates that the majority of the species present are feeding on phytodetritus and/or phytoplankton. However, the deeper Loki Castle vent field contains a much more diverse vent endemic fauna with high abundances of specialized polychaetes, gastropods and amphipods. These specializations also include symbioses with a range of chemosynthetic microorganisms. Our data show that the fauna composition is a result of high degree of local specialization with some similarities to the fauna of cold seeps along the Norwegian margin and wood-falls in the abyssal Norwegian Sea. Few species are common to both the deep and the shallow vents, but some gastropod species show a structured population difference between the sites. Our data indicate that there has been a migration of vent fauna into the Arctic Ocean from the Pacific Ocean rather than from the known vent sites further south in the Atlantic Ocean. The discovery and sampling of these new arctic vent fields provide unique data to further understand the migration of vent organisms and interactions between different deep sea chemosynthetic environments. Based on the high degree of local adaptation and specialization of fauna from the studied sites we propose the AMOR to be a new zoogeographical province for vent fauna.

Deep-convection events foster carbonate ion reduction in deep coral reefs

NASA Astrophysics Data System (ADS)

Perez, Fiz F.; Fontela, Marcos; Garcia-Ibañez, Maribel I.; Lherminier, Pascale; Zunino, Patricia; de la Paz, Mercedes; Padín, Xose A.; Alonso-Pérez, Fernando; Velo, Anton; Guallart, Elisa F.; Mercier, Herle

2017-04-01

Since millennial times, water mass circulation and deep-convection events have been transforming warm upper waters at high latitudes into cold and well-oxygenated deep waters. These processes have filled the deep North Atlantic Ocean with waters moderately saturated in calcium carbonate, thus promoting the growth of stony corals, which are hotspots of biodiversity. During the Anthropocene, the meridional circulation has been conveying cumulative amounts of more acidified waters with lower calcium carbonate saturation levels due to the incorporation of anthropogenic carbon dioxide, with very harsh conditions for deep cold-water corals projected by 2100. We evaluate the diminution of calcium carbonate saturation levels (aragonite form) due to the increase in anthropogenic carbon dioxide during the last two decades (2002-2016). We observe a strong decrease in the aragonite saturation levels concomitant with the reduction in the volume transport of aragonite-saturated waters. We estimate a 30-35% reduction in the transport of ion carbonate excess over the saturation levels with respect to the natural carbon cycle for the period 2002-2016. This reduction is associated with an increase in the downward transport of hydrogen ions. We also observe a heaving of the aragonite saturation horizons during the last 25 years, which is estimated at 6 m year-1 for the deep waters and 12-14 m year-1 for the intermediated waters. The harsh winters of 2015 and 2016 have fostered the fast addition of more acidified water into the lower layers of the North Atlantic through deep-convection events. In the future scenario of 2oC warming, the anthropogenic carbon dioxide in the water column would be double than today and the associated transport of hydrogen ions towards the bottom water would reduce the aragonite saturation levels to 60-80% with respect to preindustrial levels. This reduction in the aragonite saturation levels would suppose a strong diminution of the North Atlantic habitats where stony corals will be able to inhabit.

Hot and sour in the deep ocean

NASA Astrophysics Data System (ADS)

Sabine, Christopher L.

2017-12-01

Stable layering in the ocean limits the rate that human-derived carbon dioxide can acidify the deep ocean. Now observations show that ocean warming, however, can enhance deep-ocean acidification through increased organic matter decomposition.

Man and the Last Great Wilderness: Human Impact on the Deep Sea

PubMed Central

Ramirez-Llodra, Eva; Tyler, Paul A.; Baker, Maria C.; Bergstad, Odd Aksel; Clark, Malcolm R.; Escobar, Elva; Levin, Lisa A.; Menot, Lenaick; Rowden, Ashley A.; Smith, Craig R.; Van Dover, Cindy L.

2011-01-01

The deep sea, the largest ecosystem on Earth and one of the least studied, harbours high biodiversity and provides a wealth of resources. Although humans have used the oceans for millennia, technological developments now allow exploitation of fisheries resources, hydrocarbons and minerals below 2000 m depth. The remoteness of the deep seafloor has promoted the disposal of residues and litter. Ocean acidification and climate change now bring a new dimension of global effects. Thus the challenges facing the deep sea are large and accelerating, providing a new imperative for the science community, industry and national and international organizations to work together to develop successful exploitation management and conservation of the deep-sea ecosystem. This paper provides scientific expert judgement and a semi-quantitative analysis of past, present and future impacts of human-related activities on global deep-sea habitats within three categories: disposal, exploitation and climate change. The analysis is the result of a Census of Marine Life – SYNDEEP workshop (September 2008). A detailed review of known impacts and their effects is provided. The analysis shows how, in recent decades, the most significant anthropogenic activities that affect the deep sea have evolved from mainly disposal (past) to exploitation (present). We predict that from now and into the future, increases in atmospheric CO2 and facets and consequences of climate change will have the most impact on deep-sea habitats and their fauna. Synergies between different anthropogenic pressures and associated effects are discussed, indicating that most synergies are related to increased atmospheric CO2 and climate change effects. We identify deep-sea ecosystems we believe are at higher risk from human impacts in the near future: benthic communities on sedimentary upper slopes, cold-water corals, canyon benthic communities and seamount pelagic and benthic communities. We finalise this review with a short discussion on protection and management methods. PMID:21829635

Thermal evolution of the high-pressure ice layers beneath a buried ocean within Titan and Ganymede

NASA Astrophysics Data System (ADS)

Choblet, G.; Tobie, G.

2015-12-01

Deep interiors of massive icy satellites such as Titan and Ganymede probably harbor a buried ocean above high-pressure (HP) ice layers. The nature and location of the lower interface of the ocean is ultimately controlled by the amount of heat transferred through the surface ice Ih layer but it also involves equilibration of heat and melt transfer in the HP ices. While the Rayleigh number associated to such HP ice layers is most probably supercritical, classical subsolidus convection might not be a viable mechanism as the radial temperature gradient in the cold boundary layer is likely to exceed the slope of the melting curve. A significant part of the heat transfer could be achieved via the mass flux of warm liquid through this cold boundary layer up to the global phase boundary, a phenomenon sometimes referred to as heat-pipe mechanism. We present 3D spherical simulations of thermal convection in these HP ice layers that address for the first time this complex interplay. First, scaling relationships are proposed to describe this configuration for a large range of Rayleigh numbers and solidus curves. We then focus on a more realistic set-up where a prescribed basal heat flux is considered in a plausible range for the thermal history of Ganymede or Titan together with the expected viscosity law for HP ices.

Primary productivity and its variability in the equatorial South China Sea during the northeast monsoon

NASA Astrophysics Data System (ADS)

Ooi, S. H.; Samah, A. A.; Braesicke, P.

2013-08-01

Near coastal areas of the equatorial South China Sea (SCS) are one of the world's regions with highest primary productivity (phytoplankton growth). Concentrations of phytoplankton in the SCS depend significantly on atmospheric forcings and the oceanic state, in particular during the northeast (winter) monsoon season from November to March. Aided by new ocean-observing satellite data, we present a climatological overview of recent surface atmospheric and oceanic features in the equatorial SCS during the northeast monsoon to identify the dominant air-sea processes influencing and modulating the primary productivity of the region. Measured chlorophyll a concentrations are used as a proxy for phytoplankton amounts and the spatial and temporal variations are characterized according to meteorological conditions. Converging northeasterly surface winds support high chlorophyll a concentrations along East Malaysia's coastline in conjunction with a continual nutrient supply from the bottom of the continental shelf by vertical mixing. The mixing can be enhanced due to increased turbulence by wind-generated high waves when they approach shallow water from the deep basin during strong cold surges and monsoon disturbances. Intraseasonal variability during the winter monsoon is characterized by a coastal increase of chlorophyll a starting in November and peaking in January. A general decrease is observed in March. Interannual variability of chlorophyll a concentrations is influenced by ENSO (due to the known modulation of cold surge occurrences), with decreases during El Niño and increases during La Niña in early winter along the shore of East Malaysia. As an example, we discuss an enhanced phytoplankton growth event that occurred due to a typical cold surge-induced Borneo vortex event in January 2010.

Long-terms Change of Sea Surface Temperature in the South China Sea

NASA Astrophysics Data System (ADS)

Park, Y. G.; Choi, A.

2016-02-01

Using the Hadley Centre Global Sea Ice and Sea Surface Temperature (HadISST) the long term trend in the South China Sea (SCS) sea surface temperature (SST) between 1950 and 2008 is investigated. Both in winter and summer SST was increased by comparable amounts, but the warming patterns and the governing processes was different. During winter warming rate was greater in the deep basin in the central part, while during summer near the southern part. In winter the net heat flux into the sea was increased and could contribute to the warming. The pattern of the heat flux, however, was different from that of the warming. The heat flux was increased over the coastal area where warming was weaker, but decreased in deeper part where warming was stronger. The northeasterly monsoon wind weakened to lower the shoreward Ekman transport and the sea surface height gradient. The cyclonic gyre that transports cold northern water to south was weakened to warm the ocean. The effect manifested more strongly southward western boundary currents, and subsequently cold advection. In summer the net surface heat flux, however, was reduced and could not contribute to the warming. Over the southern part of the ocean the weakening of the southwesterly summer monsoon reduced southeastward Ekman transport, which is antiparallel to the mean SST gradient. Firstly, southeastward cold advection is reduced to warm the surface near the southeastern boundary of the SCS. The upwelling southeast of Vietnam was also weakened to raise the SST east of Vietnam. Thus the weakening of the wind in each season was the ultimate cause of the warming, but the responses of the ocean that lead to the warming were different.

Impact of Seawater Nonlinearities on Nordic Seas Circulation

NASA Astrophysics Data System (ADS)

Helber, R. W.; Wallcraft, A. J.; Shriver, J. F.

2017-12-01

The Nordic Seas (Greenland, Iceland, and Norwegian Seas) form an ocean basin important for Arctic-mid-latitude climate linkages. Cold fresh water from the Arctic Ocean and warm salty water from the North Atlantic Ocean meet in the Nordic Seas, where a delicate balance between temperature and salinity variability results in deep water formation. Seawater non-linearities are stronger at low temperatures and salinities making high-latitude oceans highly subject to thermbaricity and cabbeling. This presentation highlights and quantifies the impact of seawater non-linearities on the Nordic Seas circulation. We use two layered ocean circulation models, the Hybrid Coordinate Ocean Model (HYOCM) and the Modular Ocean Model version 6 (MOM6), that enable accurate representation of processes along and across density or neutral density surfaces. Different equations-of-state and vertical coordinates are evaluated to clarify the impact of seawater non-linearities. Present Navy systems, however, do not capture some features in the Nrodic Seas vertical structure. For example, observations from the Greenland Sea reveal a subsurface temperature maximum that deepens from approximately 1500 m during 1998 to 1800 m during 2005. We demonstrate that in terms of density, salinity is the largest source of error in Nordic Seas Navy forecasts, regional scale models can represent mesoscale features driven by thermobaricity, vertical coordinates are a critical issue in Nordic Sea circulation modeling.

Meltwater routing and the Younger Dryas

DOE PAGES

Condron, Alan; Winsor, Peter

2012-12-04

The Younger Dryas -- the last major cold episode on Earth -- is generally considered to have been triggered by a meltwater flood into the North Atlantic. The prevailing hypothesis, proposed by Broecker et al. [1989 Nature 341:318–321] more than two decades ago, suggests that an abrupt rerouting of Lake Agassiz overflow through the Great Lakes and St. Lawrence Valley inhibited deep water formation in the subpolar North Atlantic and weakened the strength of the Atlantic Meridional Overturning Circulation (AMOC).More recently, Tarasov and Peltier [2005 Nature 435:662–665] showed that meltwater could have discharged into the Arctic Ocean via the Mackenziemore » Valley ~4,000 km northwest of the St. Lawrence outlet. Here we use a sophisticated, high-resolution, ocean sea-ice model to study the delivery of meltwater from the two drainage outlets to the deep water formation regions in the North Atlantic. Unlike the hypothesis of Broecker et al., freshwater from the St. Lawrence Valley advects into the subtropical gyre ~3,000 km south of the North Atlantic deep water formation regions and weakens the AMOC by <15%. In contrast, narrow coastal boundary currents efficiently deliver meltwater from the Mackenzie Valley to the deep water formation regions of the subpolar North Atlantic and weaken the AMOC by >30%. We conclude that meltwater discharge from the Arctic, rather than the St. Lawrence Valley, was more likely to have triggered the Younger Dryas cooling.« less

Large fluctuations of dissolved oxygen in the Indian and Pacific oceans during Dansgaard-Oeschger oscillations caused by variations of North Atlantic Deep Water subduction

NASA Astrophysics Data System (ADS)

Schmittner, Andreas; Galbraith, Eric D.; Hostetler, Steven W.; Pedersen, Thomas F.; Zhang, Rong

2007-09-01

Paleoclimate records from glacial Indian and Pacific oceans sediments document millennial-scale fluctuations of subsurface dissolved oxygen levels and denitrification coherent with North Atlantic temperature oscillations. Yet the mechanism of this teleconnection between the remote ocean basins remains elusive. Here we present model simulations of the oxygen and nitrogen cycles that explain how changes in deepwater subduction in the North Atlantic can cause large and synchronous variations of oxygen minimum zones throughout the Northern Hemisphere of the Indian and Pacific oceans, consistent with the paleoclimate records. Cold periods in the North Atlantic are associated with reduced nutrient delivery to the upper Indo-Pacific oceans, thereby decreasing productivity. Reduced export production diminishes subsurface respiration of organic matter leading to higher oxygen concentrations and less denitrification. This effect of reduced oxygen consumption dominates at low latitudes. At high latitudes in the Southern Ocean and North Pacific, increased mixed layer depths and steepening of isopycnals improve ocean ventilation and oxygen supply to the subsurface. Atmospheric teleconnections through changes in wind-driven ocean circulation modify this basin-scale pattern regionally. These results suggest that changes in the Atlantic Ocean circulation, similar to those projected by climate models to possibly occur in the centuries to come because of anthropogenic climate warming, can have large effects on marine ecosystems and biogeochemical cycles even in remote areas.

The deep ocean under climate change

NASA Astrophysics Data System (ADS)

Levin, Lisa A.; Le Bris, Nadine

2015-11-01

The deep ocean absorbs vast amounts of heat and carbon dioxide, providing a critical buffer to climate change but exposing vulnerable ecosystems to combined stresses of warming, ocean acidification, deoxygenation, and altered food inputs. Resulting changes may threaten biodiversity and compromise key ocean services that maintain a healthy planet and human livelihoods. There exist large gaps in understanding of the physical and ecological feedbacks that will occur. Explicit recognition of deep-ocean climate mitigation and inclusion in adaptation planning by the United Nations Framework Convention on Climate Change (UNFCCC) could help to expand deep-ocean research and observation and to protect the integrity and functions of deep-ocean ecosystems.

Model for the Evolution of an Oceanic Core Complex and its Hydrothermal Vent on the Ultraslow-Spreading Mid Cayman Spreading Center

NASA Astrophysics Data System (ADS)

Harding, J.; Van Avendonk, H. J.; Hayman, N. W.; Grevemeyer, I.; Peirce, C.

2016-12-01

The Mid Cayman Spreading Center (MCSC) is an ultraslow-spreading center (15 mm yr-1 full rate) along the Caribbean-North American plate boundary. Despite the paradigm that ultraslow-spreading centers are amagmatic and cold, two hydrothermal vent fields have recently been discovered along the MCSC. The Beebe Vent Field is a black smoker in the northern axial deep, and the Von Damm Vent Field (VDVF) is a moderate-temperature, talc precipitating vent found atop an oceanic core complex (OCC). This OCC, "Mt. Dent", is a large (3 km high) massif that formed beneath a detachment fault, which exhumed lower crustal and upper mantle material. The CaySeis Experiment was conducted in April, 2015 in order to collect wide-angle refraction data of the MCSC crust and upper mantle. We modeled the across-axis crustal structure of Mt. Dent as well as the surrounding lithosphere using 2.5D P-wave tomography. Using this tomographic model, along with geochemistry, we propose a model for the formation and evolution of the OCC Mt. Dent and the VDVF. A detachment fault formed in a magma-poor environment due to a pulse of magmatism, producing a large gabbro body that was then exhumed and rotated into the OCC footwall. Once magmatism waned and the gabbroic body cooled, the OCC was faulted and fractured due to plate flexure and increased tectonic extensional stress in the naturally cold and thick lithosphere. These faults provide a permeable and deep network of hydrothermal pathways that mine deep lithospheric heat and expose gabbro and fresh mantle peridotite. This model is consistent with the basalt geochemistry, hydrothermal fluid geochemistry, and the distribution of brittle vs. ductile structures along the detachment shear zone. The VDVF is therefore a product of a pulse of magmatism in an overall melt-poor environment, conditions that may be found at other ultraslow-spreading ridges.

The boundary layer moist static energy budget: Convection picks up moisture and leaves footprints in the marine boundary layer

NASA Astrophysics Data System (ADS)

de Szoeke, S. P.

2017-12-01

Averaged over the tropical marine boundary layer (BL), 130 W m-2 turbulent surface moist static energy (MSE) flux, 120 W m-2 of which is evaporation, is balanced by upward MSE flux at the BL top due to 1) incorporation of cold air by downdrafts from deep convective clouds, and 2) turbulent entrainment of dry air into the BL. Cold saturated downdraft air, and warm clear air entrained into the BL have distinct thermodynamic properties. This work observationally quantifies their respective MSE fluxes in the central Indian Ocean in 2011, under different convective conditions of the intraseasonal (40-90 day) Madden Julian oscillation (MJO). Under convectively suppressed conditions, entrainment and downdraft fluxes export equal shares (60 W m-2) of MSE from the BL. Downdraft fluxes are more variable, increasing for stronger convection. In the convectively active phase of the MJO, downdrafts export 90 W m-2 from the BL, compared to 40 W m-2 by entrainment. These processes that control the internal, latent (condensation), and MSE of the tropical marine atmospheric BL determine the parcel buoyancy and strength of tropical deep convection.

Polar oceans in a changing climate.

PubMed

Barnes, David K A; Tarling, Geraint A

2017-06-05

Most of Earth's surface is blue or white, but how much of each would depend on the time of observation. Our planet has been through phases of snowball (all frozen), greenhouse (all liquid seas) and icehouse (frozen and liquid). Even during current icehouse conditions, the extent of ice versus water has changed considerably between ice ages and interglacial periods. Water has been vital for life on Earth and has driven and been influenced by transitions between greenhouse and icehouse. However, neither the possession of water nor having liquid and frozen seas are unique to Earth (Figure 1). Frozen water oceans on the moons Enceladus and Europa (and possibly others) and the liquid and frozen hydrocarbon oceans on Titan probably represent the most likely areas to find extraterrestrial life. We know very little about life in Earth's polar oceans, yet they are the engine of the thermohaline 'conveyor-belt', driving global circulation of heat, oxygen, carbon and nutrients as well as setting sea level through change in ice-mass balance. In regions of polar seas, where surface water is particularly cold and dense, it sinks to generate a tropic-ward flow on the ocean floor of the Pacific, Atlantic and Indian Oceans. Cold water holds more gas, so this sinking water exports O 2 and nutrients, thereby supporting life in the deep sea, as well as soaking up CO 2 from the atmosphere. Water from mid-depths at lower latitudes flows in to replace the sinking polar surface water. This brings heat. The poles are cold because they receive the least energy from the sun, and this extreme light climate varies on many different time scales. To us, the current warm, interglacial conditions seem normal, yet such phases have represented only ∼10% of Homo sapiens' existence. Variations in Earth's orbit (so called 'Milankovitch cycles') have driven cyclical alternation of glaciations (ice ages) and warmer interglacials. Despite this, Earth's polar regions have been our planet's most environmentally constant surface regions for several millions of years, with most land ice-covered and much of the ocean seasonally freezing. The two poles have much in common, such as light climate, temperature and water viscosity, winter calm and summer (iceberg and storm) disturbance and resources. However, they are also regions of striking contrasts: the Arctic Ocean is near surrounded by land compared with the Antarctic continent, which is surrounded by the Southern Ocean. Polar oceans contrast in size, age, isolation, depth, oceanography, biology and human factors, such as governance and human habitation. The simplest foodwebs with the smallest residents live on the 1% of Antarctica that is ice free, whilst the largest animals that have ever lived on Earth (Blue and Fin whales) feed in the Arctic and Southern Oceans. Copyright © 2017 Elsevier Ltd. All rights reserved.

Functional Innovations and the Conquest of the Oceans by Acanthomorph Fishes.

PubMed

Wainwright, Peter C; Longo, Sarah J

2017-06-05

The world's oceans are home to many fantastic creatures, including about 16,000 species of actinopterygian, or ray-finned, fishes. Notably, 85% of marine fish species come from a single actinopterygian subgroup, the acanthomorph or spiny-rayed fishes. Here, we review eight functional innovations found in marine acanthomorphs that have been instrumental in the adaptive radiation of this group in the marine realm. Jaw protrusion substantially enhances the suction feeding mechanism found in all fish. Fin spines serve as a major deterrent to predators and enhance the locomotor function of fins. Pharyngognathy, a specialization of the second pair of jaws in the pharynx, enhances the ability of fishes to process hard and tough prey. Endothermy allows fishes to function at high levels of physiological performance in cold waters and facilitates frequent movement across strong thermal gradients found in the open ocean. Intramandibular joints enhance feeding for fishes that bite and scrape prey attached to hard surfaces. Antifreeze proteins prevent ice crystal growth in extracellular fluids, allowing fish to function in cold waters that would otherwise freeze them. Air-breathing allowed fishes at the water's edge to exploit terrestrial habitats. Finally, bioluminescence functions in communication, attracting prey and in hiding from predators, particularly for fishes of the deep ocean. All of these innovations have evolved multiple times in fishes. The frequent occurrence of convergent evolution of these complex functional novelties speaks to the persistence and potency of the selective forces in marine environments that challenge fishes and stimulate innovation. Copyright © 2017 Elsevier Ltd. All rights reserved.

A tribute to Peter A. Rona: A Russian Perspective

NASA Astrophysics Data System (ADS)

Sagalevich, Anatoly; Lutz, Richard A.

2015-11-01

In July 1985 Peter Rona led a cruise of the National Oceanic and Atmospheric Administration (NOAA) ship Researcher as part of the NOAA Vents Program and discovered, for the first time, black smokers, massive sulfide deposits and vent biota in the Atlantic Ocean. The site of the venting phenomena was the Trans-Atlantic Geotraverse (TAG) Hydrothermal Field on the east wall of the rift valley of the Mid-Atlantic Ridge at 26°08‧N; 44°50‧W (Rona, 1985; Rona et al., 1986). In 1986, Peter and an international research team carried out multidisciplnary investigations of both active and inactive hydrothermal zones of the TAG field using the R/V Atlantis and DSV Alvin, discovering two new species of shrimp (Rimicaris exoculata and Chorocaris chacei) (Williams and Rona, 1986) and a hexagonal-shaped form (Paleodictyon nodosum) thought to be extinct (Rona et al., 2009). In 1991 a Russian crew aboard the R/V Akademik Mstislav Keldysh, with two deep-diving, human-occupied submersibles (Mir-1 and Mir-2) (Fig. 1), had the honor of having Peter Rona and a Canadian IMAX film crew from the Stephen Low Company on board to visit the TAG hydrothermal vent field. This was the first of many deep-sea interactions between Russian deep-sea scientists and their colleagues from both the U.S. and Canada. This expedition to the TAG site was part of a major Russian undersea program aimed at exploring extreme deep-sea environments; between 1988 and 2005, the Mir submersibles visited hydrothermal vents and cold seep areas in 20 deep-sea regions throughout the world's oceans (Sagalevich, 2002). Images of several of these areas (the TAG, Snake Pit, Lost City and 9°50‧N vent fields) were obtained using an IMAX camera system emplaced for the first time within the spheres of the Mir submersibles and DSV Alvin in conjunction with the filming of science documentaries (e.g., ;Volcanoes of the Deep Sea;) produced by the Stephen Low Company in conjunction with Emory Kristof of National Geographic and Peter Rona. The initial test of this submersible-emplaced camera system was conducted during the 1991 expedition to the TAG hydrothermal vent field.

The effect of some heat treatment parameters on the dimensional stability of AISI D2

NASA Astrophysics Data System (ADS)

Surberg, Cord Henrik; Stratton, Paul; Lingenhöle, Klaus

2008-01-01

The tool steel AISI D2 is usually processed by vacuum hardening followed by multiple tempering cycles. It has been suggested that a deep cold treatment in between the hardening and tempering processes could reduce processing time and improve the final properties and dimensional stability. Hardened blocks were then subjected to various combinations of single and multiple tempering steps (520 and 540 °C) and deep cold treatments (-90, -120 and -150 °C). The greatest dimensional stability was achieved by deep cold treatments at the lowest temperature used and was independent of the deep cold treatment time.

A record of deep-ocean dissolved O2 from the oxidation state of iron in submarine basalts.

PubMed

Stolper, Daniel A; Keller, C Brenhin

2018-01-18

The oxygenation of the deep ocean in the geological past has been associated with a rise in the partial pressure of atmospheric molecular oxygen (O 2 ) to near-present levels and the emergence of modern marine biogeochemical cycles. It has also been linked to the origination and diversification of early animals. It is generally thought that the deep ocean was largely anoxic from about 2,500 to 800 million years ago, with estimates of the occurrence of deep-ocean oxygenation and the linked increase in the partial pressure of atmospheric oxygen to levels sufficient for this oxygenation ranging from about 800 to 400 million years ago. Deep-ocean dissolved oxygen concentrations over this interval are typically estimated using geochemical signatures preserved in ancient continental shelf or slope sediments, which only indirectly reflect the geochemical state of the deep ocean. Here we present a record that more directly reflects deep-ocean oxygen concentrations, based on the ratio of Fe 3+ to total Fe in hydrothermally altered basalts formed in ocean basins. Our data allow for quantitative estimates of deep-ocean dissolved oxygen concentrations from 3.5 billion years ago to 14 million years ago and suggest that deep-ocean oxygenation occurred in the Phanerozoic (541 million years ago to the present) and potentially not until the late Palaeozoic (less than 420 million years ago).

A record of deep-ocean dissolved O2 from the oxidation state of iron in submarine basalts

NASA Astrophysics Data System (ADS)

Stolper, Daniel A.; Keller, C. Brenhin

2018-01-01

The oxygenation of the deep ocean in the geological past has been associated with a rise in the partial pressure of atmospheric molecular oxygen (O2) to near-present levels and the emergence of modern marine biogeochemical cycles. It has also been linked to the origination and diversification of early animals. It is generally thought that the deep ocean was largely anoxic from about 2,500 to 800 million years ago, with estimates of the occurrence of deep-ocean oxygenation and the linked increase in the partial pressure of atmospheric oxygen to levels sufficient for this oxygenation ranging from about 800 to 400 million years ago. Deep-ocean dissolved oxygen concentrations over this interval are typically estimated using geochemical signatures preserved in ancient continental shelf or slope sediments, which only indirectly reflect the geochemical state of the deep ocean. Here we present a record that more directly reflects deep-ocean oxygen concentrations, based on the ratio of Fe3+ to total Fe in hydrothermally altered basalts formed in ocean basins. Our data allow for quantitative estimates of deep-ocean dissolved oxygen concentrations from 3.5 billion years ago to 14 million years ago and suggest that deep-ocean oxygenation occurred in the Phanerozoic (541 million years ago to the present) and potentially not until the late Palaeozoic (less than 420 million years ago).

The deep ocean under climate change.

PubMed

Levin, Lisa A; Le Bris, Nadine

2015-11-13

The deep ocean absorbs vast amounts of heat and carbon dioxide, providing a critical buffer to climate change but exposing vulnerable ecosystems to combined stresses of warming, ocean acidification, deoxygenation, and altered food inputs. Resulting changes may threaten biodiversity and compromise key ocean services that maintain a healthy planet and human livelihoods. There exist large gaps in understanding of the physical and ecological feedbacks that will occur. Explicit recognition of deep-ocean climate mitigation and inclusion in adaptation planning by the United Nations Framework Convention on Climate Change (UNFCCC) could help to expand deep-ocean research and observation and to protect the integrity and functions of deep-ocean ecosystems. Copyright © 2015, American Association for the Advancement of Science.

A long history of equatorial deep-water upwelling in the Pacific Ocean

NASA Astrophysics Data System (ADS)

Zhang, Yi Ge; Pagani, Mark; Henderiks, Jorijntje; Ren, Haojia

2017-06-01

Cold, nutrient- and CO2-rich waters upwelling in the eastern equatorial Pacific (EEP) give rise to the Pacific cold tongue. Quasi-periodic subsidence of the thermocline and attenuation in wind strength expressed by El Niño conditions decrease upwelling rates, increase surface-water temperatures in the EEP, and lead to changes in regional climates both near and far from the equatorial Pacific. EEP surface waters have elevated CO2 concentrations during neutral (upwelling) or La Niña (strong upwelling) conditions. In contrast, approximate air-sea CO2 equilibrium characterizes El Niño events. One hypothesis proposes that changes in physical oceanography led to the establishment of a deep tropical thermocline and expanded mixed-layer prior to 3 million years ago. These effects are argued to have substantially reduced deep-water upwelling rates in the EEP and promoted a "permanent El Niño-like" climate state. For this study, we test this supposition by reconstructing EEP "excess CO2" and upwelling history for the past 6.5 million years using the alkenone-pCO2 methodology. Contrary to previous assertions, our results indicate that average temporal conditions in the EEP over the past ∼6.5 million years were characterized by substantial CO2 disequilibrium and high nutrient delivery to surface waters - characteristics that imply strong upwelling of deep waters. Upwelling appears most vigorous between ∼6.5 to 4.5 million years ago coinciding with high accumulation rates of biogenic material during the late Miocene - early Pliocene "biogenic bloom".

Deep-sea octopus (Graneledone boreopacifica) conducts the longest-known egg-brooding period of any animal.

PubMed

Robison, Bruce; Seibel, Brad; Drazen, Jeffrey

2014-01-01

Octopuses typically have a single reproductive period and then they die (semelparity). Once a clutch of fertilized eggs has been produced, the female protects and tends them until they hatch. In most shallow-water species this period of parental care can last from 1 to 3 months, but very little is known about the brooding of deep-living species. In the cold, dark waters of the deep ocean, metabolic processes are often slower than their counterparts at shallower depths. Extrapolations from data on shallow-water octopus species suggest that lower temperatures would prolong embryonic development periods. Likewise, laboratory studies have linked lower temperatures to longer brooding periods in cephalopods, but direct evidence has not been available. We found an opportunity to directly measure the brooding period of the deep-sea octopus Graneledone boreopacifica, in its natural habitat. At 53 months, it is by far the longest egg-brooding period ever reported for any animal species. These surprising results emphasize the selective value of prolonged embryonic development in order to produce competitive hatchlings. They also extend the known boundaries of physiological adaptations for life in the deep sea.

Deep-Sea Octopus (Graneledone boreopacifica) Conducts the Longest-Known Egg-Brooding Period of Any Animal

PubMed Central

Robison, Bruce; Seibel, Brad; Drazen, Jeffrey

2014-01-01

Octopuses typically have a single reproductive period and then they die (semelparity). Once a clutch of fertilized eggs has been produced, the female protects and tends them until they hatch. In most shallow-water species this period of parental care can last from 1 to 3 months, but very little is known about the brooding of deep-living species. In the cold, dark waters of the deep ocean, metabolic processes are often slower than their counterparts at shallower depths. Extrapolations from data on shallow-water octopus species suggest that lower temperatures would prolong embryonic development periods. Likewise, laboratory studies have linked lower temperatures to longer brooding periods in cephalopods, but direct evidence has not been available. We found an opportunity to directly measure the brooding period of the deep-sea octopus Graneledone boreopacifica, in its natural habitat. At 53 months, it is by far the longest egg-brooding period ever reported for any animal species. These surprising results emphasize the selective value of prolonged embryonic development in order to produce competitive hatchlings. They also extend the known boundaries of physiological adaptations for life in the deep sea. PMID:25075745

Rapid subtropical North Atlantic salinity oscillations across Dansgaard-Oeschger cycles.

PubMed

Schmidt, Matthew W; Vautravers, Maryline J; Spero, Howard J

2006-10-05

Geochemical and sedimentological evidence suggest that the rapid climate warming oscillations of the last ice age, the Dansgaard-Oeschger cycles, were coupled to fluctuations in North Atlantic meridional overturning circulation through its regulation of poleward heat flux. The balance between cold meltwater from the north and warm, salty subtropical gyre waters from the south influenced the strength and location of North Atlantic overturning circulation during this period of highly variable climate. Here we investigate how rapid reorganizations of the ocean-atmosphere system across these cycles are linked to salinity changes in the subtropical North Atlantic gyre. We combine Mg/Ca palaeothermometry and oxygen isotope ratio measurements on planktonic foraminifera across four Dansgaard-Oeschger cycles (spanning 45.9-59.2 kyr ago) to generate a seawater salinity proxy record from a subtropical gyre deep-sea sediment core. We show that North Atlantic gyre surface salinities oscillated rapidly between saltier stadial conditions and fresher interstadials, covarying with inferred shifts in the Tropical Atlantic hydrologic cycle and North Atlantic overturning circulation. These salinity oscillations suggest a reduction in precipitation into the North Atlantic and/or reduced export of deep salty thermohaline waters during stadials. We hypothesize that increased stadial salinities preconditioned the North Atlantic Ocean for a rapid return to deep overturning circulation and high-latitude warming by contributing to increased North Atlantic surface-water density on interstadial transitions.

Global reductions in seafloor biomass in response to climate change.

PubMed

Jones, Daniel O B; Yool, Andrew; Wei, Chih-Lin; Henson, Stephanie A; Ruhl, Henry A; Watson, Reg A; Gehlen, Marion

2014-06-01

Seafloor organisms are vital for healthy marine ecosystems, contributing to elemental cycling, benthic remineralization, and ultimately sequestration of carbon. Deep-sea life is primarily reliant on the export flux of particulate organic carbon from the surface ocean for food, but most ocean biogeochemistry models predict global decreases in export flux resulting from 21st century anthropogenically induced warming. Here we show that decadal-to-century scale changes in carbon export associated with climate change lead to an estimated 5.2% decrease in future (2091-2100) global open ocean benthic biomass under RCP8.5 (reduction of 5.2 Mt C) compared with contemporary conditions (2006-2015). Our projections use multi-model mean export flux estimates from eight fully coupled earth system models, which contributed to the Coupled Model Intercomparison Project Phase 5, that have been forced by high and low representative concentration pathways (RCP8.5 and 4.5, respectively). These export flux estimates are used in conjunction with published empirical relationships to predict changes in benthic biomass. The polar oceans and some upwelling areas may experience increases in benthic biomass, but most other regions show decreases, with up to 38% reductions in parts of the northeast Atlantic. Our analysis projects a future ocean with smaller sized infaunal benthos, potentially reducing energy transfer rates though benthic multicellular food webs. More than 80% of potential deep-water biodiversity hotspots known around the world, including canyons, seamounts, and cold-water coral reefs, are projected to experience negative changes in biomass. These major reductions in biomass may lead to widespread change in benthic ecosystems and the functions and services they provide. © 2013 The Authors Global Change Biology Published by John Wiley & Sons Ltd.

Cenozoic planktonic marine diatom diversity and correlation to climate change

USGS Publications Warehouse

Lazarus, David; Barron, John; Renaudie, Johan; Diver, Patrick; Türke, Andreas

2014-01-01

Marine planktonic diatoms export carbon to the deep ocean, playing a key role in the global carbon cycle. Although commonly thought to have diversified over the Cenozoic as global oceans cooled, only two conflicting quantitative reconstructions exist, both from the Neptune deep-sea microfossil occurrences database. Total diversity shows Cenozoic increase but is sample size biased; conventional subsampling shows little net change. We calculate diversity from a separately compiled new diatom species range catalog, and recalculate Neptune subsampled-in-bin diversity using new methods to correct for increasing Cenozoic geographic endemism and decreasing Cenozoic evenness. We find coherent, substantial Cenozoic diversification in both datasets. Many living cold water species, including species important for export productivity, originate only in the latest Miocene or younger. We make a first quantitative comparison of diatom diversity to the global Cenozoic benthic ∂18O (climate) and carbon cycle records (∂13C, and 20-0 Ma pCO2). Warmer climates are strongly correlated with lower diatom diversity (raw: rho = .92, p2 were only moderately higher than today. Diversity is strongly correlated to both ∂13C and pCO2 over the last 15 my (for both: r>.9, detrended r>.6, all p<.001), but only weakly over the earlier Cenozoic, suggesting increasingly strong linkage of diatom and climate evolution in the Neogene. Our results suggest that many living marine planktonic diatom species may be at risk of extinction in future warm oceans, with an unknown but potentially substantial negative impact on the ocean biologic pump and oceanic carbon sequestration. We cannot however extrapolate our my-scale correlations with generic climate proxies to anthropogenic time-scales of warming without additional species-specific information on proximate ecologic controls.

Demonstration of Remotely Operated Vehicles to Aid Underwater Inspection of Corps of Engineers Navigation Structures. Winfield Locks and Dam 13-17 August 2007

DTIC Science & Technology

2008-09-01

2 Deep Ocean Engineering Triggerfish ...Figures Figure 1. Deep Ocean Engineering Triggerfish ROV carried by two divers (top)................................... 4 Figure 2. SeaBotix...the physical parameters and approximate costs of the systems as tested. Deep Ocean Engineering Triggerfish Figure 1 shows the Deep Ocean

Evidence of strong ocean heating during glacial periods

NASA Astrophysics Data System (ADS)

Zimov, S. A.; Zimov, N.

2013-12-01

Numerous hypotheses have addressed glacial-interglacial climatic dynamics, but none of them explain the sharp 25C temperature increase in Greenland in the last deglaciation (Cuffey et al. 1995; Dahl-Jensen et al. 1998). These robust data were obtained through analyzing the temperature profile in the Greenland ice sheet where cold from the last glaciation is preserved in the depth of the glacial sheet. We suggest that during glaciations the ocean accumulated energy: interior ocean water heated up to ~20-30C and during deglaciation this energy is released. In the analogy with reconstructing the ice sheet temperature profiles, the most reliable proof of ocean interior warming during the last glaciation is the heat flux profiles in the bottom sediments. In the final reports based on temperature measurements conducted during the DSDP (Deep Sea Drilling Project) it is stated that heat flux in the bottom sediments doesn't vary with depth and consequently there were no substantial temperature changes in the ocean interior during the last glacial cycle, and heat flux on the surface of the ocean bottom is the geothermal heat flux (Erickson et al., 1975, Hyndman et al., 1987). However, we have critically investigated data in all initial reports of all deep sea drilling projects and have noticed that all temperature data show that heat flow decreases strongly with depth (a minimum of 40 mW/m2), i.e. most of the heat flux detected on the surface of the ocean floor is not the geothermal heat flux but remaining heat that bottom sediments release. Sharp shifts in heat flow are seen within boreholes at depths crossing gas hydrate bottom. All this means that during the last glacial period interior water temperature was on 25-30C degrees warmer. Conversely, in isolated seas heat flow in the sediments shows little change with depth.

Preparing to predict: The Second Autonomous Ocean Sampling Network (AOSN-II) experiment in the Monterey Bay

NASA Astrophysics Data System (ADS)

Ramp, S. R.; Davis, R. E.; Leonard, N. E.; Shulman, I.; Chao, Y.; Robinson, A. R.; Marsden, J.; Lermusiaux, P. F. J.; Fratantoni, D. M.; Paduan, J. D.; Chavez, F. P.; Bahr, F. L.; Liang, S.; Leslie, W.; Li, Z.

2009-02-01

The Autonomous Ocean Sampling Network Phase Two (AOSN-II) experiment was conducted in and offshore from the Monterey Bay on the central California coast during July 23-September 6, 2003. The objective of the experiment was to learn how to apply new tools, technologies, and analysis techniques to adaptively sample the coastal ocean in a manner demonstrably superior to traditional methodologies, and to use the information gathered to improve predictive skill for quantities of interest to end-users. The scientific goal was to study the upwelling/relaxation cycle near an open coastal bay in an eastern boundary current region, particularly as it developed and spread from a coastal headland. The suite of observational tools used included a low-flying aircraft, a fleet of underwater gliders, including several under adaptive autonomous control, and propeller-driven AUVs in addition to moorings, ships, and other more traditional hardware. The data were delivered in real time and assimilated into the Harvard Ocean Prediction System (HOPS), the Navy Coastal Ocean Model (NCOM), and the Jet Propulsion Laboratory implementation of the Regional Ocean Modeling System (JPL/ROMS). Two upwelling events and one relaxation event were sampled during the experiment. The upwelling in both cases began when a pool of cold water less than 13 °C appeared near Cape Año Nuevo and subsequently spread offshore and southward across the bay as the equatorward wind stress continued. The primary difference between the events was that the first event spread offshore and southward, while the second event spread only southward and not offshore. The difference is attributed to the position and strength of meanders and eddies of the California Current System offshore, which blocked or steered the cold upwelled water. The space and time scales of the mesoscale variability were much shorter than have been previously observed in deep-water eddies offshore. Additional process studies are needed to elucidate the dynamics of the flow.

Origin, signature and palaeoclimatic influence of the Antarctic Circumpolar Current

NASA Astrophysics Data System (ADS)

Barker, P. F.; Thomas, E.

2004-06-01

The Antarctic Circumpolar Current (ACC) is today the strongest current in the world's ocean, with a significant influence on global climate. Its assumed history and influence on palaeoclimate, while almost certainly equally profound, are here called into question. In this paper, we review 30 years of accumulated data, interpretation and speculation about the ACC, deriving mainly from DSDP and ODP drilling in the Southern Ocean. For most of this time, a conventional view of ACC development, signature and influence has held sway among palaeoceanographers and marine geologists. In this view, the ACC began at about 34 Ma, close to the Eocene-Oligocene boundary, the time of onset of significant Antarctic glaciation and the time of creation of a deep-water gap (Tasmanian Seaway) between Australia and Antarctica as the South Tasman Rise separated from North Victoria Land. This is the "smoking gun" of synchroneity. The Southern Ocean sediment record shows a latest Eocene development and subsequent geographic expansion of a siliceous biofacies, its northern limit taken to indicate the palaeo-position of the ACC axis. In addition, the ACC was considered to have caused Antarctic glaciation by isolating the continent within a cold-water annulus, reducing north-south heat transport. A different (and later) date for Antarctic-South American opening ("Drake Passage") was proposed, but the timing of ACC onset there was disputed, and the simple story survived. Recent developments, however, call it into question. Modern physical oceanography shows that all or most of present-day ACC transport is confined to narrow jets within deep-reaching circumpolar fronts, and numerical modelling has suggested that a steady reduction in greenhouse gas concentration through the Cenozoic could cause Antarctic glaciation, with or without a contribution from ocean circulation change. The rapidity of Antarctic glacial onset at the Eocene-Oligocene boundary and coeval creation of a deep-water gap south of Tasmania both survive but, in light of the new information, the presence of a siliceous biofacies cannot be claimed as evidence of the existence of a continuous, deep-reaching oceanic front and therefore of an ACC, and the possibility arises that cool and cold sea-surface temperatures were effects of Antarctic glaciation rather than evidence of a major contributor to its cause. In considering future work, we emphasise the importance of additional information from ancillary fields—better definition of the necessary and sufficient properties of oceanic fronts, additional determinations of Cenozoic atmospheric pCO 2 and further developments in models of Antarctic glaciation—but also suggest the way forward in marine geology. Our knowledge of the development and palaeoclimatic significance of the ACC will be best served by grain-size studies of bottom current strength at selected locations, and geochemical or mineralogical studies of clays and IRD as a way of examining provenance and therefore surface and bottom current directions and the existence of interocean connections. Studies of biogenic assemblages within the same sediments may be able to recover a value for the many such studies undertaken in the past and interpreted, probably erroneously, as evidence for an ACC. Mainly in view of the timing uncertainties, we propose the region south of South America as the best initial focus of future investigation.

Sensitivity of simulated deep ocean natural radiocarbon to gas exchange velocity and historical atmospheric Δ14C variations

NASA Astrophysics Data System (ADS)

Wagner, Hannes; Koeve, Wolfgang; Kriest, Iris; Oschlies, Andreas

2015-04-01

Simulated deep ocean natural radiocarbon is frequently used to assess model performance of deep ocean ventilation in Ocean General Circulation Models (OGCMs). It has been shown to be sensitive to a variety of model parameters, such as the mixing parameterization, convection scheme and vertical resolution. Here we use three different ocean models (MIT2.8, ECCO, UVic) to evaluate the sensitivity of simulated deep ocean natural radiocarbon to two other factors, while keeping the model physics constant: (1) the gas exchange velocity and (2) historic variations in atmospheric Δ^1^4C boundary conditions. We find that simulated natural Δ^1^4C decreases by 14-20 ‰ throughout the deep ocean and consistently in all three models, if the gas exchange velocity is lowered by 30 % with respect to the OCMIP-2 protocol, to become more consistent with newer estimates of the oceans uptake of bomb derived ^1^4C. Simulated deep ocean natural Δ^1^4C furthermore decreases by 3-9 ‰ throughout the deep Pacific, Indian and Southern Oceans and consistently in all three models, if the models are forced with the observed atmospheric Δ^1^4C history, instead of an often made pragmatic assumption of a constant atmospheric Δ^1^4C value of zero. Applying both improvements (gas exchange reduction, as well as atmospheric Δ^1^4C history implementation) concomitantly and accounting for the present uncertainty in gas exchange velocity estimates (between 10 and 40 % reduction with respect to the OCMIP-2 protocol) simulated deep ocean Δ^1^4C decreases by 10-30 ‰ throughout the deep Pacific, Indian and Southern Ocean. This translates to a ^1^4C-age increase of 100-300 years and indicates, that models, which in former assessments (based on the OCMIP-2 protocol) had been identified to have an accurate deep ocean ventilation, should now be regarded as rather having a bit too sluggish a ventilation. Models, which on the other hand had been identified to have a bit too fast a deep ocean ventilation, should now be regarded as rather having a more accurate ventilation.

Enhanced deep ocean ventilation and oxygenation with global warming

NASA Astrophysics Data System (ADS)

Froelicher, T. L.; Jaccard, S.; Dunne, J. P.; Paynter, D.; Gruber, N.

2014-12-01

Twenty-first century coupled climate model simulations, observations from the recent past, and theoretical arguments suggest a consistent trend towards warmer ocean temperatures and fresher polar surface oceans in response to increased radiative forcing resulting in increased upper ocean stratification and reduced ventilation and oxygenation of the deep ocean. Paleo-proxy records of the warming at the end of the last ice age, however, suggests a different outcome, namely a better ventilated and oxygenated deep ocean with global warming. Here we use a four thousand year global warming simulation from a comprehensive Earth System Model (GFDL ESM2M) to show that this conundrum is a consequence of different rates of warming and that the deep ocean is actually better ventilated and oxygenated in a future warmer equilibrated climate consistent with paleo-proxy records. The enhanced deep ocean ventilation in the Southern Ocean occurs in spite of increased positive surface buoyancy fluxes and a constancy of the Southern Hemisphere westerly winds - circumstances that would otherwise be expected to lead to a reduction in deep ocean ventilation. This ventilation recovery occurs through a global scale interaction of the Atlantic Meridional Overturning Circulation undergoing a multi-centennial recovery after an initial century of transient decrease and transports salinity-rich waters inform the subtropical surface ocean to the Southern Ocean interior on multi-century timescales. The subsequent upwelling of salinity-rich waters in the Southern Ocean strips away the freshwater cap that maintains vertical stability and increases open ocean convection and the formation of Antarctic Bottom Waters. As a result, the global ocean oxygen content and the nutrient supply from the deep ocean to the surface are higher in a warmer ocean. The implications for past and future changes in ocean heat and carbon storage will be discussed.

Decadal trends in deep ocean salinity and regional effects on steric sea level

NASA Astrophysics Data System (ADS)

Purkey, S. G.; Llovel, W.

2017-12-01

We present deep (below 2000 m) and abyssal (below 4000 m) global ocean salinity trends from the 1990s through the 2010s and assess the role of deep salinity in local and global sea level budgets. Deep salinity trends are assessed using all deep basins with available full-depth, high-quality hydrographic section data that have been occupied two or more times since the 1980s through either the World Ocean Circulation Experiment (WOCE) Hydrographic Program or the Global Ship-Based Hydrographic Investigations Program (GO-SHIP). All salinity data is calibrated to standard seawater and any intercruise offsets applied. While the global mean deep halosteric contribution to sea level rise is close to zero (-0.017 +/- 0.023 mm/yr below 4000 m), there is a large regional variability with the southern deep basins becoming fresher and northern deep basins becoming more saline. This meridional gradient in the deep salinity trend reflects different mechanisms driving the deep salinity variability. The deep Southern Ocean is freshening owing to a recent increased flux of freshwater to the deep ocean. Outside of the Southern Ocean, the deep salinity and temperature changes are tied to isopycnal heave associated with a falling of deep isopycnals in recent decades. Therefore, regions of the ocean with a deep salinity minimum are experiencing both a halosteric contraction with a thermosteric expansion. While the thermosteric expansion is larger in most cases, in some regions the halosteric compensates for as much as 50% of the deep thermal expansion, making a significant contribution to local sea level rise budgets.

Multimillennium changes in dissolved oxygen under global warming: results from an AOGCM and offline ocean biogeochemical model

NASA Astrophysics Data System (ADS)

Yamamoto, A.; Abe-Ouchi, A.; Shigemitsu, M.; Oka, A.; Takahashi, K.; Ohgaito, R.; Yamanaka, Y.

2016-12-01

Long-term oceanic oxygen change due to global warming is still unclear; most future projections (such as CMIP5) are only performed until 2100. Indeed, few previous studies using conceptual models project oxygen change in the next thousands of years, showing persistent global oxygen reduction by about 30% in the next 2000 years, even after atmospheric carbon dioxide stops rising. Yet, these models cannot sufficiently represent the ocean circulation change: the key driver of oxygen change. Moreover, considering serious effect oxygen reduction has on marine life and biogeochemical cycling, long-term oxygen change should be projected for higher validity. Therefore, we used a coupled atmosphere-ocean general circulation model (AOGCM) and an offline ocean biogeochemical model, investigating realistic long-term changes in oceanic oxygen concentration and ocean circulation. We integrated these models for 2000 years under atmospheric CO2 doubling and quadrupling. After global oxygen reduction in the first 500 years, oxygen concentration in deep ocean globally recovers and overshoots, despite surface oxygen decrease and weaker Atlantic Meridional Overturning Circulation. Deep ocean convection in the Weddell Sea recovers and overshoots, after initial cessation. Thus, enhanced deep convection and associated Antarctic Bottom Water supply oxygen-rich surface waters to deep ocean, resulting global deep ocean oxygenation. We conclude that the change in ocean circulation in the Southern Ocean potentially drives millennial-scale oxygenation in the deep ocean; contrary to past reported long-term oxygen reduction and general expectation. In presentation, we will discuss the mechanism of response of deep ocean convection in the Weddell Sea and show the volume changes of hypoxic waters.

The Vertical Profile of Ocean Mixing

NASA Astrophysics Data System (ADS)

Ferrari, R. M.; Nikurashin, M.; McDougall, T. J.; Mashayek, A.

2014-12-01

The upwelling of bottom waters through density surfaces in the deep ocean is not possible unless the sloping nature of the sea floor is taken into account. The bottom--intensified mixing arising from interaction of internal tides and geostrophic motions with bottom topography implies that mixing is a decreasing function of height in the deep ocean. This would further imply that the diapycnal motion in the deep ocean is downward, not upwards as is required by continuity. This conundrum regarding ocean mixing and upwelling in the deep ocean will be resolved by appealing to the fact that the ocean does not have vertical side walls. Implications of the conundrum for the representation of ocean mixing in climate models will be discussed.

The microbiology of deep-sea hydrothermal vent plumes: ecological and biogeographic linkages to seafloor and water column habitats.

PubMed

Dick, Gregory J; Anantharaman, Karthik; Baker, Brett J; Li, Meng; Reed, Daniel C; Sheik, Cody S

2013-01-01

Hydrothermal plumes are an important yet understudied component of deep-sea vent microbial ecosystems. The significance of plume microbial processes can be appreciated from three perspectives: (1) mediation of plume biogeochemistry, (2) dispersal of seafloor hydrothermal vent microbes between vents sites, (3) as natural laboratories for understanding the ecology, physiology, and function of microbial groups that are distributed throughout the pelagic deep sea. Plume microbiology has been largely neglected in recent years, especially relative to the extensive research conducted on seafloor and subseafloor systems. Rapidly advancing technologies for investigating microbial communities provide new motivation and opportunities to characterize this important microbial habitat. Here we briefly highlight microbial contributions to plume and broader ocean (bio)geochemistry and review recent work to illustrate the ecological and biogeographic linkages between plumes, seafloor vent habitats, and other marine habitats such as oxygen minimum zones (OMZs), cold seeps, and oil spills. 16S rRNA gene surveys and metagenomic/-transcriptomic data from plumes point to dominant microbial populations, genes, and functions that are also operative in OMZs (SUP05, ammonia-oxidizing Archaea, and SAR324 Deltaproteobacteria) and hydrocarbon-rich environments (methanotrophs). Plume microbial communities are distinct from those on the seafloor or in the subsurface but contain some signatures of these habitats, consistent with the notion that plumes are potential vectors for dispersal of microorganisms between seafloor vent sites. Finally, we put forward three pressing questions for the future of deep-sea hydrothermal plume research and consider interactions between vents and oceans on global scales.

The microbiology of deep-sea hydrothermal vent plumes: ecological and biogeographic linkages to seafloor and water column habitats

PubMed Central

Dick, Gregory J.; Anantharaman, Karthik; Baker, Brett J.; Li, Meng; Reed, Daniel C.; Sheik, Cody S.

2013-01-01

Hydrothermal plumes are an important yet understudied component of deep-sea vent microbial ecosystems. The significance of plume microbial processes can be appreciated from three perspectives: (1) mediation of plume biogeochemistry, (2) dispersal of seafloor hydrothermal vent microbes between vents sites, (3) as natural laboratories for understanding the ecology, physiology, and function of microbial groups that are distributed throughout the pelagic deep sea. Plume microbiology has been largely neglected in recent years, especially relative to the extensive research conducted on seafloor and subseafloor systems. Rapidly advancing technologies for investigating microbial communities provide new motivation and opportunities to characterize this important microbial habitat. Here we briefly highlight microbial contributions to plume and broader ocean (bio)geochemistry and review recent work to illustrate the ecological and biogeographic linkages between plumes, seafloor vent habitats, and other marine habitats such as oxygen minimum zones (OMZs), cold seeps, and oil spills. 16S rRNA gene surveys and metagenomic/-transcriptomic data from plumes point to dominant microbial populations, genes, and functions that are also operative in OMZs (SUP05, ammonia-oxidizing Archaea, and SAR324 Deltaproteobacteria) and hydrocarbon-rich environments (methanotrophs). Plume microbial communities are distinct from those on the seafloor or in the subsurface but contain some signatures of these habitats, consistent with the notion that plumes are potential vectors for dispersal of microorganisms between seafloor vent sites. Finally, we put forward three pressing questions for the future of deep-sea hydrothermal plume research and consider interactions between vents and oceans on global scales. PMID:23720658

Large fluctuations of dissolved oxygen in the Indian and Pacific oceans during Dansgaard-Oeschger oscillations caused by variations of North Atlantic Deep Water subduction

USGS Publications Warehouse

Schmittner, A.; Galbraith, E.D.; Hostetler, S.W.; Pedersen, Thomas F.; Zhang, R.

2007-01-01

Paleoclimate records from glacial Indian and Pacific oceans sediments document millennial-scale fluctuations of subsurface dissolved oxygen levels and denitrification coherent with North Atlantic temperature oscillations. Yet the mechanism of this teleconnection between the remote ocean basins remains elusive. Here we present model simulations of the oxygen and nitrogen cycles that explain how changes in deepwater subduction in the North Atlantic can cause large and synchronous variations of oxygen minimum zones, throughout the Northern Hemisphere of the Indian and Pacific oceans, consistent with the paleoclimate records. Cold periods in the North Atlantic are associated with reduced nutrient delivery to the upper Indo-Pacific oceans, thereby decreasing productivity. Reduced export production diminishes subsurface respiration of organic matter leading to higher oxygen concentrations and less denitrification. This effect of reduced oxygen consumption dominates at low latitudes. At high latitudes in the Southern Ocean and North Pacific, increased mixed layer depths and steepening of isopycnals improve ocean ventilation and oxygen supply to the subsurface. Atmospheric teleconnections through changes in wind-driven ocean circulation modify this basin-scale pattern regionally. These results suggest that changes in the Atlantic Ocean circulation, similar to those projected by climate models to possibly occur in the centuries to come because of anthropogenic climate warming, can have large effects on marine ecosystems and biogeochemical cycles even in remote areas. Copyright 2007 by the American Geophysical Union.

Waveform Tomography of the South Atlantic Region

NASA Astrophysics Data System (ADS)

Celli, N. L.; Lebedev, S.; Schaeffer, A. J.; Gaina, C.

2016-12-01

The rapid growth in broadband seismic data, along with developments in waveform tomography techniques, allow us to greatly improve the data sampling in the southern hemisphere and resolve the upper-mantle structure beneath the South Atlantic region at a new level of detail. We have gathered a very large waveform dataset, including all publicly available data from permanent and temporary networks. Our S-velocity tomographic model is constrained by vertical-component waveform fits, computed using the Automated Multimode Inversion of surface, S and multiple S waves. Each seismogram fit provides a set of linear equations describing 1D average velocity perturbations within approximate sensitivity volumes, with respect to a 3D reference model. All the equations are then combined into a large linear system and inverted jointly for a model of shear- and compressional-wave speeds and azimuthal anisotropy within the lithosphere and underlying mantle. The isotropic-average shear speeds are proxies for temperature and composition at depth, while azimuthal anisotropy provides evidence on the past and present deformation in the lithosphere and asthenosphere beneath the region. We resolve the complex boundaries of the mantle roots of South America's and Africa's cratons and the deep low-velocity anomalies beneath volcanic areas in South America. Pronounced lithospheric high seismic velocity anomalies beneath the Argentine Basin suggest that its anomalously deep seafloor, previously attributed to dynamic topography, is mainly due to anomalously cold, thick lithosphere. Major hotspots show low-velocity anomalies extending substantially deeper than those beneath the mid-ocean ridge. The Vema Hotspot shows a major, hot asthenospheric anomaly beneath thick, cold oceanic lithosphere. The mantle lithosphere beneath the Walvis Ridge—a hotspot track—shows normal cooling. The volcanic Cameroon Line, in contrast, is characterized by thin lithosphere beneath the locations of recent volcanism.

Convectively-driven cold layer and its influences on moisture in the UTLS

NASA Astrophysics Data System (ADS)

Kim, J.; Randel, W. J.; Birner, T.

2016-12-01

Characteristics of the cold anomaly in the tropical tropopause layer (TTL) that is commonly observed with deep convection are examined using CloudSat and Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) GPS radio occultation measurements. Deep convection is sampled based on the cloud top height (>17 km) from CloudSat 2B-CLDCLASS, and then temperature profiles from COSMIC are composited around the deep convection. The composite temperature shows anomalously warm troposphere (up to 14 km) and a significantly cold layer near the tropopause (at 16-18 km) in the regions of deep convection. Generally in the tropics, the cold layer has very large horizontal scale (2,000 - 6,000 km) compared to that of mesoscale convective cluster, and it lasts one or two weeks with minimum temperature anomaly of - 2K. The cold layer shows slight but clear eastward-tilted vertical structure in the deep tropics indicating a large-scale Kelvin wave response. Further analyses on circulation patterns suggest that the anomaly can be explained as a part of Gill-type response in the TTL to deep convective heating in the troposphere. Response of moisture to the cold layer is also examined in the upper troposphere and lower stratosphere using microwave limb sounder (MLS) measurements. The water vapor anomalies show coherent structures with the temperature and circulation anomalies. A clear dry anomaly is found in the cold layer and its outflow region, implying a large-scale dehydration process due to the convectively driven cold layer in the upper TTL.

Characterization of a rapid climate shift at the MIS 8/7 transition in central Spain (Valdocarros II, Autonomous Region of Madrid) by means of the herpetological assemblages

NASA Astrophysics Data System (ADS)

Blain, Hugues-Alexandre; Panera, Joaquin; Uribelarrea, David; Rubio-Jara, Susana; Pérez-González, Alfredo

2012-07-01

Climate instability with high-amplitude and rapid shifts during the Middle Pleistocene is well known from pollen records and deep-ocean sediment cores. Although poorly correlatable with such long climate/environment records, the successive fossil amphibian and reptile assemblages from the Middle Pleistocene site of Valdocarros II (Autonomous Region of Madrid, central Spain) provide a unique opportunity to characterize the climatic and environmental features of such rapid (certainly less than 1000 years) shifts from cold to warm conditions in a terrestrial sequence. As the amphibians and reptiles do not differ at species level from the extant herpetofauna of the Iberian Peninsula, they can contribute to the reconstruction of the landscape and climate. In this paper, the mutual climatic range and habitat weighting methods are applied to the herpetofaunistic assemblages in order to estimate quantitative data. The difference in mean annual temperature between "cold" and "warm" periods is estimated at 3.2 °C, with a greater increase in temperature during winter (+3 °C) than during summer (+1 °C). During "cold" periods the climate was more Oceanic (although preserving some dryness during the summers), whereas during "warm" periods the climate became Mediterranean (with mild winters and a long period of dryness in the summer and early autumn). Though higher during cold periods, the continentality (or atmospheric temperature range) remained roughly similar, in accordance with the geographical location of the site in the centre of the Iberian Peninsula. A greater amount of open landscape occurred during "cold" periods, whereas during "warm" periods the wooded areas expanded from 20% to 40% of the landscape surface. Such climatic/environmental changes, together with the numeric datings of the site, suggest that this shift may correspond to the transition from MIS 8 to MIS 7, also called Termination III.

Evaluation of vaccine cold chain in urban health centers of municipal corporation of surat city, Western India.

PubMed

Naik, Ashish K; Rupani, Mihir P; Bansal, R K

2013-12-01

The success of immunization depends highly on the level of cold chain maintenance. The aim of the study was to assess the condition of cold chain equipment, practices adopted for cold chain maintenance and knowledge of the vaccinators. It was a cross-sectional study conducted in 20 UHCs of Surat Municipal Corporation (SMC). Cold chain equipment were observed with regards to their condition, along with the practices adopted by vaccinators for cold chain maintenance. A pre-designed and pre-tested questionnaire was used to interview the vaccinators regarding their knowledge and awareness regarding cold chain practices, management and handling. Data were entered and analyzed using Epi Info v 3.5.1. Simple proportions were calculated. Absence of separate stabilizer for deep freezers and ILRs (85%), ill-maintained temperature-record register, lack of criss-cross pattern of ice packs in deep freezer (65%), presence of things other than ice packs in deep freezer (10%) and things other than vaccines in ILR (10%) indicate poor cold chain maintenance. In addition to this, expired vaccines in ILR (5%), vaccines in the "unusable" stages of VVM (15%), lack of emergency contact number nearby in case of cold chain failure (85%), lack of inverter (85%), lack of generator (85%) and failure to note time of reconstitution on the vaccine vial at the time of vaccination (25%) indicate poor cold chain practices. Lack of knowledge of defrosting of ILR and deep freezer (45%), lack of knowledge about Shake test (40%), lack of knowledge of temperature range to be maintained in deep freezer (70%) and in ILR (15%) indicate poor knowledge of vaccinators. Cold chain maintenance and practices need improvement. Knowledge of vaccinators was overall unsatisfactory.

Climate, carbon cycling, and deep-ocean ecosystems.

PubMed

Smith, K L; Ruhl, H A; Bett, B J; Billett, D S M; Lampitt, R S; Kaufmann, R S

2009-11-17

Climate variation affects surface ocean processes and the production of organic carbon, which ultimately comprises the primary food supply to the deep-sea ecosystems that occupy approximately 60% of the Earth's surface. Warming trends in atmospheric and upper ocean temperatures, attributed to anthropogenic influence, have occurred over the past four decades. Changes in upper ocean temperature influence stratification and can affect the availability of nutrients for phytoplankton production. Global warming has been predicted to intensify stratification and reduce vertical mixing. Research also suggests that such reduced mixing will enhance variability in primary production and carbon export flux to the deep sea. The dependence of deep-sea communities on surface water production has raised important questions about how climate change will affect carbon cycling and deep-ocean ecosystem function. Recently, unprecedented time-series studies conducted over the past two decades in the North Pacific and the North Atlantic at >4,000-m depth have revealed unexpectedly large changes in deep-ocean ecosystems significantly correlated to climate-driven changes in the surface ocean that can impact the global carbon cycle. Climate-driven variation affects oceanic communities from surface waters to the much-overlooked deep sea and will have impacts on the global carbon cycle. Data from these two widely separated areas of the deep ocean provide compelling evidence that changes in climate can readily influence deep-sea processes. However, the limited geographic coverage of these existing time-series studies stresses the importance of developing a more global effort to monitor deep-sea ecosystems under modern conditions of rapidly changing climate.

Molecular adaptation in the world's deepest-living animal: Insights from transcriptome sequencing of the hadal amphipod Hirondellea gigas.

PubMed

Lan, Yi; Sun, Jin; Tian, Renmao; Bartlett, Douglas H; Li, Runsheng; Wong, Yue Him; Zhang, Weipeng; Qiu, Jian-Wen; Xu, Ting; He, Li-Sheng; Tabata, Harry G; Qian, Pei-Yuan

2017-07-01

The Challenger Deep in the Mariana Trench is the deepest point in the oceans of our planet. Understanding how animals adapt to this harsh environment characterized by high hydrostatic pressure, food limitation, dark and cold is of great scientific interest. Of the animals dwelling in the Challenger Deep, amphipods have been captured using baited traps. In this study, we sequenced the transcriptome of the amphipod Hirondellea gigas collected at a depth of 10,929 m from the East Pond of the Challenger Deep. Assembly of these sequences resulted in 133,041 contigs and 22,046 translated proteins. Functional annotation of these contigs was made using the go and kegg databases. Comparison of these translated proteins with those of four shallow-water amphipods revealed 10,731 gene families, of which 5659 were single-copy orthologs. Base substitution analysis on these single-copy orthologs showed that 62 genes are positively selected in H. gigas, including genes related to β-alanine biosynthesis, energy metabolism and genetic information processing. For multiple-copy orthologous genes, gene family expansion analysis revealed that cold-inducible proteins (i.e., transcription factors II A and transcription elongation factor 1) as well as zinc finger domains are expanded in H. gigas. Overall, our results indicate that genetic adaptation to the hadal environment by H. gigas may be mediated by both gene family expansion and amino acid substitutions of specific proteins. © 2017 John Wiley & Sons Ltd.

Being There & Getting Back Again: Half a Century of Deep Ocean Research & Discovery with the Human Occupied Vehicle "Alvin"

NASA Astrophysics Data System (ADS)

German, C. R.; Fornari, D. J.; Fryer, P.; Girguis, P. R.; Humphris, S. E.; Kelley, D. S.; Tivey, M.; Van Dover, C. L.; Von Damm, K.

2012-12-01

In 2013, Alvin returns to service after significant observational and operational upgrades supported by the NSF, NAVSEA & NOAA. Here we review highlights of the first half-century of deep submergence science conducted by Alvin, describe some of the most significant improvements for the new submarine and discuss the importance of these new capabilities for 21st century ocean science and education. Alvin has a long history of scientific exploration, discovery and intervention at the deep seafloor: in pursuit of hypothesis-driven research and in response to human impacts. One of Alvin's earliest achievements, at the height of the Cold War, was to help locate & recover an H-bomb in the Mediterranean, while the last dives completed, just ahead of the current refit, were to investigate the impacts of the Deep Water Horizon oil spill. Alvin has excelled in supporting a range of Earth & Life Science programs including, in the late 1970s, first direct observations and sampling of deep-sea hydrothermal vents and the unusual fauna supported by microbial chemosynthesis. The 1980s saw expansion of Alvin's dive areas to newly discovered hot-springs in the Atlantic & NE Pacific, Alvin's first dives to the wreck of RMS Titanic and its longest excursions away from WHOI yet, via Loihi Seamount (Hawaii) to the Mariana Trench. The 1990s saw Alvin's first event-response dives to sites where volcanic eruptions had just occurred at the East Pacific Rise & Juan de Fuca Ridge while the 2000s saw Alvin discover novel off-axis venting at Lost City. Observations from these dives fundamentally changed our views of volcanic and microbial processes within young ocean crust and even the origins of life! In parallel, new deep submergence capabilities, including manipulative experiments & sensor development, relied heavily on testing using Alvin. Recently, new work has focused on ocean margins where fluid flow from the seafloor results in the release of hydrocarbons and other chemical species that can sustain chemosynthetic seep ecosystems comparable to, and sometimes sharing species with, hot vents. What will Alvin's next 50 years discover? During 2011-12, Alvin has undergone a transformation, including a larger personnel sphere with more & larger viewports to provide improved overlapping fields of view for the pilot & observers. The new Alvin will be certified for operations to 4500m depth initially, but the new sphere will be 6500m-rated and planned future upgrades will ultimately allow the vehicle to dive that deep, enabling human access to 98% of the global ocean floor. This will allow the study of processes and dynamics of Earth's largest ecosystem (the abyssal plains) as well as margin and ridge environments and the overlying water column. Meantime, the current upgrades to Alvin already include a suite of scientific enhancements including new HD video & still imaging, sophisticated data acquisition systems for seafloor observations and mapping, a new work platform with greater payload capacity and improved observer ergonomics. The new Alvin is poised to play important roles in core Earth and Life science programs and to serve large-scale programs such as the Ocean Observatory Initiative (OOI) and the International Ocean Discovery Program (IODP). It will continue to attract, engage and inspire a new generation of scientists & students to explore and study the largest ecosystem on Earth, just as it has done throughout its first half century.

Hidden impacts of ocean acidification to live and dead coral framework.

PubMed

Hennige, S J; Wicks, L C; Kamenos, N A; Perna, G; Findlay, H S; Roberts, J M

2015-08-22

Cold-water corals, such as Lophelia pertusa, are key habitat-forming organisms found throughout the world's oceans to 3000 m deep. The complex three-dimensional framework made by these vulnerable marine ecosystems support high biodiversity and commercially important species. Given their importance, a key question is how both the living and the dead framework will fare under projected climate change. Here, we demonstrate that over 12 months L. pertusa can physiologically acclimate to increased CO2, showing sustained net calcification. However, their new skeletal structure changes and exhibits decreased crystallographic and molecular-scale bonding organization. Although physiological acclimatization was evident, we also demonstrate that there is a negative correlation between increasing CO2 levels and breaking strength of exposed framework (approx. 20-30% weaker after 12 months), meaning the exposed bases of reefs will be less effective 'load-bearers', and will become more susceptible to bioerosion and mechanical damage by 2100. © 2015 The Authors.

Ocean thermal gradient as a generator of electricity. OTEC power plant

NASA Astrophysics Data System (ADS)

Enrique, Luna-Gomez Victor; Angel, Alatorre-Mendieta Miguel

2016-04-01

The OTEC (Ocean Thermal Energy Conversion) is a power plant that uses the thermal gradient of the sea water between the surface and a depth of about 700 meters. It works by supplying the heat to a steam machine, for evaporation, with sea water from the surface and cold, to condense the steam, with deep sea water. The energy generated by the power plant OTEC can be transferred to the electric power grid, another use is to desalinate seawater. During the twentieth century in some countries experimental power plants to produce electricity or obtaining drinking water they were installed. On the Mexico's coast itself this thermal gradient, as it is located in tropical seas it occurs, so it has possibilities of installing OTEC power plant type. In this paper one type OTEC power plant operation is represented in most of its components.

Deep convective clouds at the tropopause

NASA Astrophysics Data System (ADS)

Aumann, H. H.; Desouza-Machado, S. G.

2010-07-01

Data from the Advanced Infrared Sounder (AIRS) on the EOS Aqua spacecraft identify thousands of cloud tops colder than 225 K, loosely referred to as Deep Convective Clouds (DCC). Many of these cloud tops have "inverted" spectra, i.e. areas of strong water vapor, CO2 and ozone opacity, normally seen in absorption, are now seen in emission. We refer to these inverted spectra as DCCi. They are found in about 0.4% of all spectra from the tropical oceans excluding the Western Tropical Pacific (WTP), 1.1% in the WTP. The cold clouds are the anvils capping thunderstorms and consist of optically thick cirrus ice clouds. The precipitation rate associated with DCCi suggests that imbedded in these clouds, protruding above them, and not spatially resolved by the AIRS 15 km FOV, are even colder bubbles, where strong convection pushes clouds to within 5 hPa of the pressure level of the tropopause cold point. Associated with DCCi is a local upward displacement of the tropopause, a cold "bulge", which can be seen directly in the brightness temperatures of AIRS and AMSU channels with weighting function peaking between 40 and 2 hPa, without the need for a formal temperature retrieval. The bulge is not resolved by the analysis in numerical weather prediction models. The locally cold cloud tops relative to the analysis give the appearance (in the sense of an "illusion") of clouds overshooting the tropopause and penetrating into the stratosphere. Based on a simple model of optically thick cirrus clouds, the spectral inversions seen in the AIRS data do not require these clouds to penetrate into the stratosphere. However, the contents of the cold bulge may be left in the lower stratosphere as soon as the strong convection subsides. The heavy precipitation and the distortion of the temperature structure near the tropopause indicate that DCCi are associated with intense storms. Significant long-term trends in the statistical properties of DCCi could be interesting indicators of climate change.

Warming Ocean Conditions Relate to Increased Trophic Requirements of Threatened and Endangered Salmon

PubMed Central

Daly, Elizabeth A.; Brodeur, Richard D.

2015-01-01

The trophic habits, size and condition of yearling Chinook salmon (Oncorhynchus tshawytscha) caught early in their marine residence were examined during 19 survey years (1981–1985; 1998–2011). Juvenile salmon consumed distinct highly piscivorous diets in cold and warm ocean regimes with major differences between ocean regimes driven by changes in consumption of juvenile rockfishes, followed by several other fish prey, adult euphausiids and decapod larvae. Notable, Chinook salmon consumed 30% more food in the warm versus cold ocean regime in both May and June. Additionally, there were about 30% fewer empty stomachs in the warm ocean regime in May, and 10% fewer in warm June periods. The total prey energy density consumed during the warmer ocean regime was also significantly higher than in cold. Chinook salmon had lower condition factor and were smaller in fork length during the warm ocean regime, and were longer and heavier for their size during the cold ocean regime. The significant increase in foraging during the warm ocean regime occurred concurrently with lower available prey biomass. Adult return rates of juvenile Chinook salmon that entered the ocean during a warm ocean regime were lower. Notably, our long term data set contradicts the long held assertion that juvenile salmon eat less in a warm ocean regime when low growth and survival is observed, and when available prey are reduced. Comparing diet changes between decades under variable ocean conditions may assist us in understanding the effects of projected warming ocean regimes on juvenile Chinook salmon and their survival in the ocean environment. Bioenergetically, the salmon appear to require more food resources during warm ocean regimes. PMID:26675673

Warming Ocean Conditions Relate to Increased Trophic Requirements of Threatened and Endangered Salmon.

PubMed

Daly, Elizabeth A; Brodeur, Richard D

2015-01-01

The trophic habits, size and condition of yearling Chinook salmon (Oncorhynchus tshawytscha) caught early in their marine residence were examined during 19 survey years (1981-1985; 1998-2011). Juvenile salmon consumed distinct highly piscivorous diets in cold and warm ocean regimes with major differences between ocean regimes driven by changes in consumption of juvenile rockfishes, followed by several other fish prey, adult euphausiids and decapod larvae. Notable, Chinook salmon consumed 30% more food in the warm versus cold ocean regime in both May and June. Additionally, there were about 30% fewer empty stomachs in the warm ocean regime in May, and 10% fewer in warm June periods. The total prey energy density consumed during the warmer ocean regime was also significantly higher than in cold. Chinook salmon had lower condition factor and were smaller in fork length during the warm ocean regime, and were longer and heavier for their size during the cold ocean regime. The significant increase in foraging during the warm ocean regime occurred concurrently with lower available prey biomass. Adult return rates of juvenile Chinook salmon that entered the ocean during a warm ocean regime were lower. Notably, our long term data set contradicts the long held assertion that juvenile salmon eat less in a warm ocean regime when low growth and survival is observed, and when available prey are reduced. Comparing diet changes between decades under variable ocean conditions may assist us in understanding the effects of projected warming ocean regimes on juvenile Chinook salmon and their survival in the ocean environment. Bioenergetically, the salmon appear to require more food resources during warm ocean regimes.

The dynamics of Black Smokers: a heated-salty plume analog.

NASA Astrophysics Data System (ADS)

Maxworthy, Tony

2004-11-01

Experiments have been carried out on the dynamical processes that govern the evolution of hot, salty plumes injected into cold surroundings. Under the appropriate circumstances these are then used as an analoque system to understand some features of particle-laden, deep-ocean, hydrothermal plumes, e.g., Black Smokers. Details of the temperature distributions over a wide range of parameters are presented and these, coupled with flow visualization experiments, have yielded a fairly complete picture of the important features of the flow. As a result it has been concluded that cabelling processes are critical to an understanding of the flow reversals found in a certain parameter range and that double diffusive processes, though present, are of minor importance. As a final exercise an example is worked through in which the circumstances for flow reversal in deep-sea plumes have been estimated based on the best available knowledge of these interesting entities.

A New Mechanism for the Dependence of Tropical Convection on Free-Tropospheric Humidity

NASA Astrophysics Data System (ADS)

Virman, M.; Bister, M.; Sinclair, V. A.; Järvinen, H.; Räisänen, J.

2018-03-01

Atmospheric deep convection is responsible for transport of the most important greenhouse gas, water vapor, to the free-troposphere and for most of the precipitation on Earth. Observations show that deep convection is strongly sensitive to the amount of moisture in the low-to-midtroposphere. The current understanding is that this sensitivity is due to entrainment. In this study, it is found that over tropical oceans shallow warm anomalies, likely strong enough to hinder subsequent convection, are observed just above the boundary layer after precipitation, but only where the low-to-midtroposphere is dry. The results, showing a cold anomaly above the warm anomaly, suggest that evaporation of stratiform precipitation and subsidence warming below likely cause these temperature anomalies. Evaporation of stratiform precipitation should therefore be a topic of high priority for developing more realistic theories of convective weather phenomena and for improving climate and weather forecast models.

Onset and Evolution of Southern Annular Mode-Like Changes at Centennial Timescale.

PubMed

Moreno, P I; Vilanova, I; Villa-Martínez, R; Dunbar, R B; Mucciarone, D A; Kaplan, M R; Garreaud, R D; Rojas, M; Moy, C M; De Pol-Holz, R; Lambert, F

2018-02-22

The Southern Westerly Winds (SWW) are the surface expression of geostrophic winds that encircle the southern mid-latitudes. In conjunction with the Southern Ocean, they establish a coupled system that not only controls climate in the southern third of the world, but is also closely connected to the position of the Intertropical Convergence Zone and CO 2 degassing from the deep ocean. Paradoxically, little is known about their behavior since the last ice age and relationships with mid-latitude glacier history and tropical climate variability. Here we present a lake sediment record from Chilean Patagonia (51°S) that reveals fluctuations of the low-level SWW at mid-latitudes, including strong westerlies during the Antarctic Cold Reversal, anomalously low intensity during the early Holocene, which was unfavorable for glacier growth, and strong SWW since ~7.5 ka. We detect nine positive Southern Annular Mode-like events at centennial timescale since ~5.8 ka that alternate with cold/wet intervals favorable for glacier expansions (Neoglaciations) in southern Patagonia. The correspondence of key features of mid-latitude atmospheric circulation with shifts in tropical climate since ~10 ka suggests that coherent climatic shifts in these regions have driven climate change in vast sectors of the Southern Hemisphere at centennial and millennial timescales.

An Isopycnal Box Model with predictive deep-ocean structure for biogeochemical cycling applications

NASA Astrophysics Data System (ADS)

Goodwin, Philip

2012-07-01

To simulate global ocean biogeochemical tracer budgets a model must accurately determine both the volume and surface origins of each water-mass. Water-mass volumes are dynamically linked to the ocean circulation in General Circulation Models, but at the cost of high computational load. In computationally efficient Box Models the water-mass volumes are simply prescribed and do not vary when the circulation transport rates or water mass densities are perturbed. A new computationally efficient Isopycnal Box Model is presented in which the sub-surface box volumes are internally calculated from the prescribed circulation using a diffusive conceptual model of the thermocline, in which upwelling of cold dense water is balanced by a downward diffusion of heat. The volumes of the sub-surface boxes are set so that the density stratification satisfies an assumed link between diapycnal diffusivity, κd, and buoyancy frequency, N: κd = c/(Nα), where c and α are user prescribed parameters. In contrast to conventional Box Models, the volumes of the sub-surface ocean boxes in the Isopycnal Box Model are dynamically linked to circulation, and automatically respond to circulation perturbations. This dynamical link allows an important facet of ocean biogeochemical cycling to be simulated in a highly computationally efficient model framework.

Did hydrographic sampling capture global and regional deep ocean heat content trends accurately between 1990-2010?

NASA Astrophysics Data System (ADS)

Garry, Freya; McDonagh, Elaine; Blaker, Adam; Roberts, Chris; Desbruyères, Damien; King, Brian

2017-04-01

Estimates of heat content change in the deep oceans (below 2000 m) over the last thirty years are obtained from temperature measurements made by hydrographic survey ships. Cruises occupy the same tracks across an ocean basin approximately every 5+ years. Measurements may not be sufficiently frequent in time or space to allow accurate evaluation of total ocean heat content (OHC) and its rate of change. It is widely thought that additional deep ocean sampling will also aid understanding of the mechanisms for OHC change on annual to decadal timescales, including how OHC varies regionally under natural and anthropogenically forced climate change. Here a 0.25˚ ocean model is used to investigate the magnitude of uncertainties and biases that exist in estimates of deep ocean temperature change from hydrographic sections due to their infrequent timing and sparse spatial distribution during 1990 - 2010. Biases in the observational data may be due to lack of spatial coverage (not enough sections covering the basin), lack of data between occupations (typically 5-10 years apart) and due to occupations not closely spanning the time period of interest. Between 1990 - 2010, the modelled biases globally are comparatively small in the abyssal ocean below 3500 m although regionally certain biases in heat flux into the 4000 - 6000 m layer can be up to 0.05 Wm-2. Biases in the heat flux into the deep 2000 - 4000 m layer due to either temporal or spatial sampling uncertainties are typically much larger and can be over 0.1 Wm-2 across an ocean. Overall, 82% of the warming trend below 2000 m is captured by observational-style sampling in the model. However, at 2500 m (too deep for additional temperature information to be inferred from upper ocean Argo) less than two thirds of the magnitude of the global warming trend is obtained, and regionally large biases exist in the Atlantic, Southern and Indian Oceans, highlighting the need for widespread improved deep ocean temperature sampling. In addition to bias due to infrequent sampling, moving the timings of occupations by a few months generates relatively large uncertainty due to intra-annual variability in deep ocean model temperature, further strengthening the case for high temporal frequency observations in the deep ocean (as could be achieved using deep ocean autonomous float technologies). Biases due to different uncertainties can have opposing signs and differ in relative importance both regionally and with depth revealing the importance of reducing all uncertainties (both spatial and temporal) simultaneously in future deep ocean observing design.

Deep-Sea Microbes: Linking Biogeochemical Rates to -Omics Approaches

NASA Astrophysics Data System (ADS)

Herndl, G. J.; Sintes, E.; Bayer, B.; Bergauer, K.; Amano, C.; Hansman, R.; Garcia, J.; Reinthaler, T.

2016-02-01

Over the past decade substantial progress has been made in determining deep ocean microbial activity and resolving some of the enigmas in understanding the deep ocean carbon flux. Also, metagenomics approaches have shed light onto the dark ocean's microbes but linking -omics approaches to biogeochemical rate measurements are generally rare in microbial oceanography and even more so for the deep ocean. In this presentation, we will show by combining metagenomics, -proteomics and biogeochemical rate measurements on the bulk and single-cell level that deep-sea microbes exhibit characteristics of generalists with a large genome repertoire, versatile in utilizing substrate as revealed by metaproteomics. This is in striking contrast with the apparently rather uniform dissolved organic matter pool in the deep ocean. Combining the different -omics approaches with metabolic rate measurements, we will highlight some major inconsistencies and enigmas in our understanding of the carbon cycling and microbial food web structure in the dark ocean.

Deep-sea mud volcanoes - a window to alteration processes in old oceanic crust?

NASA Astrophysics Data System (ADS)

Hensen, Christian; Scholz, Florian; Nuzzo, Marianne; Valadares, Vasco; Terrinha, Pedro; Liebetrau, Volker; Kaul, Norbert; Manzoni, Sonia; Schmidt, Mark; Gràcia, Eulàlia

2013-04-01

A number of deep sea mud volcanoes (>4700 m water depth) were discovered during a recent expedition with the German research vessel Meteor along a prominent WSW-ENE trending strike-slip fault (SWIM 1; Zitellini et al., 2009) in the western extension of the Gulf of Cadiz (NE Atlantic). Mud volcanism was unambiguously related to tectonic activity along the fault and fluids expelled at these sites show a very distinct geochemical composition that has not been reported from any other mud volcano to date. In previous studies on deep-water mud volcanoes in the Western Gulf of Cadiz accretionary wedge it was hypothesized that the discharge fluids were affected by alteration processes occurring in the old (>140 Ma) and deeply buried (>4 km) oceanic crust (Scholz et al., 2009; Sallarès et al, 2011). This hypothesis is supported by recent findings at the mud volcanoes located to the west of the realm of tectonic deformation driven by the accretionary wedge of the Gulf of Cadiz. Pore water geochemical analyses revealed fluid sources from oceanic crust and oldest sedimentary strata. Regardless of the ultimate source, these findings suggest that large strike-slip faults may play a significant, yet unrecognized role in terms of fluid circulation and element redistribution. To date, hot vents and cold seeps occurring at active spreading centers and forearcs of subduction zones have been pinpointed as hotspots of fluid activity. However, bearing in mind that transform-type plate boundaries are equal in length compared to other types of plate boundaries, fluid exchange at this type of plate boundary may provide a similarly important pathway for water and element exchange between the lithosphere and ocean. Sallarès V., Gailler A., Gutscher M.-A., Graindorge D., Bartolomé R., Gràcia E., Díaz J., Dañobeitia J.J. and Zitellini N. (2011) Seismic evidence for the presence of Jurassic oceanic crust in the central Gulf of Cadiz (SW Iberian margin), Earth and Planetary Science Letters 311(1-2), 112-123. Scholz F., Hensen C., Reitz A., Romer R.L., Liebetrau V., Meixner A., Weise S.M., and Haeckel M. (2009) Isotopic evidence (87Sr/86Sr, δ7Li) for alteration of the oceanic crust at deep-rooted mud volcanoes in the Gulf of Cadiz, NE Atlantic Ocean. Geochimica et Cosmochimica Acta 73, 5444-5459. Zitellini N., Gràcia E., Matias L., Terrinha P., Abreu M.A., Dealteriis G., Henriet J.P., Dañobeitia J.J., Masson D.G., Mulder T., Ramella R., Somoza L., and Diez S. (2009) The quest for the Africa-Eurasia plate boundary west of the Strait of Gibraltar. Earth and Planetary Science Letters 280, 13-50.

Larvae from deep-sea methane seeps disperse in surface waters.

PubMed

Arellano, Shawn M; Van Gaest, Ahna L; Johnson, Shannon B; Vrijenhoek, Robert C; Young, Craig M

2014-07-07

Many species endemic to deep-sea methane seeps have broad geographical distributions, suggesting that they produce larvae with at least episodic long-distance dispersal. Cold-seep communities on both sides of the Atlantic share species or species complexes, yet larval dispersal across the Atlantic is expected to take prohibitively long at adult depths. Here, we provide direct evidence that the long-lived larvae of two cold-seep molluscs migrate hundreds of metres above the ocean floor, allowing them to take advantage of faster surface currents that may facilitate long-distance dispersal. We collected larvae of the ubiquitous seep mussel "Bathymodiolus" childressi and an associated gastropod, Bathynerita naticoidea, using remote-control plankton nets towed in the euphotic zone of the Gulf of Mexico. The timing of collections suggested that the larvae might disperse in the water column for more than a year, where they feed and grow to more than triple their original sizes. Ontogenetic vertical migration during a long larval life suggests teleplanic dispersal, a plausible explanation for the amphi-Atlantic distribution of "B." mauritanicus and the broad western Atlantic distribution of B. naticoidea. These are the first empirical data to demonstrate a biological mechanism that might explain the genetic similarities between eastern and western Atlantic seep fauna. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Influence of coupling on atmosphere, sea ice and ocean regional models in the Ross Sea sector, Antarctica

NASA Astrophysics Data System (ADS)

Jourdain, Nicolas C.; Mathiot, Pierre; Gallée, Hubert; Barnier, Bernard

2011-04-01

Air-sea ice-ocean interactions in the Ross Sea sector form dense waters that feed the global thermohaline circulation. In this paper, we develop the new limited-area ocean-sea ice-atmosphere coupled model TANGO to simulate the Ross Sea sector. TANGO is built up by coupling the atmospheric limited-area model MAR to a regional configuration of the ocean-sea ice model NEMO. A method is then developed to identify the mechanisms by which local coupling affects the simulations. TANGO is shown to simulate realistic sea ice properties and atmospheric surface temperatures. These skills are mostly related to the skills of the stand alone atmospheric and oceanic models used to build TANGO. Nonetheless, air temperatures over ocean and winter sea ice thickness are found to be slightly improved in coupled simulations as compared to standard stand alone ones. Local atmosphere ocean feedbacks over the open ocean are found to significantly influence ocean temperature and salinity. In a stand alone ocean configuration, the dry and cold air produces an ocean cooling through sensible and latent heat loss. In a coupled configuration, the atmosphere is in turn moistened and warmed by the ocean; sensible and latent heat loss is therefore reduced as compared to the stand alone simulations. The atmosphere is found to be less sensitive to local feedbacks than the ocean. Effects of local feedbacks are increased in the coastal area because of the presence of sea ice. It is suggested that slow heat conduction within sea ice could amplify the feedbacks. These local feedbacks result in less sea ice production in polynyas in coupled mode, with a subsequent reduction in deep water formation.

Global Warming, New Climate, New Atmospheric Circulation and New Water Cycle in North Africa

NASA Astrophysics Data System (ADS)

Karrouk, M. S.

2017-12-01

Global warming has now reached the energetic phase of H2O's return to the ground after the saturation of the atmosphere in evaporation since the 80s and 90s of the last century, which were characterized by severe droughts, mainly in Africa.This phase is the result of the accumulation of thermal energy exchanges in the Earth-Ocean-Atmosphere system that resulted in the thrust reversal of the energy balance toward the poles. This situation is characterized by a new thermal distribution: above the ocean, the situation is more in surplus compared to the mainland, or even opposite when the balance is negative on the land, and in the atmosphere, warm thermal advection easily reach the North Pole (planetary crests), as well as cold advection push deep into North Africa and the Gulf of Mexico (planetary valleys: Polar Vortex).This "New Ground Energy Balance" establishes a "New Meridian Atmospheric Circulation (MAC)" with an undulating character throughout the year, including the winter characterized by intense latitudinal very active energy exchanges between the surplus areas (tropical) and the deficit (polar) on the one hand, and the atmosphere, the ocean and the continent on the other.The excess radiation balance increases the potential evaporation of the atmosphere and provides a new geographical distribution of Moisture and Water worldwide: the excess water vapor is easily converted by cold advection (Polar Vortex) to heavy rains that cause floods or snow storms that paralyze the normal functioning of human activities, which creates many difficulties for users and leaves damage and casualties, but ensures water availability missing since a long time in many parts of the world, in Africa, Europe and America.The new thermal distribution reorganizes the geography of atmospheric pressure: the ocean energy concentration is transmitted directly to the atmosphere, and the excess torque is pushed northward. The Azores anticyclone is strengthened and is a global lock by the Atlantic ridge at Greenland, which imposes on the jet stream a positive ripple, very strongly marked poleward, bringing cosmic cold advection of polar air masses winter over from Europe to North Africa. Hence the enormous meridian heat exchanges north-south, and south-north.

"New Climate" Warmed, "New Atmospheric Circulation" and "Extreme" Meteorological Phenomena associated with El Niño 2015-2016

NASA Astrophysics Data System (ADS)

Karrouk, M. S.

2016-12-01

Cumulating ocean-atmospheric thermal energy caused by global warming has resulted in the reversal of the energy balance towards the poles. This situation is characterized by a new ocean-continental thermal distribution: over the ocean, the balance is more in excess than in the mainland, if not the opposite when the balance is negative inland.Thanks to satellite observation and daily monitoring of meteorological conditions for more than ten years, we have observed that the positive balance has shifted more towards the poles, mainly in the northern hemisphere. Subtropical anticyclones are strengthened and have extended to high latitudes, especially over the Atlantic and Pacific oceans. This situation creates global peaks strengthened in winter periods, and imposes on cosmic cold the deep advection toward the south under the form of planetary valleys "Polar Vortex".This situation imposes on the jet stream a pronounced ripple and installs a meridional atmospheric circulation in winter, which brings the warm tropical air masses to reach the Arctic Circle, and cold polar air masses to reach North Africa and Florida.This situation creates unusual atmospheric events, characterized by hydrothermal "extreme" conditions: excessive heat at high latitudes, accompanied by heavy rains and floods, as well as cold at low latitudes and the appearance of snow in the Sahara!The populations are profoundly influenced by the new phenomena. The socioeconomic infrastructures can no longer assume their basic functions and man when unprotected is weak and hence the advanced vulnerability of all the regions especially those belonging to poor and developing countriesRecent studies have shown that global and regional climate system is affected by extreme events of El Niño. Statistical and dynamic links have been confirmed in Northern Africa and Western Europe; hence the importance of the fall situation and winter 2015-2016.These conditions are the consequences of the "New Climate" warmed, strengthened by the strong El Niño event in 2015 decennial.These are the characteristics of "New Meteorological Events" resulting from the "New Atmospheric Circulation", caused by the "New planetary Climate" forcing by El Niño event, consequence of "Global Warming".

On the Use of Deep Convective Clouds to Calibrate AVHRR Data

NASA Technical Reports Server (NTRS)

Doelling, David R.; Nguyen, Louis; Minnis, Patrick

2004-01-01

Remote sensing of cloud and radiation properties from National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) satellites requires constant monitoring of the visible sensors. NOAA satellites do not have onboard visible calibration and need to be calibrated vicariously in order to determine the calibration and the degradation rate. Deep convective clouds are extremely bright and cold, are at the tropopause, have nearly a Lambertian reflectance, and provide predictable albedos. The use of deep convective clouds as calibration targets is developed into a calibration technique and applied to NOAA-16 and NOAA-17. The technique computes the relative gain drift over the life-span of the satellite. This technique is validated by comparing the gain drifts derived from inter-calibration of coincident AVHRR and Moderate-Resolution Imaging Spectroradiometer (MODIS) radiances. A ray-matched technique, which uses collocated, coincident, and co-angled pixel satellite radiance pairs is used to intercalibrate MODIS and AVHRR. The deep convective cloud calibration technique was found to be independent of solar zenith angle, by using well calibrated Visible Infrared Scanner (VIRS) radiances onboard the Tropical Rainfall Measuring Mission (TRMM) satellite, which precesses through all solar zenith angles in 23 days.

Exploration of the Climate Change Frontier in Polar Regions at the Land Ice-Ocean Boundary.

NASA Astrophysics Data System (ADS)

Rignot, E. J.

2014-12-01

Ice sheets are the largest contributors to sea level rise at present, and responsible for the largest uncertainty in sea level projections. Ice sheets raised sea level 5 m per century 13.5 kyr ago during one period of rapid change. Leading regions for future rapid changes include the marine-based, retrograde bed parts of Greenland (north center and east), West Antarctica (Amundsen Sea), and East Antarctica (Filchner basin and Wilkes Land). Fast changes require an increase in ice melt from a warmer ocean and an increase in iceberg calving. Our understanding of both processes remains limited due to a lack of basic observations. Understanding ocean forcing requires observations on the continental shelf, along bays and glacial fjords and at ice-ocean boundaries, beneath kilometers of ice (Antarctica) or at near-vertical calving cliffs (Greenland), of ocean temperature and sea floor bathymetry. Where such observations exist, the sea floor is much deeper than anticipated because of the carving of deep channels by multiple glacier advances. Warm subsurface waters penetrate throughout the Amundsen Sea Embayment of West Antarctica, the southeast and probably the entire west coasts of Greenland. In Greenland, discharge of subglacial water from surface runoff at the glacier grounding line increases ice melting by the ocean even if the ocean temperature remains the same. Near ice-ocean boundaries, satellite observations are challenged, airborne observations and field surveys are limited, so advanced robotic techniques for cold, deep, remote environments are ultimately required in combination with advanced numerical modeling techniques. Until such technological advances take place and advanced networks are put in place, it is critical to conduct boat surveys, install moorings, and conduct extensive airborne campaigns (for instance, gravity-derived bathymetry and air-dropped CTDs), some of which is already taking place. In the meantime, projections of ice sheet evolution in a warmer climate will remain highly conservative and perhaps misleading. Furthermore, as glaciers destabilize, iceberg calving will take over. Calving depends on the height of the calving cliff, the fracturing of ice near the ice front by strain rates or water; but the jury is also out about defining a universal calving law.

Supercontinental Cycles and the Tectonic Modulation of Earth's Climate

NASA Astrophysics Data System (ADS)

Jellinek, M.; Pierrehumbert, R.; Turchyn, A. V.; Lenardic, A.

2012-12-01

Plate tectonics involves the production of oceanic plates at spreading ridges, their destruction at subduction zones, where they sink into the underlying mantle as cold plumes, and a slow drift of buoyant continents at the surface. The resulting laterally and vertically extensive internal mantle motions cool the Earth efficiently and with remarkable consequences including long-lived hotspot volcanoes such as Hawaii, a persistent and strong magnetic field and a habitable climate. Over the last billion years, however, this regular mantle overturning and thorough thermal mixing has been punctuated by 2 transient periods during which the continents were drawn together to form the supercontinents Rodinia and Pangea. These supercontinents were encircled to differing extents by subduction zones where partial or complete "curtains" of cold downgoing oceanic slabs inhibited lateral mantle stirring, leading, in turn, to large temperature variations between the more rapidly cooled oceanic mantle and the more slowly cooled continental mantle. A key prediction from theory, numerical simulations and laboratory experiments is that, depending on the mantle thermal mixing efficiency, the relative cooling of the oceanic mantle during the formation of supercontinents will cause crustal production at spreading ridges to decline or cease entirely. We investigate two further provocative implications for Earth's climate during the Pangea and Rodinia supercontinental epochs. First, the total volcanic influx of CO2 to the ocean-atmosphere system may decline by 30-40%, probably causing a modest global cooling. Second, a near absence of basaltic crust at ridges exposes mantle rocks to seawater, which leads to extensive serpentinization and to a potentially large flux of abiogenic methane (CH4) into the deep ocean. Whereas we expect all of this CH4 to be oxidized in the oxygen-rich and biologically complex Pangean ocean, some fraction of this CH4 flux may contribute to the composition of low-oxygen Rodinian atmosphere and influence climate in remarkable ways. A particular situation we explore is whether the transient mantle dynamics of the formation and breakup of Rodinia ultimately caused Earth to enter into, and exit from, periods of global glaciation consistent with the snowball Earth hypothesis.

West Florida shelf circulation and temperature budget for the 1998 fall transition

NASA Astrophysics Data System (ADS)

He, Ruoying; Weisberg, Robert H.

2003-05-01

Mid-latitude continental shelves undergo a fall transition as the net heat flux changes from warming to cooling. Using in situ data and a numerical model we investigate the circulation on the west Florida shelf (WFS) for the fall transition of 1998. The model is a regional adaptation of the primitive equation, Princeton Ocean Model forced by NCEP reanalysis wind, air pressure, and heat flux fields, plus river inflows. After comparison with observations the model is used to draw inferences on the seasonal and synoptic scale features of the shelf circulation. By running twin experiments, one without and the other with an idealized Loop Current (LC), we explore the relative importance of local versus deep-ocean forcing. We find that local forcing largely controls the inner-shelf circulation, including changes from the Florida Panhandle in the north to regions farther south. The effects of the LC in fall 1998 are to reinforce the mid-shelf currents and to increase the across-shelf transports in the bottom Ekman layer, thereby accentuating the shoreward transport of cold, nutrient rich water of deep-ocean origin. A three-dimensional analysis of the temperature budget reveals that surface heat flux largely controls both the seasonal and synoptic scale temperature variations. Surface cooling leads to convective mixing that rapidly alters temperature gradients. One interesting consequence is that upwelling can result in near-shore warming as warmer offshore waters are advected landward. The temperature balances on the shelf are complex and fully three-dimensional.

Megafauna recovered from a cold hydrocarbon seep in the deep Alaskan Beaufort Sea, including a new species of Axinus (Thracidae: Bivalvia: Mollusca)

NASA Astrophysics Data System (ADS)

Powell, C. L.; Valentich-Scott, P.; Lorenson, T. D.; Edwards, B. D.

2011-12-01

Several specimens of a new species of Axinus and a single well-worn gastropod columella provisionally assigned to the genus Neptunea (Buccinidae: Gastropoda: Mollusca) were recently recovered from at least two cores, the longest of which is 5.72 m long, from a large seafloor mound, informally named the Canning Seafloor Mound (CSM). The CSM is located at 2,530 m water depth on the Alaskan Beaufort Sea slope north of Camden Bay and is a fluid explosion feature containing methane hydrate and methane-saturated sediments overlying a folded and faulted deep basin. Only two modern species of Axinus are currently known. Axinus grandis (Verrill & Smith, 1885) is a northern Atlantic species and the recently described species, A. cascadiensis Oliver and Holmes (2007), is only known from Baby Bare Seamount, Cascadia Basin, northeastern Pacific Ocean. Common fragments, single valves, and a single articulated specimen represent this new Axinus species. These shells were distributed over nearly the entire length of the primary core. All specimens show wear and (or) dissolution. The age of these specimens is unknown and no living representatives were encountered. The genus Axinus has a fossil record back to the early Eocene in England and the Paleocene and Eocene in Egypt. Biogeographically the genus appears to have originated in the Tethys Sea and became established in the Atlantic Ocean during the Eocene, spreading across the Arctic Ocean in the late Tertiary. With the opening of the Bering Strait in the latest Miocene or early Pliocene the genus Axinus migrated southwest into the northeast Pacific. Interestingly, hydrocarbon seep deposits are also present on the adjacent North Slope of Alaska in the Marsh Anticline at Carter Creek, Camden Bay. These rocks, the Nuwok beds, contain abundant Thracidae bivalve of the genus Thracia, but not Axinus, however the rocks also represent cold seep deposits. These rocks have been variously dated from Oligocene to Pliocene and the exact age remains uncertain. Neptunea are a predatory snails well represented in the earliest Miocene to Holocene of the northern Pacific Ocean and in the late Pliocene to Holocene of the northern Atlantic. The presence of Neptunea at CSM, if identified properly, gives a maximum age for these deposits of latest Miocene or early Pliocene, after the opening of the Bering Strait, although they could be as young as Holocene.

Deep Ocean Warming Assessed from Altimeters, GRACE, 3 In-situ Measurements, and a Non-Boussinesq OGCM

NASA Technical Reports Server (NTRS)

Song, Y. Tony; Colberg, Frank

2011-01-01

Observational surveys have shown significant oceanic bottom water warming, but they are too spatially and temporally sporadic to quantify the deep ocean contribution to the present-day sea level rise (SLR). In this study, altimetry sea surface height (SSH), Gravity Recovery and Climate Experiment (GRACE) ocean mass, and in situ upper ocean (0-700 m) steric height have been assessed for their seasonal variability and trend maps. It is shown that neither the global mean nor the regional trends of altimetry SLR can be explained by the upper ocean steric height plus the GRACE ocean mass. A non-Boussinesq ocean general circulation model (OGCM), allowing the sea level to rise as a direct response to the heat added into the ocean, is then used to diagnose the deep ocean steric height. Constrained by sea surface temperature data and the top of atmosphere (TOA) radiation measurements, the model reproduces the observed upper ocean heat content well. Combining the modeled deep ocean steric height with observational upper ocean data gives the full depth steric height. Adding a GRACE-estimated mass trend, the data-model combination explains not only the altimetry global mean SLR but also its regional trends fairly well. The deep ocean warming is mostly prevalent in the Atlantic and Indian oceans, and along the Antarctic Circumpolar Current, suggesting a strong relation to the oceanic circulation and dynamics. Its comparison with available bottom water measurements shows reasonably good agreement, indicating that deep ocean warming below 700 m might have contributed 1.1 mm/yr to the global mean SLR or one-third of the altimeter-observed rate of 3.11 +/- 0.6 mm/yr over 1993-2008.

Atlantic Meridional Overturning Circulation slowdown cooled the subtropical ocean

PubMed Central

Cunningham, Stuart A; Roberts, Christopher D; Frajka-Williams, Eleanor; Johns, William E; Hobbs, Will; Palmer, Matthew D; Rayner, Darren; Smeed, David A; McCarthy, Gerard

2013-01-01

[1] Observations show that the upper 2 km of the subtropical North Atlantic Ocean cooled throughout 2010 and remained cold until at least December 2011. We show that these cold anomalies are partly driven by anomalous air-sea exchange during the cold winters of 2009/2010 and 2010/2011 and, more surprisingly, by extreme interannual variability in the ocean's northward heat transport at 26.5°N. This cooling driven by the ocean's meridional heat transport affects deeper layers isolated from the atmosphere on annual timescales and water that is entrained into the winter mixed layer thus lowering winter sea surface temperatures. Here we connect, for the first time, variability in the northward heat transport carried by the Atlantic Meridional Overturning Circulation to widespread sustained cooling of the subtropical North Atlantic, challenging the prevailing view that the ocean plays a passive role in the coupled ocean-atmosphere system on monthly-to-seasonal timescales. PMID:26074634

Atlantic Meridional Overturning Circulation slowdown cooled the subtropical ocean.

PubMed

Cunningham, Stuart A; Roberts, Christopher D; Frajka-Williams, Eleanor; Johns, William E; Hobbs, Will; Palmer, Matthew D; Rayner, Darren; Smeed, David A; McCarthy, Gerard

2013-12-16

[1] Observations show that the upper 2 km of the subtropical North Atlantic Ocean cooled throughout 2010 and remained cold until at least December 2011. We show that these cold anomalies are partly driven by anomalous air-sea exchange during the cold winters of 2009/2010 and 2010/2011 and, more surprisingly, by extreme interannual variability in the ocean's northward heat transport at 26.5°N. This cooling driven by the ocean's meridional heat transport affects deeper layers isolated from the atmosphere on annual timescales and water that is entrained into the winter mixed layer thus lowering winter sea surface temperatures. Here we connect, for the first time, variability in the northward heat transport carried by the Atlantic Meridional Overturning Circulation to widespread sustained cooling of the subtropical North Atlantic, challenging the prevailing view that the ocean plays a passive role in the coupled ocean-atmosphere system on monthly-to-seasonal timescales.

Microbial decomposition of marine dissolved organic matter in cool oceanic crust

NASA Astrophysics Data System (ADS)

Shah Walter, Sunita R.; Jaekel, Ulrike; Osterholz, Helena; Fisher, Andrew T.; Huber, Julie A.; Pearson, Ann; Dittmar, Thorsten; Girguis, Peter R.

2018-05-01

Marine dissolved organic carbon (DOC) is one of the largest active reservoirs of reduced carbon on Earth. In the deep ocean, DOC has been described as biologically recalcitrant and has a radiocarbon age of 4,000 to 6,000 years, which far exceeds the timescale of ocean overturning. However, abiotic removal mechanisms cannot account for the full magnitude of deep-ocean DOC loss. Deep-ocean water circulates at low temperatures through volcanic crust on ridge flanks, but little is known about the associated biogeochemical processes and carbon cycling. Here we present analyses of DOC in fluids from two borehole observatories installed in crustal rocks west of the Mid-Atlantic Ridge, and show that deep-ocean DOC is removed from these cool circulating fluids. The removal mechanism is isotopically selective and causes a shift in specific features of molecular composition, consistent with microbe-mediated oxidation. We suggest organic molecules with an average radiocarbon age of 3,200 years are bioavailable to crustal microbes, and that this removal mechanism may account for at least 5% of the global loss of DOC in the deep ocean. Cool crustal circulation probably contributes to maintaining the deep ocean as a reservoir of `aged' and refractory DOC by discharging the surviving organic carbon constituents that are molecularly degraded and depleted in 14C and 13C into the deep ocean.

Break-up of the Atlantic deep western boundary current into eddies at 8 degrees S.

PubMed

Dengler, M; Schott, F A; Eden, C; Brandt, P; Fischer, J; Zantopp, R J

2004-12-23

The existence in the ocean of deep western boundary currents, which connect the high-latitude regions where deep water is formed with upwelling regions as part of the global ocean circulation, was postulated more than 40 years ago. These ocean currents have been found adjacent to the continental slopes of all ocean basins, and have core depths between 1,500 and 4,000 m. In the Atlantic Ocean, the deep western boundary current is estimated to carry (10-40) x 10(6) m3 s(-1) of water, transporting North Atlantic Deep Water--from the overflow regions between Greenland and Scotland and from the Labrador Sea--into the South Atlantic and the Antarctic circumpolar current. Here we present direct velocity and water mass observations obtained in the period 2000 to 2003, as well as results from a numerical ocean circulation model, showing that the Atlantic deep western boundary current breaks up at 8 degrees S. Southward of this latitude, the transport of North Atlantic Deep Water into the South Atlantic Ocean is accomplished by migrating eddies, rather than by a continuous flow. Our model simulation indicates that the deep western boundary current breaks up into eddies at the present intensity of meridional overturning circulation. For weaker overturning, continuation as a stable, laminar boundary flow seems possible.

Detection of Extremes with AIRS and CrIS

NASA Technical Reports Server (NTRS)

Aumann, Hartmut H.; Manning, Evan M.; Behrangi, Ali

2013-01-01

Climate change is expected to be detected first as changes in extreme values rather than in mean values. The availability of data of from two instruments in the same orbit, AIRS data for the past eleven years and AIRS and CrIS data from the past year, provides an opportunity to evaluate this using examples of climate relevance: Desertification, seen as changes in hot extremes, severe storm, seen as a change in extremely cold clouds and the warming of the polar zone. We use AIRS to establish trends for the 1%tile, the mean and 99%tile brightness temperatures measured with the 900 cm(exp -1) channel from AIRS for the past 11 years. This channel is in the clearest part of the 11 micron atmospheric window. Substantial trends are seen for land and ocean, which in the case of the 1%tile (cold) extremes are related to the current shift of deep convection from ocean to land. Changes are also seen in the 99%tile for day tropical land, but their interpretation is at present unclear. We also see dramatic changes for the mean and 99%tile of the North Polar area. The trends are an order of magnitude larger than the instrument trend of about 3 mK/year. We use the statistical distribution from the past year derived from AIRS to evaluate the accuracy of continuing the trends established with AIRS with CrIS data. We minimize the concern about differences in the spectral response functions by limiting the analysis to the channel at 900 cm(exp -1).While the two instruments agree within 100 mK for the global day/night land/ocean mean values, there are significant differences when evaluating the1% and 99%tiles. We see a consistent warm bias in the CrIS data relative to AIRS for the 1%tile (extremely cold, cloudy) data in the tropical zone, particularly for tropical land, but the bias is not day/night land/ocean consistent. At this point the difference appears to be due to differences in the radiometric response of AIRS and CrIS to differences in the day/night land/ocean cloud types. Unless the effect can be mitigated by a future reprocessing the CrIS data, it will significantly complicate the concatenation of the AIRS and CrIS data records for the continuation of trends in extreme values.

Responses of the deep ocean carbonate system to carbon reorganization during the Last Glacial-interglacial cycle

NASA Astrophysics Data System (ADS)

Yu, Jimin; Anderson, Robert F.; Jin, Zhangdong; Rae, James W. B.; Opdyke, Bradley N.; Eggins, Stephen M.

2013-09-01

We present new deep water carbonate ion concentration ([CO32-]) records, reconstructed using Cibicidoides wuellerstorfi B/Ca, for one core from Caribbean Basin (water depth = 3623 m, sill depth = 1.8 km) and three cores located at 2.3-4.3 km water depth from the equatorial Pacific Ocean during the Last Glacial-interglacial cycle. The pattern of deep water [CO32-] in the Caribbean Basin roughly mirrors that of atmospheric CO2, reflecting a dominant influence from preformed [CO32-] in the North Atlantic Ocean. Compared to the amplitude of ˜65 μmol/kg in the deep Caribbean Basin, deep water [CO32-] in the equatorial Pacific Ocean has varied by no more than ˜15 μmol/kg due to effective buffering of CaCO3 on deep-sea pH in the Pacific Ocean. Our results suggest little change in the global mean deep ocean [CO32-] between the Last Glacial Maximum (LGM) and the Late Holocene. The three records from the Pacific Ocean show long-term increases in [CO32-] by ˜7 μmol/kg from Marine Isotope Stage (MIS) 5c to mid MIS 3, consistent with the response of the deep ocean carbonate system to a decline in neritic carbonate production associated with ˜60 m drop in sea-level (the “coral-reef” hypothesis). Superimposed upon the long-term trend, deep water [CO32-] in the Pacific Ocean displays transient changes, which decouple with δ13C in the same cores, at the start and end of MIS 4. These changes in [CO32-] and δ13C are consistent with what would be expected from vertical nutrient fractionation and carbonate compensation. The observed ˜4 μmol/kg [CO32-] decline in the two Pacific cores at >3.4 km water depth from MIS 3 to the LGM indicate further strengthening of deep ocean stratification, which contributed to the final step of atmospheric CO2 drawdown during the last glaciation. The striking similarity between deep water [CO32-] and 230Th-normalized CaCO3 flux at two adjacent sites from the central equatorial Pacific Ocean provides convincing evidence that deep-sea carbonate dissolution dominantly controlled CaCO3 preservation at these sites in the past. Our results offer new and quantitative constraints from deep ocean carbonate chemistry to understand roles of various mechanisms in atmospheric CO2 changes over the Last Glacial-interglacial cycle.

First biological measurements of deep-sea corals from the Red Sea

PubMed Central

Roder, C.; Berumen, M. L.; Bouwmeester, J.; Papathanassiou, E.; Al-Suwailem, A.; Voolstra, C. R.

2013-01-01

It is usually assumed that metabolic constraints restrict deep-sea corals to cold-water habitats, with ‘deep-sea’ and ‘cold-water’ corals often used as synonymous. Here we report on the first measurements of biological characters of deep-sea corals from the central Red Sea, where they occur at temperatures exceeding 20°C in highly oligotrophic and oxygen-limited waters. Low respiration rates, low calcification rates, and minimized tissue cover indicate that a reduced metabolism is one of the key adaptations to prevailing environmental conditions. We investigated four sites and encountered six species of which at least two appear to be undescribed. One species is previously reported from the Red Sea but occurs in deep cold waters outside the Red Sea raising interesting questions about presumed environmental constraints for other deep-sea corals. Our findings suggest that the present understanding of deep-sea coral persistence and resilience needs to be revisited. PMID:24091830

First biological measurements of deep-sea corals from the Red Sea.

PubMed

Roder, C; Berumen, M L; Bouwmeester, J; Papathanassiou, E; Al-Suwailem, A; Voolstra, C R

2013-10-03

It is usually assumed that metabolic constraints restrict deep-sea corals to cold-water habitats, with 'deep-sea' and 'cold-water' corals often used as synonymous. Here we report on the first measurements of biological characters of deep-sea corals from the central Red Sea, where they occur at temperatures exceeding 20°C in highly oligotrophic and oxygen-limited waters. Low respiration rates, low calcification rates, and minimized tissue cover indicate that a reduced metabolism is one of the key adaptations to prevailing environmental conditions. We investigated four sites and encountered six species of which at least two appear to be undescribed. One species is previously reported from the Red Sea but occurs in deep cold waters outside the Red Sea raising interesting questions about presumed environmental constraints for other deep-sea corals. Our findings suggest that the present understanding of deep-sea coral persistence and resilience needs to be revisited.

Ocean chemistry. Dilution limits dissolved organic carbon utilization in the deep ocean.

PubMed

Arrieta, Jesús M; Mayol, Eva; Hansman, Roberta L; Herndl, Gerhard J; Dittmar, Thorsten; Duarte, Carlos M

2015-04-17

Oceanic dissolved organic carbon (DOC) is the second largest reservoir of organic carbon in the biosphere. About 72% of the global DOC inventory is stored in deep oceanic layers for years to centuries, supporting the current view that it consists of materials resistant to microbial degradation. An alternative hypothesis is that deep-water DOC consists of many different, intrinsically labile compounds at concentrations too low to compensate for the metabolic costs associated to their utilization. Here, we present experimental evidence showing that low concentrations rather than recalcitrance preclude consumption of a substantial fraction of DOC, leading to slow microbial growth in the deep ocean. These findings demonstrate an alternative mechanism for the long-term storage of labile DOC in the deep ocean, which has been hitherto largely ignored. Copyright © 2015, American Association for the Advancement of Science.

The Southern Ocean's role in carbon exchange during the last deglaciation.

PubMed

Burke, Andrea; Robinson, Laura F

2012-02-03

Changes in the upwelling and degassing of carbon from the Southern Ocean form one of the leading hypotheses for the cause of glacial-interglacial changes in atmospheric carbon dioxide. We present a 25,000-year-long Southern Ocean radiocarbon record reconstructed from deep-sea corals, which shows radiocarbon-depleted waters during the glacial period and through the early deglaciation. This depletion and associated deep stratification disappeared by ~14.6 ka (thousand years ago), consistent with the transfer of carbon from the deep ocean to the surface ocean and atmosphere via a Southern Ocean ventilation event. Given this evidence for carbon exchange in the Southern Ocean, we show that existing deep-ocean radiocarbon records from the glacial period are sufficiently depleted to explain the ~190 per mil drop in atmospheric radiocarbon between ~17 and 14.5 ka.

Deep-ocean basalts: inert gas content and uncertainties in age dating.

PubMed

Noble, C S; Naughton, J J

1968-10-11

The radiogenic argon and helium contents of three basalts erupted into the deep ocean from an active volcano (Kilauea) have been measured. Ages calculated from these measurements increase with sample depth up to 22 million years for lavas deduced to be recent. Caution is urged in applying dates from deep-ocean basalts in studies on ocean-floor spreading.

Upper Ocean Evolution Across the Beaufort Sea Marginal Ice Zone from Autonomous Gliders

NASA Astrophysics Data System (ADS)

Lee, Craig; Rainville, Luc; Perry, Mary Jane

2016-04-01

The observed reduction of Arctic summertime sea ice extent and expansion of the marginal ice zone (MIZ) have profound impacts on the balance of processes controlling sea ice evolution, including the introduction of several positive feedback mechanisms that may act to accelerate melting. Examples of such feedbacks include increased upper ocean warming though absorption of solar radiation, elevated internal wave energy and mixing that may entrain heat stored in subsurface watermasses (e.g., the relatively warm Pacific Summer (PSW) and Atlantic (AW) waters), and elevated surface wave energy that acts to deform and fracture sea ice. Spatial and temporal variability in ice properties and open water fraction impact these processes. To investigate how upper ocean structure varies with changing ice cover, and how the balance of processes shift as a function of ice fraction and distance from open water, four long-endurance autonomous Seagliders occupied sections that extended from open water, through the marginal ice zone, deep into the pack during summer 2014 in the Beaufort Sea. Sections reveal strong fronts where cold, ice-covered waters meet waters that have been exposed to solar warming, and O(10 km) scale eddies near the ice edge. In the pack, Pacific Summer Water and a deep chlorophyll maximum form distinct layers at roughly 60 m and 80 m, respectively, which become increasingly diffuse as they progress through the MIZ and into open water. The isopynal layer between 1023 and 1024 kgm-3, just above the PSW, consistently thickens near the ice edge, likely due to mixing or energetic vertical exchange associated with strong lateral gradients in this region. This presentation will discuss the upper ocean variability, its relationship to sea ice extent, and evolution over the summer to the start of freeze up.

Upper Ocean Evolution Across the Beaufort Sea Marginal Ice Zone from Autonomous Gliders

NASA Astrophysics Data System (ADS)

Lee, C.; Rainville, L.; Perry, M. J.

2016-02-01

The observed reduction of Arctic summertime sea ice extent and expansion of the marginal ice zone (MIZ) have profound impacts on the balance of processes controlling sea ice evolution, including the introduction of several positive feedback mechanisms that may act to accelerate melting. Examples of such feedbacks include increased upper ocean warming though absorption of solar radiation, elevated internal wave energy and mixing that may entrain heat stored in subsurface watermasses (e.g., the relatively warm Pacific Summer (PSW) and Atlantic (AW) waters), and elevated surface wave energy that acts to deform and fracture sea ice. Spatial and temporal variability in ice properties and open water fraction impact these processes. To investigate how upper ocean structure varies with changing ice cover, and how the balance of processes shift as a function of ice fraction and distance from open water, four long-endurance autonomous Seagliders occupied sections that extended from open water, through the marginal ice zone, deep into the pack during summer 2014 in the Beaufort Sea. Sections reveal strong fronts where cold, ice-covered waters meet waters that have been exposed to solar warming, and O(10 km) scale eddies near the ice edge. In the pack, Pacific Summer Water and a deep chlorophyll maximum form distinct layers at roughly 60 m and 80 m, respectively, which become increasingly diffuse as they progress through the MIZ and into open water. The isopynal layer between 1023 and 1024 kg m-3, just above the PSW, consistently thickens near the ice edge, likely due to mixing or energetic vertical exchange associated with strong lateral gradients in this region. This presentation will discuss the upper ocean variability, its relationship to sea ice extent, and evolution over the summer to the start of freeze up.

The Ocean`s Thermohaline Circulation in a Fish Tank

NASA Astrophysics Data System (ADS)

Lavender, K.; Joyce, P.; Graziano, L.; Harris, S.; Jaroslow, G.; Lea, C.; Schell, J.; Witting, J.

2005-12-01

This demonstration develops intuition about density stratification, a concept critical to understanding the ocean`s thermohaline circulation. In addition, students learn how temperature and salinity affect density, how these characteristics may be density-compensating, and students gain practice in graphing and interpreting vertical profiles and temperature-salinity (T-S) diagrams. The demonstration requires a rectangular fish tank (5-10 gallons) with a plexiglass partition, preparation of three colored ''water masses'' representing surface water (warm and fresh), ''mystery'' Mediterranean Water (warm and salty), and North Atlantic Deep Water (NADW; cold and salty), a kitchen sponge, and a temperature and salinity probe. Density may be computed using an Equation of State calculator (e.g. online version at http://fermi.jhuapl.edu/denscalc.html). The larger side of the fish tank is filled halfway with NADW, then surface water is layered on top by carefully pouring it on a floating sponge. A student volunteer measures the temperature and salinity of the two water masses, while another computes the densities. Students draw vertical profiles and T-S diagrams representing the temperature, salinity, and density of the water column. The properties of the ''mystery'' water are measured and students predict what will happen when the water is poured on the opposite side of the partition and is allowed to overflow into the layered water. If the density gradients are sufficiently large, a beautiful internal wave develops as the mystery water overflows the sill and becomes intermediate Mediterranean Water. If time permits, having a student blow on the surface illustrates the limited influence of ''wind'' with depth; an internal wave may by forced by depressing the thermocline with a large, flat spoon; and pouring extra NADW on the sponge floating at the surface may illustrate deep convection.

A Satellite View of a Back-door Cold Front

NASA Image and Video Library

2014-05-29

A "backdoor cold front" is bringing April temperatures to the U.S. northeast and Mid-Atlantic today, May 29. The backdoor cold front brings relief to the Mid-Atlantic after temperatures in Washington, D.C. hit 92F on Tuesday, May 27 and 88F on Wednesday, May 28 at Reagan National Airport, according to the National Weather Service (NWS). NWS forecasters expect the high temperature for May 29 to only reach 60F in the District of Columbia. NOAA's GOES-East satellite captured a view of the clouds associated with the backdoor cold front that stretch from southern Illinois to North Carolina. The National Weather Service forecast expects the backdoor cold front to bring showers to the Midwest, Northeast, and Mid-Atlantic today, May 29. According to the National Oceanic and Atmospheric Administration, a backdoor cold front is a cold front moving south or southwest along the Atlantic seaboard and Great Lakes; these are especially common during the spring months. This visible image was taken by NOAA's GOES-East satellite on May 29 at 12:30 UTC (8:30 a.m. EDT). The image was created at NASA/NOAA's GOES Project at NASA's Goddard Space Flight Center in Greenbelt, Maryland. In addition to the backdoor cold front clouds, the GOES-East image shows clouds circling around a low pressure area located in eastern Texas. That low pressure area is expected to bring rain from Texas eastward over the southeastern U.S. According to NOAA's National Weather Service, the slow-moving low pressure area in the Deep South "will bring heavy showers and thunderstorms from Louisiana to Alabama through Thursday. This area is already saturated from previous rainfall, so flash flooding will be possible." Image: NASA/NOAA GOES Project Caption: NASA Goddard/Rob Gutro

Artificial upwelling using the energy of surface waves

NASA Astrophysics Data System (ADS)

Soloviev, A.

2016-02-01

The ocean is an important component of climate and climate change, since the heat capacity of a few meters of the upper ocean is equivalent to the heat capacity of the entire atmosphere. (Solar radiation and IR balance in the atmosphere are of course major factors as well.) Artificial upwelling devices using the energy of surface waves, similar to those developed by Vershinskiy, Pshenichnyy, and Soloviev (1987), can bring cold water from below the thermocline to the sea surface. Their wave-inertia pump consisted of a vertical tube, a valve, and a buoy to keep the device afloat. The device operated by using energy of surface waves to create an upward flow of water in the tube. An outlet valve at the top of the unit synchronized the operation of the device with surface waves and prevented back-splashing. A single device with a 100 m long and 1.2 m diameter tube is able to produce up to 1 m3s-1 flow of deep water to the surface. With a 10oC temperature difference over 100 m depth, the negative heat supply rate to the sea surface is 42 MW, which is equivalent to a 42 Wm-2 heat flux, if distributed over 1 km2 area. Such flux is comparable to the average net air-sea flux. This type of artificial upwelling can cool down the sea surface, modify climate on a regional scale and possibly help mitigate hurricanes. The cold water brought from the deep layer, however, has a larger density than the surface water and therefore has a tendency to sink back down. In this work, the efficiency of wave-inertia pumps has been estimated for different environmental conditions using a computational fluid dynamics model. The cooled near-surface layer of the ocean will be getting more heat from the sun, which is a detrimental consequence. Cloud seeding can help to mitigate this extra warming. A synergistic approach to climate engineering can thus reduce detriments and increase potential benefits of this system to society.

The Closure History of the Central American Seaway and its Relationship to Ocean Circulation and Climate

NASA Astrophysics Data System (ADS)

Waite, A. J.; Martin, E. E.; Lawrence, K. T.; Ladlow, C. G.; Newkirk, D.

2014-12-01

Paleoceanographic and ecologic studies suggest that gradual shoaling of the Central American Seaway (CAS) as the Isthmus of Panama rose between ~13 to 2 Ma caused a stepwise shutdown of deep, intermediate, and shallow Pacific water flow through the seaway into the Caribbean. This diminishing communication is thought to have significantly influenced surface currents, ocean circulation at depth, and ultimately regional and global climate. However, new studies of Panama's volcanic/tectonic history suggest the isthmus rose much earlier than previous estimates, calling into question many of our accepted implications for this gateway event under the 'Panama Hypothesis,' including strengthened thermohaline circulation, North Atlantic Deep Water production, increased North Atlantic temperature, and ties to Northern Hemisphere glaciation. Despite considerable research, few paleoceanographic studies have directly examined the possibility of earlier events in the closure history of the CAS and thus the precise linkages and timing are not well defined. To investigate early restricted CAS flow related to sill formation or pulsed exhumation events, we examine two sets of independent paleoceanographic reconstructions from Ocean Drilling Program sediment cores from the region. We assess the presence of Pacific waters within the Caribbean over the last 30 Ma via the Nd-isotopic composition of fish teeth from several Caribbean sites; these records point to sustained transport of Pacific waters into the Caribbean from at least 30 to 10 Ma. Further, alkenone-derived sea surface temperature (SST) reconstructions from the Eastern Equatorial Pacific (EEP) indicate the presence of consistently warm (>27 °C) waters in the EEP from ~12 to ~5 Ma, after which time SSTs at sites within the modern cold tongue begin to cool appreciably. The SST data imply that the EEP cold tongue, which some studies suggest is linked in part to the rise of the Panamanian isthmus, did not develop until after 5 Ma. Collectively, these paleoceanographic reconstructions and model outputs indicate notable communication of water between the Pacific and the Caribbean until at least 10 Ma and provide improved understanding of the sequence of events associated with the rise of the Isthmus of Panama and closure of the CAS.

Edge systems in the deep ocean

NASA Astrophysics Data System (ADS)

Coon, Andrew; Earp, Samuel L.

2010-04-01

DARPA has initiated a program to explore persistent presence in the deep ocean. The deep ocean is difficult to access and presents a hostile environment. Persistent operations in the deep ocean will require new technology for energy, communications and autonomous operations. Several fundamental characteristics of the deep ocean shape any potential system architecture. The deep sea presents acoustic sensing opportunities that may provide significantly enhanced sensing footprints relative to sensors deployed at traditional depths. Communication limitations drive solutions towards autonomous operation of the platforms and automation of data collection and processing. Access to the seabed presents an opportunity for fixed infrastructure with no important limitations on size and weight. Difficult access and persistence impose requirements for long-life energy sources and potentially energy harvesting. The ocean is immense, so there is a need to scale the system footprint for presence over tens of thousands and perhaps hundreds of thousands of square nautical miles. This paper focuses on the aspect of distributed sensing, and the engineering of networks of sensors to cover the required footprint.

Deep Ocean Circulation and Nutrient Contents from Atlantic-Pacific Gradients of Neodymium and Carbon Isotopes During the Last 1 Ma

NASA Astrophysics Data System (ADS)

Piotrowski, A. M.; Elderfield, H.; Howe, J. N. W.

2014-12-01

The last few million years saw changing boundary conditions to the Earth system which set the stage for bi-polar glaciation and Milankovich-forced glacial-interglacial cycles which dominate Quaternary climate variability. Recent studies have highlighted the relative importance of temperature, ice volume and ocean circulation changes during the Mid-Pleistocene Transition at ~900 ka (Elderfield et al., 2012, Pena and Goldstein, 2014). Reconstructing the history of global deep water mass propagation and its carbon content is important for fully understanding the ocean's role in amplifying Milankovich changes to cause glacial-interglacial transitions. A new foraminiferal-coating Nd isotope record from ODP Site 1123 on the deep Chatham Rise is interpreted as showing glacial-interglacial changes in the bottom water propagation of Atlantic-sourced waters into the Pacific via the Southern Ocean during the last 1 million years. This is compared to globally-distributed bottom water Nd isotope records; including a new deep western equatorial Atlantic Ocean record from ODP Site 929, as well as published records from ODP 1088 and Site 1090 in the South Atlantic (Pena and Goldstein, 2014), and ODP 758 in the deep Indian Ocean (Gourlan et al., 2010). Atlantic-to-Pacific gradients in deep ocean neodymium isotopes are constructed for key time intervals to elucidate changes in deep water sourcing and circulation pathways through the global ocean. Benthic carbon isotopes are used to estimate deep water nutrient contents of deep water masses and constrain locations and modes of deep water formation. References: Elderfield et al. Science 337, 704 (2012) Pena and Goldstein, Science 345, 318 (2014) Gourlan et al., Quaternary Science Reviews 29, 2484-2498 (2010)

Atmospheric and Oceanic Response to Southern Ocean Deep Convection Oscillations on Decadal to Centennial Time Scales in Climate Models

NASA Astrophysics Data System (ADS)

Martin, T.; Reintges, A.; Park, W.; Latif, M.

2014-12-01

Many current coupled global climate models simulate open ocean deep convection in the Southern Ocean as a recurring event with time scales ranging from a few years to centennial (de Lavergne et al., 2014, Nat. Clim. Ch.). The only observation of such event, however, was the occurrence of the Weddell Polynya in the mid-1970s, an open water area of 350 000 km2 within the Antarctic sea ice in three consecutive winters. Both the wide range of modeled frequency of occurrence and the absence of deep convection in the Weddell Sea highlights the lack of understanding concerning the phenomenon. Nevertheless, simulations indicate that atmospheric and oceanic responses to the cessation of deep convection in the Southern Ocean include a strengthening of the low-level atmospheric circulation over the Southern Ocean (increasing SAM index) and a reduction in the export of Antarctic Bottom Water (AABW), potentially masking the regional effects of global warming (Latif et al., 2013, J. Clim.; Martin et al., 2014, Deep Sea Res. II). It is thus of great importance to enhance our understanding of Southern Ocean deep convection and clarify the associated time scales. In two multi-millennial simulations with the Kiel Climate Model (KCM, ECHAM5 T31 atmosphere & NEMO-LIM2 ~2˚ ocean) we showed that the deep convection is driven by strong oceanic warming at mid-depth periodically overriding the stabilizing effects of precipitation and ice melt (Martin et al., 2013, Clim. Dyn.). Sea ice thickness also affects location and duration of the deep convection. A new control simulation, in which, amongst others, the atmosphere grid resolution is changed to T42 (~2.8˚), yields a faster deep convection flip-flop with a period of 80-100 years and a weaker but still significant global climate response similar to CMIP5 simulations. While model physics seem to affect the time scale and intensity of the phenomenon, the driving mechanism is a rather robust feature. Finally, we compare the atmospheric and oceanic responses among CMIP5 models. Since open ocean convection is the dominant mode of AABW formation in these models, the northward extent and strength of the AABW cell in the Atlantic correlates with the deep convection intensity but varies between models. Likewise, atmospheric response patterns outside the Southern Ocean region are not consistent among models.

The interaction between sea ice and salinity-dominated ocean circulation: implications for halocline stability and rapid changes of sea-ice cover

NASA Astrophysics Data System (ADS)

Jensen, M. F.; Nilsson, J.; Nisancioglu, K. H.

2016-02-01

In this study, we develop a simple conceptual model to examine how interactions between sea ice and oceanic heat and freshwater transports affect the stability of an upper-ocean halocline in a semi-enclosed basin. The model represents a sea-ice covered and salinity stratified ocean, and consists of a sea-ice component and a two-layer ocean; a cold, fresh surface layer above a warmer, more saline layer. The sea-ice thickness depends on the atmospheric energy fluxes as well as the ocean heat flux. We introduce a thickness-dependent sea-ice export. Whether sea ice stabilizes or destabilizes against a freshwater perturbation is shown to depend on the representation of the vertical mixing. In a system where the vertical diffusivity is constant, the sea ice acts as a positive feedback on a freshwater perturbation. If the vertical diffusivity is derived from a constant mixing energy constraint, the sea ice acts as a negative feedback. However, both representations lead to a circulation that breaks down when the freshwater input at the surface is small. As a consequence, we get rapid changes in sea ice. In addition to low freshwater forcing, increasing deep-ocean temperatures promote instability and the disappearance of sea ice. Generally, the unstable state is reached before the vertical density difference disappears, and small changes in temperature and freshwater inputs can provoke abrupt changes in sea ice.

(Tele)presenting Secrets from the Deep Southern California Margin

NASA Astrophysics Data System (ADS)

Levin, L. A.; Girguis, P. R.; Brennan, M.; German, C. R.; Raineault, N.; Le, J. T.; Grupe, B.; Gallo, N.; Inderbitzen, K. E.; Tuzun, S.; Wagner, J.

2016-02-01

This past summer scientists, students and the public participated through telepresence in 2 weeks of deep-sea exploration via the EV Nautilus, visiting a tremendous diversity of sites found along the southern California continental margin (200-900m). We observed previously unknown cold seeps; new and unexpected assemblages and species distributions; and novel animal behaviors; all under the overarching influence of strong oxygen gradients from the East Pacific oxygen minimum zone (OMZ). The expedition discovered four new methane seep sites, each with distinct biota reflecting varying depth and oxygen levels. OMZ specialists such as lucinid clams, hagfish, and thornyhead fishes coexisted with seep biota (vesicoymid clams) at a 1.4-km long seep off Point Dume (Malibu, CA), forming a blended ecosystem with distinct zonation. A range of habitats (canyons, knolls, mounds) within the OMZ hosted fish, crustacean, echinoderm and cnidarian species with unusual hypoxia tolerance to < 3 µM O2 or lower. Organic falls (a sunken whale and naturally occurring kelp holdfasts) hosted many invertebrates and served as clear magnets for scavengers and predators. In situ observations revealed unusual behaviors including "parasailing" snails and drifting benthic siphonophores in the Santa Monica Basin, fish aggregating at seep carbonates, and cruising catsharks and their egg cases at methane seeps. Many of these observations advance understanding of the ecosystem services provided by deep-sea, margin habitats, while stimulating public interest in ocean exploration. Telepresence permitted broad engagement of students and scientists from as near as Los Angeles and as far as South Africa, as well as meaningful interactions with the public. In situ exploration and observation can and will play increasingly important roles in environmental management of the deep ocean as disturbance from resource extraction and climate change intensify.

Pathways of upwelling deep waters to the surface of the Southern Ocean

NASA Astrophysics Data System (ADS)

Tamsitt, Veronica; Drake, Henri; Morrison, Adele; Talley, Lynne; Dufour, Carolina; Gray, Alison; Griffies, Stephen; Mazloff, Matthew; Sarmiento, Jorge; Wang, Jinbo; Weijer, Wilbert

2017-04-01

Upwelling of Atlantic, Indian and Pacific deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of anthropogenic carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. Here we go beyond the two-dimensional view of Southern Ocean upwelling, to show detailed Southern Ocean upwelling pathways in three dimensions, using hydrographic observations and particle tracking in high-resolution ocean and climate models. The northern deep waters enter the Antarctic Circumpolar Current (ACC) via narrow southward currents along the boundaries of the three ocean basins, before spiraling southeastward and upward through the ACC. Upwelling is greatly enhanced at five major topographic features, associated with vigorous mesoscale eddy activity. Deep water reaches the upper ocean predominantly south of the southern ACC boundary, with a spatially nonuniform distribution, regionalizing warm water supply to Antarctic ice shelves and the delivery of nutrient and carbon-rich water to the sea surface. The timescale for half of the deep water to upwell from 30°S to the mixed layer is on the order of 60-90 years, which has important implications for the timescale for signals to propagate through the deep ocean. In addition, we quantify the diabatic transformation along particle trajectories, to identify where diabatic processes are important along the upwelling pathways.

Assessing the living and dead proportions of cold-water coral colonies: implications for deep-water Marine Protected Area monitoring in a changing ocean.

PubMed

Vad, Johanne; Orejas, Covadonga; Moreno-Navas, Juan; Findlay, Helen S; Roberts, J Murray

2017-01-01

Coral growth patterns result from an interplay of coral biology and environmental conditions. In this study colony size and proportion of live and dead skeletons in the cold-water coral (CWC) Lophelia pertusa (Linnaeus, 1758) were measured using video footage from Remotely Operated Vehicle (ROV) transects conducted at the inshore Mingulay Reef Complex (MRC) and at the offshore PISCES site (Rockall Bank) in the NE Atlantic. The main goal of this paper was to explore the development of a simple method to quantify coral growth and its potential application as an assessment tool of the health of these remote habitats. Eighteen colonies were selected and whole colony and dead/living layer size were measured. Live to dead layer ratios for each colony were then determined and analysed. The age of each colony was estimated using previously published data. Our paper shows that: (1) two distinct morphotypes can be described: at the MRC, colonies displayed a 'cauliflower-shaped' morphotype whereas at the PISCES site, colonies presented a more flattened 'bush-shaped' morphotype; (2) living layer size was positively correlated with whole colony size; (3) live to dead layer ratio was negatively correlated to whole colony size; (4) live to dead layer ratio never exceeded 0.27. These results suggest that as a colony develops and its growth rate slows down, the proportion of living polyps in the colony decreases. Furthermore, at least 73% of L. pertusa colonies are composed of exposed dead coral skeleton, vulnerable to ocean acidification and the associated shallowing of the aragonite saturation horizon, with significant implications for future deep-sea reef framework integrity. The clear visual contrast between white/pale living and grey/dark dead portions of the colonies also gives a new way by which they can be visually monitored over time. The increased use of marine autonomous survey vehicles offers an important new platform from which such a surveying technique could be applied to monitor deep-water marine protected areas in the future.

Nonlinear Gulf Stream Interaction with the Deep Western Boundary Current System: Observations and a Numerical Simulation

NASA Technical Reports Server (NTRS)

Dietrich, David E.; Mehra, Avichal; Haney, Robert L.; Bowman, Malcolm J.; Tseng, Yu-Heng

2003-01-01

Gulf Stream (GS) separation near its observed Cape Hatteras (CH) separation location, and its ensuing path and dynamics, is a challenging ocean modeling problem. If a model GS separates much farther north than CH, then northward GS meanders, which pinch off warm core eddies (rings), are not possible or are strongly constrained by the Grand Banks shelfbreak. Cold core rings pinch off the southward GS meanders. The rings are often re-absorbed by the GS. The important warm core rings enhance heat exchange and, especially, affect the northern GS branch after GS bifurcation near the New England Seamount Chain. This northern branch gains heat by contact with the southern branch water upstream of bifurcation, and warms the Arctic Ocean and northern seas, thus playing a major role in ice dynamics, thermohaline circulation and possible global climate warming. These rings transport heat northward between the separated GS and shelf slope/Deep Western Boundary Current system (DWBC). This region has nearly level time mean isopycnals. The eddy heat transport convergence/divergence enhances the shelfbreak and GS front intensities and thus also increases watermass transformation. The fronts are maintained by warm advection by the Florida Current and cool advection by the DWBC. Thus, the GS interaction with the DWBC through the intermediate eddy field is climatologically important.

South Atlantic circulation in a world ocean model

NASA Astrophysics Data System (ADS)

England, Matthew H.; Garçon, Véronique C.

1994-09-01

The circulation in the South Atlantic Ocean has been simulated within a global ocean general circulation model. Preliminary analysis of the modelled ocean circulation in the region indicates a rather close agreement of the simulated upper ocean flows with conventional notions of the large-scale geostrophic currents in the region. The modelled South Atlantic Ocean witnesses the return flow and export of North Atlantic Deep Water (NADW) at its northern boundary, the inflow of a rather barotropic Antarctic Circumpolar Current (ACC) through the Drake Passage, and the inflow of warm saline Agulhas water around the Cape of Good Hope. The Agulhas leakage amounts to 8.7 Sv, within recent estimates of the mass transport shed westward at the Agulhas retroflection. Topographic steering of the ACC dominates the structure of flow in the circumpolar ocean. The Benguela Current is seen to be fed by a mixture of saline Indian Ocean water (originating from the Agulhas Current) and fresher Subantarctic surface water (originating in the ACC). The Benguela Current is seen to modify its flow and fate with depth; near the surface it flows north-westwards bifurcating most of its transport northward into the North Atlantic Ocean (for ultimate replacement of North Atlantic surface waters lost to the NADW conveyor). Deeper in the water column, more of the Benguela Current is destined to return with the Brazil Current, though northward flows are still generated where the Benguela Current extension encounters the coast of South America. At intermediate levels, these northward currents trace the flow of Antarctic Intermediate Water (AAIW) equatorward, though even more AAIW is seen to recirculate poleward in the subtropical gyre. In spite of the model's rather coarse resolution, some subtle features of the Brazil-Malvinas Confluence are simulated rather well, including the latitude at which the two currents meet. Conceptual diagrams of the recirculation and interocean exchange of thermocline, intermediate and deep waters are constructed from an analysis of flows bound between isothermal and isobaric surfaces. This analysis shows how the return path of NADW is partitioned between a cold water route through the Drake Passage (6.5 Sv), a warm water route involving the Agulhas Current sheeding thermocline water westward (2.5 Sv), and a recirculation of intermediate water originating in the Indian Ocean (1.6 Sv).

Hydrological and Biogeochemical Controls on Absorption and Fluorescence of Dissolved Organic Matter in the Northern South China Sea

NASA Astrophysics Data System (ADS)

Wang, Chao; Guo, Weidong; Li, Yan; Stubbins, Aron; Li, Yizhen; Song, Guodong; Wang, Lei; Cheng, Yuanyue

2017-12-01

The Kuroshio intrusion from the West Philippine Sea (WPS) and mesoscale eddies are important hydrological features in the northern South China Sea (SCS). In this study, absorption and fluorescence of dissolved organic matter (CDOM and FDOM) were determined to assess the impact of these hydrological features on DOM dynamics in the SCS. DOM in the upper 100 m of the northern SCS had higher absorption, fluorescence, and degree of humification than in the Kuroshio Current of the WPS. The results of an isopycnal mixing model showed that CDOM and humic-like FDOM inventories in the upper 100 m of the SCS were modulated by the Kuroshio intrusion. However, protein-like FDOM was influenced by in situ processes. This basic trend was modified by mesoscale eddies, three of which were encountered during the fieldwork (one warm eddy and two cold eddies). DOM optical properties inside the warm eddy resembled those of DOM in the WPS, indicating that warm eddies could derive from the Kuroshio Current through Luzon Strait. DOM at the center of cold eddies was enriched in humic-like fluorescence and had lower spectral slopes than in eddy-free waters, suggesting inputs of humic-rich DOM from upwelling and enhanced productivity inside the eddy. Excess CDOM and FDOM in northern SCS intermediate water led to export to the Pacific Ocean interior, potentially delivering refractory carbon to the deep ocean. This study demonstrated that DOM optical properties are promising tools to study active marginal sea-open ocean interactions.

Metastable mantle phase transformations and deep earthquakes in subducting oceanic lithosphere

USGS Publications Warehouse

Kirby, S.H.; Stein, S.; Okal, E.A.; Rubie, David C.

1996-01-01

Earth's deepest earthquakes occur as a population in subducting or previously subducted lithosphere at depths ranging from about 325 to 690 km. This depth interval closely brackets the mantle transition zone, characterized by rapid seismic velocity increases resulting from the transformation of upper mantle minerals to higher-pressure phases. Deep earthquakes thus provide the primary direct evidence for subduction of the lithosphere to these depths and allow us to investigate the deep thermal, thermodynamic, and mechanical ferment inside slabs. Numerical simulations of reaction rates show that the olivine ??? spinel transformation should be kinetically hindered in old, cold slabs descending into the transition zone. Thus wedge-shaped zones of metastable peridotite probably persist to depths of more than 600 km. Laboratory deformation experiments on some metastable minerals display a shear instability called transformational faulting. This instability involves sudden failure by localized superplasticity in thin shear zones where the metastable host mineral transforms to a denser, finer-grained phase. Hence in cold slabs, such faulting is expected for the polymorphic reactions in which olivine transforms to the spinel structure and clinoenstatite transforms to ilmenite. It is thus natural to hypothesize that deep earthquakes result from transformational faulting in metastable peridotite wedges within cold slabs. This consideration of the mineralogical states of slabs augments the traditional largely thermal view of slab processes and explains some previously enigmatic slab features. It explains why deep seismicity occurs only in the approximate depth range of the mantle transition zone, where minerals in downgoing slabs should transform to spinel and ilmenite structures. The onset of deep shocks at about 325 km is consistent with the onset of metastability near the equilibrium phase boundary in the slab. Even if a slab penetrates into the lower mantle, earthquakes should cease at depths near 700 km, because the seismogenic phase transformations in the slab are completed or can no longer occur. Substantial metastability is expected only in old, cold slabs, consistent with the observed restriction of deep earthquakes to those settings. Earthquakes should be restricted to the cold cores of slabs, as in any model in which the seismicity is temperature controlled, via the distribution of metastability. However, the geometries of recent large deep earthquakes pose a challenge for any such models. Transformational faulting may give insight into why deep shocks lack appreciable aftershocks and why their source characteristics, including focal mechanisms indicating localized shear failure rather than implosive deformation, are so similar to those of shallow earthquakes. Finally, metastable phase changes in slabs would produce an internal source of stress in addition to those due to the weight of the sinking slab. Such internal stresses may explain the occurrence of earthquakes in portions of lithosphere which have foundered to the bottom of the transition zone and/or are detached from subducting slabs. Metastability in downgoing slabs could have considerable geodynamic significance. Metastable wedges would reduce the negative buoyancy of slabs, decrease the driving force for subduction, and influence the state of stress in slabs. Heat released by metastable phase changes would raise temperatures within slabs and facilitate the transformation of spinel to the lower mantle mineral assemblage, causing slabs to equilibrate more rapidly with the ambient mantle and thus contribute to the cessation of deep seismicity. Because wedge formation should occur only for fast subducting slabs, it may act as a "parachute" and contribute to regulating plate speeds. Wedge formation would also have consequences for mantle evolution because the density of a slab stagnated near the bottom of the transition zone would increase as it heats up and the wedge tra

Metastable mantle phase transformations and deep earthquakes in subducting oceanic lithosphere

NASA Astrophysics Data System (ADS)

Kirby, Stephen H.; Stein, Seth; Okal, Emile A.; Rubie, David C.

1996-05-01

Earth's deepest earthquakes occur as a population in subducting or previously subducted lithosphere at depths ranging from about 325 to 690 km. This depth interval closely brackets the mantle transition zone, characterized by rapid seismic velocity increases resulting from the transformation of upper mantle minerals to higher-pressure phases. Deep earthquakes thus provide the primary direct evidence for subduction of the lithosphere to these depths and allow us to investigate the deep thermal, thermodynamic, and mechanical ferment inside slabs. Numerical simulations of reaction rates show that the olivine → spinel transformation should be kinetically hindered in old, cold slabs descending into the transition zone. Thus wedge-shaped zones of metastable peridotite probably persist to depths of more than 600 km. Laboratory deformation experiments on some metastable minerals display a shear instability called transformational faulting. This instability involves sudden failure by localized superplasticity in thin shear zones where the metastable host mineral transforms to a denser, finer-grained phase. Hence in cold slabs, such faulting is expected for the polymorphic reactions in which olivine transforms to the spinel structure and clinoenstatite transforms to ilmenite. It is thus natural to hypothesize that deep earthquakes result from transformational faulting in metastable peridotite wedges within cold slabs. This consideration of the mineralogical states of slabs augments the traditional largely thermal view of slab processes and explains some previously enigmatic slab features. It explains why deep seismicity occurs only in the approximate depth range of the mantle transition zone, where minerals in downgoing slabs should transform to spinel and ilmenite structures. The onset of deep shocks at about 325 km is consistent with the onset of metastability near the equilibrium phase boundary in the slab. Even if a slab penetrates into the lower mantle, earthquakes should cease at depths near 700 km, because the seismogenic phase transformations in the slab are completed or can no longer occur. Substantial metastability is expected only in old, cold slabs, consistent with the observed restriction of deep earthquakes to those settings. Earthquakes should be restricted to the cold cores of slabs, as in any model in which the seismicity is temperature controlled, via the distribution of metastability. However, the geometries of recent large deep earthquakes pose a challenge for any such models. Transformational faulting may give insight into why deep shocks lack appreciable aftershocks and why their source characteristics, including focal mechanisms indicating localized shear failure rather than implosive deformation, are so similar to those of shallow earthquakes. Finally, metastable phase changes in slabs would produce an internal source of stress in addition to those due to the weight of the sinking slab. Such internal stresses may explain the occurrence of earthquakes in portions of lithosphere which have foundered to the bottom of the transition zone and/or are detached from subducting slabs. Metastability in downgoing slabs could have considerable geodynamic significance. Metastable wedges would reduce the negative buoyancy of slabs, decrease the driving force for subduction, and influence the state of stress in slabs. Heat released by metastable phase changes would raise temperatures within slabs and facilitate the transformation of spinel to the lower mantle mineral assemblage, causing slabs to equilibrate more rapidly with the ambient mantle and thus contribute to the cessation of deep seismicity. Because wedge formation should occur only for fast subducting slabs, it may act as a "parachute" and contribute to regulating plate speeds. Wedge formation would also have consequences for mantle evolution because the density of a slab stagnated near the bottom of the transition zone would increase as it heats up and the wedge transforms to denser spinel, favoring the subsequent sinking of the slab into the lower mantle.

APL-UW Deep Water Propagation 2015-2017: Philippine Sea Data Analysis

DTIC Science & Technology

2015-09-30

DISTRIBUTION STATEMENT A: Approved for public release: distribution is unlimited APL-UW Deep Water Propagation 2015-2017: Philippine Sea Data...the fundamental statistics of broadband low-frequency acoustical signals evolve during propagation through a dynamically-varying deep ocean. OBJECTIVES...Current models of signal randomization over long ranges in the deep ocean were developed for and tested in the North Pacific Ocean gyre. The

Deep seafloor arrivals: an unexplained set of arrivals in long-range ocean acoustic propagation.

PubMed

Stephen, Ralph A; Bolmer, S Thompson; Dzieciuch, Matthew A; Worcester, Peter F; Andrew, Rex K; Buck, Linda J; Mercer, James A; Colosi, John A; Howe, Bruce M

2009-08-01

Receptions, from a ship-suspended source (in the band 50-100 Hz) to an ocean bottom seismometer (about 5000 m depth) and the deepest element on a vertical hydrophone array (about 750 m above the seafloor) that were acquired on the 2004 Long-Range Ocean Acoustic Propagation Experiment in the North Pacific Ocean, are described. The ranges varied from 50 to 3200 km. In addition to predicted ocean acoustic arrivals and deep shadow zone arrivals (leaking below turning points), "deep seafloor arrivals," that are dominant on the seafloor geophone but are absent or very weak on the hydrophone array, are observed. These deep seafloor arrivals are an unexplained set of arrivals in ocean acoustics possibly associated with seafloor interface waves.

Gene flow between Atlantic and Pacific Ocean basins in three lineages of deep-sea clams (Bivalvia: Vesicomyidae: Pliocardiinae) and subsequent limited gene flow within the Atlantic

NASA Astrophysics Data System (ADS)

LaBella, Abigail Leavitt; Van Dover, Cindy L.; Jollivet, Didier; Cunningham, Clifford W.

2017-03-01

Pliocardiin (vesicomyid) clams rely on microbial symbionts for nutrition and are obligate inhabitants of deep-sea chemosynthetic ecosystems. Unlike many other invertebrate hosts of chemosynthetic microbes, pliocardiin clams are found in every ocean in a variety of reducing habitats, including hydrothermal vents, cold seeps, organic falls and deep-sea fans. The global distribution of pliocardiin clams suggests historical gene flow between ocean basins. We focus on 3 pliocardiin genera-'Pliocardia' I, Calyptogena and Abyssogena-each of which has a pair of sister clades in the Atlantic and Pacific. Our work tests the hypothesis that historical gene flow between the Atlantic and Pacific Oceans within these genera was interrupted by the closure of the Panamanian seaway and tests whether isolation between the ocean basins is the result of vicariance or past colonization. These questions are investigated in the context of fossil evidence, biogeography and phylogenetics. This study revealed a set of substitution rates consistent with other invertebrate studies (μ=0.8%/My/lineage), and a set consistent with much lower rates often attributed to deep-sea organisms (μ=0.3%/My/lineage). Among the Pacific/Atlantic sister pairs, 'Pliocardia' I COI divergence per lineage is intermediate (2.5%), Calyptogena is the highest (6.1%) and Abyssogena the lowest (0.8%). The substitution rates suggest that 'Pliocardia' I and Calyptogena have histories of at least 2.8 My in the Atlantic, with Calyptogena likely older. The slower rate, however, is inconsistent with both the maximum age of the family and several well studied fossils: leaving the faster rate preferred. With the faster rate, the Abyssogena southwardae clade diverged from its Pacific sister clade around 1 Mya, which likely post-dates the closure of the Isthmus of Panama and the opening of the Bering Strait. In light of this recent divergence, we test the previously proposed hypothesis that there is a high level of ongoing gene flow between Atlantic populations of A. southwardae. A. southwardae has colonized a broad geographic range of seep sites including the West Florida Escarpment, the Barbados Accretionary Prism, the Lobes of Congo, and the Mid-Atlantic Ridge north and south of the Romanche Transform Fault. Coalescent methods detect gene flow between Barbados and the Mid-Atlantic ridge; and between the West Florida Escarpment and the Lobes of Congo. All other comparisons failed to detect gene flow, contrary to prevailing interpretations of connectivity across the entire Atlantic Basin.

Open oceanic productivity changes at mid-latitudes during interglacials and its relation to the Atlantic Meridional Overturning Circulation

NASA Astrophysics Data System (ADS)

Nave, Silvia; Lebreiro, S.; Kissel, C.; Guihou, A.; Figueiredo, M. O.; Silva, T. P.; Michel, E.; Cortijo, E.; Labeyrie, L.; Voelker, A.

2010-05-01

Variations in the interactions between marine ecosystems, thermohaline circulation, external forcing and atmospheric greenhouse gases concentrations are not yet fully represented in detailed models of the glacial-interglacial transitions. Most of the research on past productivity changes has been focused so far on high-productivity areas such as upwelling areas (i.e. equatorial or coastal upwelling areas) even though those regions appraise only a little part of the ocean. Accordingly, the importance of oceanic productivity changes over glacial/interglacial cycles should be better known, as it may also play an important role on the loss of photosynthetically generated carbon as a central mechanism in the global carbon cycle. Its understanding will help quantifying the parameters needed to run comprehensive climate models, and subsequently help to better predict climate change for the near future. A high-resolution study of oceanic productivity, bottom water flow speed, surface and deep-water mass, bottom water ventilation, and terrestrial input changes during two interglacials (Holocene and Marine Isotope Stage [MIS] 5), at an open ocean site approximately 300 km west off Portugal [IMAGES core MD01-2446: 39°03'N, 12°37'W, 3547 m water depth] was conducted within the AMOCINT project (ESF-EUROCORES programme, 06-EuroMARC-FP-008). Even though siliceous productivity is expectedly low for oceanic regions, it shows a robust and consistent pattern with increased values during cold phases of MIS 5, and during the glacial stages 4 and 6 suggesting higher nutrient availability, during these periods. The same pattern is observed for MIS2 and the last deglaciation. The opal record is fully supported by the organic carbon content and to the estimated productivity using foraminifera based FA20 and SIMMAX.28 transfer functions for a near location. The benthic δ13C record suggests less North Atlantic Deep Water (NADW) coincident with periods of higher productivity. The grain-size variations and magnetic properties, suggests stronger/faster bottom currents during cold phases, in agreement with a stronger component of Antarctic sourced Bottom Water (AABW) at the Eastern Atlantic Margin. The probable enhancement of AABW during these periods may also account for a higher preservation of siliceous biogenic particles at the ocean floor sediment/water interface. Given that MD01-2446 is placed far from the continent, productivity records should mainly reflect local conditions. Still, we should not fully discard the preservation of punctual influence of coastal processes derived from upwelling filament plumes at the Estremadura Plateau. Lebreiro et al., 1997 [Paleoceanography, 12, 718-727] reported for a near location, the dominance of pre-upwelling and post-upwelling related foraminifera species during MIS 6 implying less intense or persistent upwelling during MIS 6 than MIS 4. On the contrary, opal and organic carbon data reveals a clear increase in productivity also during MIS 6, reinforcing the idea that productivity variations are likely related to open ocean conditions and therefore, nutrients availability associated to the Atlantic Meridional Oceanic Circulation.

Sr/Ca ratios in cold-water corals - a 'low-resolution' temperature archive?

NASA Astrophysics Data System (ADS)

Rüggeberg, Andres; Riethdorf, Jan-Rainer; Raddatz, Jacek; López Correa, Matthias; Montagna, Paolo; Dullo, Wolf-Christian; Freiwald, André

2010-05-01

One of the basic data to understand global change and past global changes is the measurement and the reconstruction of temperature of marine water masses. E.g. seawater temperature controls the density of seawater and in combination with salinity is the major driving force for the oceans circulation system. Geochemical investigations on cold-water corals Lophelia pertusa and Desmophyllum cristagalli indicated the potential of these organisms as high-resolution archives of environmental parameters from intermediate and deeper water masses (Adkins and Boyle 1997). Some studies tried to use cold-water corals as a high-resolution archive of temperature and salinity (Smith et al. 2000, 2002; Blamart et al. 2005; Lutringer et al. 2005). However, the fractionation of stable isotopes (delta18O and delta13C) and element ratios (Sr/Ca, Mg/Ca, U/Ca) are strongly influenced by vital effects (Shirai et al. 2005; Cohen et al. 2006), and difficult to interpret. Nevertheless, ongoing studies indicate the potential of a predominant temperature dependent fractionation of distinct isotopes and elements (e.g. Li/Ca, Montagna et al. 2008; U/Ca, Mg/Ca, delta18O, Lòpez Correa et al. 2008; delta88/86Sr, Rüggeberg et al. 2008). Within the frame of DFG-Project TRISTAN and Paläo-TRISTAN (Du 129/37-2 and 37-3) we investigated live-collected specimens of cold-water coral L. pertusa from all along the European continental margin (Northern and mid Norwegian shelves, Skagerrak, Rockall and Porcupine Bank, Galicia Bank, Gulf of Cadiz, Mediterranean Sea). These coral samples grew in waters characterized by temperatures between 6°C and 14°C. Electron Microprobe investigations along the growth direction of individual coral polyps were applied to determine the relationship between the incorporation of distinct elements (Sr, Ca, Mg, S). Cohen et al. (2006) showed for L. pertusa from the Kosterfjord, Skagerrak, that ~25% of the coral's Sr/Ca ratio is related to temperature, while 75% are influenced by the calcification rate of the organism. However, the Sr/Ca-temperature relation of our L. pertusa specimens suggest, that mean values are more reliable for temperature reconstruction along a larger temperature range than local high-resolution investigations. Additionally, our results plot on same line of Sr/Ca-temperature relationship like tropical corals indicating a similar behaviour of element incorporation during calcification. References: Adkins JF, Boyle EA (1997) Changing atmospheric ∆14C and the record of deep water paleoventilation ages. Paleoceanography 12:337-344 Blamart D, Rollion-Bard C, Cuif J-P, Juillet-Leclerc A, Lutringer A, Weering Tv, Henriet J-P (2005) C and O isotopes in a deep-sea coral (Lophelia pertusa) related to skeletal microstructure. In: Freiwald A, Roberts JM (eds) Cold-water Corals and Ecosystems. Springer-Verlag, Berlin Heidelberg, p 1005-1020 Cohen AL, Gaetani GA, Lundälv T, Corliss BH, George RY (2006) Compositional variability in a cold-water scleractinian, Lophelia pertusa: New insights into vital effects. Geochemistry, Geophysics, Geosystems 7:Q12004, doi:12010.11029/12006GC001354 López Correa M, Montagna P, Rüggeberg A, McCulloch M, Taviani M, Freiwald A (2008) Trace elements and stable isotopes in recent North Atlantic Lophelia pertusa along a latitudal gradient and from fossil Mediterranean sites. ASLO 2008 Summer Meeting, St. John's, Newfoundland & Labrador, Canada, 08.06.-13.06.2008, p. 47 Lutringer A, Blamart D, Frank N, Labeyrie L (2005) Paleotemperatures from deep-sea corals: scale effects. In: Freiwald A, Roberts JM (eds) Cold-water Corals and Ecosystems. Springer-Verlag, Berlin, Heidelberg, p 1081-1096 Montagna P, López-Correa M, Rüggeberg A, McCulloch M, Rodolfo-Metalpa R, Dullo W-C, Ferrier-Pagès C, Freiwald A, Henderson G, Mazzoli C, Russo S, Silenzi S, Taviani M (2008) Coral Li/Ca in micro-structural domains as a temperature proxy. Goldschmidt Conference, Vancouver, British Columbia, Canada Rüggeberg A, Fietzke J, Liebetrau V, Eisenhauer A, Dullo W-C, Freiwald A (2008) Stable strontium isotopes (delta88/86Sr) in cold-water corals — A new proxy for reconstruction of intermediate ocean water temperatures. Earth and Planetary Science Letters 269:569-574 Shirai K, Kusakabe M, Nakai S, Ishii T, Watanabe T, Hiyagon H, Sano Y (2005) Deep-sea coral geochemistry: Implication for the vital effect. Chemical Geology 224:212-222 Smith JE, Schwarcz HP, Risk MJ (2002) Patterns of isotopic disequilibria in azooxanhtellate coral skeletons. Hydrobiologia 471:111-115 Smith JE, Schwarcz HP, Risk MJ, McConnaughey TA, Keller N (2000) Paleotemperatures from deep-sea corals: Overcoming 'vital effects'. Palaios 15:25-32

Pole-to-pole biogeography of surface and deep marine bacterial communities

PubMed Central

Ghiglione, Jean-François; Galand, Pierre E.; Pommier, Thomas; Pedrós-Alió, Carlos; Maas, Elizabeth W.; Bakker, Kevin; Bertilson, Stefan; Kirchman, David L.; Lovejoy, Connie; Yager, Patricia L.; Murray, Alison E.

2012-01-01

The Antarctic and Arctic regions offer a unique opportunity to test factors shaping biogeography of marine microbial communities because these regions are geographically far apart, yet share similar selection pressures. Here, we report a comprehensive comparison of bacterioplankton diversity between polar oceans, using standardized methods for pyrosequencing the V6 region of the small subunit ribosomal (SSU) rRNA gene. Bacterial communities from lower latitude oceans were included, providing a global perspective. A clear difference between Southern and Arctic Ocean surface communities was evident, with 78% of operational taxonomic units (OTUs) unique to the Southern Ocean and 70% unique to the Arctic Ocean. Although polar ocean bacterial communities were more similar to each other than to lower latitude pelagic communities, analyses of depths, seasons, and coastal vs. open waters, the Southern and Arctic Ocean bacterioplankton communities consistently clustered separately from each other. Coastal surface Southern and Arctic Ocean communities were more dissimilar from their respective open ocean communities. In contrast, deep ocean communities differed less between poles and lower latitude deep waters and displayed different diversity patterns compared with the surface. In addition, estimated diversity (Chao1) for surface and deep communities did not correlate significantly with latitude or temperature. Our results suggest differences in environmental conditions at the poles and different selection mechanisms controlling surface and deep ocean community structure and diversity. Surface bacterioplankton may be subjected to more short-term, variable conditions, whereas deep communities appear to be structured by longer water-mass residence time and connectivity through ocean circulation. PMID:23045668

The role of Southern Ocean mixing and upwelling in glacial-interglacial atmospheric CO2 change

NASA Astrophysics Data System (ADS)

Watson, Andrew J.; Naveira Garabato, Alberto C.

2006-02-01

Decreased ventilation of the Southern Ocean in glacial time is implicated in most explanations of lower glacial atmospheric CO2. Today, the deep (>2000 m) ocean south of the Polar Front is rapidly ventilated from below, with the interaction of deep currents with topography driving high mixing rates well up into the water column. We show from a buoyancy budget that mixing rates are high in all the deep waters of the Southern Ocean. Between the surface and ~2000 m depth, water is upwelled by a residual meridional overturning that is directly linked to buoyancy fluxes through the ocean surface. Combined with the rapid deep mixing, this upwelling serves to return deep water to the surface on a short time scale. We propose two new mechanisms by which, in glacial time, the deep Southern Ocean may have been more isolated from the surface. Firstly, the deep ocean appears to have been more stratified because of denser bottom water resulting from intense sea ice formation near Antarctica. The greater stratification would have slowed the deep mixing. Secondly, subzero atmospheric temperatures may have meant that the present-day buoyancy flux from the atmosphere to the ocean surface was reduced or reversed. This in turn would have reduced or eliminated the upwelling (contrary to a common assumption, upwelling is not solely a function of the wind stress but is coupled to the air-sea buoyancy flux too). The observed very close link between Antarctic temperatures and atmospheric CO2 could then be explained as a natural consequence of the connection between the air-sea buoyancy flux and upwelling in the Southern Ocean, if slower ventilation of the Southern Ocean led to lower atmospheric CO2. Here we use a box model, similar to those of previous authors, to show that weaker mixing and reduced upwelling in the Southern Ocean can explain the low glacial atmospheric CO2 in such a formulation.

Antarctic climate, Southern Ocean circulation patterns, and deep water formation during the Eocene

NASA Astrophysics Data System (ADS)

Huck, Claire E.; van de Flierdt, Tina; Bohaty, Steven M.; Hammond, Samantha J.

2017-07-01

We assess early-to-middle Eocene seawater neodymium (Nd) isotope records from seven Southern Ocean deep-sea drill sites to evaluate the role of Southern Ocean circulation in long-term Cenozoic climate change. Our study sites are strategically located on either side of the Tasman Gateway and are positioned at a range of shallow (<500 m) to intermediate/deep ( 1000-2500 m) paleowater depths. Unradiogenic seawater Nd isotopic compositions, reconstructed from fish teeth at intermediate/deep Indian Ocean pelagic sites (Ocean Drilling Program (ODP) Sites 738 and 757 and Deep Sea Drilling Project (DSDP) Site 264), indicate a dominant Southern Ocean-sourced contribution to regional deep waters (ɛNd(t) = -9.3 ± 1.5). IODP Site U1356 off the coast of Adélie Land, a locus of modern-day Antarctic Bottom Water production, is identified as a site of persistent deep water formation from the early Eocene to the Oligocene. East of the Tasman Gateway an additional local source of intermediate/deep water formation is inferred at ODP Site 277 in the SW Pacific Ocean (ɛNd(t) = -8.7 ± 1.5). Antarctic-proximal shelf sites (ODP Site 1171 and Site U1356) reveal a pronounced erosional event between 49 and 48 Ma, manifested by 2 ɛNd unit negative excursions in seawater chemistry toward the composition of bulk sediments at these sites. This erosional event coincides with the termination of peak global warmth following the Early Eocene Climatic Optimum and is associated with documented cooling across the study region and increased export of Antarctic deep waters, highlighting the complexity and importance of Southern Ocean circulation in the greenhouse climate of the Eocene.

Spiraling pathways of global deep waters to the surface of the Southern Ocean.

PubMed

Tamsitt, Veronica; Drake, Henri F; Morrison, Adele K; Talley, Lynne D; Dufour, Carolina O; Gray, Alison R; Griffies, Stephen M; Mazloff, Matthew R; Sarmiento, Jorge L; Wang, Jinbo; Weijer, Wilbert

2017-08-02

Upwelling of global deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. However, the exact pathways and role of topography in Southern Ocean upwelling remain largely unknown. Here we show detailed upwelling pathways in three dimensions, using hydrographic observations and particle tracking in high-resolution models. The analysis reveals that the northern-sourced deep waters enter the Antarctic Circumpolar Current via southward flow along the boundaries of the three ocean basins, before spiraling southeastward and upward through the Antarctic Circumpolar Current. Upwelling is greatly enhanced at five major topographic features, associated with vigorous mesoscale eddy activity. Deep water reaches the upper ocean predominantly south of the Antarctic Circumpolar Current, with a spatially nonuniform distribution. The timescale for half of the deep water to upwell from 30° S to the mixed layer is ~60-90 years.Deep waters of the Atlantic, Pacific and Indian Oceans upwell in the Southern Oceanbut the exact pathways are not fully characterized. Here the authors present a three dimensional view showing a spiralling southward path, with enhanced upwelling by eddy-transport at topographic hotspots.

Cenozoic Planktonic Marine Diatom Diversity and Correlation to Climate Change

PubMed Central

Lazarus, David; Barron, John; Renaudie, Johan; Diver, Patrick; Türke, Andreas

2014-01-01

Marine planktonic diatoms export carbon to the deep ocean, playing a key role in the global carbon cycle. Although commonly thought to have diversified over the Cenozoic as global oceans cooled, only two conflicting quantitative reconstructions exist, both from the Neptune deep-sea microfossil occurrences database. Total diversity shows Cenozoic increase but is sample size biased; conventional subsampling shows little net change. We calculate diversity from a separately compiled new diatom species range catalog, and recalculate Neptune subsampled-in-bin diversity using new methods to correct for increasing Cenozoic geographic endemism and decreasing Cenozoic evenness. We find coherent, substantial Cenozoic diversification in both datasets. Many living cold water species, including species important for export productivity, originate only in the latest Miocene or younger. We make a first quantitative comparison of diatom diversity to the global Cenozoic benthic ∂18O (climate) and carbon cycle records (∂13C, and 20-0 Ma pCO2). Warmer climates are strongly correlated with lower diatom diversity (raw: rho = .92, p<.001; detrended, r = .6, p = .01). Diatoms were 20% less diverse in the early late Miocene, when temperatures and pCO2 were only moderately higher than today. Diversity is strongly correlated to both ∂13C and pCO2 over the last 15 my (for both: r>.9, detrended r>.6, all p<.001), but only weakly over the earlier Cenozoic, suggesting increasingly strong linkage of diatom and climate evolution in the Neogene. Our results suggest that many living marine planktonic diatom species may be at risk of extinction in future warm oceans, with an unknown but potentially substantial negative impact on the ocean biologic pump and oceanic carbon sequestration. We cannot however extrapolate our my-scale correlations with generic climate proxies to anthropogenic time-scales of warming without additional species-specific information on proximate ecologic controls. PMID:24465441

Cenozoic planktonic marine diatom diversity and correlation to climate change.

PubMed

Lazarus, David; Barron, John; Renaudie, Johan; Diver, Patrick; Türke, Andreas

2014-01-01

Marine planktonic diatoms export carbon to the deep ocean, playing a key role in the global carbon cycle. Although commonly thought to have diversified over the Cenozoic as global oceans cooled, only two conflicting quantitative reconstructions exist, both from the Neptune deep-sea microfossil occurrences database. Total diversity shows Cenozoic increase but is sample size biased; conventional subsampling shows little net change. We calculate diversity from a separately compiled new diatom species range catalog, and recalculate Neptune subsampled-in-bin diversity using new methods to correct for increasing Cenozoic geographic endemism and decreasing Cenozoic evenness. We find coherent, substantial Cenozoic diversification in both datasets. Many living cold water species, including species important for export productivity, originate only in the latest Miocene or younger. We make a first quantitative comparison of diatom diversity to the global Cenozoic benthic ∂(18)O (climate) and carbon cycle records (∂(13)C, and 20-0 Ma pCO2). Warmer climates are strongly correlated with lower diatom diversity (raw: rho = .92, p<.001; detrended, r = .6, p = .01). Diatoms were 20% less diverse in the early late Miocene, when temperatures and pCO2 were only moderately higher than today. Diversity is strongly correlated to both ∂(13)C and pCO2 over the last 15 my (for both: r>.9, detrended r>.6, all p<.001), but only weakly over the earlier Cenozoic, suggesting increasingly strong linkage of diatom and climate evolution in the Neogene. Our results suggest that many living marine planktonic diatom species may be at risk of extinction in future warm oceans, with an unknown but potentially substantial negative impact on the ocean biologic pump and oceanic carbon sequestration. We cannot however extrapolate our my-scale correlations with generic climate proxies to anthropogenic time-scales of warming without additional species-specific information on proximate ecologic controls.

Sensitivity of climate and atmospheric CO2 to deep-ocean and shallow-ocean carbonate burial

NASA Technical Reports Server (NTRS)

Volk, Tyler

1989-01-01

A model of the carbonate-silicate geochemical cycle is presented that distinguishes carbonate masses produced by shallow-ocean and deep-ocean carbonate burial and shows that reasonable increases in deep-ocean burial could produce substantial warmings over a few hundred million years. The model includes exchanges between crust and mantle; transients from burial shifts are found to be sensitive to the fraction of nondegassed carbonates subducted into the mantle. Without the habitation of the open ocean by plankton such as foraminifera and coccolithophores, today's climate would be substantially colder.

Sensitivity of Coupled Tropical Pacific Model Biases to Convective Parameterization in CESM1

NASA Astrophysics Data System (ADS)

Woelfle, M. D.; Yu, S.; Bretherton, C. S.; Pritchard, M. S.

2018-01-01

Six month coupled hindcasts show the central equatorial Pacific cold tongue bias development in a GCM to be sensitive to the atmospheric convective parameterization employed. Simulations using the standard configuration of the Community Earth System Model version 1 (CESM1) develop a cold bias in equatorial Pacific sea surface temperatures (SSTs) within the first two months of integration due to anomalous ocean advection driven by overly strong easterly surface wind stress along the equator. Disabling the deep convection parameterization enhances the zonal pressure gradient leading to stronger zonal wind stress and a stronger equatorial SST bias, highlighting the role of pressure gradients in determining the strength of the cold bias. Superparameterized hindcasts show reduced SST bias in the cold tongue region due to a reduction in surface easterlies despite simulating an excessively strong low-level jet at 1-1.5 km elevation. This reflects inadequate vertical mixing of zonal momentum from the absence of convective momentum transport in the superparameterized model. Standard CESM1simulations modified to omit shallow convective momentum transport reproduce the superparameterized low-level wind bias and associated equatorial SST pattern. Further superparameterized simulations using a three-dimensional cloud resolving model capable of producing realistic momentum transport simulate a cold tongue similar to the default CESM1. These findings imply convective momentum fluxes may be an underappreciated mechanism for controlling the strength of the equatorial cold tongue. Despite the sensitivity of equatorial SST to these changes in convective parameterization, the east Pacific double-Intertropical Convergence Zone rainfall bias persists in all simulations presented in this study.

An OSSE Study for Deep Argo Array using the GFDL Ensemble Coupled Data Assimilation System

NASA Astrophysics Data System (ADS)

Chang, You-Soon; Zhang, Shaoqing; Rosati, Anthony; Vecchi, Gabriel A.; Yang, Xiaosong

2018-03-01

An observing system simulation experiment (OSSE) using an ensemble coupled data assimilation system was designed to investigate the impact of deep ocean Argo profile assimilation in a biased numerical climate system. Based on the modern Argo observational array and an artificial extension to full depth, "observations" drawn from one coupled general circulation model (CM2.0) were assimilated into another model (CM2.1). Our results showed that coupled data assimilation with simultaneous atmospheric and oceanic constraints plays a significant role in preventing deep ocean drift. However, the extension of the Argo array to full depth did not significantly improve the quality of the oceanic climate estimation within the bias magnitude in the twin experiment. Even in the "identical" twin experiment for the deep Argo array from the same model (CM2.1) with the assimilation model, no significant changes were shown in the deep ocean, such as in the Atlantic meridional overturning circulation and the Antarctic bottom water cell. The small ensemble spread and corresponding weak constraints by the deep Argo profiles with medium spatial and temporal resolution may explain why the deep Argo profiles did not improve the deep ocean features in the assimilation system. Additional studies using different assimilation methods with improved spatial and temporal resolution of the deep Argo array are necessary in order to more thoroughly understand the impact of the deep Argo array on the assimilation system.

Deep-sea piezosphere and piezophiles: geomicrobiology and biogeochemistry.

PubMed

Fang, Jiasong; Zhang, Li; Bazylinski, Dennis A

2010-09-01

The deep-sea piezosphere accounts for approximately 75% of the total ocean volume and hosts active and diverse biological communities. Evidence obtained thus far suggests that the microbial biomass present in the piezosphere is significant. Continued international interest in exploring the deep ocean provides impetus to increase our understanding of the deep-sea piezosphere and of the influence of piezophilic microbial communities on the global ocean environment and on biogeochemical cycling occurring in the deep sea. Here, we review the diversity, metabolic characteristics, geomicrobiology and biogeochemistry of the deep-sea piezophiles. Copyright 2010 Elsevier Ltd. All rights reserved.

The deep-sea under global change.

PubMed

Danovaro, Roberto; Corinaldesi, Cinzia; Dell'Anno, Antonio; Snelgrove, Paul V R

2017-06-05

The deep ocean encompasses 95% of the oceans' volume and is the largest and least explored biome of Earth's Biosphere. New life forms are continuously being discovered. The physiological mechanisms allowing organisms to adapt to extreme conditions of the deep ocean (high pressures, from very low to very high temperatures, food shortage, lack of solar light) are still largely unknown. Some deep-sea species have very long life-spans, whereas others can tolerate toxic compounds at high concentrations; these characteristics offer an opportunity to explore the specialized biochemical and physiological mechanisms associated with these responses. Widespread symbiotic relationships play fundamental roles in driving host functions, nutrition, health, and evolution. Deep-sea organisms communicate and interact through sound emissions, chemical signals and bioluminescence. Several giants of the oceans hunt exclusively at depth, and new studies reveal a tight connection between processes in the shallow water and some deep-sea species. Limited biological knowledge of the deep-sea limits our capacity to predict future response of deep-sea organisms subject to increasing human pressure and changing global environmental conditions. Molecular tools, sensor-tagged animals, in situ and laboratory experiments, and new technologies can enable unprecedented advancement of deep-sea biology, and facilitate the sustainable management of deep ocean use under global change. Copyright © 2017. Published by Elsevier Ltd.

Eastern Pacific cooling and Atlantic overturning circulation during the last deglaciation.

PubMed

Kienast, Markus; Kienast, Stephanie S; Calvert, Stephen E; Eglinton, Timothy I; Mollenhauer, Gesine; François, Roger; Mix, Alan C

2006-10-19

Surface ocean conditions in the equatorial Pacific Ocean could hold the clue to whether millennial-scale global climate change during glacial times was initiated through tropical ocean-atmosphere feedbacks or by changes in the Atlantic thermohaline circulation. North Atlantic cold periods during Heinrich events and millennial-scale cold events (stadials) have been linked with climatic changes in the tropical Atlantic Ocean and South America, as well as the Indian and East Asian monsoon systems, but not with tropical Pacific sea surface temperatures. Here we present a high-resolution record of sea surface temperatures in the eastern tropical Pacific derived from alkenone unsaturation measurements. Our data show a temperature drop of approximately 1 degrees C, synchronous (within dating uncertainties) with the shutdown of the Atlantic meridional overturning circulation during Heinrich event 1, and a smaller temperature drop of approximately 0.5 degrees C synchronous with the smaller reduction in the overturning circulation during the Younger Dryas event. Both cold events coincide with maxima in surface ocean productivity as inferred from 230Th-normalized carbon burial fluxes, suggesting increased upwelling at the time. From the concurrence of equatorial Pacific cooling with the two North Atlantic cold periods during deglaciation, we conclude that these millennial-scale climate changes were probably driven by a reorganization of the oceans' thermohaline circulation, although possibly amplified by tropical ocean-atmosphere interaction as suggested before.

A Stratification Boomerang: Nonlinear Dependence of Deep Southern Ocean Ventilation on PCO2

NASA Astrophysics Data System (ADS)

Galbraith, E. D.; Merlis, T. M.

2014-12-01

Strong correlations between atmospheric CO2, Antarctic temperatures, and marine proxy records have hinted that ventilation of the deep Southern Ocean may have played a central role in the variations of CO2 over glacial-interglacial cycles. One proposition is that, in general, the Southern Ocean ventilates the deep more strongly under higher CO2, due to a change in winds and/or the dominance of thermal stratification in a warm ocean, which weakens ocean biological carbon storage. Here, we explore this idea with a suite of multi-millennial simulations using the GFDL CM2Mc global coupled model. The results are, indeed, consistent with increasing ventilation of the Southern Ocean as pCO2 increases above modern. However, they reveal a surprising twist under low pCO2: increased salinity of the Southern Ocean, due in part to weakening atmospheric moisture transport, actually increases ventilation rate of the deep ocean under low pCO2 as well. This implies that a nadir of Southern Ocean ventilation occurs at intermediate pCO2, which the model estimates as being close to that of the present-day. This is at odds with the interpretation that weak ventilation of the deep Southern Ocean was the unifying coupled mechanism for the glacial pCO2 cycles. Rather, it suggests that factors other than the ventilation rate of the deep Southern Ocean, such as iron fertilization, ecosystem changes, water mass distributions, and sea ice cover, were key players in the glacial-interglacial CO2 changes.

Spreading continents kick-started plate tectonics.

PubMed

Rey, Patrice F; Coltice, Nicolas; Flament, Nicolas

2014-09-18

Stresses acting on cold, thick and negatively buoyant oceanic lithosphere are thought to be crucial to the initiation of subduction and the operation of plate tectonics, which characterizes the present-day geodynamics of the Earth. Because the Earth's interior was hotter in the Archaean eon, the oceanic crust may have been thicker, thereby making the oceanic lithosphere more buoyant than at present, and whether subduction and plate tectonics occurred during this time is ambiguous, both in the geological record and in geodynamic models. Here we show that because the oceanic crust was thick and buoyant, early continents may have produced intra-lithospheric gravitational stresses large enough to drive their gravitational spreading, to initiate subduction at their margins and to trigger episodes of subduction. Our model predicts the co-occurrence of deep to progressively shallower mafic volcanics and arc magmatism within continents in a self-consistent geodynamic framework, explaining the enigmatic multimodal volcanism and tectonic record of Archaean cratons. Moreover, our model predicts a petrological stratification and tectonic structure of the sub-continental lithospheric mantle, two predictions that are consistent with xenolith and seismic studies, respectively, and consistent with the existence of a mid-lithospheric seismic discontinuity. The slow gravitational collapse of early continents could have kick-started transient episodes of plate tectonics until, as the Earth's interior cooled and oceanic lithosphere became heavier, plate tectonics became self-sustaining.

Deep ocean communities impacted by changing climate over 24 y in the abyssal northeast Pacific Ocean.

PubMed

Smith, Kenneth L; Ruhl, Henry A; Kahru, Mati; Huffard, Christine L; Sherman, Alana D

2013-12-03

The deep ocean, covering a vast expanse of the globe, relies almost exclusively on a food supply originating from primary production in surface waters. With well-documented warming of oceanic surface waters and conflicting reports of increasing and decreasing primary production trends, questions persist about how such changes impact deep ocean communities. A 24-y time-series study of sinking particulate organic carbon (food) supply and its utilization by the benthic community was conducted in the abyssal northeast Pacific (~4,000-m depth). Here we show that previous findings of food deficits are now punctuated by large episodic surpluses of particulate organic carbon reaching the sea floor, which meet utilization. Changing surface ocean conditions are translated to the deep ocean, where decadal peaks in supply, remineralization, and sequestration of organic carbon have broad implications for global carbon budget projections.

Deep ocean communities impacted by changing climate over 24 y in the abyssal northeast Pacific Ocean

PubMed Central

Smith, Kenneth L.; Ruhl, Henry A.; Kahru, Mati; Huffard, Christine L.; Sherman, Alana D.

2013-01-01

The deep ocean, covering a vast expanse of the globe, relies almost exclusively on a food supply originating from primary production in surface waters. With well-documented warming of oceanic surface waters and conflicting reports of increasing and decreasing primary production trends, questions persist about how such changes impact deep ocean communities. A 24-y time-series study of sinking particulate organic carbon (food) supply and its utilization by the benthic community was conducted in the abyssal northeast Pacific (∼4,000-m depth). Here we show that previous findings of food deficits are now punctuated by large episodic surpluses of particulate organic carbon reaching the sea floor, which meet utilization. Changing surface ocean conditions are translated to the deep ocean, where decadal peaks in supply, remineralization, and sequestration of organic carbon have broad implications for global carbon budget projections. PMID:24218565

Mechanism for the recent ocean warming events on the Scotian Shelf of eastern Canada

NASA Astrophysics Data System (ADS)

Brickman, D.; Hebert, D.; Wang, Z.

2018-03-01

In 2012, 2014, and 2015 anomalous warm events were observed in the subsurface waters in the Scotian Shelf region of eastern Canada. Monthly output from a high resolution numerical ocean model simulation of the North Atlantic ocean for the period 1990-2015 is used to investigate this phenomenon. It is found that the model shows skill in simulating the anomaly fields derived from various sources of data, and the observed warming trend over the last decade. From analysis of the model run it is found that the anomalies originate from the interaction between the Gulf Stream and the Labrador Current at the tail of the Grand Banks (south of Newfoundland). This interaction results in the creation of anomalous warm/salty (or cold/fresh) eddies that travel east-to-west along the shelfbreak. These anomalies penetrate into the Gulf of St. Lawrence, onto the Scotian Shelf, and into the Gulf of Maine via deep channels along the shelfbreak. The observed warming trend can be attributed to an increase in the frequency of creation of warm anomalies during the last decade. Strong anomalous events are commonly observed in the data and model, and thus should be considered as part of the natural variability of the coupled atmosphere-ocean system.

Dependence of Subduction Zone seismicity on Strain-Rate-Dependent Critical Homologous Temperature

NASA Astrophysics Data System (ADS)

Davis, P. M.

2016-12-01

Earthquakes mainly occur in crust or mantle that is below a critical temperature for the tectonic strain-rate, such that stress builds up to the breaking point before it can relax due to creep. Then long-range stress correlation gives rise to power law seismicity with large events. The limiting temperature depends on pressure, which is taken into account by finding a critical homologous temperature THc=T/TM above which earthquakes are rarely observed. We find that THc for ocean plates is ˜0.55. For California earthquakes, it is also close to 0.55. The uppermost mantle layer of oceanic plates of thickness ˜50 km is composed of harzburgite and depleted peridotite from which basalt has been removed to form ocean crust. Thus it has a higher melting temperature than the peridotite of the surrounding mantle, or the lower halves of plates. Thicknesses of seismicity in deep subduction zones, determined from 2D polynomial fits to a relocated catalog, are ˜50 km, which suggests that the earthquake channel is confined to this layer. We construct models to find homologous temperatures in slabs, and find that seismicity thicknesses are also, on average, confined to TH ≤ 0.55 ± 0.05. The associated rheology is compared with that obtained from flexure models of ocean lithosphere. The brittle-ductile transition occurs where viscosity drops from high values in the cold cores of slabs to values of 1022 to $1023 Pa s, i.e., where creep strain-rates become comparable to tectonic rates. The cutoff for deep earthquakes is not sharp. However they appear unlikely to occur if homologous temperature is high TH>0.55. Exceptions to the rule are anomalously deep earthquakes such as those beneath the Iceland and the Hawaiian hotspots, and the Newport Inglewood Fault. These are smaller events with short-range stress correlation, and can be explained if strain-rates are 2 to 3 orders of magnitude higher than those associated with earthquakes located where TH ≤0.55. We conclude that the brittle-ductile transition corresponds to the transition from long-range to short-range stress correlation.

Deep South Atlantic carbonate chemistry and increased interocean deep water exchange during last deglaciation

NASA Astrophysics Data System (ADS)

Yu, Jimin; Anderson, Robert F.; Jin, Zhangdong; Menviel, Laurie; Zhang, Fei; Ryerson, Fredrick J.; Rohling, Eelco J.

2014-04-01

Carbon release from the deep ocean at glacial terminations is a critical component of past climate change, but the underlying mechanisms remain poorly understood. We present a 28,000-year high-resolution record of carbonate ion concentration, a key parameter of the global carbon cycle, at 5-km water depth in the South Atlantic. We observe similar carbonate ion concentrations between the Last Glacial Maximum and the late Holocene, despite elevated concentrations in the glacial surface ocean. This strongly supports the importance of respiratory carbon accumulation in a stratified deep ocean for atmospheric CO2 reduction during the last ice age. After ˜9 μmol/kg decline during Heinrich Stadial 1, deep South Atlantic carbonate ion concentration rose by ˜24 μmol/kg from the onset of Bølling to Pre-boreal, likely caused by strengthening North Atlantic Deep Water formation (Bølling) or increased ventilation in the Southern Ocean (Younger Drays) or both (Pre-boreal). The ˜15 μmol/kg decline in deep water carbonate ion since ˜10 ka is consistent with extraction of alkalinity from seawater by deep-sea CaCO3 compensation and coral reef growth on continental shelves during the Holocene. Between 16,600 and 15,000 years ago, deep South Atlantic carbonate ion values converged with those at 3.4-km water depth in the western equatorial Pacific, as did carbon isotope and radiocarbon values. These observations suggest a period of enhanced lateral exchange of carbon between the deep South Atlantic and Pacific Oceans, probably due to an increased transfer of momentum from southern westerlies to the Southern Ocean. By spreading carbon-rich deep Pacific waters around Antarctica for upwelling, invigorated interocean deep water exchange would lead to more efficient CO2 degassing from the Southern Ocean, and thus to an atmospheric CO2 rise, during the early deglaciation.

Formation of the southern Bay of Bengal cold pool

NASA Astrophysics Data System (ADS)

Das, Umasankar; Vinayachandran, P. N.; Behara, Ambica

2016-09-01

A pool of relatively cooler water, called here as the southern Bay of Bengal cold pool, exists around Sri Lanka and southern tip of India during the summer monsoon. This cold pool is enveloped by the larger Indian Ocean warm pool and is believed to affect the intraseasonal variations of summer monsoon rainfall. In this study, we have investigated the mechanisms responsible for the formation of the cold pool using a combination of both satellite data sets and a general circulation model of the Indian Ocean. Sea surface temperature (SST) within the cold pool, after the steady increase during the February-April period, decreases first during a pre-monsoon spell in April and then with the monsoon onset during May. The onset cooling is stronger (~1.8°C) than the pre-monsoon cooling (~0.8°C) and culminates in the formation of the cold pool. Analysis of the model temperature equation shows that SST decrease during both events is primarily due to a decrease in incoming solar radiation and an increase in latent heat loss. These changes in the net heat flux are brought about by the arrival of cloud bands above the cold pool during both periods. During the pre-monsoon period, a cloud band originates in the western equatorial Indian Ocean and subsequently arrives above the cold pool. Similarly, during the monsoon onset, a band of clouds originating in the eastern equatorial Indian Ocean comes over the cold pool region. A lead-lag correlation calculation between daily SST and rainfall anomalies suggest that cooling in SST occurs in response to rainfall events with a lag of 5 days. These sequence of events occur every year with certain amount of interannual variability.

TOPEX/El Niño Watch - Pacific Ocean Conditions are Split: Cold in East, Hot in West, July 27, 1999

NASA Image and Video Library

1999-08-23

The North Pacific Ocean continues to run hot and cold, with abnormally low sea levels and cool waters in the northeastern Pacific contrasting with unusually high sea levels and warm waters in the northwestern Pacific.

Microbe-mediated transformations of marine dissolved organic matter during 2,100 years of natural incubation in the cold, oxic crust of the Mid-Atlantic Ridge.

NASA Astrophysics Data System (ADS)

Shah Walter, S. R.; Jaekel, U.; Huber, J. A.; Dittmar, T.; Girguis, P. R.

2015-12-01

On the western flank of the Mid-Atlantic Ridge, oxic seawater from the deep ocean is downwelled into the basaltic crust, supplying the crustal aquifer with an initial inoculum of organic matter and electron acceptors. Studies have shown that fluids circulating within the crust are minimally altered from original seawater, making this subsurface environment a unique natural experiment in which the fate of marine organic matter and the limitations of microbial adaptability in the context of reduced carbon supply can be examined. To make the subsurface crustal aquifer accessible, two CORK (Circulation Obviation Retrofit Kit) observatories have been installed at North Pond, a sediment-filled depression beneath the oligotrophic Sargasso Sea. Radiocarbon analysis of dissolved inorganic (DIC) and organic carbon (DOC) in samples recovered from these observatories show uncoupled aging between DOC and DIC with Δ14C values of DOC as low as -933‰ despite isolation from the open ocean for, at most, 2,100 years. This extreme value is part of a general trend of decreasing DOC δ13C and Δ14C values with increasing incubation time within the aquifer. Combined with reduced concentrations of DOC, our results argue for selective microbial oxidation of the youngest, most 13C-enriched components of downwelled DOC, possibly identifying these as characteristics of the more bioavailable fractions of deep-ocean dissolved organic matter. They also suggest that microbial oxidation during low-temperature hydrothermal circulation could be an important sink for aged marine dissolved organic matter.

Seasonal monitoring of deep-sea megabenthos in Barkley Canyon cold seep by internet operated vehicle (IOV)

PubMed Central

Doya, Carolina; Chatzievangelou, Damianos; Bahamon, Nixon; Purser, Autun; De Leo, Fabio C.; Juniper, S. Kim; Thomsen, Laurenz; Aguzzi, Jacopo

2017-01-01

Knowledge of the processes shaping deep-sea benthic communities at seasonal scales in cold-seep environments is incomplete. Cold seeps within highly dynamic regions, such as submarine canyons, where variable current regimes may occur, are particularly understudied. Novel Internet Operated Vehicles (IOVs), such as tracked crawlers, provide new techniques for investigating these ecosystems over prolonged periods. In this study a benthic crawler connected to the NEPTUNE cabled infrastructure operated by Ocean Networks Canada was used to monitor community changes across 60 m2 of a cold-seep area of the Barkley Canyon, North East Pacific, at ~890 m depth within an Oxygen Minimum Zone (OMZ). Short video-transects were run at 4-h intervals during the first week of successive calendar months, over a 14 month period (February 14th 2013 to April 14th 2014). Within each recorded transect video megafauna abundances were computed and changes in environmental conditions concurrently measured. The responses of fauna to environmental conditions as a proxy of seasonality were assessed through analysis of abundances in a total of 438 video-transects (over 92 h of total footage). 7698 fauna individuals from 6 phyla (Cnidaria, Ctenophora, Arthropoda, Echinodermata, Mollusca, and Chordata) were logged and patterns in abundances of the 7 most abundant taxa (i.e. rockfish Sebastidae, sablefish Anoplopoma fimbria, hagfish Eptatretus stoutii, buccinids (Buccinoidea), undefined small crabs, ctenophores Bolinopsis infundibulum, and Scyphomedusa Poralia rufescens) were identified. Patterns in the reproductive behaviour of the grooved tanner crab (Chionnecetes tanneri) were also indicated. Temporal variations in biodiversity and abundance in megabenthic fauna was significantly influenced by variabilities in flow velocity flow direction (up or down canyon), dissolved oxygen concentration and month of study. Also reported here for the first time are transient mass aggregations of grooved tanner crabs through these depths of the canyon system, in early spring and likely linked to the crab’s reproductive cycle. PMID:28557992

Seasonal monitoring of deep-sea megabenthos in Barkley Canyon cold seep by internet operated vehicle (IOV).

PubMed

Doya, Carolina; Chatzievangelou, Damianos; Bahamon, Nixon; Purser, Autun; De Leo, Fabio C; Juniper, S Kim; Thomsen, Laurenz; Aguzzi, Jacopo

2017-01-01

Knowledge of the processes shaping deep-sea benthic communities at seasonal scales in cold-seep environments is incomplete. Cold seeps within highly dynamic regions, such as submarine canyons, where variable current regimes may occur, are particularly understudied. Novel Internet Operated Vehicles (IOVs), such as tracked crawlers, provide new techniques for investigating these ecosystems over prolonged periods. In this study a benthic crawler connected to the NEPTUNE cabled infrastructure operated by Ocean Networks Canada was used to monitor community changes across 60 m2 of a cold-seep area of the Barkley Canyon, North East Pacific, at ~890 m depth within an Oxygen Minimum Zone (OMZ). Short video-transects were run at 4-h intervals during the first week of successive calendar months, over a 14 month period (February 14th 2013 to April 14th 2014). Within each recorded transect video megafauna abundances were computed and changes in environmental conditions concurrently measured. The responses of fauna to environmental conditions as a proxy of seasonality were assessed through analysis of abundances in a total of 438 video-transects (over 92 h of total footage). 7698 fauna individuals from 6 phyla (Cnidaria, Ctenophora, Arthropoda, Echinodermata, Mollusca, and Chordata) were logged and patterns in abundances of the 7 most abundant taxa (i.e. rockfish Sebastidae, sablefish Anoplopoma fimbria, hagfish Eptatretus stoutii, buccinids (Buccinoidea), undefined small crabs, ctenophores Bolinopsis infundibulum, and Scyphomedusa Poralia rufescens) were identified. Patterns in the reproductive behaviour of the grooved tanner crab (Chionnecetes tanneri) were also indicated. Temporal variations in biodiversity and abundance in megabenthic fauna was significantly influenced by variabilities in flow velocity flow direction (up or down canyon), dissolved oxygen concentration and month of study. Also reported here for the first time are transient mass aggregations of grooved tanner crabs through these depths of the canyon system, in early spring and likely linked to the crab's reproductive cycle.

Tracer constraints on organic particle transfer efficiency to the deep ocean

NASA Astrophysics Data System (ADS)

Weber, T. S.; Cram, J. A.; Deutsch, C. A.

2016-02-01

The "transfer efficiency" of sinking organic particles through the mesopelagic zone is a critical determinant of ocean carbon sequestration timescales, and the atmosphere-ocean partition of CO2. Our ability to detect large-scale variations in transfer efficiency is limited by the paucity of particle flux data from the deep ocean, and the potential biases of bottom-moored sediment traps used to collect it. Here we show that deep-ocean particle fluxes can be reconstructed by diagnosing the rate of phosphate accumulation and oxygen disappearance along deep circulation pathways in an observationally constrained Ocean General Circulation Model (OGCM). Combined with satellite and model estimates of carbon export from the surface ocean, these diagnosed fluxes reveal a global pattern of transfer efficiency to 1000m and 2000m that is high ( 20%) at high latitudes and negligible (<5%) throughout subtropical gyres, with intermediate values in the tropics. This pattern is at odds with previous estimates of deep transfer efficiency derived from bottom-moored sediment traps, but is consistent with upper-ocean flux profiles measured by neutrally buoyant sediment traps, which show strong attenuation of low latitude particle fluxes over the top 500m. Mechanistically, the pattern can be explained by spatial variations in particle size distributions, and the temperature-dependence of remineralization. We demonstrate the biogeochemical significance of our findings by comparing estimates of deep-ocean carbon sequestration in a scenario with spatially varying transfer efficiency to one with a globally uniform "Martin-curve" particle flux profile.

Molecular mechanisms underlying the physiological responses of the cold-water coral Desmophyllum dianthus to ocean acidification

NASA Astrophysics Data System (ADS)

Carreiro-Silva, M.; Cerqueira, T.; Godinho, A.; Caetano, M.; Santos, R. S.; Bettencourt, R.

2014-06-01

Cold-water corals (CWCs) are thought to be particularly vulnerable to ocean acidification (OA) due to increased atmospheric pCO2, because they inhabit deep and cold waters where the aragonite saturation state is naturally low. Several recent studies have evaluated the impact of OA on organism-level physiological processes such as calcification and respiration. However, no studies to date have looked at the impact at the molecular level of gene expression. Here, we report results of a long-term, 8-month experiment to compare the physiological responses of the CWC Desmophyllum dianthus to OA at both the organismal and gene expression levels under two pCO2/pH treatments: ambient pCO2 (460 μatm, pHT = 8.01) and elevated pCO2 (997 μatm, pHT = 7.70). At the organismal level, no significant differences were detected in the calcification and respiration rates of D. dianthus. Conversely, significant differences were recorded in gene expression profiles, which showed an up-regulation of genes involved in cellular stress (HSP70) and immune defence (mannose-binding c-type lectin). Expression of alpha-carbonic anhydrase, a key enzyme involved in the synthesis of coral skeleton, was also significantly up-regulated in corals under elevated pCO2, indicating that D. dianthus was under physiological reconditioning to calcify under these conditions. Thus, gene expression profiles revealed physiological impacts that were not evident at the organismal level. Consequently, understanding the molecular mechanisms behind the physiological processes involved in a coral's response to elevated pCO2 is critical to assess the ability of CWCs to acclimate or adapt to future OA conditions.

Comparative analysis between protist communities from the deep-sea pelagic ecosystem and specific deep hydrothermal habitats.

PubMed

Sauvadet, Anne-Laure; Gobet, Angélique; Guillou, Laure

2010-11-01

Protist communities associated with deep seawater and bivalves from six hydrothermal sites in the Pacific Ocean were characterized by microscopy and molecular rRNA gene surveys (18S rRNA) and compared with planktonic communities from Pacific deep-pelagic seawater (from 500 to 3000 m in depth). Genetic libraries from larger size fractions (>3 µm) of deep-pelagic water were mainly dominated by Dinophyceae, whereas small size fractions (<3 µm) mainly revealed radiolarians and Syndiniales. In contrast, more specific opportunistic detritivores and grazers, mostly belonging to Stramenopiles and Cercozoa, were detected from water surrounding vent chimneys. Protist communities were different in the pallial cavity of the giant hydrothermal bivalves Bathymodiolus thermophilus and Calyptogena magnifica, dominated by Ciliophora (primarily belonging to Phyllopharyngea, Oligohymenophorea and Oligotrichea) and Cercozoa. Interestingly, protist communities retrieved from the pallial cavity liquid of hydrothermal bivalves were remarkably homogeneous along the Southern East Pacific Rise, in contrast to bivalves collected on the Mid-Atlantic Ridge hydrothermal vents and cold seeps from the Gulf of Mexico. Hence, complex protist communities seem to occur inside hydrothermal bivalves, and these metazoa may constitute a stable micro-niche for micro-eukaryotes, including grazers, detritivores, symbionts and potential parasites. From these communities, new lineages within the ciliates may emerge. © 2010 Society for Applied Microbiology and Blackwell Publishing Ltd.

Tropical Cyclone Induced Air-Sea Interactions Over Oceanic Fronts

NASA Astrophysics Data System (ADS)

Shay, L. K.

2012-12-01

Recent severe tropical cyclones underscore the inherent importance of warm background ocean fronts and their interactions with the atmospheric boundary layer. Central to the question of heat and moisture fluxes, the amount of heat available to the tropical cyclone is predicated by the initial mixed layer depth and strength of the stratification that essentially set the level of entrainment mixing at the base of the mixed layer. In oceanic regimes where the ocean mixed layers are thin, shear-induced mixing tends to cool the upper ocean to form cold wakes which reduces the air-sea fluxes. This is an example of negative feedback. By contrast, in regimes where the ocean mixed layers are deep (usually along the western part of the gyres), warm water advection by the nearly steady currents reduces the levels of turbulent mixing by shear instabilities. As these strong near-inertial shears are arrested, more heat and moisture transfers are available through the enthalpy fluxes (typically 1 to 1.5 kW m-2) into the hurricane boundary layer. When tropical cyclones move into favorable or neutral atmospheric conditions, tropical cyclones have a tendency to rapidly intensify as observed over the Gulf of Mexico during Isidore and Lili in 2002, Katrina, Rita and Wilma in 2005, Dean and Felix in 2007 in the Caribbean Sea, and Earl in 2010 just north of the Caribbean Islands. To predict these tropical cyclone deepening (as well as weakening) cycles, coupled models must have ocean models with realistic ocean conditions and accurate air-sea and vertical mixing parameterizations. Thus, to constrain these models, having complete 3-D ocean profiles juxtaposed with atmospheric profiler measurements prior, during and subsequent to passage is an absolute necessity framed within regional scale satellite derived fields.

Exploring frontiers of the deep biosphere through scientific ocean drilling

NASA Astrophysics Data System (ADS)

Inagaki, F.; D'Hondt, S.; Hinrichs, K. U.

2015-12-01

Since the first deep biosphere-dedicated Ocean Drilling Program (ODP) Leg 201 using the US drill ship JOIDES Resolution in 2002, scientific ocean drilling has offered unique opportunities to expand our knowledge of the nature and extent of the deep biosphere. The latest estimate of the global subseafloor microbial biomass is ~1029cells, accounting for 4 Gt of carbon and ~1% of the Earth's total living biomass. The subseafloor microbial communities are evolutionarily diverse and their metabolic rates are extraordinarily slow. Nevertheless, accumulating activity most likely plays a significant role in elemental cycles over geological time. In 2010, during Integrated Ocean Drilling Program (IODP) Expedition 329, the JOIDES Resolutionexplored the deep biosphere in the open-ocean South Pacific Gyre—the largest oligotrophic province on our planet. During Expedition 329, relatively high concentrations of dissolved oxygen and significantly low biomass of microbial populations were observed in the entire sediment column, indicating that (i) there is no limit to life in open-ocean sediment and (ii) a significant amount of oxygen reaches through the sediment to the upper oceanic crust. This "deep aerobic biosphere" inhabits the sediment throughout up to ~37 percent of the world's oceans. The remaining ~63 percent of the oceans is comprised of higher productivity areas that contain the "deep anaerobic biosphere". In 2012, during IODP Expedition 337, the Japanese drill ship Chikyu explored coal-bearing sediments down to 2,466 meters below the seafloor off the Shimokita Peninsula, Japan. Geochemical and microbiological analyses consistently showed the occurrence of methane-producing communities associated with the coal beds. Cell concentrations in deep sediments were notably lower than those expected from the global regression line, implying that the bottom of the deep biosphere is approached in these beds. Taxonomic composition of the deep coal-bearing communities profoundly differs from those in shallower marine sediments and instead resembles organotrophic communities in forest soils. These findings suggest that the terrigenous microbial ecosystem has been partly retained from the original depositional setting over 20 million years and contributed to deep carbon cycling ever since.

The effect of ocean alkalinity and carbon transfer on deep-sea carbonate ion concentration during the past five glacial cycles

NASA Astrophysics Data System (ADS)

Kerr, Joanna; Rickaby, Rosalind; Yu, Jimin; Elderfield, Henry; Sadekov, Aleksey Yu.

2017-08-01

Glacial-interglacial deep Indo-Pacific carbonate ion concentration ([CO32-]) changes were mainly driven by two mechanisms that operated on different timescales: 1) a long-term increase during glaciation caused by a carbonate deposition reduction on shelves (i.e., the coral reef hypothesis), and 2) transient carbonate compensation responses to deep ocean carbon storage changes. To investigate these mechanisms, we have used benthic foraminiferal B/Ca to reconstruct deep-water [CO32-] in cores from the deep Indian and Equatorial Pacific Oceans during the past five glacial cycles. Based on our reconstructions, we suggest that the shelf-to-basin shift of carbonate deposition raised deep-water [CO32-], on average, by 7.3 ± 0.5 (SE) μmol/kg during glaciations. Oceanic carbon reorganisations during major climatic transitions caused deep-water [CO32-] deviations away from the long-term trend, and carbonate compensation processes subsequently acted to restore the ocean carbonate system to new steady state conditions. Deep-water [CO32-] showed similar patterns to sediment carbonate content (%CaCO3) records on glacial-interglacial timescales, suggesting that past seafloor %CaCO3 variations were dominated by deep-water carbonate preservation changes at our studied sites.

Causes of strong ocean heating during glacial periods

NASA Astrophysics Data System (ADS)

Zimov, N.; Zimov, S. A.

2013-12-01

During the last deglaciation period, the strongest climate changes occurred across the North Atlantic regions. Analyses of borehole temperatures from the Greenland ice sheet have yielded air temperature change estimates of 25°C over the deglaciation period (Dahl-Jensen et al. 1998). Such huge temperature changes cannot currently be explained in the frames of modern knowledge about climate. We propose that glacial-interglacial cycles are connected with gradual warming of ocean interior waters over the course of glaciations and quick transport of accumulated heat from ocean to the atmosphere during the deglaciation periods. Modern day ocean circulation is dominated by thermal convection with cold waters subsiding in the Northern Atlantic and filling up the ocean interior with cold and heavy water. However during the glaciation thermal circulation stopped and ocean circulation was driven by 'haline pumps' -Red and Mediterranean seas connected with ocean with only narrow but deep straights acts as evaporative basins, separating ocean water into fresh water which returns to the ocean surface (precipitation) and warm but salty, and therefore heavy, water which flows down to the ocean floor. This haline pump is stratifying the ocean, allowing warmer water locate under the colder water and thus stopping thermal convection in the ocean. Additional ocean interior warming is driven by geothermal heat flux and decomposition of organic rain. To test the hypothesis we present simple ocean box model that describes thermohaline circulation in the World Ocean. The first box is the Red and Mediterranean sea, the second is united high-latitude seas, the third is the ocean surface, and the fourth the ocean interior. The volume of these water masses and straight cross-sections are taken to be close to real values. We have accepted that the exchange of water between boxes is proportional to the difference in water density in these boxes, Sun energy inputs to the ocean and sea surface are taken as constant. Energy income to the interior box from the geothermal heat flux is also taken as constant. Even though energy inputs are taken as constants, the model manages to recreate the glacial-interglacial cycles. In the glacial periods only haline circulation takes place, the ocean is strongly stratified, and the interior box accumulates heat, while high-latitudes accumulate ice. 112,000 years after glaciation starts, water density on the ocean bottom becomes equal to the density of water in high-latitude seas, strong thermal convection take place, and the ocean quickly (within 14,600 years) releases the heat. The magnitude and duration of such cycles correspond with magnitudes and durations reconstructed for actual glacial-interglacial cycles. From the proposed mechanism it follows that during the glaciations it is likely that the Arctic Ocean was a big reservoir of isotopically light fresh ice. If in a glacial period, the World Ocean were half filled with warm water from the Red Sea and bioproductivity of the ocean declined because of the slow circulation, then carbon storage within the ocean reservoir would decline by ~2000 Pg (10^15 g) of carbon.

Terrestrial aftermath of the Moon-forming impact.

PubMed

Sleep, Norman H; Zahnle, Kevin J; Lupu, Roxana E

2014-09-13

Much of the Earth's mantle was melted in the Moon-forming impact. Gases that were not partially soluble in the melt, such as water and CO2, formed a thick, deep atmosphere surrounding the post-impact Earth. This atmosphere was opaque to thermal radiation, allowing heat to escape to space only at the runaway greenhouse threshold of approximately 100 W m(-2). The duration of this runaway greenhouse stage was limited to approximately 10 Myr by the internal energy and tidal heating, ending with a partially crystalline uppermost mantle and a solid deep mantle. At this point, the crust was able to cool efficiently and solidified at the surface. After the condensation of the water ocean, approximately 100 bar of CO2 remained in the atmosphere, creating a solar-heated greenhouse, while the surface cooled to approximately 500 K. Almost all this CO2 had to be sequestered by subduction into the mantle by 3.8 Ga, when the geological record indicates the presence of life and hence a habitable environment. The deep CO2 sequestration into the mantle could be explained by a rapid subduction of the old oceanic crust, such that the top of the crust would remain cold and retain its CO2. Kinematically, these episodes would be required to have both fast subduction (and hence seafloor spreading) and old crust. Hadean oceanic crust that formed from hot mantle would have been thicker than modern crust, and therefore only old crust underlain by cool mantle lithosphere could subduct. Once subduction started, the basaltic crust would turn into dense eclogite, increasing the rate of subduction. The rapid subduction would stop when the young partially frozen crust from the rapidly spreading ridge entered the subduction zone. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Southern Ocean bottom water characteristics in CMIP5 models

NASA Astrophysics Data System (ADS)

Heuzé, CéLine; Heywood, Karen J.; Stevens, David P.; Ridley, Jeff K.

2013-04-01

Southern Ocean deep water properties and formation processes in climate models are indicative of their capability to simulate future climate, heat and carbon uptake, and sea level rise. Southern Ocean temperature and density averaged over 1986-2005 from 15 CMIP5 (Coupled Model Intercomparison Project Phase 5) climate models are compared with an observed climatology, focusing on bottom water. Bottom properties are reasonably accurate for half the models. Ten models create dense water on the Antarctic shelf, but it mixes with lighter water and is not exported as bottom water as in reality. Instead, most models create deep water by open ocean deep convection, a process occurring rarely in reality. Models with extensive deep convection are those with strong seasonality in sea ice. Optimum bottom properties occur in models with deep convection in the Weddell and Ross Gyres. Bottom Water formation processes are poorly represented in ocean models and are a key challenge for improving climate predictions.

Convective Available Potential Energy of World Ocean

NASA Astrophysics Data System (ADS)

Su, Z.; Ingersoll, A. P.; Thompson, A. F.

2012-12-01

Here, for the first time, we propose the concept of Ocean Convective Available Potential Energy (OCAPE), which is the maximum kinetic energy (KE) per unit seawater mass achievable by ocean convection. OCAPE occurs through a different mechanism from atmospheric CAPE, and involves the interplay of temperature and salinity on the equation of state of seawater. The thermobaric effect, which arises because the thermal coefficient of expansion increases with depth, is an important ingredient of OCAPE. We develop an accurate algorithm to calculate the OCAPE for a given temperature and salinity profile. We then validate our calculation of OCAPE by comparing it with the conversion of OCAPE to KE in a 2-D numerical model. We propose that OCAPE is an important energy source of ocean deep convection and contributes to deep water formation. OCAPE, like Atmospheric CAPE, can help predict deep convection and may also provide a useful constraint for modelling deep convection in ocean GCMs. We plot the global distribution of OCAPE using data from the World Ocean Atlas 2009 (WOA09) and see many important features. These include large values of OCAPE in the Labrador, Greenland, Weddell and Mediterranean Seas, which are consistent with our present observations and understanding, but also identify some new features like the OCAPE pattern in the Antarctic Circumpolar Current (ACC). We propose that the diagnosis of OCAPE can improve our understanding of global patterns of ocean convection and deep water formation as well as ocean stratification, the meridional overturning circulation and mixed layer processes. The background of this work is briefly introduced as below. Open-ocean deep convection can significantly modify water properties both at the ocean surface and throughout the water column (Gordon 1982). Open-ocean convection is also an important mechanism for Ocean Deep Water formation and the transport of heat, freshwater and nutrient (Marshall and Schott 1999). Open-ocean convection may arise through strong surface buoyancy fluxes (Schott et al. 1996), or by thermobaric instability (Akitomo 1999a, b). Ingersoll (2005) demonstrated that thermobaric-induced deep convection is due to the abrupt release of ocean potential energy into kinetic energy. In atmospheric dynamics, Convective Available Potential Energy (CAPE) has long been an important thermodynamic variable (Arakawa and Schubert 1974) that has been used to forecast moist convection (Doswell and Rasmussen 1994) and to test the performance of GCMs (Ye et al. 1998). However, the development of a similar diagnostic in the ocean has received little attention.; World Ocean Convective Available Potential Energy distribution in North-Hemisphere Autumn (J/kg)

Direct observations of seasonal exchange through the Bab el Mandab Strait

NASA Astrophysics Data System (ADS)

Murray, Stephen P.; Johns, William

The exchange flow between the Red Sea and the Gulf of Aden-Indian Ocean through the Bab el Mandab Strait was measured continuously for 10 months, June 1995-March 1996. ADCP and temperature-salinity chain moorings allow an unprecedented look at the magnitude and seasonal evolution of the inflow layer from the Gulf of Aden, and the high salinity outflow layer from the Red Sea. The timing, structure, and evolution of the summer season mid-depth intrusion of cold, low salinity water into the Red Sea from the Gulf of Aden is measured for the complete intrusion cycle of 1995. We unexpectedly find the deep outflow still strong in June 1995, with speeds of 0.6 m/sec and transport of 0.4 Sv (1 Sv = 106 m³/sec). From July to mid-September, the deep outflow persists but is attenuated to speeds of 0.2 m/sec and transport of 0.05 Sv. The dominant summer feature, the cold low salinity intermediate layer intrusion, persists for 3 months, occupies 70% of the water column in the Strait and carries approximately 1.7 × 1012 m³ of cold nutrient-rich water into the Red Sea. The winter regime begins in mid-September, is fully developed by early November, and continues to the end of our first observation interval in March 1996. Speeds in the lower layer are 0.8-1.0 m/sec and 0.4-0.6 m/sec in the upper layer. At maximum exchange in mid-February, outflow transport reaches 0.7 Sv. Ubiquitous oscillations in current and salinity at synoptic and intraseasonal periods appear closely related to fluctuations in the along-channel wind forcing and perhaps to coastally-trapped waves.

View of cold water eddies in Falkland Current off southern Argentina

NASA Image and Video Library

1973-12-14

SL4-137-3608 (14 Dec. 1973) --- A view of cold water eddies in the Falkland Current off the South Atlantic coast of southern Argentina as seen from the Skylab space station in Earth orbit. This picture was taken by one of the Skylab 4 crewmen using a hand-held 70mm Hasselblad camera. This land area (left corner) extends south along the coast from Puerto Deseado (center left border) for about 50 miles. Within the ocean, several light blue areas are visible and represent the occurrence of plankton with the Falkland Current. Over the ocean, the cold water eddies are identified by the circular cloud-free areas within the cloud street pattern and bordered by cumulus cloud buildup (white). The cloud streets indicate the wind is from the southwest and do not form over eddies because energy form the atmosphere is absorbed by the cold ocean water. On the downwind side of the eddies, cumulus clouds tend to form as the cold moist air flows over the warmer water. Similar cloud and eddy features have been observed by the Skylab 4 crewmen in the Yucatan Current off Yucatan Peninsula and in some parts of the South Pacific. Studies are underway by Dr. George Maul, NOAA, and Dr. Robert Stevenson, ONR, to determine the significance of the cold water eddies to ocean dynamics. Photo credit: NASA

Effects of High Hydrostatic Pressure on Coastal Bacterial Community Abundance and Diversity

PubMed Central

Marietou, Angeliki

2014-01-01

Hydrostatic pressure is an important parameter influencing the distribution of microbial life in the ocean. In this study, the response of marine bacterial populations from surface waters to pressures representative of those under deep-sea conditions was examined. Southern California coastal seawater collected 5 m below the sea surface was incubated in microcosms, using a range of temperatures (16 to 3°C) and hydrostatic pressure conditions (0.1 to 80 MPa). Cell abundance decreased in response to pressure, while diversity increased. The morphology of the community also changed with pressurization to a predominant morphotype of small cocci. The pressure-induced community changes included an increase in the relative abundance of Alphaproteobacteria, Gammaproteobacteria, Actinobacteria, and Flavobacteria largely at the expense of Epsilonproteobacteria. Culturable high-pressure-surviving bacteria were obtained and found to be phylogenetically similar to isolates from cold and/or deep-sea environments. These results provide novel insights into the response of surface water bacteria to changes in hydrostatic pressure. PMID:25063663

Outlet Glacier-Ice Shelf-Ocean Interactions: Is the Tail Wagging the Dog?

NASA Astrophysics Data System (ADS)

Parizek, B. R.; Walker, R. T.; Rinehart, S. K.

2009-12-01

While the massive interior regions of the Antarctic and Greenland Ice Sheets are presently ``resting quietly", the lower elevations of many outlet glaciers are experiencing dramatic adjustments due to changes in ice dynamics and/or surface mass balance. Oceanic and/or atmospheric forcing in these marginal regions often leads to mass deficits for entire outlet basins. Therefore, coupling the wagging tail of ice-ocean interactions with the vast ice-sheet reservoirs is imperative for accurate assessments of future sea-level rise. To study ice-ocean dynamic processes, we couple an ocean-plume model that simulates ice-shelf basal melting rates based on temperature and salinity profiles combined with plume dynamics associated with the geometry of the ice-shelf cavity (following Jenkins, 1991 and Holland and Jenkins, 1999) with a two-dimensional, isothermal model of outlet glacier-ice shelf flow (as used in Alley et al., 2007; Walker et al., 2008; Parizek et al., in review). Depending on the assigned temperature and salinity profiles, the ocean model can simulate both water-mass end-members: either cold High Salinity Shelf Water (HSSW) or relatively warm Circumpolar Deep Water (CDW), as well as between-member conditions. Notably, the coupled system exhibits sensitivity to the initial conditions. In particular, melting concentrated near the grounding line has the greatest effect in forcing grounding-line retreat. Retreat is further enhanced by a positive feedback between the ocean and ice, as the focused melt near the grounding line leads to an increase in the local slope of the basal ice, thereby enhancing buoyancy-driven plume flow and subsequent melt rates.

Novel lineages of Prochlorococcus and Synechococcus in the global oceans.

PubMed

Huang, Sijun; Wilhelm, Steven W; Harvey, H Rodger; Taylor, Karen; Jiao, Nianzhi; Chen, Feng

2012-02-01

Picocyanobacteria represented by Prochlorococcus and Synechococcus have an important role in oceanic carbon fixation and nutrient cycling. In this study, we compared the community composition of picocyanobacteria from diverse marine ecosystems ranging from estuary to open oceans, tropical to polar oceans and surface to deep water, based on the sequences of 16S-23S rRNA internal transcribed spacer (ITS). A total of 1339 ITS sequences recovered from 20 samples unveiled diverse and several previously unknown clades of Prochlorococcus and Synechococcus. Six high-light (HL)-adapted Prochlorococcus clades were identified, among which clade HLVI had not been described previously. Prochlorococcus clades HLIII, HLIV and HLV, detected in the Equatorial Pacific samples, could be related to the HNLC clades recently found in the high-nutrient, low-chlorophyll (HNLC), iron-depleted tropical oceans. At least four novel Synechococcus clades (out of six clades in total) in subcluster 5.3 were found in subtropical open oceans and the South China Sea. A niche partitioning with depth was observed in the Synechococcus subcluster 5.3. Members of Synechococcus subcluster 5.2 were dominant in the high-latitude waters (northern Bering Sea and Chukchi Sea), suggesting a possible cold-adaptation of some marine Synechococcus in this subcluster. A distinct shift of the picocyanobacterial community was observed from the Bering Sea to the Chukchi Sea, which reflected the change of water temperature. Our study demonstrates that oceanic systems contain a large pool of diverse picocyanobacteria, and further suggest that new genotypes or ecotypes of picocyanobacteria will continue to emerge, as microbial consortia are explored with advanced sequencing technology.

Evolution of South Atlantic density and chemical stratification across the last deglaciation

PubMed Central

Skinner, Luke C.; Peck, Victoria L.; Kender, Sev; Elderfield, Henry; Waelbroeck, Claire; Hodell, David A.

2016-01-01

Explanations of the glacial–interglacial variations in atmospheric pCO2 invoke a significant role for the deep ocean in the storage of CO2. Deep-ocean density stratification has been proposed as a mechanism to promote the storage of CO2 in the deep ocean during glacial times. A wealth of proxy data supports the presence of a “chemical divide” between intermediate and deep water in the glacial Atlantic Ocean, which indirectly points to an increase in deep-ocean density stratification. However, direct observational evidence of changes in the primary controls of ocean density stratification, i.e., temperature and salinity, remain scarce. Here, we use Mg/Ca-derived seawater temperature and salinity estimates determined from temperature-corrected δ18O measurements on the benthic foraminifer Uvigerina spp. from deep and intermediate water-depth marine sediment cores to reconstruct the changes in density of sub-Antarctic South Atlantic water masses over the last deglaciation (i.e., 22–2 ka before present). We find that a major breakdown in the physical density stratification significantly lags the breakdown of the deep-intermediate chemical divide, as indicated by the chemical tracers of benthic foraminifer δ13C and foraminifer/coral 14C. Our results indicate that chemical destratification likely resulted in the first rise in atmospheric pCO2, whereas the density destratification of the deep South Atlantic lags the second rise in atmospheric pCO2 during the late deglacial period. Our findings emphasize that the physical and chemical destratification of the ocean are not as tightly coupled as generally assumed. PMID:26729858

Evolution of South Atlantic density and chemical stratification across the last deglaciation.

PubMed

Roberts, Jenny; Gottschalk, Julia; Skinner, Luke C; Peck, Victoria L; Kender, Sev; Elderfield, Henry; Waelbroeck, Claire; Vázquez Riveiros, Natalia; Hodell, David A

2016-01-19

Explanations of the glacial-interglacial variations in atmospheric pCO2 invoke a significant role for the deep ocean in the storage of CO2. Deep-ocean density stratification has been proposed as a mechanism to promote the storage of CO2 in the deep ocean during glacial times. A wealth of proxy data supports the presence of a "chemical divide" between intermediate and deep water in the glacial Atlantic Ocean, which indirectly points to an increase in deep-ocean density stratification. However, direct observational evidence of changes in the primary controls of ocean density stratification, i.e., temperature and salinity, remain scarce. Here, we use Mg/Ca-derived seawater temperature and salinity estimates determined from temperature-corrected δ(18)O measurements on the benthic foraminifer Uvigerina spp. from deep and intermediate water-depth marine sediment cores to reconstruct the changes in density of sub-Antarctic South Atlantic water masses over the last deglaciation (i.e., 22-2 ka before present). We find that a major breakdown in the physical density stratification significantly lags the breakdown of the deep-intermediate chemical divide, as indicated by the chemical tracers of benthic foraminifer δ(13)C and foraminifer/coral (14)C. Our results indicate that chemical destratification likely resulted in the first rise in atmospheric pCO2, whereas the density destratification of the deep South Atlantic lags the second rise in atmospheric pCO2 during the late deglacial period. Our findings emphasize that the physical and chemical destratification of the ocean are not as tightly coupled as generally assumed.

Shifting the Perspective: Artists in the Ocean

NASA Astrophysics Data System (ADS)

Van Dover, C. L.

2014-12-01

The deep ocean is to most of us a place unknown. Few of us experience the sea far from shore, fewer still dive to the seafloor at great depths. When scientists report on the outcome of deep-ocean exploration, their technical prose captures facts and insights, but fails to capture the emotional power of place and process. Through batik, watercolor illustrations, music, digital art, cartoon, and experimental video, six artists have created a portfolio of work that communicates the human experience of the deep ocean.

Monsoon control on faunal composition of planktic foraminifera in the Arabian Sea

NASA Astrophysics Data System (ADS)

Munz, P.; Siccha, M.; Kucera, M.; Schulz, H.

2013-12-01

Being among the most productive open ocean basins, sea surface properties in the Arabian Sea are highly influenced by the seasonal reversal of the monsoonal wind system. During boreal summer wind direction from the southwest induces strong upwelling along the coast off Somalia and Oman. Vertical transport of cold and nutrient-rich deep-water masses by Ekman pumping reduces sea surface temperature and triggers primary productivity. Reversed cold and dry winds during boreal winter lead to cooling of the surface- and subsurface-waters and hereby to deep convective mixing, bringing nutrients into the photic zone and enhancing primary productivity especially in the northern part of the Arabian Sea. Here, we study the influence of the different seasonal monsoon systems on the faunal composition of planktic foraminifera, in order to improve our understanding how the faunal community record is influenced by the respective monsoon systems and to provide baseline information for the reconstruction of ancient monsoon conditions. We used published core-top foraminiferal databases, significantly increased in spatial coverage by new contributions. The resulting combined database consists of 413 core-top samples spanning the Arabian Sea and the Northern Indian Ocean to 10° S. The seasonal sea surface properties at these stations could be binned into categories of different monsoon influence, based on satellite-derived chlorophyll-a concentrations. Interpretation of species response to environmental control is based on multivariate statistical analyses of each of the categorical bins. First results show that samples influenced only by winter- and summer monsoon conditions, respectively, feature specifiable faunal composition. Globigerina bulloides is mostly associated with summer upwelling conditions, whereas Globigerina falconensis and Pulleniatina obliquiloculata are typical species of winter conditions. Redundancy analysis reveals preferences of species populations with respect to particular environmental gradients and may help to disentangle winter- from summer monsoon impact on modern and fossil faunas.

A Deep-Sea Coral Clumped Isotope Record From Southern Ocean Intermediate Water Spanning the Most Recent Glacial Termination

NASA Astrophysics Data System (ADS)

Hines, S.; Eiler, J. M.; Adkins, J. F.

2015-12-01

Movement of intermediate waters plays an important role in global heat and carbon transport in the ocean and changes in their distribution are closely tied to glacial-interglacial climate change. Ocean temperature is necessarily linked to circulation because density is a function of temperature and salinity. In the modern ocean, stratification is dominated by differences in temperature, but this may not have been the case in the past. Coupled radiocarbon and U/Th dates on deep-sea Desmophyllum dianthus corals allow for the reconstruction of past intermediate water circulation rates. The addition of temperature measurements further aids in understanding of the mechanisms driving the observed signals, since there are different boundary conditions for resetting these two properties at the surface. In the modern Southern Ocean, temperature and radiocarbon are broadly correlated. At the surface there are meridional gradients of these properties, with colder, more radiocarbon-depleted water closer to the Antarctic continent. We present a high-resolution time series of clumped isotope temperature measurements on 30 corals spanning the Last Glacial Maximum through the end of the Antarctic Cold Reversal (ACR). These samples have previously been U/Th and radiocarbon dated. Corals were collected south of Tasmania from depths of between ~1450 - 1900 m, with 70% between 1500 and 1700 m. Uranium and thorium measurements were made by MC-ICP-MS on a ThermoFinnigan Neptune, radiocarbon was measured by AMS at the KCCAMS Laboratory at UC Irvine, and clumped isotope temperatures were measured on a MAT 253 attached to an automated carbonate preparation line. Preliminary results show constant temperature between ~20 - 18 ka, a gradual rise of ~6 ºC through Heinrich Stadial 1 (~18 - 15 ka), an abrupt drop of ~7 ºC directly preceeding the start of the Bølling at 14.7 ka, and another slight rise of ~4 ºC through the ACR (14.7 - 12.8 ka). The addition of clumped isotope temperatures to this time series allows for a unique examination of Southern Ocean dynamics through the most recent glacial termination.

Differential response of two Mediterranean cold-water coral species to ocean acidification

NASA Astrophysics Data System (ADS)

Movilla, Juancho; Orejas, Covadonga; Calvo, Eva; Gori, Andrea; López-Sanz, Àngel; Grinyó, Jordi; Domínguez-Carrió, Carlos; Pelejero, Carles

2014-09-01

Cold-water coral (CWC) reefs constitute one of the most complex deep-sea habitats harboring a vast diversity of associated species. Like other tropical or temperate framework builders, these systems are facing an uncertain future due to several threats, such as global warming and ocean acidification. In the case of Mediterranean CWC communities, the effect may be exacerbated due to the greater capacity of these waters to absorb atmospheric CO2 compared to the global ocean. Calcification in these organisms is an energy-demanding process, and it is expected that energy requirements will be greater as seawater pH and the availability of carbonate ions decrease. Therefore, studies assessing the effect of a pH decrease in skeletal growth, and metabolic balance are critical to fully understand the potential responses of these organisms under a changing scenario. In this context, the present work aims to investigate the medium- to long-term effect of a low pH scenario on calcification and the biochemical composition of two CWCs from the Mediterranean, Dendrophyllia cornigera and Desmophyllum dianthus. After 314 d of exposure to acidified conditions, a significant decrease of 70 % was observed in Desmophyllum dianthus skeletal growth rate, while Dendrophyllia cornigera showed no differences between treatments. Instead, only subtle differences between treatments were observed in the organic matter amount, lipid content, skeletal microdensity, or porosity in both species, although due to the high variability of the results, these differences were not statistically significant. Our results also confirmed a heterogeneous effect of low pH on the skeletal growth rate of the organisms depending on their initial weight, suggesting that those specimens with high calcification rates may be the most susceptible to the negative effects of acidification.

Use of a free ocean CO₂ enrichment (FOCE) system to evaluate the effects of ocean acidification on the foraging behavior of a deep-sea urchin.

PubMed

Barry, James P; Lovera, Chris; Buck, Kurt R; Peltzer, Edward T; Taylor, Josi R; Walz, Peter; Whaling, Patrick J; Brewer, Peter G

2014-08-19

The influence of ocean acidification in deep-sea ecosystems is poorly understood but is expected to be large because of the presumed low tolerance of deep-sea taxa to environmental change. We used a newly developed deep-sea free ocean CO2 enrichment (dp-FOCE) system to evaluate the potential consequences of future ocean acidification on the feeding behavior of a deep-sea echinoid, the sea urchin, Strongylocentrotus fragilis. The dp-FOCE system simulated future ocean acidification inside an experimental enclosure where observations of feeding behavior were performed. We measured the average movement (speed) of urchins as well as the time required (foraging time) for S. fragilis to approach its preferred food (giant kelp) in the dp-FOCE chamber (-0.46 pH units) and a control chamber (ambient pH). Measurements were performed during each of 4 trials (days -2, 2, 24, 27 after CO2 injection) during the month-long period when groups of urchins were continuously exposed to low pH or control conditions. Although urchin speed did not vary significantly in relation to pH or time exposed, foraging time was significantly longer for urchins in the low-pH treatment. This first deep-sea FOCE experiment demonstrated the utility of the FOCE system approach and suggests that the chemosensory behavior of a deep-sea urchin may be impaired by ocean acidification.

Implications of Warm Rain in Shallow Cumulus and Congestus Clouds for Large-Scale Circulations

NASA Astrophysics Data System (ADS)

Nuijens, Louise; Emanuel, Kerry; Masunaga, Hirohiko; L'Ecuyer, Tristan

2017-11-01

Space-borne observations reveal that 20-40% of marine convective clouds below the freezing level produce rain. In this paper we speculate what the prevalence of warm rain might imply for convection and large-scale circulations over tropical oceans. We present results using a two-column radiative-convective model of hydrostatic, nonlinear flow on a non-rotating sphere, with parameterized convection and radiation, and review ongoing efforts in high-resolution modeling and observations of warm rain. The model experiments investigate the response of convection and circulation to sea surface temperature (SST) gradients between the columns and to changes in a parameter that controls the conversion of cloud condensate to rain. Convection over the cold ocean collapses to a shallow mode with tops near 850 hPa, but a congestus mode with tops near 600 hPa can develop at small SST differences when warm rain formation is more efficient. Here, interactive radiation and the response of the circulation are crucial: along with congestus a deeper moist layer develops, which leads to less low-level radiative cooling, a smaller buoyancy gradient between the columns, and therefore a weaker circulation and less subsidence over the cold ocean. The congestus mode is accompanied with more surface precipitation in the subsiding column and less surface precipitation in the deep convecting column. For the shallow mode over colder oceans, circulations also weaken with more efficient warm rain formation, but only marginally. Here, more warm rain reduces convective tops and the boundary layer depth—similar to Large-Eddy Simulation (LES) studies—which reduces the integrated buoyancy gradient. Elucidating the impact of warm rain can benefit from large-domain high-resolution simulations and observations. Parameterizations of warm rain may be constrained through collocated cloud and rain profiling from ground, and concurrent changes in convection and rain in subsiding and convecting branches of circulations may be revealed from a collocation of space-borne sensors, including the Global Precipitation Measurement (GPM) and upcoming Aeolus missions.

Decade-long deep-ocean warming detected in the subtropical South Pacific

PubMed Central

Volkov, Denis L.; Lee, Sang-Ki; Landerer, Felix W.; Lumpkin, Rick

2017-01-01

The persistent energy imbalance at the top of the atmosphere, inferred from satellite measurements, indicates that the Earth’s climate system continues to accumulate excess heat. As only sparse and irregular measurements of ocean heat below 2000 m depth exist, one of the most challenging questions in global climate change studies is whether the excess heat has already penetrated into the deep ocean. Here we perform a comprehensive analysis of satellite and in situ measurements to report that a significant deep-ocean warming occurred in the subtropical South Pacific Ocean over the past decade (2005–2014). The local accumulation of heat accounted for up to a quarter of the global ocean heat increase, with directly and indirectly inferred deep ocean (below 2000 m) contribution of 2.4 ± 1.4 and 6.1–10.1 ± 4.4%, respectively. We further demonstrate that this heat accumulation is consistent with a decade-long intensification of the subtropical convergence, possibly linked to the persistent La Niña-like state. PMID:29200536

Decade-long deep-ocean warming detected in the subtropical South Pacific.

PubMed

Volkov, Denis L; Lee, Sang-Ki; Landerer, Felix W; Lumpkin, Rick

2017-01-28

The persistent energy imbalance at the top of the atmosphere, inferred from satellite measurements, indicates that the Earth's climate system continues to accumulate excess heat. As only sparse and irregular measurements of ocean heat below 2000 m depth exist, one of the most challenging questions in global climate change studies is whether the excess heat has already penetrated into the deep ocean. Here we perform a comprehensive analysis of satellite and in situ measurements to report that a significant deep-ocean warming occurred in the subtropical South Pacific Ocean over the past decade (2005-2014). The local accumulation of heat accounted for up to a quarter of the global ocean heat increase, with directly and indirectly inferred deep ocean (below 2000 m) contribution of 2.4 ± 1.4 and 6.1-10.1 ± 4.4%, respectively. We further demonstrate that this heat accumulation is consistent with a decade-long intensification of the subtropical convergence, possibly linked to the persistent La Niña-like state.

New Planetary Energy Balance, Ocean-Atmosphere Interaction and their Effects on Extreme Events in North Atlantic

NASA Astrophysics Data System (ADS)

Karrouk, Mohammed-Said

2016-04-01

Global warming has now reached the energetic phase of H2O's return to the ground after the saturation of the atmosphere in evaporation since the 80s and 90s of the last century, which were characterized by severe droughts, mainly in Africa. This phase is the result of the accumulation of thermal energy exchanges in the Earth-Ocean-Atmosphere system that resulted in the thrust reversal of the energy balance toward the poles. This situation is characterized by a new thermal distribution: above the ocean, the situation is more in surplus compared to the mainland, or even opposite when the balance is negative on the land, and in the atmosphere, warm thermal advection easily reach the North Pole (planetary crests), as well as cold advection push deep into North Africa and the Gulf of Mexico (planetary valleys). This "New Ground Energy Balance" establishes a "New Meridian Atmospheric Circulation (MAC)" with an undulating character throughout the year, including the winter characterized by intense latitudinal very active energy exchanges between the surplus areas (tropical) and the deficit (polar) on the one hand, and the atmosphere, the ocean and the continent on the other. The excess radiation balance increases the potential evaporation of the atmosphere and provides a new geographical distribution of H2O worldwide: the excess water vapor is easily converted by cold advection (polar vortex) to heavy rains that cause floods or snow storms that paralyze the normal functioning of human activities, which creates many difficulties for users and leaves damage and casualties, but ensures water availability missing since a long time in many parts of the world, in Africa, Europe and America. The new thermal distribution reorganizes the geography of atmospheric pressure: the ocean energy concentration is transmitted directly to the atmosphere, and the excess torque is pushed northward. The Azores anticyclone is strengthened and is a global lock by the Atlantic ridge at Greenland, which imposes on the jet stream a positive ripple, very strongly marked poleward, bringing cosmic cold advection of polar air masses winter over from Europe to North Africa. Hence the enormous meridian heat exchanges north-south, and south-north. This new spatial thermal provision therefore imposes on the jet-stream a positive ripple on the North Atlantic (Greenland) and eastern Pacific (Alaska); this is the cause of the heat and drought of California, followed by negative waves in eastern US, and Europe. This is the "New Atmospheric Circulation" predominantly "Meridian", due to the "New Climate" caused by global warming.

Economic contribution of 'artificial upwelling' mariculture to sea-thermal power generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roels, O.A.

1976-07-01

Deep-sea water has two valuable properties: it is uniformly cold and, compared to surface water, it is rich in nutrients such as nitrate and phosphate which are necessary for plant growth. In tropical and subtropical areas, the temperature difference between the warm surface water and the cold deep water can be used for sea-thermal power generation or other cooling applications such as air-conditioning, ice-making, desalination, and cooling of refineries, power plants, etc. Once the deep water is brought to the surface, utilization of both the cold temperature and the nutrient content is likely to be more advantageous than the usemore » of only one of them. Claude demonstrated the technical feasibility of sea-thermal power generation in Cuba in 1930. The technical feasibility of artificial upwelling mariculture in the St. Croix installation has been demonstrated. Results to date demonstrate that the gross sales value of the potential mariculture yield from a given volume of deep-sea water is many times that of the sales value of the power which can be generated by the Claude process from the same volume of deep water. Utilizing both the nutrient content and the cold temperature of the deep water may therefore make sea-thermal power generation economically feasible.« less

Convective structure of the planetary boundary layer of the ocean during gale

NASA Technical Reports Server (NTRS)

Melfi, S. H.; Boers, R.

1986-01-01

The structure of the Planetary Boundary Layer (PBL) was measured, using an airborne lidar, over the Atlantic Ocean during several intensive observation periods of the Genesis of Atlantic Lows Experiment (GALE). Primary emphasis is on the understanding of the convective structure within the PBL during cold air outbreaks. Cold outbreaks generally occur in between the development of coastal storms; and behind a cold front sweeping down from Canada out across the Atlantic. As the cold dry air moves over the relatively warm ocean, it is heated and moistened. The transfer of latent and sensible heat during these events accounts for most of the heat transfer between the ocean and atmosphere during winter. Moistening of the PBL during these eventsis believed to be an important factor in determining the strength of development of the storm system which follows. In general, the more PBL moisture available as latent heat the higher the probability the storm will intensify. The major mechanism for vertical mixing of heat and mositure within the PBL is cellular convection. Knowlede of the organization and structure of the convection is important for understanding the process.

The transcriptome of Bathymodiolus azoricus gill reveals expression of genes from endosymbionts and free-living deep-sea bacteria.

PubMed

Egas, Conceição; Pinheiro, Miguel; Gomes, Paula; Barroso, Cristina; Bettencourt, Raul

2012-08-01

Deep-sea environments are largely unexplored habitats where a surprising number of species may be found in large communities, thriving regardless of the darkness, extreme cold, and high pressure. Their unique geochemical features result in reducing environments rich in methane and sulfides, sustaining complex chemosynthetic ecosystems that represent one of the most surprising findings in oceans in the last 40 years. The deep-sea Lucky Strike hydrothermal vent field, located in the Mid Atlantic Ridge, is home to large vent mussel communities where Bathymodiolus azoricus represents the dominant faunal biomass, owing its survival to symbiotic associations with methylotrophic or methanotrophic and thiotrophic bacteria. The recent transcriptome sequencing and analysis of gill tissues from B. azoricus revealed a number of genes of bacterial origin, hereby analyzed to provide a functional insight into the gill microbial community. The transcripts supported a metabolically active microbiome and a variety of mechanisms and pathways, evidencing also the sulfur and methane metabolisms. Taxonomic affiliation of transcripts and 16S rRNA community profiling revealed a microbial community dominated by thiotrophic and methanotrophic endosymbionts of B. azoricus and the presence of a Sulfurovum-like epsilonbacterium.

Mobile Robot for Exploring Cold Liquid/Solid Environments

NASA Technical Reports Server (NTRS)

Bergh, Charles; Zimmerman, Wayne

2006-01-01

The Planetary Autonomous Amphibious Robotic Vehicle (PAARV), now at the prototype stage of development, was originally intended for use in acquiring and analyzing samples of solid, liquid, and gaseous materials in cold environments on the shores and surfaces, and at shallow depths below the surfaces, of lakes and oceans on remote planets. The PAARV also could be adapted for use on Earth in similar exploration of cold environments in and near Arctic and Antarctic oceans and glacial and sub-glacial lakes.

Hydrothermal systems are a sink for dissolved black carbon in the deep ocean

NASA Astrophysics Data System (ADS)

Niggemann, J.; Hawkes, J. A.; Rossel, P. E.; Stubbins, A.; Dittmar, T.

2016-02-01

Exposure to heat during fires on land or geothermal processes in Earth's crust induces modifications in the molecular structure of organic matter. The products of this thermogenesis are collectively termed black carbon. Dissolved black carbon (DBC) is a significant component of the oceanic dissolved organic carbon (DOC) pool. In the deep ocean, DBC accounts for 2% of DOC and has an apparent radiocarbon age of 18,000 years. Thus, DBC is much older than the bulk DOC pool, suggesting that DBC is highly refractory. Recently, it has been shown that recalcitrant deep-ocean DOC is efficiently removed during hydrothermal circulation. Here, we hypothesize that hydrothermal circulation is also a net sink for deep ocean DBC. We analyzed DBC in samples collected at different vent sites in the Atlantic, Pacific and Southern oceans. DBC was quantified in solid-phase extracts as benzenepolycarboxylic acids (BPCAs) following nitric acid digestion. Concentrations of DBC were much lower in hydrothermal fluids than in surrounding deep ocean seawater, confirming that hydrothermal circulation acts as a net sink for oceanic DBC. The relative contribution of DBC to bulk DOC did not change during hydrothermal circulation, indicating that DBC is removed at similar rates as bulk DOC. The ratio of the oxidation products benzenehexacarboxylic acid (B6CA) to benzenepentacarboxylic acid (B5CA) was significantly higher in hydrothermally altered samples compared to ratios typically found in the deep ocean, reflecting a higher degree of condensation of DBC molecules after hydrothermal circulation. Our study identified hydrothermal circulation as a quantitatively important sink for refractory DBC in the deep ocean. In contrast to photodegradation of DBC at the sea surface, which is more efficient for more condensed DBC, i.e. decreasing the B6CA/B5CA ratio, hydrothermal processing increases the B6CA/B5CA ratio, introducing a characteristic hydrothermal DBC signature.

Deep Water Ocean Acoustics

DTIC Science & Technology

2016-08-03

Militia Drive Lexington, MA 02421 Date Submitted: Aug 3, 2016 Notices : Distribution Statement A. Approved for public release...distribution is unlimited. OASIS, INC. 2 Report No. QSR-14C0172-Ocean Acoustics-063016 Contents Notices ...the impact of the ocean and seafloor environmental variability on deep-water (long-range) ocean acoustic propagation and to develop methodologies

The salinity, temperature, and delta18O of the glacial deep ocean.

PubMed

Adkins, Jess F; McIntyre, Katherine; Schrag, Daniel P

2002-11-29

We use pore fluid measurements of the chloride concentration and the oxygen isotopic composition from Ocean Drilling Program cores to reconstruct salinity and temperature of the deep ocean during the Last Glacial Maximum (LGM). Our data show that the temperatures of the deep Pacific, Southern, and Atlantic oceans during the LGM were relatively homogeneous and within error of the freezing point of seawater at the ocean's surface. Our chloride data show that the glacial stratification was dominated by salinity variations, in contrast with the modern ocean, for which temperature plays a primary role. During the LGM the Southern Ocean contained the saltiest water in the deep ocean. This reversal of the modern salinity contrast between the North and South Atlantic implies that the freshwater budget at the poles must have been quite different. A strict conversion of mean salinity at the LGM to equivalent sea-level change yields a value in excess of 140 meters. However, the storage of fresh water in ice shelves and/or groundwater reserves implies that glacial salinity is a poor predictor of mean sea level.

Objective estimates of mantle 3He in the ocean and implications for constraining the deep ocean circulation

NASA Astrophysics Data System (ADS)

Holzer, Mark; DeVries, Timothy; Bianchi, Daniele; Newton, Robert; Schlosser, Peter; Winckler, Gisela

2017-01-01

Hydrothermal vents along the ocean's tectonic ridge systems inject superheated water and large amounts of dissolved metals that impact the deep ocean circulation and the oceanic cycling of trace metals. The hydrothermal fluid contains dissolved mantle helium that is enriched in 3He relative to the atmosphere, providing an isotopic tracer of the ocean's deep circulation and a marker of hydrothermal sources. This work investigates the potential for the 3He/4He isotope ratio to constrain the ocean's mantle 3He source and to provide constraints on the ocean's deep circulation. We use an ensemble of 11 data-assimilated steady-state ocean circulation models and a mantle helium source based on geographically varying sea-floor spreading rates. The global source distribution is partitioned into 6 regions, and the vertical profile and source amplitude of each region are varied independently to determine the optimal 3He source distribution that minimizes the mismatch between modeled and observed δ3He. In this way, we are able to fit the observed δ3He distribution to within a relative error of ∼15%, with a global 3He source that ranges from 640 to 850 mol yr-1, depending on circulation. The fit captures the vertical and interbasin gradients of the δ3He distribution very well and reproduces its jet-sheared saddle point in the deep equatorial Pacific. This demonstrates that the data-assimilated models have much greater fidelity to the deep ocean circulation than other coarse-resolution ocean models. Nonetheless, the modelled δ3He distributions still display some systematic biases, especially in the deep North Pacific where δ3He is overpredicted by our models, and in the southeastern tropical Pacific, where observed westward-spreading δ3He plumes are not well captured. Sources inferred by the data-assimilated transport with and without isopycnally aligned eddy diffusivity differ widely in the Southern Ocean, in spite of the ability to match the observed distributions of CFCs and radiocarbon for either eddy parameterization.

Evidence for infragravity wave-tide resonance in deep oceans.

PubMed

Sugioka, Hiroko; Fukao, Yoshio; Kanazawa, Toshihiko

2010-10-05

Ocean tides are the oscillatory motions of seawater forced by the gravitational attraction of the Moon and Sun with periods of a half to a day and wavelengths of the semi-Pacific to Pacific scale. Ocean infragravity (IG) waves are sea-surface gravity waves with periods of several minutes and wavelengths of several dozen kilometres. Here we report the first evidence of the resonance between these two ubiquitous phenomena, mutually very different in period and wavelength, in deep oceans. The evidence comes from long-term, large-scale observations with arrays of broadband ocean-bottom seismometers located at depths of more than 4,000 m in the Pacific Ocean. This observational evidence is substantiated by a theoretical argument that IG waves and the tide can resonantly couple and that such coupling occurs over unexpectedly wide areas of the Pacific Ocean. Through this resonant coupling, some of ocean tidal energy is transferred in deep oceans to IG wave energy.

The oxygenation of the atmosphere and oceans

PubMed Central

Holland, Heinrich D

2006-01-01

The last 3.85 Gyr of Earth history have been divided into five stages. During stage 1 (3.85–2.45 Gyr ago (Ga)) the atmosphere was largely or entirely anoxic, as were the oceans, with the possible exception of oxygen oases in the shallow oceans. During stage 2 (2.45–1.85 Ga) atmospheric oxygen levels rose to values estimated to have been between 0.02 and 0.04 atm. The shallow oceans became mildly oxygenated, while the deep oceans continued anoxic. Stage 3 (1.85–0.85 Ga) was apparently rather ‘boring’. Atmospheric oxygen levels did not change significantly. Most of the surface oceans were mildly oxygenated, as were the deep oceans. Stage 4 (0.85–0.54 Ga) saw a rise in atmospheric oxygen to values not much less than 0.2 atm. The shallow oceans followed suit, but the deep oceans were anoxic, at least during the intense Neoproterozoic ice ages. Atmospheric oxygen levels during stage 5 (0.54 Ga–present) probably rose to a maximum value of ca 0.3 atm during the Carboniferous before returning to its present value. The shallow oceans were oxygenated, while the oxygenation of the deep oceans fluctuated considerably, perhaps on rather geologically short time-scales. PMID:16754606

Cold Fronts in RegCM/HadGEM simulations over South America

NASA Astrophysics Data System (ADS)

Pampuch, Luana; Marcos de Jesus, Eduardo; Porfírio da Rocha, Rosmeri; Ambrizzi, Tércio

2017-04-01

Cold front is one of the most important systems that contribute for precipitation over South America. The representation of this system in climate models is important for a better representation of the precipitation. The Regional Climate Model RegCM is widely used for climate studies in South America, being important to understand how this model represents the cold fronts. A climatology (from 1979-2004) of the number of cold fronts in each season for RegCM4 simulations over South America CORDEX domain nested in HadGEM2-ES. The simulated climatology was compared with ERA-Interim reanalysis cold fronts climatology over the South America and adjacent South Atlantic Ocean. The cold fronts tracking for the model and the reanalysis were performed using an objective methodology based on decrease of air temperature in 925hPa, shift of meridional wind in 925hPa from northern to southern quadrant and increased in sea level pressure. The main differences were observed on summer and winter. On summer the model overestimate the number of cold fronts over southeastern South America and adjacent Atlantic Ocean; and underestimate it over central-south Argentina and Atlantic Ocean. On winter, the signs were opposite of that summer. On autumn and spring the differences were smaller and occurs mainly over all South Atlantic and north Argentina.

In situ Detection of Microbial Life in the Deep Biosphere in Igneous Ocean Crust.

PubMed

Salas, Everett C; Bhartia, Rohit; Anderson, Louise; Hug, William F; Reid, Ray D; Iturrino, Gerardo; Edwards, Katrina J

2015-01-01

The deep biosphere is a major frontier to science. Recent studies have shown the presence and activity of cells in deep marine sediments and in the continental deep biosphere. Volcanic lavas in the deep ocean subsurface, through which substantial fluid flow occurs, present another potentially massive deep biosphere. We present results from the deployment of a novel in situ logging tool designed to detect microbial life harbored in a deep, native, borehole environment within igneous oceanic crust, using deep ultraviolet native fluorescence spectroscopy. Results demonstrate the predominance of microbial-like signatures within the borehole environment, with densities in the range of 10(5) cells/mL. Based on transport and flux models, we estimate that such a concentration of microbial cells could not be supported by transport through the crust, suggesting in situ growth of these communities.

Ubiquitous healthy diatoms in the deep sea confirm deep carbon injection by the biological pump

PubMed Central

Agusti, S.; González-Gordillo, J. I.; Vaqué, D.; Estrada, M.; Cerezo, M. I.; Salazar, G.; Gasol, J. M.; Duarte, C. M.

2015-01-01

The role of the ocean as a sink for CO2 is partially dependent on the downward transport of phytoplankton cells packaged within fast-sinking particles. However, whether such fast-sinking mechanisms deliver fresh organic carbon down to the deep bathypelagic sea and whether this mechanism is prevalent across the ocean requires confirmation. Here we report the ubiquitous presence of healthy photosynthetic cells, dominated by diatoms, down to 4,000 m in the deep dark ocean. Decay experiments with surface phytoplankton suggested that the large proportion (18%) of healthy photosynthetic cells observed, on average, in the dark ocean, requires transport times from a few days to a few weeks, corresponding to sinking rates (124–732 m d−1) comparable to those of fast-sinking aggregates and faecal pellets. These results confirm the expectation that fast-sinking mechanisms inject fresh organic carbon into the deep sea and that this is a prevalent process operating across the global oligotrophic ocean. PMID:26158221

Ocean science: Radiocarbon variability in the western North Atlantic during the last deglaciation

USGS Publications Warehouse

Robinson, L.F.; Adkins, J.F.; Keigwin, L.D.; Southon, J.; Fernandez, D.P.; Wang, S.-L.; Scheirer, D.S.

2005-01-01

We present a detailed history of glacial to Holocene radiocarbon in the deep western North Atlantic from deep-sea corals and paired benthic-planktonic foraminifera. The deglaciation is marked by switches between radiocarbon-enriched and -depleted waters, leading to large radiocarbon gradients in the water column. These changes played an important role in modulating atmospheric radiocarbon. The deep-ocean record supports the notion of a bipolar seesaw with increased Northern-source deep-water formation linked to Northern Hemisphere warming and the reverse. In contrast, the more frequent radiocarbon variations in the intermediate/deep ocean are associated with roughly synchronous changes at the poles.

Ocean sequestration of crop residue carbon: recycling fossil fuel carbon back to deep sediments.

PubMed

Strand, Stuart E; Benford, Gregory

2009-02-15

For significant impact any method to remove CO2 from the atmosphere must process large amounts of carbon efficiently, be repeatable, sequester carbon for thousands of years, be practical, economical and be implemented soon. The only method that meets these criteria is removal of crop residues and burial in the deep ocean. We show here that this method is 92% efficient in sequestration of crop residue carbon while cellulosic ethanol production is only 32% and soil sequestration is about 14% efficient. Deep ocean sequestration can potentially capture 15% of the current global CO2 annual increase, returning that carbon backto deep sediments, confining the carbon for millennia, while using existing capital infrastructure and technology. Because of these clear advantages, we recommend enhanced research into permanent sequestration of crop residues in the deep ocean.

U, Th, and Pb isotopes in hot springs on the Juan de Fuca Ridge

NASA Technical Reports Server (NTRS)

Chen, J. H.

1987-01-01

Concentrations and isotopic compositions of U, Th, and Pb in three hydrothermal fluids from the Juan de Fuca Ridge were determined from samples obtained by the Alvin submersible. The samples were enriched in Pb and Th relative to deep-sea water, and were deficient in U. No clear relationship with Mg was found, suggesting nonideal mixing between the hot hydrothermal fluids and the cold ambient seawater. Values for U-234/U-238 have a seawater signature, and show a U-234 enrichment relative to the equilibrium value. The Pb isotopic composition has a uniform midocean ridge basalt signature, and it is suggested that Pb in these fluids may represent the best average value of the local oceanic crust.

Upper Ocean Response to the Atmospheric Cold Pools Associated With the Madden-Julian Oscillation

NASA Astrophysics Data System (ADS)

Pei, Suyang; Shinoda, Toshiaki; Soloviev, Alexander; Lien, Ren-Chieh

2018-05-01

Atmospheric cold pools are frequently observed during the Madden-Julian Oscillation events and play an important role in the development and organization of large-scale convection. They are generally associated with heavy precipitation and strong winds, inducing large air-sea fluxes and significant sea surface temperature (SST) fluctuations. This study provides a first detailed investigation of the upper ocean response to the strong cold pools associated with the Madden-Julian Oscillation, based on the analysis of in situ data collected during the Dynamics of the Madden-Julian Oscillation (DYNAMO) field campaign and one-dimensional ocean model simulations validated by the data. During strong cold pools, SST drops rapidly due to the atmospheric cooling in a shoaled mixed layer caused by the enhanced near-surface salinity stratification generated by heavy precipitation. Significant contribution also comes from the component of surface heat flux produced by the cold rain temperature. After the period of heavy rain, while net surface cooling remains, SST gradually recovers due to the enhanced entrainment of warmer waters below the mixed layer.

Using Argo-O2 data to examine the impact of deep-water formation events on oxygen uptake in the Labrador Sea

NASA Astrophysics Data System (ADS)

Wolf, M. K.; Hamme, R. C.; Gilbert, D.; Yashayaev, I.

2016-02-01

Deep-water formation allows the deep ocean to communicate with the atmosphere, facilitating exchanges of heat as well as important gases such as CO2 and oxygen. The Labrador Sea is the most studied location of deep convection in the North Atlantic Ocean and a strong contributor to the global thermohaline circulation. Since there are no internal sources of oxygen below the euphotic zone, deep-water formation is vital for oxygen transport to the deep ocean. Recent studies document large interannual variability in the strength and depth of convection in the Labrador Sea, from mixed layers of 100m to greater than 1000m. A weakening of this deep convection starves the deep ocean of oxygen, disrupting crucial deep sea biological processes, as well as reducing oceanic CO2 uptake and ocean circulation. We used data from the extensive Argo float network to examine these deep-water formation events in the Labrador Sea. The oxygen optodes onboard many Argo floats suffer from biases whose amplitude must be determined; therefore we investigated and applied various optode calibration methods. Using calibrated vertical profiles of oxygen, temperature, and salinity, we observed the timing, magnitude, and location of deep convection, restratification, and spring phytoplankton blooms. In addition, we used surface oxygen values along with NCEP wind speeds to calculate the air-sea oxygen flux using a range of air-sea gas exchange parameterizations. We then compared this oxygen flux to the rate of change of the measured oxygen inventory. Where the inventory and flux did not agree, we identified other oceanic processes such as biological activity or lateral advection of water masses occurring, or advection of the float itself into a new area. The large role that horizontal advection of water or the float has on oxygen uptake and cycling leads us to conclude that this data cannot be easily interpreted as a 1-D system. Oxygen exchanges with the atmosphere at a faster rate than CO2, is more affected by bubble injection, and reacts differently to temperature change. Oxygen is also produced and consumed by photosynthesis and respiration respectively at a specific ratio to CO2. These properties enable us to use oxygen as a separate constraint from carbon to determine the effect these various processes have on gas cycling, and the global ocean circulation.

Statistical Features of Deep-ocean Tsunamis Based on 30 Years of Bottom Pressure Observations in the Northeast Pacific

NASA Astrophysics Data System (ADS)

Fine, I.; Thomson, R.; Chadwick, W. W., Jr.; Davis, E. E.; Fox, C. G.

2016-12-01

We have used a set of high-resolution bottom pressure recorder (BPR) time series collected at Axial Seamount on the Juan de Fuca Ridge beginning in 1986 to examine tsunami waves of seismological origin in the northeast Pacific. These data are a combination of autonomous, internally-recording battery-powered instruments and cabled instruments on the OOI Cabled Array. Of the total of 120 tsunami events catalogued for the coasts of Japan, Alaska, western North America and Hawaii, we found evidence for 38 events in the Axial Seamount BPR records. Many of these tsunamis were not observed along the adjacent west coast of the USA and Canada because of the much higher noise level of coastal locations and the lack of digital tide gauge data prior to 2000. We have also identified several tsunamis of apparent seismological origin that were observed at coastal stations but not at the deep ocean site. Careful analysis of these observations suggests that they were likely of meteorological origin. Analysis of the pressure measurements from Axial Seamount, along with BPR measurements from a nearby ODP CORK (Ocean Drilling Program Circulation Obviation Retrofit Kit) borehole and DART (Deep-ocean Assessment and Reporting of Tsunamis) locations, reveals features of deep-ocean tsunamis that are markedly different from features observed at coastal locations. Results also show that the energy of deep-ocean tsunamis can differ significantly among the three sets of stations despite their close spatial spacing and that this difference is strongly dependent on the direction of the incoming tsunami waves. These deep-ocean observations provide the most comprehensive statistics possible for tsunamis in the Pacific Ocean over the past 30 years. New insight into the distribution of tsunami amplitudes and wave energy derived from the deep-ocean sites should prove useful for long-term tsunami prediction and mitigation for coastal communities along the west coast of the USA and Canada.

The Effects of Natural Iron Fertilisation on Deep-Sea Ecology: The Crozet Plateau, Southern Indian Ocean

PubMed Central

Wolff, George A.; Billett, David S. M.; Bett, Brian J.; Holtvoeth, Jens; FitzGeorge-Balfour, Tania; Fisher, Elizabeth H.; Cross, Ian; Shannon, Roger; Salter, Ian; Boorman, Ben; King, Nicola J.; Jamieson, Alan; Chaillan, Frédéric

2011-01-01

The addition of iron to high-nutrient low-chlorophyll (HNLC) oceanic waters stimulates phytoplankton, leading to greater primary production. Large-scale artificial ocean iron fertilization (OIF) has been proposed as a means of mitigating anthropogenic atmospheric CO2, but its impacts on ocean ecosystems below the photic zone are unknown. Natural OIF, through the addition of iron leached from volcanic islands, has been shown to enhance primary productivity and carbon export and so can be used to study the effects of OIF on life in the ocean. We compared two closely-located deep-sea sites (∼400 km apart and both at ∼4200 m water depth) to the East (naturally iron fertilized; +Fe) and South (HNLC) of the Crozet Islands in the southern Indian Ocean. Our results suggest that long-term geo-engineering of surface oceanic waters via artificial OIF would lead to significant changes in deep-sea ecosystems. We found that the +Fe area had greater supplies of organic matter inputs to the seafloor, including polyunsaturated fatty acid and carotenoid nutrients. The +Fe site also had greater densities and biomasses of large deep-sea animals with lower levels of evenness in community structuring. The species composition was also very different, with the +Fe site showing similarities to eutrophic sites in other ocean basins. Moreover, major differences occurred in the taxa at the +Fe and HNLC sites revealing the crucial role that surface oceanic conditions play in changing and structuring deep-sea benthic communities. PMID:21695118

Intensified diapycnal mixing in the midlatitude western boundary currents.

PubMed

Jing, Zhao; Wu, Lixin

2014-12-10

The wind work on oceanic near-inertial motions is suggested to play an important role in furnishing the diapycnal mixing in the deep ocean which affects the uptake of heat and carbon by the ocean as well as climate changes. However, it remains a puzzle where and through which route the near-inertial energy penetrates into the deep ocean. Using the measurements collected in the Kuroshio extension region during January 2005, we demonstrate that the diapycnal mixing in the thermocline and deep ocean is tightly related to the shear variance of wind-generated near-inertial internal waves with the diapycnal diffusivity 6 × 10(-5) m(2)s(-1) almost an order stronger than that observed in the circulation gyre. It is estimated that 45%-62% of the local near-inertial wind work 4.5 × 10(-3) Wm(-2) radiates into the thermocline and deep ocean and accounts for 42%-58% of the energy required to furnish mixing there. The elevated mixing is suggested to be maintained by the energetic near-inertial wind work and strong eddy activities causing enhanced downward near-inertial energy flux than earlier findings. The western boundary current turns out to be a key region for the penetration of near-inertial energy into the deep ocean and a hotspot for the diapycnal mixing in winter.

Global rates of mantle serpentinization and H2 release at oceanic transform faults

NASA Astrophysics Data System (ADS)

Ruepke, Lars; Hasenclever, Joerg

2017-04-01

The cycling of seawater through the ocean floor is the dominant mechanism of biogeochemical exchange between the solid earth and the global ocean. Crustal fluid flow appears to be typically associated with major seafloor structures, and oceanic transform faults (OTF) are one of the most striking yet poorly understood features of the global mid-ocean ridge systems. Fracture zones and transform faults have long been hypothesized to be sites of substantial biogeochemical exchange between the solid Earth and the global ocean. This is particularly interesting with regard to the ocean biome. Deep ocean ecosystems constitute 60% of it but their role in global ocean biogeochemical cycles is much overlooked. There is growing evidence that life is supported by chemosynthesis at hydrothermal vents but also in the crust, and therefore this may be a more abundant process than previously thought. In this context, the serpentine forming interaction between seawater and cold lithospheric mantle rocks is particularly interesting as it is also a mechanism of abiotic hydrogen and methane formation. Interestingly, a quantitative global assessment of mantle serpentinization at oceanic transform faults in the context of the biogeochemical exchange between the seafloor and the global ocean is still largely missing. Here we present the results of a set of 3-D thermo-mechanical model calculations that investigate mantle serpentinization at OTFs for the entire range of globally observed slip rates and fault lengths. These visco-plastic models predict the OTF thermal structure and the location of crustal-scale brittle deformation, which is a prerequisite for mantle serpentinization to occur. The results of these simulations are integrated with information on the global distribution of OTF lengths and slip rates yielding global estimates on mantle serpentinization and associated H2 release. We find that OTFs are potentially sites of intense crustal fluid flow and are in terms of H2 release almost as important as MOR-related serpentinization.

In situ Detection of Microbial Life in the Deep Biosphere in Igneous Ocean Crust

PubMed Central

Salas, Everett C.; Bhartia, Rohit; Anderson, Louise; Hug, William F.; Reid, Ray D.; Iturrino, Gerardo; Edwards, Katrina J.

2015-01-01

The deep biosphere is a major frontier to science. Recent studies have shown the presence and activity of cells in deep marine sediments and in the continental deep biosphere. Volcanic lavas in the deep ocean subsurface, through which substantial fluid flow occurs, present another potentially massive deep biosphere. We present results from the deployment of a novel in situ logging tool designed to detect microbial life harbored in a deep, native, borehole environment within igneous oceanic crust, using deep ultraviolet native fluorescence spectroscopy. Results demonstrate the predominance of microbial-like signatures within the borehole environment, with densities in the range of 105 cells/mL. Based on transport and flux models, we estimate that such a concentration of microbial cells could not be supported by transport through the crust, suggesting in situ growth of these communities. PMID:26617595

Deep Water Ocean Acoustics (DWOA): The Philippine Sea, OBSANP, and THAAW Experiments

DTIC Science & Technology

2015-09-30

the travel times. 4 The ocean state estimates were then re-computed to fit the acoustic travel times as integrals of the sound speed, and...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Deep Water Ocean Acoustics (DWOA): The Philippine Sea...deep-water acoustic propagation and ambient noise has been collected in a wide variety of environments over the last few years with ONR support

Numerical analysis of seawater circulation in carbonate platforms: I. Geothermal convection

USGS Publications Warehouse

Sanford, W.E.; Whitaker, F.F.; Smart, P.L.; Jones, G.

1998-01-01

Differences in fluid density between cold ocean water and warm ground water can drive the circulation of seawater through carbonate platforms. The circulating water can be the major source of dissolved constituents for diagenetic reactions such as dolomitization. This study was undertaken to investigate the conditions under which such circulation can occur and to determine which factors control both the flux and the patterns of fluid circulation and temperature distribution, given the expected ranges of those factors in nature. Results indicate that the magnitude and distribution of permeability within a carbonate platform are the most important parameters. Depending on the values of horizontal and vertical permeability, heat transport within a platform can occur by one of three mechanisms: conduction, forced convection, or free convection. Depth-dependent relations for porosity and permeability in carbonate platforms suggest circulation may decrease rapidly with depth. The fluid properties of density and viscosity are controlled primarily by their dependency on temperature. The bulk thermal conductivity of the rocks within the platform affects the conductive regime to some extent, especially if evaporite minerals are present within the section. Platform geometry has only a second-order effect on circulation. The relative position of sealevel can create surface conditions that range from exposed (with a fresh-water lens present) to shallow water (with hypersaline conditions created by evaporation in constricted flow conditions) to submerged or drowned (with free surface water circulation), but these boundary conditions and associated ocean temperature profiles have only a second-order effect on fluid circulation. Deep, convective circulation can be caused by horizon tal temperature gradients and can occur even at depths below the ocean bottom. Temperature data from deep holes in the Florida and Bahama platforms suggest that geothermal circulation is actively occurring today to depths as great as several kilometers.

Ventilation of the deep Southern Ocean and changes in atmospheric CO2 during the last deglacial and glacial periods

NASA Astrophysics Data System (ADS)

Gottschalk, J.; Skinner, L. C.; Lippold, J. A.; Jaccard, S.; Vogel, H.; Frank, N.; Waelbroeck, C.

2014-12-01

The Southern Ocean is thought to have played a key role in atmospheric CO2 (CO2,atm) variations, both via its role in bringing carbon-rich deep-waters into contact with the atmosphere, and via its capacity for enhanced biologically mediated carbon export into the deep sea. The governing mechanisms of millennial scale rises in CO2,atm during the last deglacial and glacial periods have been linked controversially either with variations in biological export productivity, possibly driven by fluctuations in airborne dust supply, or to variations in southern high-latitude vertical mixing, possibly driven by changes in westerly wind stress or density stratification across the Southern Ocean water column. However, the impact of these processes on deep, southern high-latitude carbon sequestration and ocean-atmosphere CO2 exchange remain ambiguous. We present proxy evidence for the link between deep carbon storage in the sub-Antarctic Atlantic with changes in CO2,atm during the last 70 ka from sub-millennially resolved changes in bottom water oxygenation based on the uranium accumulation in authigenic coatings on foraminiferal shells and the δ13C offset between epibenthic and infaunal foraminifera (Δδ13C). We compare our results with reconstructed opal fluxes and sediment model output data to assess the impact of physical and biological processes on Southern Ocean carbon storage. While variations in sub-Antarctic Atlantic export production are intrinsically linked with changes in airborne dust supply supporting the major impact of dust on the biological soft-tissue pump, they cannot account for observed changes in pore water organic carbon respiration indicated by increasing Δδ13C and therefore, bottom water oxygen changes in the deep sub-Antarctic Atlantic. This is in strong support of millennial-scale fluctuations in deep Southern Ocean carbon storage primarily controlled by the ventilation of the deep ocean by southern-sourced water masses, which emphasize the strong control of vertical mixing and upwelling of CO2-rich water masses in the Southern Ocean on the ocean-atmosphere exchange of CO2 and variation in CO2,atm over both glacial-interglacial and millennial time scales.

Lytic viral infection of bacterioplankton in deep waters of the western Pacific Ocean

NASA Astrophysics Data System (ADS)

Li, Y.; Luo, T.; Sun, J.; Cai, L.; Jiao, N.; Zhang, R.

2013-12-01

As the most abundant biological entities in the ocean, viruses can influence host mortality and nutrients recycling mainly through lytic infection. Yet ecological characteristics of virioplankton and viral impacts on host mortality and biogeochemical cycling in the deep sea are largely unknown. In present study, viral abundance and lytic infection was investigated throughout the water column in the western Pacific Ocean. Both the prokaryotic and viral abundance and production showed a significantly decreasing trend from epipelagic to meso- and bathypelagic waters. Viral abundance decreased from 0.36-1.05 × 1010 particles L-1 to 0.43-0.80 × 109 particles L-1, while the virus : prokaryote ratio varied from 7.21-16.23 to 2.45-23.40, at surface and 2000 m depth, respectively. The lytic viral production rates in surface and 2000 m waters were, averagely, 1.03 × 1010 L-1 day-1 and 5.74 × 108 L-1 day-1, respectively. Relatively high percentages of prokaryotic cells lysed by virus in 1000 m and 2000 m were observed, suggesting a significant contribution of viruses to prokaryotic mortality in deep ocean. The carbon released by viral lysis in deep western Pacific Ocean waters was from 0.03 to 2.32 μg C L-1 day-1. Our findings demonstrated a highly dynamic and active viral population in the deep western Pacific Ocean and suggested that virioplankton play an important role in the microbial loop and subsequently biogeochemical cycling in deep oceans.

Putting the Deep Biosphere on the Map for Oceanography Courses: Gas Hydrates As a Case Study for the Deep Biosphere

NASA Astrophysics Data System (ADS)

Sikorski, J. J.; Briggs, B. R.

2014-12-01

The ocean is essential for life on our planet. It covers 71% of the Earth's surface, is the source of the water we drink, the air we breathe, and the food we eat. Yet, the exponential growth in human population is putting the ocean and thus life on our planet at risk. However, based on student evaluations from our introductory oceanography course it is clear that our students have deficiencies in ocean literacy that impact their ability to recognize that the ocean and humans are inextricably connected. Furthermore, life present in deep subsurface marine environments is also interconnected to the study of the ocean, yet the deep biosphere is not typically covered in undergraduate oceanography courses. In an effort to improve student ocean literacy we developed an instructional module on the deep biosphere focused on gas hydrate deposits. Specifically, our module utilizes Google Earth and cutting edge research about microbial life in the ocean to support three inquiry-based activities that each explore different facets of gas hydrates (i.e. environmental controls, biologic controls, and societal implications). The relevant nature of the proposed module also makes it possible for instructors of introductory geology courses to modify module components to discuss related topics, such as climate, energy, and geologic hazards. This work, which will be available online as a free download, is a solid contribution toward increasing the available teaching resources focused on the deep biosphere for geoscience educators.

A new multi-proxy reconstruction of Atlantic deep ocean circulation during the warm mid-Pliocene

NASA Astrophysics Data System (ADS)

Riesselman, C. R.; Dowsett, H. J.; Scher, H. D.; Robinson, M. M.

2011-12-01

The mid-Pliocene (3.264 - 3.025 Ma) is the most recent interval in Earth's history with sustained global temperatures in the range of warming predicted for the 21st century, providing an appealing analog with which to examine the Earth system changes we might encounter in the coming century. Ongoing sea surface and deep ocean temperature reconstructions and coupled ocean-atmosphere general circulation model simulations by the USGS PRISM (Pliocene Research Interpretation and Synoptic Mapping) Group identify a dramatic North Atlantic warm anomaly coupled with increased evaporation in the mid-Pliocene, possibly driving enhanced meridional overturning circulation and North Atlantic Deep Water production. However deep ocean temperature is not a conclusive proxy for water mass, and most coupled model simulations predict transient decreases in North Atlantic Deep Water production in 21st century, presenting a contrasting picture of future warmer worlds. Here, we present early results from a new multi-proxy reconstruction of Atlantic deep ocean circulation during the warm mid-Pliocene, using δ13C of benthic foraminifera as a proxy for water mass age and the neodymium isotopic imprint on fossil fish teeth as a proxy for water mass source region along a three-site depth transect from the Walvis Ridge (subtropical South Atlantic). The deep ocean circulation reconstructions resulting from this project will add a new dimension to the PRISM effort and will be useful for both initialization and evaluation of future model simulations.

Deep ocean nutrients during the Last Glacial Maximum deduced from sponge silicon isotopic compositions

NASA Astrophysics Data System (ADS)

Hendry, Katharine R.; Georg, R. Bastian; Rickaby, Rosalind E. M.; Robinson, Laura F.; Halliday, Alex N.

2010-04-01

The relative importance of biological and physical processes within the Southern Ocean for the storage of carbon and atmospheric pCO 2 on glacial-interglacial timescales remains uncertain. Understanding the impact of surface biological production on carbon export in the past relies on the reconstruction of the nutrient supply from upwelling deep waters. In particular, the upwelling of silicic acid (Si(OH) 4) is tightly coupled to carbon export in the Southern Ocean via diatom productivity. Here, we address how changes in deep water Si(OH) 4 concentrations can be reconstructed using the silicon isotopic composition of deep-sea sponges. We report δ30Si of modern deep-sea sponge spicules and show that they reflect seawater Si(OH) 4 concentration. The fractionation factor of sponge δ30Si compared to seawater δ30Si shows a positive relationship with Si(OH) 4, which may be a growth rate effect. Application of this proxy in two down-core records from the Scotia Sea reveals that Si(OH) 4 concentrations in the deep Southern Ocean during the Last Glacial Maximum (LGM) were no different than today. Our result does not support a coupling of carbon and nutrient build up in an isolated deep ocean reservoir during the LGM. Our data, combined with records of stable isotopes from diatoms, are only consistent with enhanced LGM Southern Ocean nutrient utilization if there was also a concurrent reduction in diatom silicification or a shift from siliceous to organic-walled phytoplankton.

Real Time Control of CO2 Enrichment Experiments on the Sea Floor Enabled by the MARS Cabled Observatory

NASA Astrophysics Data System (ADS)

Brewer, P. G.; Mbari Foce Team

2010-12-01

We report on progress on FOCE (Free Ocean CO2 Enrichment) techniques designed to accomplish realistic (that is not contained within land-based aquaria) experiments on the response of deep-sea animals and biogeochemical cycles to ocean acidification. Such experiments have long been carried out on ecosystems on land, and the outcome has differed significantly from CO2 enrichment in enclosed greenhouse systems, thereby undoing much of the hope for an increase in the large-scale biosphere draw down of atmospheric CO2. It is a far bigger step if deep-sea animals and systems are removed from their cold, dark, high pressure and low oxygen native habitat. The equivalent problem in the ocean is far more difficult because of (1) the very different physical forcing; (2) the complex reaction rates between CO2 and water require delay times between addition and entry to the experimental space; (3) the lack of supporting infrastructure and of adequate sensors; and (4) the need for sophisticated and robust control techniques in both hardware and software. We have overcome almost all of these challenges, and related working systems have already been successfully deployed on the Great Barrier Reef coralline flats with Australian colleagues. We have used the MBARI MARS (Monterey Accelerated Research System) cabled observatory to carry out deep-ocean (880m depth) experiments. The basic experimental unit is a 1m x 1m x 50cm chamber with side arms of ~ 3m length to provide the required chemical delay times for the reaction between admixed CO2 enriched sea water and emergence of the flow into the main chamber. Controllable thrusters, operated by user commands, help maintain a steady flow of seawater through the experiment. The site is slightly below the depth of the O2 minimum where small changes in either O2 from ocean warming, or CO2 from ocean acidification can lead to the formation of dead zones. Shallow (near shore) experiments are now also in the late planning stages. We have developed extremely low noise pH sensors that show for the first time the scale and frequency of the tidally driven background pH fluctuations in the ocean. This helps establish the limits in background pH that deep-sea animals are adapted to. We have developed software to control this complex system in real time and to make control possible over the web. A graphical user interface allows operator observation of flow and background conditions, and full choice of experimental settings. CO2 enrichment is provided by ROV delivery of ~50-100 L of liquid CO2 which is contained by its buoyancy within a box set immediately above the side arm opening. The dissolution rate of liquid CO2 through the hydrate skin is ~0.5 μmol/cm2/sec thereby providing a working fluid in the reservoir which is drawn upon as needed. Experiments of 2-3 weeks duration are possible from a single filling. Figure 1. pH changes created in FOCE by a series of CO2 enriched sea water additions under varying flow conditions.

Development, Testing and Operation of a Large Suspended Ocean Measurement Structure for Deep-Ocean Use

DTIC Science & Technology

1992-05-01

and systems for developing , testing, and operating the system. A new, lightweight cable de- used this evolving technology base in the ensuing years...Funding Numbers. Development , Testing, and Operation of a Large Suspended Ocean Contrac Measurement Structure for Deep-Ocean Use Program Element No...Research L.aboratory Report Number. Ocean Acoutics and Technology Directorate PR 91:132:253 Stennis Space Center, MS 39529-5004 9. Sponsoring

Long-term Variation of the East Sea Throughflow and its Possible Influences on the East Sea Warming

NASA Astrophysics Data System (ADS)

Kang, H.; Lee, H.; Kang, S.; Jung, K.

2006-12-01

The prominent long-term change of the East Sea (Japan Sea) is the deep water warming and the depletion of oxygen in the deep layer during the last 40 years. The cause of this phenomena explained mainly by the slow down of the deep convection in the northern region influenced by the global warming. A distinguished feature of the East Sea is the upper layer flow through the three major straits connected to the Pacific Ocean. Generally, East Sea Throughflow (EST) supplies the warm water through the Korea Strait and drains relatively cold water through the Tsugaru and the Soya Straits. In this study, the role of the EST transport variation on the East Sea warming has been investigated. To understand the EST transport variablililty, monthly mean EST transport time series extracted from the Simple Ocean Data Assimilation (SODA 1.4.2) data during the period of 1958 to 2001. It shows that winter time transport anomaly seems to have overall increasing trend with PDO (Pacific Decadal Oscillation) like fluctuation. The relation between the EST transport anomaly and the local or remote wind stress anomaly has been studied. We have also carried out a numerical experiment using a three-dimensional regional model to understand the East Sea response to the long-term EST transport change. Though the throughflow confined in the upper layer, it is interesting to note that the EST can affect on the meridional overturning strength by way of changing the heat transport amount to the convection favorable region. Possible influences of the EST transport variablity on the East Sea warming are discussed.

Slab Ocean El Niño atmospheric feedbacks in Coupled Climate Models and its relationship to the Recharge Oscillator

NASA Astrophysics Data System (ADS)

Bayr, Tobias; Wengel, Christian; Latif, Mojib

2016-04-01

Dommenget (2010) found that El Niño-like variability, termed Slab Ocean El Niño, can exist in the absence of ocean dynamics and is driven by the interaction of the atmospheric surface heat fluxes and the heat content of the upper ocean. Further, Dommenget et al. (2014) report the Slab Ocean El Niño is not an artefact of the ECHAM5-AGCM coupled to a slab ocean model. In fact, atmospheric feedbacks crucial to the Slab Ocean El Niño can also be found in many state-of-the-art coupled climate models participating in CMIP3 and CMIP5, so that ENSO in many CMIP models can be understood as a mixed recharge oscillator/Slab Ocean El Niño mode. Here we show further analysis of the Slab Ocean El Niño atmospheric feedbacks in coupled models. The BCCR_CM2.0 climate model from the CMIP3 data base, which has a very large equatorial cold bias, has an El Niño that is mostly driven by Slab Ocean El Niño atmospheric feedbacks and is used as an example to describe Slab Ocean El Niño atmospheric feedbacks in a coupled model. In the BCCR_CM2.0, the ENSO-related variability in the 20°C isotherm (Z20), a measure of upper ocean heat content, is decoupled from the first mode of the seasonal cycle-related variability, while the two are coupled in observations, with ENSO being phase-locked to the seasonal cycle. Further analysis of the seasonal cycle in Z20 using SODA Ocean Reanalysis reveals two different regimes in the seasonal cycle along the equator: The first regime, to which ENSO is phase-locked, extends over the west and central equatorial Pacific and is driven by subsurface ocean dynamics. The second regime, extending in observations only over the cold tongue region, is driven by the seasonal cycle at the sea surface and is shifted by roughly six months relative to the first regime. In a series of experiments with the Kiel Climate Model (KCM) with different mean states due to tuning in the convection parameters, we can show that the strength of the equatorial cold bias and the coupling strength between the seasonal cycle of Z20 and ENSO are anti-correlated, i.e. a strong equatorial cold bias suppresses recharge oscillator dynamics and enhances Slab Ocean El Niño atmospheric feedbacks, supporting the results from the BCCR_CM2.0. This can be explained as with a stronger cold bias the second regime of the seasonal cycle in Z20, which extends in observations only over the small cold tongue region, expands westward and becomes more important, so that it decouples ENSO from the seasonal cycle in Z20. This has implications for some major characteristics of the ENSO like the propagation of SST anomalies, the phase locking of SST to the seasonal cycle, or the nonlinearity of ENSO. Dommenget, D., 2010: The slab ocean El Niño. Geophys. Res. Lett., 37, L20701, doi:10.1029/2010GL044888. - - , S. Haase, T. Bayr, and C. Frauen, 2014: Analysis of the Slab Ocean El Niño atmospheric feedbacks in observed and simulated ENSO dynamics. Clim. Dyn., doi:10.1007/s00382-014-2057-0.

Southern Ocean Bottom Water Characteristics in CMIP5 Models

NASA Astrophysics Data System (ADS)

Heuzé, Céline; Heywood, Karen; Stevens, David; Ridley, Jeff

2013-04-01

The depiction of Southern Ocean deep water properties and formation processes in climate models is an indicator of their capability to simulate future climate, heat and carbon uptake, and sea level rise. Southern Ocean potential temperature and density averaged over 1986-2005 from fifteen CMIP5 climate models are compared with an observed climatology, focusing on bottom water properties. The mean bottom properties are reasonably accurate for half of the models, but the other half may not yet have approached an equilibrium state. Eleven models create dense water on the Antarctic shelf, but it does not spill off and propagate northwards, alternatively mixing rapidly with less dense water. Instead most models create deep water by open ocean deep convection. Models with large deep convection areas are those with a strong seasonal cycle in sea ice. The most accurate bottom properties occur in models hosting deep convection in the Weddell and Ross gyres.

Irminger Sea deep convection injects oxygen and anthropogenic carbon to the ocean interior

PubMed Central

Fröb, F.; Olsen, A.; Våge, K.; Moore, G. W. K.; Yashayaev, I.; Jeansson, E.; Rajasakaren, B.

2016-01-01

Deep convection in the subpolar North Atlantic ventilates the ocean for atmospheric gases through the formation of deep water masses. Variability in the intensity of deep convection is believed to have caused large variations in North Atlantic anthropogenic carbon storage over the past decades, but observations of the properties during active convection are missing. Here we document the origin, extent and chemical properties of the deepest winter mixed layers directly observed in the Irminger Sea. As a result of the deep convection in winter 2014–2015, driven by large oceanic heat loss, mid-depth oxygen concentrations were replenished and anthropogenic carbon storage rates almost tripled compared with Irminger Sea hydrographic section data in 1997 and 2003. Our observations provide unequivocal evidence that ocean ventilation and anthropogenic carbon uptake take place in the Irminger Sea and that their efficiency can be directly linked to atmospheric forcing. PMID:27786263

Role of surface heat fluxes underneath cold pools

PubMed Central

Garelli, Alix; Park, Seung‐Bu; Nie, Ji; Torri, Giuseppe; Kuang, Zhiming

2016-01-01

Abstract The role of surface heat fluxes underneath cold pools is investigated using cloud‐resolving simulations with either interactive or horizontally homogenous surface heat fluxes over an ocean and a simplified land surface. Over the ocean, there are limited changes in the distribution of the cold pool temperature, humidity, and gust front velocity, yet interactive heat fluxes induce more cold pools, which are smaller, and convection is then less organized. Correspondingly, the updraft mass flux and lateral entrainment are modified. Over the land surface, the heat fluxes underneath cold pools drastically impact the cold pool characteristics with more numerous and smaller pools, which are warmer and more humid and accompanied by smaller gust front velocities. The interactive fluxes also modify the updraft mass flux and reduce convective organization. These results emphasize the importance of interactive surface fluxes instead of prescribed flux boundary conditions, as well as the formulation of surface heat fluxes, when studying convection. PMID:27134320

WHATS-3: An improved flow-through multi-bottle fluid sampler for deep-sea geofluid research

NASA Astrophysics Data System (ADS)

Miyazaki, Junichi; Makabe, Akiko; Matsui, Yohei; Ebina, Naoya; Tsutsumi, Saki; Ishibashi, Jun-ichiro; Chen, Chong; Kaneko, Sho; Takai, Ken; Kawagucci, Shinsuke

2017-06-01

Deep-sea geofluid systems, such as hydrothermal vents and cold seeps, are key to understanding subseafloor environments of Earth. Fluid chemistry, especially, provides crucial information towards elucidating the physical, chemical and biological processes that occur in these ecosystems. To accurately assess fluid and gas properties of deep-sea geofluids, well-designed pressure-tight fluid samplers are indispensable and as such they are important assets of deep-sea geofluid research. Here, the development of a new flow-through, pressure-tight fluid sampler capable of four independent sampling events (two subsamples for liquid and gas analyses from each) is reported. This new sampler, named WHATS-3, is a new addition to the WHATS-series samplers and a major upgrade from the previous WHATS-2 sampler with improvements in sample number, valve operational time, physical robustness, and ease of maintenance. Routine laboratory-based pressure tests proved that it is suitable for operation up to 35 MPa pressure. Successful field tests of the new sampler were also carried out in five hydrothermal fields, two in Indian Ocean and three in Okinawa Trough (max. depth 3,300 m). Relations of Mg and major ion species demonstrated bimodal mixing trends between a hydrothermal fluid and seawater, confirming the high-quality of fluids sampled. The newly developed WHATS-3 sampler is well-balanced in sampling capability, field usability, and maintenance feasibility, and can serve as one of the best geofluid samplers available at present to conduct efficient research of deep-sea geofluid systems.

Simulation of global oceanic upper layers forced at the surface by an optimal bulk formulation derived from multi-campaign measurements.

NASA Astrophysics Data System (ADS)

Garric, G.; Pirani, A.; Belamari, S.; Caniaux, G.

2006-12-01

order to improve the air/sea interface for the future MERCATOR global ocean operational system, we have implemented the new bulk formulation developed by METEO-FRANCE (French Meteo office) in the MERCATOR 2 degree global ocean-ice coupled model (ORCA2/LIM). A single bulk formulation for the drag, temperature and moisture exchange coefficients is derived from an extended consistent database gathering 10 years of measurements issued from five experiments dedicated to air-sea fluxes estimates (SEMAPHORE, CATCH, FETCH, EQUALANT99 and POMME) in various oceanic basins (from Northern to equatorial Atlantic). The available database (ALBATROS) cover the widest range of atmospheric and oceanic conditions, from very light (0.3 m/s) to very strong (up to 29 m/s) wind speeds, and from unstable to extremely stable atmospheric boundary layer stratification. We have defined a work strategy to test this new formulation in a global oceanic context, by using this multi- campaign bulk formulation to derive air-sea fluxes from base meteorological variables produces by the ECMWF (European Centre for Medium Range and Weather Forecast) atmospheric forecast model, in order to get surface boundary conditions for ORCA2/LIM. The simulated oceanic upper layers forced at the surface by the previous air/sea interface are compared to those forced by the optimal bulk formulation. Consecutively with generally weaker transfer coefficient, the latter formulation reduces the cold bias in the equatorial Pacific and increases the too weak summer sea ice extent in Antarctica. Compared to a recent mixed layer depth (MLD) climatology, the optimal bulk formulation reduces also the too deep simulated MLDs. Comparison with in situ temperature and salinity profiles in different areas allowed us to evaluate the impact of changing the air/sea interface in the vertical structure.

On the relationship between satellite-estimated bio-optical and thermal properties in the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Jolliff, Jason K.; Kindle, John C.; Penta, Bradley; Helber, Robert; Lee, Zhongping; Shulman, Igor; Arnone, Robert; Rowley, Clark D.

2008-03-01

Three years of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color data were combined with three-dimensional thermal fields generated by the U.S. Navy's Modular Ocean Data Assimilation System (MODAS) in order to examine the interdependencies between bio-optical fields and their relationship to seasonal and mesoscale changes in upper ocean thermal structure. The combined data set suggests that the oceanic boundary layer within the Gulf of Mexico may be broadly defined by two seasonally occurring bio-thermal periods. A winter mixing period, characterized by net heat losses to the atmosphere, deepening of the isothermal layer depth, and annual maxima of satellite-estimated colored detrital matter (CDM) absorption coefficients and surface pigment concentration, was followed by a thermally stratified period characterized by net surface ocean heating, reduced isothermal layer depths, and annual minima in surface bio-optical fields. Variability in the interdependencies of ocean color products was used to diagnose an attendant shift in the size-structure of surface phytoplankton communities as well as identify CDM as the constituent responsible for the majority of blue-light absorption in Gulf of Mexico surface waters. The mesoscale circulation, as resolved by MODAS thermal fields into cold and warm-core eddies, appears to significantly modulate the seasonal bio-optical cycle of CDM absorption and surface pigment concentration. An empirical model was developed to describe CDM absorption as a function of upper ocean thermal energy. The model accounted for nearly half the variance in the satellite-estimate of this bio-optical variable. Large mismatches between the model and satellite data implied episodes of shelf water export to the deep Gulf of Mexico.

Microbiota associated with tubes of Escarpia sp. from cold seeps in the southwestern Atlantic Ocean constitutes a community distinct from that of surrounding marine sediment and water.

PubMed

Medina-Silva, Renata; Oliveira, Rafael R; Trindade, Fernanda J; Borges, Luiz G A; Lopes Simão, Taiz L; Augustin, Adolpho H; Valdez, Fernanda P; Constant, Marcelo J; Simundi, Carolina L; Eizirik, Eduardo; Groposo, Claudia; Miller, Dennis J; da Silva, Priscila Reis; Viana, Adriano R; Ketzer, João M M; Giongo, Adriana

2018-04-01

As the depth increases and the light fades in oceanic cold seeps, a variety of chemosynthetic-based benthic communities arise. Previous assessments reported polychaete annelids belonging to the family Siboglinidae as part of the fauna at cold seeps, with the 'Vestimentifera' clade containing specialists that depend on microbial chemosynthetic endosymbionts for nutrition. Little information exists concerning the microbiota of the external portion of the vestimentiferan trunk wall. We employed 16S rDNA-based metabarcoding to describe the external microbiota of the chitin tubes from the vestimentiferan Escarpia collected from a chemosynthetic community in a cold seep area at the southwestern Atlantic Ocean. The most abundant operational taxonomic unit (OTU) belonged to the family Pirellulaceae (phylum Planctomycetes), and the second most abundant OTU belonged to the order Methylococcales (phylum Proteobacteria), composing an average of 21.1 and 15.4% of the total reads on tubes, respectively. These frequencies contrasted with those from the surrounding environment (sediment and water), where they represent no more than 0.1% of the total reads each. Moreover, some taxa with lower abundances were detected only in Escarpia tube walls. These data constitute on the first report of an epibiont microbial community found in close association with external surface of a cold-seep metazoan, Escarpia sp., from a chemosynthetic community in the southwestern Atlantic Ocean.

The Evolution of Deep Ocean Chemistry and Respired Carbon in the Eastern Equatorial Pacific Over the Last Deglaciation

NASA Astrophysics Data System (ADS)

de la Fuente, Maria; Calvo, Eva; Skinner, Luke; Pelejero, Carles; Evans, David; Müller, Wolfgang; Povea, Patricia; Cacho, Isabel

2017-12-01

It has been shown that the deep Eastern Equatorial Pacific (EEP) region was poorly ventilated during the Last Glacial Maximum (LGM) relative to Holocene values. This finding suggests a more efficient biological pump, which indirectly supports the idea of increased carbon storage in the deep ocean contributing to lower atmospheric CO2 during the last glacial. However, proxies related to respired carbon are needed in order to directly test this proposition. Here we present Cibicides wuellerstorfi B/Ca ratios from Ocean Drilling Program Site 1240 measured by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) as a proxy for deep water carbonate saturation state (Δ[CO32-], and therefore [CO32-]), along with δ13C measurements. In addition, the U/Ca ratio in foraminiferal coatings has been analyzed as an indicator of oxygenation changes. Our results show lower [CO32-], δ13C, and [O2] values during the LGM, which would be consistent with higher respired carbon levels in the deep EEP driven, at least in part, by reduced deep water ventilation. However, the difference between LGM and Holocene [CO32-] observed at our site is relatively small, in accordance with other records from across the Pacific, suggesting that a "counteracting" mechanism, such as seafloor carbonate dissolution, also played a role. If so, this mechanism would have increased average ocean alkalinity, allowing even more atmospheric CO2 to be "sequestered" by the ocean. Therefore, the deep Pacific Ocean very likely stored a significant amount of atmospheric CO2 during the LGM, specifically due to a more efficient biological carbon pump and also an increase in average ocean alkalinity.

Glacial CO2 Cycles: A Composite Scenario

NASA Astrophysics Data System (ADS)

Broecker, W. S.

2015-12-01

There are three main contributors to the glacial drawdown of atmospheric CO2 content: starvation of the supply of carbon to the ocean-atmosphere reservoir, excess CO2 storage in the deep sea, and surface-ocean cooling. In this talk, I explore a scenario in which all three play significant roles. Key to this scenario is the assumption that deep ocean storage is related to the extent of nutrient stratification of the deep Atlantic. The stronger this stratification, the larger the storage of respiration CO2. Further, it is my contention that the link between Milankovitch insolation cycles and climate is reorganizations of the ocean's thermohaline circulation leading to changes in the deep ocean's CO2 storage. If this is the case, the deep Atlantic d13C record kept in benthic foraminifera shells tells us that deep ocean CO2 storage follows Northern Hemisphere summer insolation cycles and thus lacks the downward ramp so prominent in the records of sea level, benthic 18O and CO2. Rather, the ramp is created by the damping of planetary CO2 emissions during glacial time intervals. As it is premature to present a specific scenario, I provide an example as to how these three contributors might be combined. As their magnitudes and shapes remain largely unconstrained, the intent of this exercise is to provoke creative thinking.

1.5 My benthic foraminiferal B/Ca record of carbonate chemistry in the deep Atlantic: Implications for ocean alkalinity and atmospheric CO2

NASA Astrophysics Data System (ADS)

Rosenthal, Y.; Sosdian, S. M.; Toggweiler, J. R.

2017-12-01

Most hypotheses to explain glacial-interglacial changes in atmospheric CO2 invoke shifts in ocean alkalinity explain roughly half the reduction in glacial CO2 via CaCO3 compensatory mechanism. It follows that changes in CaCO3 burial occur in response to an increase in deep ocean respired carbon content. To date our understanding of this process comes from benthic carbon isotope and %CaCO3 records. However, to understand the nature of the ocean's buffering capacity and its role in modulating pCO2, orbitally resolved reconstructions of the deep ocean carbonate system parameters are necessary. Here we present a 1.5 Myr orbitally resolved deep ocean calcite saturation record (ΔCO32-) derived from benthic foraminiferal B/Ca ratios in the North Atlantic. Glacial B/Ca values decline across the mid-Pleistocene transition (MPT) suggesting increased sequestration of carbon in the deep Atlantic. The magnitude, timing, and structure of deep Atlantic Ocean ΔCO32- and %CaCO3 cycles contrast with the small amplitude, anti-phased swings in IndoPacific ΔCO32- and %CaCO3 during the mid-to-late Pleistocene. Increasing corrosivity of the deep Atlantic causes the locus of CaCO3 burial to shift into the equatorial Pacific where the flux of CaCO3 to the seafloor is high enough to establish and maintain a new "hot spot". We propose that the CO32- in the deep IndoPacific rises in response to the same mechanism that keeps the CO32- in the deep Atlantic low and the atmospheric CO2 low. The increase in interglacial atmospheric pCO2 levels following the Mid-Brunhes event ( 400ka) are associated with increased G/IG ΔCO3 amplitude, expressed by a decrease in the glacial ΔCO32- values. We propose the low persistent ΔCO32- levels at Marine Isotope Stage (MIS) 12 set the stage for the high pCO2 levels at MIS 11 via an increase in whole ocean alkalinity followed by enhanced CaCO3 preservation. Based on this, we suggest that the development of classic (`anticorrelated') CaCO3 patterns was driven by increased stratification and worsening ventilation in the deep Atlantic across the MPT.

Investigation of Deep Ocean Circulation and Mixing Using Ar-39 (Invited)

NASA Astrophysics Data System (ADS)

Smethie, W. M.; Schlosser, P.

2013-12-01

Ar-39 is a radioactive noble gas that forms in the atmosphere by cosmic ray interaction with Ar-40. It has a half-life of 269 years and its production rate in the atmosphere has varied no more than 7% during the past 1000 years. It enters the surface ocean with an average equilibration time of about one month and thus the entire surface ocean, except for ice covered regions at high latitudes, is in quasi-equilibrium with the atmospheric Ar-39:Ar ratio. The well known input to the ocean, radioactive decay constant and chemical inertness make Ar-39 an ideal tracer of circulation and mixing in the deep ocean, where anthropogenic transient tracers such as CFCs and tritium have not yet penetrated. However, due to the difficult measurement, only about 125 oceanic Ar-39 samples have been measured to date. This was done by counting the decays of Ar-39 atoms and required a half liter of argon gas per sample, extracted from about 1500 liters of water. The 125 samples that have been measured provide a glimpse of the information that can be gained from Ar-39 observations. In the Pacific Ocean three vertical profiles show a decrease in Ar-39 from the surface mixed layer through the thermocline to a minimum at intermediate depths and an increase from there to the bottom. This reflects formation of bottom water around the Antarctic continent, spreading of this water northward and upwelling and mixing into intermediate depths. The lowest concentration was 6×4% modern which is equivalent to a 900-1600 year isolation time from the surface. In the Atlantic Ocean newly formed North Atlantic Deep Water has an Ar-39 concentration of about 85% modern compared to 55% modern for newly formed Antarctic Bottom Water and reach values as low as about 40% modern in the interior reflecting the more rapid ventilation of the deep Atlantic Ocean relative to the deep Pacific Ocean. In the Arctic Ocean the mean residence time of deep water in the Nansen, Amundsen and Makarov Basins based on Ar-39 are about 270, 190, and 330 years respectively. Radiocarbon also provides information on circulation and mixing in the deep ocean and thousands of measurements have been made. However, the distributions of Ar-39 and C-14 are different due to the large difference in their half-lives (269 years and 5730 years respectively). Measurement of both tracers provides information on the relative importance of advection and mixing in the deep ocean and provides more accurate transit times than can be obtained with only one of these tracers. In the Atlantic Ocean, where the deep water is roughly a two-end member mixture of northern component and southern component water, the age of the two components can be estimated from simultaneous measurement of Ar-39 and C-14. The few existing measurements suggest that the northern component water has an age range of 40-200 years and the southern component water a range of 60-600 years. Development of the ATTA method for measuring radioactive noble gases offers great potential to dramatically increase the number of samples that can be measured for Ar-39, which could greatly improve our understanding of mixing and circulation in the deep ocean.

Not Just About the Science: Cold War Politics and the International Indian Ocean Expedition

NASA Astrophysics Data System (ADS)

Harper, K.

2016-12-01

The International Indian Ocean Expedition broke ground for a series of multi-national oceanographic expeditions starting in the late 1950s. In and of itself, it would have been historically significant—like the International Geophysical Year (1957-58)—for pulling together the international scientific community during the Cold War. However, US support for this and follow-on Indian Ocean expeditions were not just about the science; they were also about diplomacy, specifically efforts to bring non-aligned India into the US political orbit and out of the clutches of its Cold War enemy, the Soviet Union. This paper examines the behind-the-scenes efforts at the highest reaches of the US government to extract international political gain out of a large-scale scientific effort.

Deep oceans may acidify faster than anticipated due to global warming

NASA Astrophysics Data System (ADS)

Chen, Chen-Tung Arthur; Lui, Hon-Kit; Hsieh, Chia-Han; Yanagi, Tetsuo; Kosugi, Naohiro; Ishii, Masao; Gong, Gwo-Ching

2017-12-01

Oceans worldwide are undergoing acidification due to the penetration of anthropogenic CO2 from the atmosphere1-4. The rate of acidification generally diminishes with increasing depth. Yet, slowing down of the thermohaline circulation due to global warming could reduce the pH in the deep oceans, as more organic material would decompose with a longer residence time. To elucidate this process, a time-series study at a climatically sensitive region with sufficient duration and resolution is needed. Here we show that deep waters in the Sea of Japan are undergoing reduced ventilation, reducing the pH of seawater. As a result, the acidification rate near the bottom of the Sea of Japan is 27% higher than the rate at the surface, which is the same as that predicted assuming an air-sea CO2 equilibrium. This reduced ventilation may be due to global warming and, as an oceanic microcosm with its own deep- and bottom-water formations, the Sea of Japan provides an insight into how future warming might alter the deep-ocean acidification.

Spatial scales of bacterial community diversity at cold seeps (Eastern Mediterranean Sea)

PubMed Central

Pop Ristova, Petra; Wenzhöfer, Frank; Ramette, Alban; Felden, Janine; Boetius, Antje

2015-01-01

Cold seeps are highly productive, fragmented marine ecosystems that form at the seafloor around hydrocarbon emission pathways. The products of microbial utilization of methane and other hydrocarbons fuel rich chemosynthetic communities at these sites, with much higher respiration rates compared with the surrounding deep-sea floor. Yet little is known as to the richness, composition and spatial scaling of bacterial communities of cold seeps compared with non-seep communities. Here we assessed the bacterial diversity across nine different cold seeps in the Eastern Mediterranean deep-sea and surrounding seafloor areas. Community similarity analyses were carried out based on automated ribosomal intergenic spacer analysis (ARISA) fingerprinting and high-throughput 454 tag sequencing and were combined with in situ and ex situ geochemical analyses across spatial scales of a few tens of meters to hundreds of kilometers. Seep communities were dominated by Deltaproteobacteria, Epsilonproteobacteria and Gammaproteobacteria and shared, on average, 36% of bacterial types (ARISA OTUs (operational taxonomic units)) with communities from nearby non-seep deep-sea sediments. Bacterial communities of seeps were significantly different from those of non-seep sediments. Within cold seep regions on spatial scales of only tens to hundreds of meters, the bacterial communities differed considerably, sharing <50% of types at the ARISA OTU level. Their variations reflected differences in porewater sulfide concentrations from anaerobic degradation of hydrocarbons. This study shows that cold seep ecosystems contribute substantially to the microbial diversity of the deep-sea. PMID:25500510

The abiotically driven biological pump in the ocean and short-term fluctuations in atmospheric CO 2 contents

NASA Astrophysics Data System (ADS)

Ittekkot, Venugopalan

1993-07-01

Current debates on the significance of the oceanic "biological pump" in the removal of atmospheric CO 2 pay more attention to the act of biological carbon-dioxide fixation (primary productivity) in the sea, but pay less or no attention to the equally relevant aspect of the transfer of the fixed carbon to a sink before its oxidation back to CO 2. The upper ocean obviously disqualifies as a sink for biologically fixed CO 2 because of gas-exchange with the atmosphere. The deep ocean, on the other hand, can be a sink at least at time scales of the ocean turnover. Transfer of newly-fixed CO 2 to the deep sea can be accelerated by abiogenic matter introduced to the sea surface from terrestrial sources. This matter acts as ballast and increases the density and settling rates of aggregates of freshly synthesized organic matter thereby facilitating their rapid removal from the upper ocean. Higher supply of abiogenic matter enhances the sequestering of fresh organic matter and in effect shifts the zone of organic matter remineralization from the upper ocean to the deep sea. Consistent with this abiogenic forcing, the rate of organic matter remineralization and the subsequent storage of the remineralized carbon in the deep sea are linked to bulk fluxes (mass accumulation rates) in the deep sea. This mechanism acts as an "abiotic boost" in the workings of the oceanic "biological pump" and results in an increase in deep sea carbon storage; the magnitude of carbon thus stored could have caused the observed short term fluctuations in atmospheric CO 2-contents during the glacial-interglacial cycles.

Upper Ocean Evolution Across the Beaufort Sea Marginal Ice Zone

NASA Astrophysics Data System (ADS)

Lee, C.; Rainville, L.; Gobat, J. I.; Perry, M. J.; Freitag, L. E.; Webster, S.

2016-12-01

The observed reduction of Arctic summertime sea ice extent and expansion of the marginal ice zone (MIZ) have profound impacts on the balance of processes controlling sea ice evolution, including the introduction of several positive feedback mechanisms that may act to accelerate melting. Examples of such feedbacks include increased upper ocean warming though absorption of solar radiation, elevated internal wave energy and mixing that may entrain heat stored in subsurface watermasses (e.g., the relatively warm Pacific Summer and Atlantic waters), and elevated surface wave energy that acts to deform and fracture sea ice. Spatial and temporal variability in ice properties and open water fraction impact these processes. To investigate how upper ocean structure varies with changing ice cover, how the balance of processes shift as a function of ice fraction and distance from open water, and how these processes impact sea ice evolution, a network of autonomous platforms sampled the atmosphere-ice-ocean system in the Beaufort, beginning in spring, well before the start of melt, and ending with the autumn freeze-up. Four long-endurance autonomous Seagliders occupied sections that extended from open water, through the marginal ice zone, deep into the pack during summer 2014 in the Beaufort Sea. Gliders penetrated up to 200 km into the ice pack, under complete ice cover for up to 10 consecutive days. Sections reveal strong fronts where cold, ice-covered waters meet waters that have been exposed to solar warming, and O(10 km) scale eddies near the ice edge. In the pack, Pacific Summer Water and a deep chlorophyll maximum form distinct layers at roughly 60 m and 80 m, respectively, which become increasingly diffuse late in the season as they progress through the MIZ and into open water. Stratification just above the Pacific Summer Water rapidly weakens near the ice edge and temperature variance increases, likely due to mixing or energetic vertical exchange associated with strong lateral gradients at the MIZ. This presentation will discuss the evolution of the Arctic upper ocean over the summer to the start of freeze up and the relationship of its variability to sea ice extent and atmospheric forcing.

Assessing Deep Ocean Carbon Storage Across the Mid-Pleistocene Transition

NASA Astrophysics Data System (ADS)

Haynes, L.; Hoenisch, B.; Farmer, J. R.; Ford, H. L.; Raymo, M. E.; Yehudai, M.; Goldstein, S. L.; Pena, L. D.; Bickert, T.

2017-12-01

The Mid-Pleistocene Transition (MPT) was a profound reorganization of the climate system between 0.8 to 1.2 million years ago (Ma) that led to the establishment of 100 thousand year (kyr)-paced glacial cycles. At the midpoint of the transition at around 900 ka (the "900 ka event"), observations of a globally synchronous decrease in benthic δ13C suggest a large-scale perturbation to the oceanic carbon cycle. While the cause of the MPT remains elusive, recent geochemical evidence suggests that this δ13C minimum was concurrent with an increased presence of Southern Sourced Waters (SSW) in the South Atlantic, a decrease in Δ[CO32-] in the deep North Atlantic, and a decrease in glacial atmospheric CO2, pointing to increased carbon storage in the deep ocean as a possible amplifier for glacial intensification. Here we utilize the B/Ca proxy for carbonate saturation ( Δ[CO32-]) in the benthic foraminifer C. wuellerstorfi to investigate the storage of carbon in the deep western equatorial Atlantic at ODP sites 925 and 926 (3040 and 3590 m water depths, respectively). Reconstructed Δ[CO32-] covaries with benthic δ13C and follows the slope anticipated from the Redfield relationship predicted from organic matter degradation, suggesting control of respired CO2 content on the deep ocean's saturation state. Data spanning the 900-ka event suggest a decrease in minimum Δ[CO32-] of deep waters during glacial periods, concurrent with the documented expansion of SSW as captured by records of ɛNd. The coherence between shifts in δ13C, ɛNd, and Δ[CO32-] point to ocean circulation as a partial driver for increased oceanic CO2 storage. Comparison of Atlantic data to new records from the deep Pacific will explore the consequences of weakening Atlantic overturning across the MPT for CO2 storage in this expansive deep ocean reservoir.

Intensified Diapycnal Mixing in the Midlatitude Western Boundary Currents

PubMed Central

Jing, Zhao; Wu, Lixin

2014-01-01

The wind work on oceanic near-inertial motions is suggested to play an important role in furnishing the diapycnal mixing in the deep ocean which affects the uptake of heat and carbon by the ocean as well as climate changes. However, it remains a puzzle where and through which route the near-inertial energy penetrates into the deep ocean. Using the measurements collected in the Kuroshio extension region during January 2005, we demonstrate that the diapycnal mixing in the thermocline and deep ocean is tightly related to the shear variance of wind-generated near-inertial internal waves with the diapycnal diffusivity 6 × 10−5 m2s−1 almost an order stronger than that observed in the circulation gyre. It is estimated that 45%–62% of the local near-inertial wind work 4.5 × 10−3 Wm−2 radiates into the thermocline and deep ocean and accounts for 42%–58% of the energy required to furnish mixing there. The elevated mixing is suggested to be maintained by the energetic near-inertial wind work and strong eddy activities causing enhanced downward near-inertial energy flux than earlier findings. The western boundary current turns out to be a key region for the penetration of near-inertial energy into the deep ocean and a hotspot for the diapycnal mixing in winter. PMID:25491363

Dependence of the brittle ductile transition on strain-rate-dependent critical homologous temperature

NASA Astrophysics Data System (ADS)

Davis, Paul M.

2017-05-01

Earthquakes mainly occur in crust or mantle that is below a critical temperature for the tectonic strain-rate, \\dot{e}_t, such that stress builds up to the breaking point before it can relax due to creep. Then long-range stress correlation gives rise to power law seismicity including large events. The limiting temperature depends on pressure, which is taken into account by finding a critical homologous temperature THc = T/TM above which earthquakes are rarely observed (where T, TM are temperature and average melting temperature of constituent minerals). We find that THc for ocean plates is ∼0.55. For California earthquakes, it is also close to 0.55. The uppermost mantle layer of oceanic plates of thickness ∼50 km is composed of harzburgite and depleted peridotite from which basalt has been removed to form ocean crust. Thus it has a higher melting temperature than the peridotite of the surrounding mantle, or the lower halves of plates. Thicknesses of seismicity in deep subduction zones, determined from 2-D polynomial fits to a relocated catalogue, are ∼50 km, which suggests that the earthquake channel is confined to this layer. We construct models to find homologous temperatures in slabs, and find that seismicity thicknesses are also, on average, confined to TH ≤ 0.55 ± 0.05. The associated rheology is compared with that obtained from flexure models of ocean lithosphere. The brittle-ductile transition occurs where viscosity drops from high values in the cold cores of slabs to values of 1022-1023 Pa s, that is, where creep strain-rates become comparable to tectonic rates. The cut-off for deep earthquakes is not sharp. However they appear unlikely to occur if homologous temperature is high TH > 0.55. Exceptions to the rule are anomalously deep earthquakes such as those beneath the Iceland and the Hawaiian hotspots, and the Newport Inglewood Fault. These are smaller events with short-range stress correlation, and can be explained if strain-rates are two to three orders of magnitude higher than those associated with earthquakes located where TH ≤ 0.55. We conclude that the brittle-ductile transition corresponds to the transition from long-range (regional) to short-range (localized on asperities) stress correlation.

The Oceanic Flux Program: A three decade time-series of particle flux in the deep Sargasso Sea

NASA Astrophysics Data System (ADS)

Weber, J. C.; Conte, M. H.

2010-12-01

The Oceanic Flux Program (OFP), 75 km SE of Bermuda, is the longest running time-series of its kind. Initiated in 1978, the OFP has produced an unsurpassed, nearly continuous record of temporal variability in deep ocean fluxes, with a >90% temporal coverage at 3200m depth. The OFP, in conjunction with the co-located Bermuda-Atlantic Time Series (BATS) and the Bermuda Testbed Mooring (BTM) time-series, has provided key observations enabling detailed assessment of how seasonal and non-seasonal variability in the deep ocean is linked with the overlying physical and biogeochemical environment. This talk will focus on the short-term flux variability that overlies the seasonal flux pattern in the Sargasso Sea, emphasizing episodic extreme flux events. Extreme flux events are responsible for much of the year-to-year variability in mean annual flux and are most often observed during early winter and late spring when surface stratification is weak or transient. In addition to biological phenomena (e.g. salp blooms), passage of productive meso-scale features such as eddies, which alter surface water mixing characteristics and surface export fluxes, may initiate some extreme flux events. Yet other productive eddies show a minimal influence on the deep flux, underscoring the importance of upper ocean ecosystem structure and midwater processes on the coupling between the surface ocean environment and deep fluxes. Using key organic and inorganic tracers, causative processes that influence deep flux generation and the strength of the coupling with the surface ocean environment can be identified.

Insights into Deep-Sea Sediment Fungal Communities from the East Indian Ocean Using Targeted Environmental Sequencing Combined with Traditional Cultivation

PubMed Central

Zhang, Xiao-yong; Tang, Gui-ling; Xu, Xin-ya; Nong, Xu-hua; Qi, Shu-Hua

2014-01-01

The fungal diversity in deep-sea environments has recently gained an increasing amount attention. Our knowledge and understanding of the true fungal diversity and the role it plays in deep-sea environments, however, is still limited. We investigated the fungal community structure in five sediments from a depth of ∼4000 m in the East India Ocean using a combination of targeted environmental sequencing and traditional cultivation. This approach resulted in the recovery of a total of 45 fungal operational taxonomic units (OTUs) and 20 culturable fungal phylotypes. This finding indicates that there is a great amount of fungal diversity in the deep-sea sediments collected in the East Indian Ocean. Three fungal OTUs and one culturable phylotype demonstrated high divergence (89%–97%) from the existing sequences in the GenBank. Moreover, 44.4% fungal OTUs and 30% culturable fungal phylotypes are new reports for deep-sea sediments. These results suggest that the deep-sea sediments from the East India Ocean can serve as habitats for new fungal communities compared with other deep-sea environments. In addition, different fungal community could be detected when using targeted environmental sequencing compared with traditional cultivation in this study, which suggests that a combination of targeted environmental sequencing and traditional cultivation will generate a more diverse fungal community in deep-sea environments than using either targeted environmental sequencing or traditional cultivation alone. This study is the first to report new insights into the fungal communities in deep-sea sediments from the East Indian Ocean, which increases our knowledge and understanding of the fungal diversity in deep-sea environments. PMID:25272044

Deep-Sea coral evidence for rapid change in ventilation of the deep north atlantic 15,400 years Ago

PubMed

Adkins; Cheng; Boyle; Druffel; Edwards

1998-05-01

Coupled radiocarbon and thorium-230 dates from benthic coral species reveal that the ventilation rate of the North Atlantic upper deep water varied greatly during the last deglaciation. Radiocarbon ages in several corals of the same age, 15.41 +/- 0.17 thousand years, and nearly the same depth, 1800 meters, in the western North Atlantic Ocean increased by as much as 670 years during the 30- to 160-year life spans of the samples. Cadmium/calcium ratios in one coral imply that the nutrient content of these deep waters also increased. Our data show that the deep ocean changed on decadal-centennial time scales during rapid changes in the surface ocean and the atmosphere.

Paleoclimatic and paleolatitude settings of accumulation of radiolarian siliceous-volcanogenic sequences in the middle Mesozoic Pacific: Evidence from allochthons of East Asia

NASA Astrophysics Data System (ADS)

Vishnevskaya, V. S.; Filatova, N. I.

2017-09-01

Jurassic-Cretaceous siliceous-volcanogenic rocks from nappes of tectonostratigraphic sequences of the East Asia Middle Cretaceous Okhotsk-Koryak orogenic belt are represented by a wide range of geodynamic sedimentation settings: oceanic (near-spreading zones, seamounts, and deep-water basins), marginal seas, and island arcs. The taxonomic compositions of radiolarian communities are used as paleolatitude indicators in the Northern Pacific. In addition, a tendency toward climate change in the Mesozoic is revealed based on these communities: from the warm Triassic to the cold Jurassic with intense warming from the Late Jurassic to the Early Cretaceous. Cretaceous warming led to heating of ocean waters even at moderately high latitudes and to the development of Tethyan radiolarians there. These data are confirmed by a global Cretaceous temperature peak coinciding with a high-activity pulse of the planetary mantle superplume system, which created thermal anomalies and the greenhouse effect. In addition, the Pacific superplume attributed to this system caused accelerated movement of oceanic plates, which resulted in a compression setting on the periphery of the Pacific and the formation of the Okhotsk-Koryak orogenic belt on its northwestern framing in the Middle Cretaceous, where Mesozoic rocks of different geodynamic and latitudinal-climate settings were juxtaposed into allochthonous units.

Novel Thermal Powered Technology for UUV Persistent Surveillance

NASA Technical Reports Server (NTRS)

Jones, Jack A.; Chao, Yi

2006-01-01

Buoyancy Generation: Various technology attempts include melting a wax, which pushes directly against a piston (U.S. Patent 5,291,847) or against a bladder (Webb Research), using ammonia or Freon 21 (U.S. Patent 5,303,552), and using solar heat to expand an oil (www.space.com, April, 10, 2002). All these heat-activated buoyancy control designs have thus far proved impractical and have ultimately failed during repeated cycling in ocean testing. JPL has demonstrated fully reversible 10 C encapsulated wax phase change, which can be used to change buoyancy without electrical hydraulic pumps. This technique has greatly improved heat transfer and much better reversibility than previous designs. Power Generation: Ocean Thermal Energy Conversion (OTEC) systems have been designed that transfer deep, cold sea water to the surface to generate electricity using turbine cycles with ammonia or water as the working fluid. JPL has designed several UUV systems: 1) Using a propeller water turbine to generate power on a gliding submersible; 2) Employing a compact CO2 turbine cycle powered by moving through thermoclines; and 3) Using melted wax to directly produce power through a piston-geared generator.

How cold pool triggers deep convection?

NASA Astrophysics Data System (ADS)

Yano, Jun-Ichi

2014-05-01

The cold pool in the boundary layer is often considered a major triggering mechanism of convection. Here, presented are basic theoretical considerations on this issue. Observations suggest that cold pool-generated convective cells is available for shallow maritime convection (Warner et al. 1979; Zuidema et al. 2012), maritime deep convection (Barnes and Garstang 1982; Addis et al. 1984; Young et al. 1995) and continental deep convection (e.g., Lima and Wilson 2008; Flamant 2009; Lothon et al. 2011; Dione et al. 2013). Moreover, numerical studies appear to suggest that cold pools promote the organization of clouds into larger structures and thereby aid the transition from shallow to deep convection (Khairoutdinov and Randall 2006, Boing et al. 2012, Schlemmer and Hohenegger, 2014). Even a cold--pool parameterization coupled with convection is already proposed (Grandpeix and Lafore 2010: but see also Yano 2012). However, the suggested link between the cold pool and deep convection so far is phenomenological at the best. A specific process that the cold pool leads to a trigger of deep convection must still to be pinned down. Naively, one may imagine that a cold pool lifts up the air at the front as it propagates. Such an uplifting leads to a trigger of convection. However, one must realize that a shift of air along with its propagation does not necessarily lead to an uplifting, and even if it may happen, it would not far exceed a depth of the cold pool itself. Thus, the uplifting can never be anything vigorous. Its thermodynamic characteristics do help much either for inducing convection. The cold-pool air is rather under rapid recovering process before it can induce convection under a simple parcel-lifting argument. The most likely reason that the cold pool may induce convection is its gust winds that may encounter an air mass from an opposite direction. This induces a strong convergence, also leading to a strong uplifting. This is an argument essentially developed by Moncrieff and Liu (1999). As a whole, in attempting a statistical description of boundary-layer processes, the cold pool is essentially nothing other than an additional contribution to a TKE (turbulent kinetic energy) budget. Significance of trigger of convection by cold pool in context of convection parameterization must also be seen with much caution. Against a common misunderstanding, current convection parameterization is not designed to describe a trigger process of individual convection. In this respect, process studies on cold pool do not contribute to improvements of convection parameterization until a well-defined parameterization formulation for individual convection processes is developed. Even before then a question should also be posed whether such a development is necessary. Under a current mass-flux convection parameterization, a more important process to consider is re-evaporative cooling of detrained cloudy air, which may also be associated with downdraft, possibly further leading to a generation of a cold pool. Yano and Plant (2012) suggest, from a point of view of the convective-energy cycle, what follows would be far less important than the fact the re-evaporation induces a generation of convective kinetic energy (though it may initially be considered TKE). Both well-focused convective process studies as well as convection parameterization formulation would be much needed.

Deep-sea bioluminescence blooms after dense water formation at the ocean surface.

PubMed

Tamburini, Christian; Canals, Miquel; Durrieu de Madron, Xavier; Houpert, Loïc; Lefèvre, Dominique; Martini, Séverine; D'Ortenzio, Fabrizio; Robert, Anne; Testor, Pierre; Aguilar, Juan Antonio; Samarai, Imen Al; Albert, Arnaud; André, Michel; Anghinolfi, Marco; Anton, Gisela; Anvar, Shebli; Ardid, Miguel; Jesus, Ana Carolina Assis; Astraatmadja, Tri L; Aubert, Jean-Jacques; Baret, Bruny; Basa, Stéphane; Bertin, Vincent; Biagi, Simone; Bigi, Armando; Bigongiari, Ciro; Bogazzi, Claudio; Bou-Cabo, Manuel; Bouhou, Boutayeb; Bouwhuis, Mieke C; Brunner, Jurgen; Busto, José; Camarena, Francisco; Capone, Antonio; Cârloganu, Christina; Carminati, Giada; Carr, John; Cecchini, Stefano; Charif, Ziad; Charvis, Philippe; Chiarusi, Tommaso; Circella, Marco; Coniglione, Rosa; Costantini, Heide; Coyle, Paschal; Curtil, Christian; Decowski, Patrick; Dekeyser, Ivan; Deschamps, Anne; Donzaud, Corinne; Dornic, Damien; Dorosti, Hasankiadeh Q; Drouhin, Doriane; Eberl, Thomas; Emanuele, Umberto; Ernenwein, Jean-Pierre; Escoffier, Stéphanie; Fermani, Paolo; Ferri, Marcelino; Flaminio, Vincenzo; Folger, Florian; Fritsch, Ulf; Fuda, Jean-Luc; Galatà, Salvatore; Gay, Pascal; Giacomelli, Giorgio; Giordano, Valentina; Gómez-González, Juan-Pablo; Graf, Kay; Guillard, Goulven; Halladjian, Garadeb; Hallewell, Gregory; van Haren, Hans; Hartman, Joris; Heijboer, Aart J; Hello, Yann; Hernández-Rey, Juan Jose; Herold, Bjoern; Hößl, Jurgen; Hsu, Ching-Cheng; de Jong, Marteen; Kadler, Matthias; Kalekin, Oleg; Kappes, Alexander; Katz, Uli; Kavatsyuk, Oksana; Kooijman, Paul; Kopper, Claudio; Kouchner, Antoine; Kreykenbohm, Ingo; Kulikovskiy, Vladimir; Lahmann, Robert; Lamare, Patrick; Larosa, Giuseppina; Lattuada, Dario; Lim, Gordon; Presti, Domenico Lo; Loehner, Herbert; Loucatos, Sotiris; Mangano, Salvatore; Marcelin, Michel; Margiotta, Annarita; Martinez-Mora, Juan Antonio; Meli, Athina; Montaruli, Teresa; Moscoso, Luciano; Motz, Holger; Neff, Max; Nezri, Emma Nuel; Palioselitis, Dimitris; Păvălaş, Gabriela E; Payet, Kevin; Payre, Patrice; Petrovic, Jelena; Piattelli, Paolo; Picot-Clemente, Nicolas; Popa, Vlad; Pradier, Thierry; Presani, Eleonora; Racca, Chantal; Reed, Corey; Riccobene, Giorgio; Richardt, Carsten; Richter, Roland; Rivière, Colas; Roensch, Kathrin; Rostovtsev, Andrei; Ruiz-Rivas, Joaquin; Rujoiu, Marius; Russo, Valerio G; Salesa, Francisco; Sánchez-Losa, Augustin; Sapienza, Piera; Schöck, Friederike; Schuller, Jean-Pierre; Schussler, Fabian; Shanidze, Rezo; Simeone, Francesco; Spies, Andreas; Spurio, Maurizio; Steijger, Jos J M; Stolarczyk, Thierry; Taiuti, Mauro G F; Toscano, Simona; Vallage, Bertrand; Van Elewyck, Véronique; Vannoni, Giulia; Vecchi, Manuela; Vernin, Pascal; Wijnker, Guus; Wilms, Jorn; de Wolf, Els; Yepes, Harold; Zaborov, Dmitry; De Dios Zornoza, Juan; Zúñiga, Juan

2013-01-01

The deep ocean is the largest and least known ecosystem on Earth. It hosts numerous pelagic organisms, most of which are able to emit light. Here we present a unique data set consisting of a 2.5-year long record of light emission by deep-sea pelagic organisms, measured from December 2007 to June 2010 at the ANTARES underwater neutrino telescope in the deep NW Mediterranean Sea, jointly with synchronous hydrological records. This is the longest continuous time-series of deep-sea bioluminescence ever recorded. Our record reveals several weeks long, seasonal bioluminescence blooms with light intensity up to two orders of magnitude higher than background values, which correlate to changes in the properties of deep waters. Such changes are triggered by the winter cooling and evaporation experienced by the upper ocean layer in the Gulf of Lion that leads to the formation and subsequent sinking of dense water through a process known as "open-sea convection". It episodically renews the deep water of the study area and conveys fresh organic matter that fuels the deep ecosystems. Luminous bacteria most likely are the main contributors to the observed deep-sea bioluminescence blooms. Our observations demonstrate a consistent and rapid connection between deep open-sea convection and bathypelagic biological activity, as expressed by bioluminescence. In a setting where dense water formation events are likely to decline under global warming scenarios enhancing ocean stratification, in situ observatories become essential as environmental sentinels for the monitoring and understanding of deep-sea ecosystem shifts.

Deep-sea ostracods from the South Atlantic sector of the Southern ocean during the Last 370,000 years

USGS Publications Warehouse

Yasuhara, Moriaki; Cronin, T. M.; Hunt, G.; Hodell, D.A.

2009-01-01

We report changes of deep-sea ostracod fauna during the last 370,000 yr from the Ocean Drilling Program (ODP) Hole 704A in the South Atlantic sector of the Southern Ocean. The results show that faunal changes are coincident with glacial/interglacial-scale deep-water circulation changes, even though our dataset is relatively small and the waters are barren of ostracods until mid-MIS (Marine Isotope Stage) 5. Krithe and Poseidonamicus were dominant during the Holocene interglacial period and the latter part of MIS 5, when this site was under the influence of North Atlantic Deep Water (NADW). Conversely, Henryhowella and Legitimocythere were dominant during glacial periods, when this site was in the path of Circumpolar Deep Water (CPDW). Three new species (Aversovalva brandaoae, Poseidonamicus hisayoae, and Krithe mazziniae) are described herein. This is the first report of Quaternary glacial/interglacial scale deep-sea ostracod faunal changes in the Southern and South Atlantic Oceans, a key region for understanding Quaternary climate and deep-water circulation, although the paucity of Quaternary ostracods in this region necessitates further research. ?? 2009 The Paleontological Society.

Exchanges between the open Black Sea and its North West shelf

NASA Astrophysics Data System (ADS)

Shapiro, Georgy; Wobus, Fred; Zhou, Feng

2014-05-01

Exchanges between the vast NW shelf and the deep basin of the Black Sea play a significant role in maintaining the balance of nutrients, heat content and salinity of the shelf waters. Nearly 87 % of the Black Sea is entirely anoxic below 70 to 200m and contains high levels of hydrogen sulphide (Zaitsev et al, 2001), and this makes the shelf waters particularly valuable for maintaining the Black Sea ecosystem in good health. The increase in salinity of shelf waters occurs partially due to exchanges with more saline open sea waters and represents a threat to relics and endemic species. The shelf-break is commonly considered the bottle-neck of the shelf-deep sea exchanges (e.g. (Huthnance, 1995, Ivanov et al, 1997). Due to conservation of potential vorticity, the geostrophic currents flow along the contours of constant depth. However the ageostrophic flows (Ekman drift, mesoscale eddies, filaments, internal waves) are not subject to the same constraints. It has been shown that during the winter well mixed cold waters formed on the North West shelf propagate into the deep sea, providing an important mechanism for the replenishment of the Cold Intermediate Layer ( Staneva and Stanev, 1997). However, much less is known about exchanges in the warm season. In this study, the transports of water, heat and salt between the northwestern shelf and the adjacent deep basin of the Black Sea are investigated using a high-resolution three-dimensional primitive equation model, NEMO-SHELF-BLS (Shapiro et al, 2013). It is shown that during the period from April to August, 2005, both onshore and offshore cross-shelf break transports in the top 20 m were as high as 0.24 Sv on average, which was equivalent to the replacement of 60% of the volume of surface shelf waters (0 - 20 m) per month. Two main exchange mechanisms are studied: (i) Ekman transport, and (ii) transport by mesoscale eddies and associated meanders of the Rim Current. The Ekman drift causes nearly uniform onshore or offshore flow over a large section of the shelf break. Due to the short duration of strong wind effects (4-7 days) the horizontal extent of cross-shelf-break exchanges is limited to the outer shelf. The effect of Ekman drift is confined to the upper layers. In contrast, eddies and meanders penetrate deep down to the bottom, but they are restricted laterally. During the strong wind events of April 15 - 22 and July 1 - 4, some 0.66×1012 and 0.44×1012 m3of water were removed from the northwestern shelf respectively. In comparison, the single long-lived Sevastopol Eddy generated a much larger offshore transfer of 2.84×1012 m3 over the period April 23 to June 30, which is equivalent to 102% of the volume of northwestern shelf waters. This result is consistent with the data obtained from satellite derived information (Shapiro et al, 2010). The open Black Sea is generally warmer and more saline than the northwest shelf. Hence the exchanges contribute to the increase in both salinity and temperature of shelf waters. Over the study period, salt exchanges increased the average density of the shelf waters by 0.67 kg m-3 and reduced the density contrast between the shelf and deep sea, while lateral heat exchanges reduced the density of the shelf waters by 0.16 kg m-3 and thus enhanced density contrast across the shelf break. This study was supported by the EU (via PERSEUS grant FP7-OCEAN-2011-287600 and MyOcean SPA.2011.1.5-01 grant 283367), Ministry of Science and Technology of China (Grant 2011CB409803), the Natural Science Foundation of China (Grant 41276031), Zhejiang Association for International Exchange of Personnel, and the University of Plymouth Marine Institute Innovation Fund. References Huthnance, J. M., 1995. Circulation, exchange and water masses at the ocean margin: the role of physical processes at the shelf edge, Prog Oceanogr, 35(4), 353-431, Ivanov L.I., Besiktepe S., Ozsoy E., 1997. In: E.Ozsoy and A.Mikaelyan (eds). Sensitivity to change: Black Sea , Baltic Sea and North Sea. NATO ASI Series, Vol. 27, Kluwer Academic Publishers, 253-264. Shapiro, G.I. , S.V. Stanichny, R.R. Stanychna, 2010. Anatomy of shelf-deep sea exchanges by a mesoscale eddy in the North West Black Sea as derived from remotely sensed data. Remote Sensing of Environment, 114 , 867-875. Shapiro, G., Luneva, M., Pickering, J., and Storkey, D., 2013. The effect of various vertical discretization schemes and horizontal diffusion parameterization on the performance of a 3-D ocean model: the Black Sea case study, Ocean Science, 9, 377-390. Staneva, J. V. and E. V. Stanev, 1997. Cold water mass formation in the Black Sea. Analysis on numerical model simulations. In: E. Ozsoy and A. Mikaelyan (eds.), Sensitivity to change: Black Sea, Baltic Sea and North Sea. NATO ASI Series, Vol. 27, Kluwer Academic Publishers, 375-393. Zaitsev Yu.P., B.G. Alexandrov, N.A. Berlinsky, A. Zenetos, 2001. Europe's biodiversity - biogeographical regions and seas. The Black Sea. European Environment Agency.

Natural biogeochemical cycle of mercury in a global three-dimensional ocean tracer model

NASA Astrophysics Data System (ADS)

Zhang, Yanxu; Jaeglé, Lyatt; Thompson, LuAnne

2014-05-01

We implement mercury (Hg) biogeochemistry in the offline global 3-D ocean tracer model (OFFTRAC) to investigate the natural Hg cycle, prior to any anthropogenic input. The simulation includes three Hg tracers: dissolved elemental (Hg0aq), dissolved divalent (HgIIaq), and particle-bound mercury (HgPaq). Our Hg parameterization takes into account redox chemistry in ocean waters, air-sea exchange of Hg0, scavenging of HgIIaq onto sinking particles, and resupply of HgIIaq at depth by remineralization of sinking particles. Atmospheric boundary conditions are provided by a global simulation of the natural atmospheric Hg cycle in the GEOS-Chem model. In the surface ocean, the OFFTRAC model predicts global mean concentrations of 0.16 pM for total Hg, partitioned as 80% HgIIaq, 14% Hg0aq, and 6% HgPaq. Total Hg concentrations increase to 0.38 pM in the thermocline/intermediate waters (between the mixed layer and 1000 m depth) and 0.82 pM in deep waters (below 1000 m), reflecting removal of Hg from the surface to the subsurface ocean by particle sinking followed by remineralization at depth. Our model predicts that Hg concentrations in the deep North Pacific Ocean (>2000 m) are a factor of 2-3 higher than in the deep North Atlantic Ocean. This is the result of cumulative input of Hg from particle remineralization as deep waters transit from the North Atlantic to the North Pacific on their ~2000 year journey. The model is able to reproduce the relatively uniform concentrations of total Hg observed in the old deep waters of the North Pacific Ocean (observations: 1.2 ± 0.4 pM; model: 1.1 ± 0.04 pM) and Southern Ocean (observations: 1.1 ± 0.2 pM; model: 0.8 ± 0.02 pM). However, the modeled concentrations are factors of 5-6 too low compared to observed concentrations in the surface ocean and in the young water masses of the deep North Atlantic Ocean. This large underestimate for these regions implies a factor of 5-6 anthropogenic enhancement in Hg concentrations.

How does mesoscale impact deep convection? Answers from ensemble Northwestern Mediterranean Sea simulations.

NASA Astrophysics Data System (ADS)

Waldman, Robin; Herrmann, Marine; Somot, Samuel; Arsouze, Thomas; Benshila, Rachid; Bosse, Anthony; Chanut, Jérôme; Giordani, Hervé; Pennel, Romain; Sevault, Florence; Testor, Pierre

2017-04-01

Ocean deep convection is a major process of interaction between surface and deep ocean. The Gulf of Lions is a well-documented deep convection area in the Mediterranean Sea, and mesoscale dynamics is a known factor impacting this phenomenon. However, previous modelling studies don't allow to address the robustness of its impact with respect to the physical configuration and ocean intrinsic variability. In this study, the impact of mesoscale on ocean deep convection in the Gulf of Lions is investigated using a multi-resolution ensemble simulation of the northwestern Mediterranean sea. The eddy-permitting Mediterranean model NEMOMED12 (6km resolution) is compared to its eddy-resolving counterpart with the 2-way grid refinement AGRIF in the northwestern Mediterranean (2km resolution). We focus on the well-documented 2012-2013 period and on the multidecadal timescale (1979-2013). The impact of mesoscale on deep convection is addressed in terms of its mean and variability, its impact on deep water transformations and on associated dynamical structures. Results are interpreted by diagnosing regional mean and eddy circulation and using buoyancy budgets. We find a mean inhibition of deep convection by mesoscale with large interannual variability. It is associated with a large impact on mean and transient circulation and a large air-sea flux feedback.

Integrated Metagenomic and Metatranscriptomic Analyses of Microbial Communities in the Meso- and Bathypelagic Realm of North Pacific Ocean

PubMed Central

Wu, Jieying; Gao, Weimin; Johnson, Roger H.; Zhang, Weiwen; Meldrum, Deirdre R.

2013-01-01

Although emerging evidence indicates that deep-sea water contains an untapped reservoir of high metabolic and genetic diversity, this realm has not been studied well compared with surface sea water. The study provided the first integrated meta-genomic and -transcriptomic analysis of the microbial communities in deep-sea water of North Pacific Ocean. DNA/RNA amplifications and simultaneous metagenomic and metatranscriptomic analyses were employed to discover information concerning deep-sea microbial communities from four different deep-sea sites ranging from the mesopelagic to pelagic ocean. Within the prokaryotic community, bacteria is absolutely dominant (~90%) over archaea in both metagenomic and metatranscriptomic data pools. The emergence of archaeal phyla Crenarchaeota, Euryarchaeota, Thaumarchaeota, bacterial phyla Actinobacteria, Firmicutes, sub-phyla Betaproteobacteria, Deltaproteobacteria, and Gammaproteobacteria, and the decrease of bacterial phyla Bacteroidetes and Alphaproteobacteria are the main composition changes of prokaryotic communities in the deep-sea water, when compared with the reference Global Ocean Sampling Expedition (GOS) surface water. Photosynthetic Cyanobacteria exist in all four metagenomic libraries and two metatranscriptomic libraries. In Eukaryota community, decreased abundance of fungi and algae in deep sea was observed. RNA/DNA ratio was employed as an index to show metabolic activity strength of microbes in deep sea. Functional analysis indicated that deep-sea microbes are leading a defensive lifestyle. PMID:24152557

Global Ocean Circulation During Cretaceous Time

NASA Astrophysics Data System (ADS)

Haupt, B. J.; Seidov, D.

2001-12-01

Present--day global thermohaline ocean circulation (TOC) is usually associated with high--latitude deep-water formation due to surface cooling. In this understanding of the TOC driven by the deep--water production, the warm deep ocean during Mesozoic--Cenozoic time is a challenge. It may be questioned whether warm deep--ocean water, which is direct geologic evidence, does reflect warm polar surface--ocean regions. For the warm Cretaceous, it is difficult to maintain strong poleward heat transport in the case of reduced oceanic thermal contrasts. Usually, atmospheric feedbacks, in conjunction with the increase of atmospheric concentrations of greenhouse gases, are employed in order to explain the warm equable Cretaceous--Eocene climate. However, there is no feasible physical mechanism that could maintain warm subpolar surface oceans in both hemispheres, an assumption often used in atmospheric modeling. Our numerical experiments indicate that having a relatively cool but saltier high--latitude sea surface in at least one hemisphere is sufficient for driving a strong meridional overturning. Thus freshwater impacts in the high latitudes may be responsible for a vigorous conveyor capable of maintaining sufficient poleward oceanic heat transport needed to keep the polar oceans ice--free. These results imply that evaporation-precipitation patterns during warm climates are especially important climatic factors that can redistribute freshwater to create hemispheric asymmetry of sea surface conditions capable of generating a sufficiently strong TOC, otherwise impossible in warm climates.

Nonhydrostatic thermohaline convection in the polar oceans

NASA Astrophysics Data System (ADS)

Potts, Mark Allen

Sea ice cover in the polar and sub-polar seas is an important and sensitive component of the Earth's climate system. It mediates the transfer of heat and momentum between the ocean and the atmosphere in high latitude oceans. Where open patches occur in the ice cover a large transfer of heat from the ocean to the atmosphere occurs that accounts for a large fraction of energy exchange between the wintertime polar ocean and atmosphere. Although the circumstances under which leads and polynyas form are considerably different, similar brine driven convection occurs under both. Convection beneath freezing ice in leads and polynyas can be modeled using either the hydrostatic or nonhydrostatic form of the governing equations. One important question is the degree of nonhydrostaticity, which depends on the vertical accelerations present. This issue is addressed through the application of a nonhydrostatic model, with accurate treatment of the turbulent mixing. The results suggest that mixing and re-freezing considerably modify the fluid dynamical processes underneath, such as the periodic shedding of saline plumes. It also appears that overall, the magnitude of the nonhydrostaticity is small, and hydrostatic models are generally adequate to deal with the problem of convection under leads. Strong wintertime cooling drives deep convection in sub-polar seas and in the coastal waters surrounding Antarctica. Deep convection results in formation of deep water in the global oceans, which is of great importance to the maintenance of the stratification of its deep interior, and the resulting meridional circulation is central to the Earth's climatic state. Deep convection falls into two general categories: open ocean deep convection, which occurs in deep stretches of the high latitude seas far from topographical influences, and convection on or near the continental shelves, where topography exerts a considerable influence. Nonhydrostatic models are central to the study of deep convection, but the presence of the bottom leads to significant complications in shallower waters. This issue of deep convection in the presence of topography is addressed for the first time with a non-hydrostatic model through the adaptation of the virtual boundary method and used to simulate convection over the Mertz Glacier polynya in the Antarctic in both two and three dimensions.

Recent 121-year variability of western boundary upwelling in the northern South China Sea

NASA Astrophysics Data System (ADS)

Liu, Yi; Peng, Zicheng; Shen, Chuan-Chou; Zhou, Renjun; Song, Shaohua; Shi, Zhengguo; Chen, Tegu; Wei, Gangjian; Delong, Kristine L.

2013-06-01

upwelling is typically related to the eastern boundary upwelling system, whereas the powerful southwest Asian summer monsoon can also generate significant cold, nutrient-rich deep water in western coastal zones. Here we present a sea surface temperature record (A.D. 1876-1996) derived from coral Porites Sr/Ca for an upwelling zone in the northern South China Sea. The upwelling-induced sea surface temperature anomaly record reveals prominent multidecadal variability driven by Asian summer monsoon dynamics with an abrupt transition from warmer to colder conditions in 1930, and a return to warmer conditions after 1960. Previous studies suggest the expected increase in atmospheric CO2 for the coming decades may result in intensification in the eastern boundary upwelling system, which could enhance upwelling of CO2-rich deep water thus exacerbating the impact of acidification in these productive zones. In contrast, the weakening trend since 1961 in the upwelling time series from the northern South China Sea suggests moderate regional ocean acidification from upwelling thus a stress relief for marine life in this region.

Cultivation and Characterization of Oil-Degrading Microbes and the Environmental Controls on Hydrocarbon Biodegradation Patterns

NASA Astrophysics Data System (ADS)

Redmond, M. C.

2016-02-01

The Deepwater Horizon oil spill highlighted the ability of microbes to degrade hydrocarbons in both cold, deep water and at the warm sea surface. However, the temperature and differing hydrocarbons in the deep ocean and sea surface led to different microbial communities and biodegradation patterns. In order to develop a better understanding of the factors that control microbial community composition and biodegradation patterns, we conducted laboratory microcosm studies with seawater samples from coastal South Carolina and hydrocarbon seeps in the Gulf of Mexico, incubated with different hydrocarbons, at different temperatures, and in static or shaking incubation conditions. We analyzed microbial community composition after three weeks and used successive transfers on liquid and then solid media to isolate cultures. More rapid growth was observed at 28 degrees than 4 degrees, with hexadecane compared to benzene, cyclohexane, or crude oil, and in shaking incubations compared to static. However, we were able to successfully culture microbes under all conditions. Physiological and genetic characterization of isolated strains is ongoing, and will be combined with assessment of hydrocarbon substrate preferences and kinetics under different environmental conditions.

Eukaryotic microbes, principally fungi and labyrinthulomycetes, dominate biomass on bathypelagic marine snow

PubMed Central

Bochdansky, Alexander B; Clouse, Melissa A; Herndl, Gerhard J

2017-01-01

In the bathypelagic realm of the ocean, the role of marine snow as a carbon and energy source for the deep-sea biota and as a potential hotspot of microbial diversity and activity has not received adequate attention. Here, we collected bathypelagic marine snow by gentle gravity filtration of sea water onto 30 μm filters from ~1000 to 3900 m to investigate the relative distribution of eukaryotic microbes. Compared with sediment traps that select for fast-sinking particles, this method collects particles unbiased by settling velocity. While prokaryotes numerically exceeded eukaryotes on marine snow, eukaryotic microbes belonging to two very distant branches of the eukaryote tree, the fungi and the labyrinthulomycetes, dominated overall biomass. Being tolerant to cold temperature and high hydrostatic pressure, these saprotrophic organisms have the potential to significantly contribute to the degradation of organic matter in the deep sea. Our results demonstrate that the community composition on bathypelagic marine snow differs greatly from that in the ambient water leading to wide ecological niche separation between the two environments. PMID:27648811

Inter-annual variability of exchange processes at the outer Black Sea shelf

NASA Astrophysics Data System (ADS)

Shapiro, Georgy; Wobus, Fred; Yuan, Dongliang; Wang, Zheng

2014-05-01

The advection of cold water below the surface mixed layer has a significant role in shaping the properties of the Cold Intermediate Layer (CIL) in the Black Sea, and thus the horizontal redistribution of nutrients. The minimal temperature of the CIL in the southwest deep region of the sea in summer was shown to be lower than the winter surface temperature at the same location, indicating the horizontal advective nature of CIL formation in the area (Kolesnikov, 1953). In addition to advection in the deep area of the sea, the transport of cold waters from the northwest Black Sea shelf across the shelf break in winter was shown to contribute to the formation of the CIL (Filippov, 1968; Staneva and Stanev, 1997). However less is known of the exchanges between the CIL waters and the outer shelf areas in summer, when a surface mixed layer and the underlying seasonal thermocline are formed. Ivanov et al. (1997) suggested that the cross frontal exchange within the CIL is strongly inhibited, so that CIL waters formed in the deep sea (i.e. offshore of the Rim Current) do not replenish the CIL waters onshore of the Rim Current (also known as near-bottom shelf waters, or BSW), due to strong cross frontal gradients in potential vorticity (PV). To the contrary, Shapiro et al. (2011) analysed in-situ observations over the period of 1950-2001 and showed a high correlation between the CIL temperatures in the open sea and outer shelf. However, the statistical methods alone were not able to clearly establish the relation between the cause and the consequences. In this study we use a 3D numerical model of the Black Sea (NEMO-SHELF-BLS) to quantify the exchange of CIL waters between the open sea and the outer northwest Black Sea shelf and to assess its significance for the replenishment of BSW on the outer shelf. The model has a resolution of 1/16º latitude × 1/12º longitude and 33 levels in the vertical. In order to represent near-bottom processes better, the model uses a hybrid vertical discretisation (s-on-top-of-z) and other improved parameters of the model set-up as in Shapiro et al. (2013). The model was run for the period from 1979 to 2012 with water discharges from 8 main rivers, exchanges through Bosporus and meteo forcing from the Drakkar Forcing Set 5.2 (Brodeau et al, 2010). The model was spun-up from climatological temperature and salinity in January using a semi-diagnostic adjustment method. Each annual simulation started from the same initial state on 1 January without data assimilation. The data for the warm period from 1 May to 31 October of each year were used for the following analysis. The model has been validated against in-situ (based on 77867 stations) and night-time satellite monthly mean SST observations. The model also captures well the major features seen on snapshot satellite images. A simulated daily climatology was created by averaging the temperature values over the 34-year simulation. Anomalies were calculated as the deviations of the snapshot temperatures from their climatological values. The correlation between the temperature anomalies of BSW on the outer shelf and those in the CIL waters in the deep sea were computed as well as water transports between these water masses across the shelf break. The BSW on the outer shelf are defined as the waters between the density level σθ=14.2 kg m3 (i.e. the bottom of the surface mixed layer) and the seabed (max z=150 m at the shelf break). The corresponding data from open sea CIL waters in the northwest part of the deep Black Sea were taken from the depth range between σθ=14.2 and z=150 m. The computed Pierson correlation between summer temperatures of BSW and the deep sea CIL is R = 0.90. This significant correlation is in agreement with the analysis from observational data of Shapiro et al. (2011). In order to reveal a physical link between the BSW and CIL, the in-out transports of water with σθ ≥14.2 across the shelf break were computed for each day and then averaged over the warm periods of each year. Over the 34 year time span, the on-shelf and off-shelf transports between the CIL and BSW fluctuate in the range of 0.22 to 0.45 Sv, with the maximum values in 1996 and the minimum in 1990. The net cross-shelf transport is small, approximately 0.03 Sv, due to volume conservation, and is directed off-shore due to river discharges. The years with high values of transport correspond to the situation when a 'channel' of constant PV connecting the BSW and CIL exists, forming a conduit for the waters to move across the shelf break. In the years of reduced transport, there was a PV 'barrier', i.e. a band of significant PV gradient along the shelf break, which inhibits exchanges. The efficiency of the exchange can be represented by the average renewal time of BSW, which is defined as the ratio of BSW volume to the onshore transport. This value, as well as the volumes and the transports vary over the 34 years. The renewal time is within the range between 18 to 42 days. The short renewal time (31 days on average) compared to the seasonal time scales, suggests an efficient exchange between bottom waters on the outer shelf and the CIL in the deep sea during the warm season. This study was partially supported by the EU (via PERSEUS grant FP7-OCEAN-2011-287600 and MyOcean SPA.2011.1.5-01 grant 283367), Institute of Oceanology, Chinese Academy of Sciences and the University of Plymouth Marine Institute Innovation Fund. References Brodeau L., B. Barnier, A.-M. Treguier, T.Penduff, S.Gulev, 2010. An ERA40-based atmospheric forcing for global ocean circulation models, Ocean Modelling, 31 (3-4), 88-104. Kolesnikov, A.G., 1953. Intra-annual variability of temperature, stability and vertical turbulent exchange of heat in the open area of the Black Sea. In: Proceedings of the Marine Hydrophysical Institute, issue 3. Filippov D.M., 1968. Water Circulation and Structure of the Black Sea. Nauka, Moscow, 136 pp. Ivanov, L. I., Besiktepe, S. and E. Özsoy, 1997. The Black Sea Cold Intermediate Layer, in: Özsoy, E. and A. Mikaelyan (editors), Sensitivity to Change: Black Sea, Baltic Sea and North Sea, NATO ASI Series (Partnership Sub-series, Environment, 27), Kluwer Academic Publishers, Dordrecht, 536 pp. Shapiro, G.I., F. Wobus, D.L. Aleynik, 2011. Seasonal and inter-annual temperature variability in the bottom waters over the western Black Sea shelf, Ocean Science 7, 585-596. Shapiro, G., Luneva, M., Pickering, J., and Storkey, D., 2013. The effect of various vertical discretization schemes and horizontal diffusion parameterization on the performance of a 3-D ocean model: the Black Sea case study, Ocean Science, 9, 377-390. Staneva, J. V. and E. V. Stanev, 1997. Cold water mass formation in the Black Sea. Analysis on numerical model simulations. In: E. Ozsoy and A. Mikaelyan (eds.), Sensitivity to change: Black Sea, Baltic Sea and North Sea. NATO ASI Series, Vol. 27, Kluwer Academic Publishers, 375-393.

Ice-Shelf Melting Around Antarctica

NASA Astrophysics Data System (ADS)

Rignot, E.; Jacobs, S.; Mouginot, J.; Scheuchl, B.

2013-07-01

We compare the volume flux divergence of Antarctic ice shelves in 2007 and 2008 with 1979 to 2010 surface accumulation and 2003 to 2008 thinning to determine their rates of melting and mass balance. Basal melt of 1325 ± 235 gigatons per year (Gt/year) exceeds a calving flux of 1089 ± 139 Gt/year, making ice-shelf melting the largest ablation process in Antarctica. The giant cold-cavity Ross, Filchner, and Ronne ice shelves covering two-thirds of the total ice-shelf area account for only 15% of net melting. Half of the meltwater comes from 10 small, warm-cavity Southeast Pacific ice shelves occupying 8% of the area. A similar high melt/area ratio is found for six East Antarctic ice shelves, implying undocumented strong ocean thermal forcing on their deep grounding lines.

Broadening our View of the MOC using Satellite Altimetry and Two Moored Arrays in the Atlantic: MOVE 16N and RAPID 26N

NASA Astrophysics Data System (ADS)

Duchez, A.; Frajka-Williams, E.; Lankhorst, M. J.; Koelling, J.; Send, U.

2016-02-01

The Atlantic meridional overturning circulation (MOC) carries heat northwards in the top 1000m of the Atlantic, with a deep, cold return flow below. Climate simulations predict a slowing of the AMOC in the coming years, while present day observations from boundary arrays demonstrate substantial variability on weekly- to interannual timescales. Using simultaneous observations from the MOVE 16N and RAPID 26N arrays in the Atlantic, we investigate transport and property variability. On long timescales, the tendencies in deep densities are similar between the two latitudes (towards lighter water in the west), resulting in a change in the thermal wind balance across the Atlantic. This tendency is punctuated by a more abrupt change in late 2009 at 26N and 7 months later at 16N. In situ arrays such as RAPID 26N and MOVE 16N provide detailed depth structure of transport variability, but are necessarily limited to individual latitudes. Using satellite altimetry, we show that the sea surface height (SSH) anomalies in the western half of the Atlantic covary with in situ transport estimates on interannual timescales. We use satellite altimetry to extend estimates of depth-integrated ocean transports back in time to 1993, then investigate how the spatial pattern of SSH variability broadens our view of Atlantic MOC structure beyond individual latitudes. This analysis investigates two decade+ long time series of ocean transports, and complements the findings with satellite observations.

Bahamian Pleistocene model for some Mississippian oolites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bain, R.J.

1989-08-01

San Salvador Island, unlike most Bahamian islands, is a narrow isolated platform surrounded by deep ocean. Therefore, sedimentary deposits on San Salvador must be explained in terms of processes and settings on this narrow, isolated shelf. Pleistocene oolite occurs between Illinoian and Wisconsinan paleosols. Dune ridges of up to 120 ft are composed of Pleistocene cross-bedded oolitic grainstone, whereas interdunal deposits are bioclastic packstone and wackestone containing abundant Chione cancellata. In lower dunal deposits, bioclastic content increases and the degree of sorting decreases. A fenestral porosity zone occurs approximately 5 ft above present-day sea level. In several ridges, oolite drapesmore » over older paleosol-capped bioclastic ridges. During the Sangamonian, sea water flooded the platform, however some remnant Aftonian ridges remained above sea level. As cold water from the surrounding deep ocean warmed on the shelf, ooids were generated and were washed onto beaches and blown into dunes. Remnant ridges restricted water movement and acted as nucleii for eolian ooid dunes. As sea level continued to rise, ooids were replaced by lagoonal bioclastic deposits. Ooid production was restricted to the swash zone along beaches resulting in the mixture of ooids and bioclastic sand in later Sangamonian deposits. Numerous Mississippian oolites display features similar to the Pleistocene oolite of San Salvador Island. Possible comparisons include thick lenses of Ste. Genevieve and Bangor limestones, paleosols in the Ste. Genevieve halo-shaped bodies of Greenbrier oolite, and the relationship of nearly all olites with bioclastic facies.« less

Lytic viral infection of bacterioplankton in deep waters of the western Pacific Ocean

NASA Astrophysics Data System (ADS)

Li, Y.; Luo, T.; Sun, J.; Cai, L.; Liang, Y.; Jiao, N.; Zhang, R.

2014-05-01

As the most abundant biological entities in the ocean, viruses influence host mortality and nutrient recycling mainly through lytic infection. Yet, the ecological characteristics of virioplankton and viral impacts on host mortality and biogeochemical cycling in the deep sea are largely unknown. In the present study, viral abundance and lytic infection were investigated throughout the water column in the western Pacific Ocean. Both the prokaryotic and viral abundance and production showed a significantly decreasing trend from epipelagic to meso- and bathypelagic waters. Viral abundance decreased from 0.36-1.05 × 1010 particles L-1 to 0.43-0.80 × 109 particles L-1, while the virus : prokaryote ratio varied from 7.21 to 16.23 to 2.45-23.40, at the surface and 2000 m, respectively. Lytic viral production rates in surface and 2000 m waters were, on average, 1.03 × 1010 L-1 day-1 and 5.74 × 108 L-1 day-1. Relatively high percentages of prokaryotic cells lysed by viruses at 1000 and 2000 m were observed, suggesting a significant contribution of viruses to prokaryotic mortality in the deep ocean. The carbon released by viral lysis in deep western Pacific Ocean waters was from 0.03 to 2.32 μg C L-1 day-1. Our findings demonstrated a highly dynamic and active viral population in these deep waters and suggested that virioplankton play an important role in the microbial loop and subsequently biogeochemical cycling in deep oceans.

Trench motion-controlled slab morphology and stress variations: Implications for the isolated 2015 Bonin Islands deep earthquake

NASA Astrophysics Data System (ADS)

Yang, Ting; Gurnis, Michael; Zhan, Zhongwen

2017-07-01

The subducted old and cold Pacific Plate beneath the young Philippine Sea Plate at the Izu-Bonin trench over the Cenozoic hosts regional deep earthquakes. We investigate slab morphology and stress regimes under different trench motion histories with mantle convection models. Viscosity, temperature, and deviatoric stress are inherently heterogeneous within the slab, which we link to the occurrence of isolated earthquakes. Models expand on previous suggestions that observed slab morphology variations along the Izu-Bonin subduction zone, exhibited as shallow slab dip angles in the north and steeper dip angles in the south, are mainly due to variations in the rate of trench retreat from the north (where it is fast) to the south (where it is slow). Geodynamic models consistent with the regional plate tectonics, including oceanic plate age, plate convergence rate, and trench motion history, reproduce the seismologically observed principal stress direction and slab morphology. We suggest that the isolated 680 km deep, 30 May 2015 Mw 7.9 Bonin Islands earthquake, which lies east of the well-defined Benioff zone and has its principal compressional stress direction oriented toward the tip of the previously defined Benioff zone, can be explained by Pacific slab buckling in response to the slow trench retreat.

The search for life on Europa: limiting environmental factors, potential habitats, and Earth analogues.

PubMed

Marion, Giles M; Fritsen, Christian H; Eicken, Hajo; Payne, Meredith C

2003-01-01

The putative ocean of Europa has focused considerable attention on the potential habitats for life on Europa. By generally clement Earth standards, these Europan habitats are likely to be extreme environments. The objectives of this paper were to examine: (1) the limits for biological activity on Earth with respect to temperature, salinity, acidity, desiccation, radiation, pressure, and time; (2) potential habitats for life on Europa; and (3) Earth analogues and their limitations for Europa. Based on empirical evidence, the limits for biological activity on Earth are: (1) the temperature range is from 253 to 394 K; (2) the salinity range is a(H2O) = 0.6-1.0; (3) the desiccation range is from 60% to 100% relative humidity; (4) the acidity range is from pH 0 to 13; (5) microbes such as Deinococcus are roughly 4,000 times more resistant to ionizing radiation than humans; (6) the range for hydrostatic pressure is from 0 to 1,100 bars; and (7) the maximum time for organisms to survive in the dormant state may be as long as 250 million years. The potential habitats for life on Europa are the ice layer, the brine ocean, and the seafloor environment. The dual stresses of lethal radiation and low temperatures on or near the icy surface of Europa preclude the possibility of biological activity anywhere near the surface. Only at the base of the ice layer could one expect to find the suitable temperatures and liquid water that are necessary for life. An ice layer turnover time of 10 million years is probably rapid enough for preserving in the surface ice layers dormant life forms originating from the ocean. Model simulations demonstrate that hypothetical oceans could exist on Europa that are too cold for biological activity (T < 253 K). These simulations also demonstrate that salinities are high, which would restrict life to extreme halophiles. An acidic ocean (if present) could also potentially limit life. Pressure, per se, is unlikely to directly limit life on Europa. But indirectly, pressure plays an important role in controlling the chemical environments for life. Deep ocean basins such as the Mariana Trench are good analogues for the cold, high-pressure ocean of Europa. Many of the best terrestrial analogues for potential Europan habitats are in the Arctic and Antarctica. The six factors likely to be most important in defining the environments for life on Europa and the focus for future work are liquid water, energy, nutrients, low temperatures, salinity, and high pressures.

Deep thermal structure of Southeast Asia constrained by S-velocity data

NASA Astrophysics Data System (ADS)

Yu, Chuanhai; Shi, Xiaobin; Yang, Xiaoqiu; Zhao, Junfeng; Chen, Mei; Tang, Qunshu

2017-12-01

Southeast Asia, located in the southeastern part of the Eurasian Plate, is surrounded by tectonically active margins, exhibiting intense seismicity and volcanism, contains complex geological units with a perplexing evolution history. Because tectonic evolution is closely related to the deep thermal structure, an accurate estimation of the lithosphere thermal structure and thickness is important in extracting information on tectonics and geodynamics. However, there are significant uncertainties in the calculated deep thermal state constrained only by the observed surface heat flow. In this study, in order to obtain a better-constrained deep thermal state, we first calculate the deep thermal structure of Southeast Asia by employing an empirical relation between S-velocity and temperature, and then we estimate the base of the thermal lithosphere from the calculated temperature-depth profiles. The results show that, in general, the temperature is higher than the dry mantle solidus below the top of the seismic low-velocity zone, possibly indicating the presence of partial melt in the asthenosphere, particularly beneath oceanic basins such as the South China Sea. The temperature at a depth of 80 km in rifted and oceanic basins such as the Thailand Rift Basin, Thailand Bay, Andaman Sea, and South China Sea is about 200 °C higher than in plateaus and subduction zones such as the Khorat Plateau, Sumatra Island, and Philippine Trench regions. We suggest that the relatively cold and thick lithosphere block of the Khorat Plateau has not experienced significant internal deformation and might be extruded and rotated as a rigid block in response to the Indo-Eurasia collision. Our results show that the surface heat flow in the South China Sea is mainly dominated by the deep thermal state. There is a thermal anomaly in the Leiqiong area and in the areas adjacent to the northern margin of the South China Sea, indicating the presence of a high-temperature and thin lithosphere in the area of the well-known and controversial Hainan plume. The thermal lithosphere-asthenosphere boundary uplift area along the Xisha and southeastern Vietnam margin, in the western margin of South China Sea, which corresponds to the volcanic belt around this area, might indicate upwelling of hot mantle materials. The temperature values at 100 and 120 km depths through most regions of Southeast Asia are about 1400-1500 and 1550-1600 °C, respectively, which are nearly uniform with a small temperature difference. Our results also show that the lithosphere becomes thinner from the continent blocks toward the oceanic basins, with the smaller thickness values of 65-70 km in the South China Sea. The estimated base of the lithosphere corresponds approximately to the 1400 °C isotherm and shows good correlation with the tectonic setting.

Advection in polar and sub-polar environments: Impacts on high latitude marine ecosystems

NASA Astrophysics Data System (ADS)

Hunt, George L.; Drinkwater, Kenneth F.; Arrigo, Kevin; Berge, Jørgen; Daly, Kendra L.; Danielson, Seth; Daase, Malin; Hop, Haakon; Isla, Enrique; Karnovsky, Nina; Laidre, Kristin; Mueter, Franz J.; Murphy, Eugene J.; Renaud, Paul E.; Smith, Walker O.; Trathan, Philip; Turner, John; Wolf-Gladrow, Dieter

2016-12-01

We compare and contrast the ecological impacts of atmospheric and oceanic circulation patterns on polar and sub-polar marine ecosystems. Circulation patterns differ strikingly between the north and south. Meridional circulation in the north provides connections between the sub-Arctic and Arctic despite the presence of encircling continental landmasses, whereas annular circulation patterns in the south tend to isolate Antarctic surface waters from those in the north. These differences influence fundamental aspects of the polar ecosystems from the amount, thickness and duration of sea ice, to the types of organisms, and the ecology of zooplankton, fish, seabirds and marine mammals. Meridional flows in both the North Pacific and the North Atlantic oceans transport heat, nutrients, and plankton northward into the Chukchi Sea, the Barents Sea, and the seas off the west coast of Greenland. In the North Atlantic, the advected heat warms the waters of the southern Barents Sea and, with advected nutrients and plankton, supports immense biomasses of fish, seabirds and marine mammals. On the Pacific side of the Arctic, cold waters flowing northward across the northern Bering and Chukchi seas during winter and spring limit the ability of boreal fish species to take advantage of high seasonal production there. Southward flow of cold Arctic waters into sub-Arctic regions of the North Atlantic occurs mainly through Fram Strait with less through the Barents Sea and the Canadian Archipelago. In the Pacific, the transport of Arctic waters and plankton southward through Bering Strait is minimal. In the Southern Ocean, the Antarctic Circumpolar Current and its associated fronts are barriers to the southward dispersal of plankton and pelagic fishes from sub-Antarctic waters, with the consequent evolution of Antarctic zooplankton and fish species largely occurring in isolation from those to the north. The Antarctic Circumpolar Current also disperses biota throughout the Southern Ocean, and as a result, the biota tends to be similar within a given broad latitudinal band. South of the Southern Boundary of the ACC, there is a large-scale divergence that brings nutrient-rich water to the surface. This divergence, along with more localized upwelling regions and deep vertical convection in winter, generates elevated nutrient levels throughout the Antarctic at the end of austral winter. However, such elevated nutrient levels do not support elevated phytoplankton productivity through the entire Southern Ocean, as iron concentrations are rapidly removed to limiting levels by spring blooms in deep waters. However, coastal regions, with the upward mixing of iron, maintain greatly enhanced rates of production, especially in coastal polynyas. In these coastal areas, elevated primary production supports large biomasses of zooplankton, fish, seabirds, and mammals. As climate warming affects these advective processes and their heat content, there will likely be major changes in the distribution and abundance of polar biota, in particular the biota dependent on sea ice.

Restricted Inter-ocean Exchange and Attenuated Biological Export Caused Enhanced Carbonate Preservation in the PETM Ocean

NASA Astrophysics Data System (ADS)

Luo, Y.; Boudreau, B. P.; Dickens, G. R.; Sluijs, A.; Middelburg, J. J.

2015-12-01

Carbon dioxide (CO2) release during the Paleocene-Eocene Thermal Maximum (PETM, 55.8 Myr BP) acidified the oceans, causing a decrease in calcium carbonate (CaCO3) preservation. During the subsequent recovery from this acidification, the sediment CaCO3 content came to exceed pre-PETM values, known as over-deepening or over-shooting. Past studies claim to explain these trends, but have failed to reproduce quantitatively the time series of CaCO3 preservation. We employ a simple biogeochemical model to recreate the CaCO3 records preserved at Walvis Ridge of the Atlantic Ocean. Replication of the observed changes, both shallowing and the subsequent over-deepening, requires two conditions not previously considered: (1) limited deep-water exchange between the Indo-Atlantic and Pacific oceans and (2) a ~50% reduction in the export of CaCO3 to the deep sea during acidification. Contrary to past theories that attributed over-deepening to increased riverine alkalinity input, we find that over-deepening is an emergent property, generated at constant riverine input when attenuation of CaCO3 export causes an unbalanced alkalinity input to the deep oceans (alkalinization) and the development of deep super-saturation. Restoration of CaCO3 export, particularly in the super-saturated deep Indo-Atlantic ocean, later in the PETM leads to greater accumulation of carbonates, ergo over-shooting, which returns the ocean to pre-PETM conditions over a time scale greater than 200 kyr. While this feedback between carbonate export and the riverine input has not previously been considered, it appears to constitute an important modification of the classic carbonate compensation concept used to explain oceanic response to acidification.

Picocyanobacteria and deep-ocean fluorescent dissolved organic matter share similar optical properties

NASA Astrophysics Data System (ADS)

Zhao, Zhao; Gonsior, Michael; Luek, Jenna; Timko, Stephen; Ianiri, Hope; Hertkorn, Norbert; Schmitt-Kopplin, Philippe; Fang, Xiaoting; Zeng, Qinglu; Jiao, Nianzhi; Chen, Feng

2017-05-01

Marine chromophoric dissolved organic matter (CDOM) and its related fluorescent components (FDOM), which are widely distributed but highly photobleached in the surface ocean, are critical in regulating light attenuation in the ocean. However, the origins of marine FDOM are still under investigation. Here we show that cultured picocyanobacteria, Synechococcus and Prochlorococcus, release FDOM that closely match the typical fluorescent signals found in oceanic environments. Picocyanobacterial FDOM also shows comparable apparent fluorescent quantum yields and undergoes similar photo-degradation behaviour when compared with deep-ocean FDOM, further strengthening the similarity between them. Ultrahigh-resolution mass spectrometry (MS) and nuclear magnetic resonance spectroscopy reveal abundant nitrogen-containing compounds in Synechococcus DOM, which may originate from degradation products of the fluorescent phycobilin pigments. Given the importance of picocyanobacteria in the global carbon cycle, our results indicate that picocyanobacteria are likely to be important sources of marine autochthonous FDOM, which may accumulate in the deep ocean.

Picocyanobacteria and deep-ocean fluorescent dissolved organic matter share similar optical properties

PubMed Central

Zhao, Zhao; Gonsior, Michael; Luek, Jenna; Timko, Stephen; Ianiri, Hope; Hertkorn, Norbert; Schmitt-Kopplin, Philippe; Fang, Xiaoting; Zeng, Qinglu; Jiao, Nianzhi; Chen, Feng

2017-01-01

Marine chromophoric dissolved organic matter (CDOM) and its related fluorescent components (FDOM), which are widely distributed but highly photobleached in the surface ocean, are critical in regulating light attenuation in the ocean. However, the origins of marine FDOM are still under investigation. Here we show that cultured picocyanobacteria, Synechococcus and Prochlorococcus, release FDOM that closely match the typical fluorescent signals found in oceanic environments. Picocyanobacterial FDOM also shows comparable apparent fluorescent quantum yields and undergoes similar photo-degradation behaviour when compared with deep-ocean FDOM, further strengthening the similarity between them. Ultrahigh-resolution mass spectrometry (MS) and nuclear magnetic resonance spectroscopy reveal abundant nitrogen-containing compounds in Synechococcus DOM, which may originate from degradation products of the fluorescent phycobilin pigments. Given the importance of picocyanobacteria in the global carbon cycle, our results indicate that picocyanobacteria are likely to be important sources of marine autochthonous FDOM, which may accumulate in the deep ocean. PMID:28513605

Tsunami Speed Variations in Density-stratified Compressible Global Oceans

NASA Astrophysics Data System (ADS)

Watada, S.

2013-12-01

Recent tsunami observations in the deep ocean have accumulated unequivocal evidence that tsunami traveltime delays compared with the linear long-wave tsunami simulations occur during tsunami propagation in the deep ocean. The delay is up to 2% of the tsunami traveltime. Watada et al. [2013] investigated the cause of the delay using the normal mode theory of tsunamis and attributed the delay to the compressibility of seawater, the elasticity of the solid earth, and the gravitational potential change associated with mass motion during the passage of tsunamis. Tsunami speed variations in the deep ocean caused by seawater density stratification is investigated using a newly developed propagator matrix method that is applicable to seawater with depth-variable sound speeds and density gradients. For a 4-km deep ocean, the total tsunami speed reduction is 0.45% compared with incompressible homogeneous seawater; two thirds of the reduction is due to elastic energy stored in the water and one third is due to water density stratification mainly by hydrostatic compression. Tsunami speeds are computed for global ocean density and sound speed profiles and characteristic structures are discussed. Tsunami speed reductions are proportional to ocean depth with small variations, except for in warm Mediterranean seas. The impacts of seawater compressibility and the elasticity effect of the solid earth on tsunami traveltime should be included for precise modeling of trans-oceanic tsunamis. Data locations where a vertical ocean profile deeper than 2500 m is available in World Ocean Atlas 2009. The dark gray area indicates the Pacific Ocean defined in WOA09. a) Tsunami speed variations. Red, gray and black bars represent global, Pacific, and Mediterranean Sea, respectively. b) Regression lines of the tsunami velocity reduction for all oceans. c)Vertical ocean profiles at grid points indicated by the stars in Figure 1.

Bioproductivity in the Southern Ocean since the last Interglacial - new high-resolution biogenic opal flux records from the Scotia Sea

NASA Astrophysics Data System (ADS)

Sprenk, D.; Weber, M. E.; Kuhn, G.; Rosén, P.; Röhling, H.-G.

2012-04-01

The Southern Ocean plays an important role in transferring CO2 via wind-induced upwelling from the deep sea to the atmosphere. It is therefore one of the key areas to study climate change. Bioproductivity in the Southern Ocean is mostly influenced by the extent of sea ice, upwelling of cold nutrient- and silica-rich water, and the availability of light. Biogenic opal (BSi) is a significant nutrient in the Southern Ocean, and according to recent investigations only marginally affected by preservation changes. It can therefore be used as bioproductivity proxy. Here we present several methods to determine BSi, discuss them and put the results into context with respect to regional bioproductivity changes in Southern Ocean during the last glacial cycle. We studied deep-sea sediment core sites MD07-3133 and MD07-3134 from the central Scotia Sea with extraordinary high sedimentation rates of up to 2.1 to 1.2 m/kyr, respectively covering the last 92.5 kyr. BSi leaching according to Müller & Schneider (1993) is very time-consuming and expensive, so we measured only 253 samples from large-amplitude variation core sections. In addition, we determined BSi using non-destructive measurements of sediment colour b*, wet-bulk density, and Ti/Si count ratios. Furthermore, we provide the first attempts to estimate BSi in marine sediment using Fourier transform infrared spectroscopy (FTIRS), a cost-efficient method, which requires only 11 mg of sediment. All estimation methods capture the main BSi trends, however FTIRS seems to be the most promising one. In the central Scotia Sea, south of the modern Antarctic Polar Front, the BSi flux reflects a relatively complicated glacial-to-interglacial pattern with large-amplitude, millennial-scale fluctuations in bioproductivity. During Antarctic Isotopic Maxima, BSi fluxes were generally increased. Lowest bioproductivity occur at the Last Glacial Maximum, while upwelling of mid-depth water was reduced, atmospheric CO2 low, and sea-ice cover intensified. Around 17 ka BSi flux rose abruptly, corresponding to decreasing seasonal sea-ice cover and rising atmospheric CO2 concentration. Our investigations show that BSi flux in the Central Scotia Sea reflects bioproductivity changes. Furthermore it is correlated to atmospheric CO2 variations and sea-ice cover fluctuations. Distribution of sea ice may be the reason for pronounced regional differences of bioproductivity in the Southern Ocean.

75 FR 34929 - Safety Zones: Neptune Deep Water Port, Atlantic Ocean, Boston, MA

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-21

...-AA00 Safety Zones: Neptune Deep Water Port, Atlantic Ocean, Boston, MA AGENCY: Coast Guard, DHS. ACTION..., Boston, MA; Final Rule (USCG-2009-0589), to protect vessels from the hazard posed by the presence of the... read as follows: Sec. 165.T01-0542 Safety Zones: Neptune Deepwater Port, Atlantic Ocean, Boston, MA. (a...

Global decadal climate variability driven by Southern Ocean convection

NASA Astrophysics Data System (ADS)

Marinov, I.; Cabre, A.

2016-02-01

Here we suggest a set of new "teleconnections" by which the Southern Ocean (SO) can induce anomalies in the tropical oceans and atmosphere. A 5000-year long control simulation in a coupled atmosphere-ocean model (CM2Mc, a low-resolution GFDL model) shows a natural, highly regular multi-decadal oscillation between periods of SO open sea convection and non-convective periods. This process happens naturally, with different frequencies and durations of convection across the majority of CMIP5 under preindustrial forcing (deLavergne et al., 2014). In our model, oscillations in Weddell Sea convection drive multidecadal variability in SO and global SSTs, as well as SO heat storage, with convective decades warm due to the heat released from the Circumpolar Deep Water and non-convective decades cold due to subsurface heat storage. Convective pulses drive local SST and sea ice variations south of 60S, immediately triggering changes in the Ferrell and Hadley cells, atmospheric energy budget and cross-equatorial heat exchange, ultimately influencing the position of the Intertropical Convergence Zone and rain patterns in the tropics. Additionally, the SO convection pulse is propagated to the tropics and the North Atlantic MOC via oceanic pathways on relatively fast (decadal) timescales, in agreement with recent observational constraints. Open sea convection is the major mode of Antarctic Bottom Water (AABW) formation in the CMIP5 models. Future improvements in the representation of shelf convection and sea-ice interaction in the SO are a clear necessity. These model improvements should render the AABW representation more realistic, and might influence (a) the connectivity of the SO with the rest of the planet, as described above and (b) the oceanic and global carbon cycle, of which the AABW is a fundamental conduit.

Earthquakes drive large-scale submarine canyon development and sediment supply to deep-ocean basins.

PubMed

Mountjoy, Joshu J; Howarth, Jamie D; Orpin, Alan R; Barnes, Philip M; Bowden, David A; Rowden, Ashley A; Schimel, Alexandre C G; Holden, Caroline; Horgan, Huw J; Nodder, Scott D; Patton, Jason R; Lamarche, Geoffroy; Gerstenberger, Matthew; Micallef, Aaron; Pallentin, Arne; Kane, Tim

2018-03-01

Although the global flux of sediment and carbon from land to the coastal ocean is well known, the volume of material that reaches the deep ocean-the ultimate sink-and the mechanisms by which it is transferred are poorly documented. Using a globally unique data set of repeat seafloor measurements and samples, we show that the moment magnitude ( M w ) 7.8 November 2016 Kaikōura earthquake (New Zealand) triggered widespread landslides in a submarine canyon, causing a powerful "canyon flushing" event and turbidity current that traveled >680 km along one of the world's longest deep-sea channels. These observations provide the first quantification of seafloor landscape change and large-scale sediment transport associated with an earthquake-triggered full canyon flushing event. The calculated interevent time of ~140 years indicates a canyon incision rate of 40 mm year -1 , substantially higher than that of most terrestrial rivers, while synchronously transferring large volumes of sediment [850 metric megatons (Mt)] and organic carbon (7 Mt) to the deep ocean. These observations demonstrate that earthquake-triggered canyon flushing is a primary driver of submarine canyon development and material transfer from active continental margins to the deep ocean.

The tropopause cold trap in the Australian Monsoon during STEP/AMEX 1987

NASA Technical Reports Server (NTRS)

Selkirk, Henry B.

1993-01-01

The relationship between deep convection and tropopause cold trap conditions is examined for the tropical northern Australia region during the 1986-87 summer monsoon season, emphasizing the Australia Monsoon Experiment (AMEX) period when the NASA Stratosphere-Troposphere Exchange Project (STEP) was being conducted. The factors related to the spatial and temporal variability of the cold point potential temperature (CPPT) are investigated. A framework is developed for describing the relationships among surface average equivalent potential temperature in the surface layer (AEPTSL) the height of deep convection, and stratosphere-troposphere exchange. The time-mean pattern of convection, large-scale circulation, and surface AEPTSL in the Australian monsoon and the evolution of the convective environment during the monsoon period and the extended transition season which preceded it are described. The time-mean fields of cold point level variables are examined and the statistical relationships between mean CPPT, surface AEPTSL, and deep convection are described. Day-to-day variations of CPPT are examined in terms of these time mean relationships.

North Atlantic deep water formation and AMOC in CMIP5 models

NASA Astrophysics Data System (ADS)

Heuzé, Céline

2017-07-01

Deep water formation in climate models is indicative of their ability to simulate future ocean circulation, carbon and heat uptake, and sea level rise. Present-day temperature, salinity, sea ice concentration and ocean transport in the North Atlantic subpolar gyre and Nordic Seas from 23 CMIP5 (Climate Model Intercomparison Project, phase 5) models are compared with observations to assess the biases, causes and consequences of North Atlantic deep convection in models. The majority of models convect too deep, over too large an area, too often and too far south. Deep convection occurs at the sea ice edge and is most realistic in models with accurate sea ice extent, mostly those using the CICE model. Half of the models convect in response to local cooling or salinification of the surface waters; only a third have a dynamic relationship between freshwater coming from the Arctic and deep convection. The models with the most intense deep convection have the warmest deep waters, due to a redistribution of heat through the water column. For the majority of models, the variability of the Atlantic Meridional Overturning Circulation (AMOC) is explained by the volumes of deep water produced in the subpolar gyre and Nordic Seas up to 2 years before. In turn, models with the strongest AMOC have the largest heat export to the Arctic. Understanding the dynamical drivers of deep convection and AMOC in models is hence key to realistically forecasting Arctic oceanic warming and its consequences for the global ocean circulation, cryosphere and marine life.

Liquid Water Oceans in Ice Giants

NASA Technical Reports Server (NTRS)

Wiktorowicz, Sloane J.; Ingersoll, Andrew P.

2007-01-01

Aptly named, ice giants such as Uranus and Neptune contain significant amounts of water. While this water cannot be present near the cloud tops, it must be abundant in the deep interior. We investigate the likelihood of a liquid water ocean existing in the hydrogen-rich region between the cloud tops and deep interior. Starting from an assumed temperature at a given upper tropospheric pressure (the photosphere), we follow a moist adiabat downward. The mixing ratio of water to hydrogen in the gas phase is small in the photosphere and increases with depth. The mixing ratio in the condensed phase is near unity in the photosphere and decreases with depth; this gives two possible outcomes. If at some pressure level the mixing ratio of water in the gas phase is equal to that in the deep interior, then that level is the cloud base. The gas below the cloud base has constant mixing ratio. Alternately, if the mixing ratio of water in the condensed phase reaches that in the deep interior, then the surface of a liquid ocean will occur. Below this ocean surface, the mixing ratio of water will be constant. A cloud base occurs when the photospheric temperature is high. For a family of ice giants with different photospheric temperatures, the cooler ice giants will have warmer cloud bases. For an ice giant with a cool enough photospheric temperature, the cloud base will exist at the critical temperature. For still cooler ice giants, ocean surfaces will result. A high mixing ratio of water in the deep interior favors a liquid ocean. We find that Neptune is both too warm (photospheric temperature too high) and too dry (mixing ratio of water in the deep interior too low) for liquid oceans to exist at present. To have a liquid ocean, Neptune s deep interior water to gas ratio would have to be higher than current models allow, and the density at 19 kbar would have to be approx. equal to 0.8 g/cu cm. Such a high density is inconsistent with gravitational data obtained during the Voyager flyby. In our model, Neptune s water cloud base occurs around 660 K and 11 kbar, and the density there is consistent with Voyager gravitational data. As Neptune cools, the probability of a liquid ocean increases. Extrasolar "hot Neptunes," which presumably migrate inward toward their parent stars, cannot harbor liquid water oceans unless they have lost almost all of the hydrogen and helium from their deep interiors.

Biogeochemistry: Deep ocean iron balance

NASA Astrophysics Data System (ADS)

Homoky, William B.

2017-02-01

Dissolved iron is mysteriously pervasive in deep ocean hydrothermal plumes. An analysis of gas, metals and particles from a 4,000 km plume transect suggests that dissolved iron is maintained by rapid and reversible exchanges with sinking particles.

Role of surface heat fluxes underneath cold pools

DOE PAGES

Gentine, Pierre; Garelli, Alix; Park, Seung -Bu; ...

2016-01-05

In this paper, the role of surface heat fluxes underneath cold pools is investigated using cloud–resolving simulations with either interactive or horizontally homogenous surface heat fluxes over an ocean and a simplified land surface. Over the ocean, there are limited changes in the distribution of the cold pool temperature, humidity, and gust front velocity, yet interactive heat fluxes induce more cold pools, which are smaller, and convection is then less organized. Correspondingly, the updraft mass flux and lateral entrainment are modified. Over the land surface, the heat fluxes underneath cold pools drastically impact the cold pool characteristics with more numerousmore » and smaller pools, which are warmer and more humid and accompanied by smaller gust front velocities. The interactive fluxes also modify the updraft mass flux and reduce convective organization. These results emphasize the importance of interactive surface fluxes instead of prescribed flux boundary conditions, as well as the formulation of surface heat fluxes, when studying convection.« less

North Pacific Acoustic Laboratory: Deep Water Acoustic Propagation in the Philippine Sea

DTIC Science & Technology

2016-06-21

the "Special Issue on Deep-water Ocean Acoustics" in the Journal of the Acoustical Society of America (Vol. 134, No . 4, Pt. 2 of 2 , October20 13...also listed. Fourteen (14) of these publications appeared in the " Special Issue on Deep-water Ocean Acoustics" in the Journal of the Acoustical

Does seismic activity control carbon exchanges between transform-faults in old ocean crust and the deep sea? A hypothesis examined by the EU COST network FLOWS

NASA Astrophysics Data System (ADS)

Lever, M. A.

2014-12-01

The European Cooperation in Science and Technology (COST)-Action FLOWS (http://www.cost.eu/domains_actions/essem/Actions/ES1301) was initiated on the 25th of October 2013. It is a consortium formed by members of currently 14 COST countries and external partners striving to better understand the interplay between earthquakes and fluid flow at transform-faults in old oceanic crust. The recent occurrence of large earthquakes and discovery of deep fluid seepage calls for a revision of the postulated hydrogeological inactivity and low seismic activity of old oceanic transform-type plate boundaries, and indicates that earthquakes and fluid flow are intrinsically associated. This Action merges the expertise of a large number of research groups and supports the development of multidisciplinary knowledge on how seep fluid (bio)chemistry relates to seismicity. It aims to identify (bio)geochemical proxies for the detection of precursory seismic signals and to develop innovative physico-chemical sensors for deep-ocean seismogenic faults. National efforts are coordinated through Working Groups (WGs) focused on 1) geophysical and (bio)geochemical data acquisition; 2) modelling of structure and seismicity of faults; 3) engineering of deep-ocean physico-chemical seismic sensors; and 4) integration and dissemination. This poster will illustrate the overarching goals of the FLOWS Group, with special focus to research goals concerning the role of seismic activity in controlling the release of carbon from the old ocean crust into the deep ocean.

Reconstructing Deep Ocean Circulation in the North Atlantic from Bermuda Rise, and Beyond

NASA Astrophysics Data System (ADS)

McManus, J. F.

2016-12-01

The large-scale subsurface circulation of the ocean is an important component of the Earth's climate system, and contributes to the global and regional transport of heat and mass. Assessing how this system has changed in the past is thus a priority for understanding natural climate variability. A long-coring campaign on Bermuda Rise has provided additional abundant high-quality sediments from this site of rapid accumulation in the deep western basin, situated beneath the subtropical gyre of the North Atlantic Ocean. These sediments allow the high-resolution reconstruction of deepwater chemistry and export from this key location throughout the last 150,000 years, covering the entire last glacial cycle in a continuous section of 35 meters in core KNR191-CDH19. The suite of proxy indicators analyzed includes uranium-series disequilibria, neodymium isotopes, and benthic stable isotopes. Combined with multiple previous studies of nearby cores on Bermuda Rise, the published and new proxy data from CDH19 confirm the variability of the deep circulation in the Atlantic Ocean in association with past climate changes. The multiple indicators, along with complementary data from other locations, display coherent evidence for contrasts between deep circulation during glacial and interglacial intervals, with persistent strong, deep ventilation only within the peak interglacial of marine isotope stage 5e (MIS 5e) and the Holocene. In contrast, repeated, dramatic variability in deep ocean circulation accompanied the millennial climate changes of the last glaciation and deglaciation. The largest magnitude circulation shifts occurred at the transitions into stadials associated with the Hudson strait iceberg discharges and between them and the ensuing northern interstadial warmings, significantly exceeding that of the overall glacial-interglacial difference, highlighting the potential oceanographic and climatic importance of short-term perturbations to the deep ocean circulation.

Ejecta from Ocean Impacts

NASA Technical Reports Server (NTRS)

Kyte, Frank T.

2003-01-01

Numerical simulations of deep-ocean impact provide some limits on the size of a projectile that will not mix with the ocean floor during a deep-ocean impact. For a vertical impact at asteroidal velocities (approx. 20 km/s), mixing is only likely when the projectile diameter is greater than 112 of the water depth. For oblique impacts, even larger projectiles will not mix with ocean floor silicates. Given the typical water depths of 4 to 5 km in deep-ocean basins, asteroidal projectiles with diameters as large as 2 or 3 km may commonly produce silicate ejecta that is composed only of meteoritic materials and seawater salts. However, the compressed water column beneath the projectile can still disrupt and shock metamorphose the ocean floor. Therefore, production of a separate, terrestrial ejecta component is not ruled out in the most extreme case. With increasing projectile size (or energy) relative to water depths, there must be a gradation between oceanic impacts and more conventional continental impacts. Given that 60% of the Earth's surface is covered by oceanic lithosphere and 500 m projectiles impact the Earth on 10(exp 5) y timescales, there must be hundreds of oceanic impact deposits in the sediment record awaiting discovery.

Active Pacific meridional overturning circulation (PMOC) during the warm Pliocene.

PubMed

Burls, Natalie J; Fedorov, Alexey V; Sigman, Daniel M; Jaccard, Samuel L; Tiedemann, Ralf; Haug, Gerald H

2017-09-01

An essential element of modern ocean circulation and climate is the Atlantic meridional overturning circulation (AMOC), which includes deep-water formation in the subarctic North Atlantic. However, a comparable overturning circulation is absent in the Pacific, the world's largest ocean, where relatively fresh surface waters inhibit North Pacific deep convection. We present complementary measurement and modeling evidence that the warm, ~400-ppmv (parts per million by volume) CO 2 world of the Pliocene supported subarctic North Pacific deep-water formation and a Pacific meridional overturning circulation (PMOC) cell. In Pliocene subarctic North Pacific sediments, we report orbitally paced maxima in calcium carbonate accumulation rate, with accompanying pigment and total organic carbon measurements supporting deep-ocean ventilation-driven preservation as their cause. Together with high accumulation rates of biogenic opal, these findings require vigorous bidirectional communication between surface waters and interior waters down to ~3 km in the western subarctic North Pacific, implying deep convection. Redox-sensitive trace metal data provide further evidence of higher Pliocene deep-ocean ventilation before the 2.73-Ma (million years) transition. This observational analysis is supported by climate modeling results, demonstrating that atmospheric moisture transport changes, in response to the reduced meridional sea surface temperature gradients of the Pliocene, were capable of eroding the halocline, leading to deep-water formation in the western subarctic Pacific and a strong PMOC. This second Northern Hemisphere overturning cell has important implications for heat transport, the ocean/atmosphere cycle of carbon, and potentially the equilibrium response of the Pacific to global warming.

Transformation of Deep Water Masses Along Lagrangian Upwelling Pathways in the Southern Ocean

NASA Astrophysics Data System (ADS)

Tamsitt, V.; Abernathey, R. P.; Mazloff, M. R.; Wang, J.; Talley, L. D.

2018-03-01

Upwelling of northern deep waters in the Southern Ocean is fundamentally important for the closure of the global meridional overturning circulation and delivers carbon and nutrient-rich deep waters to the sea surface. We quantify water mass transformation along upwelling pathways originating in the Atlantic, Indian, and Pacific and ending at the surface of the Southern Ocean using Lagrangian trajectories in an eddy-permitting ocean state estimate. Recent related work shows that upwelling in the interior below about 400 m depth is localized at hot spots associated with major topographic features in the path of the Antarctic Circumpolar Current, while upwelling through the surface layer is more broadly distributed. In the ocean interior upwelling is largely isopycnal; Atlantic and to a lesser extent Indian Deep Waters cool and freshen while Pacific deep waters are more stable, leading to a homogenization of water mass properties. As upwelling water approaches the mixed layer, there is net strong transformation toward lighter densities due to mixing of freshwater, but there is a divergence in the density distribution as Upper Circumpolar Deep Water tends become lighter and dense Lower Circumpolar Deep Water tends to become denser. The spatial distribution of transformation shows more rapid transformation at eddy hot spots associated with major topography where density gradients are enhanced; however, the majority of cumulative density change along trajectories is achieved by background mixing. We compare the Lagrangian analysis to diagnosed Eulerian water mass transformation to attribute the mechanisms leading to the observed transformation.

Taxonomic revision of deep-sea Ostracoda from the Arctic Ocean

USGS Publications Warehouse

Yasuhara, Moriaki; Stepanova, Anna; Okahashi, Hisayo; Cronin, Thomas M.; Brouwers, Elisabeth M.

2015-01-01

Taxonomic revision of deep-sea Ostracoda from the Arctic Ocean was conducted to reduce taxonomic uncertainty that will improve our understanding of species ecology, biogeography and relationship to faunas from other deep-sea regions. Fifteen genera and 40 species were examined and (re-)illustrated with high-resolution scanning electron microscopy images, covering most of known deep-sea species in the central Arctic Ocean. Seven new species are described: Bythoceratina lomonosovensis n. sp., Cytheropteron parahamatum n. sp., Cytheropteron lanceae n. sp.,Cytheropteron irizukii n. sp., Pedicythere arctica n. sp., Cluthiawhatleyi n. sp., Krithe hunti n. sp. This study provides a robust taxonomic baseline for application to paleoceanographical reconstruction and biodiversity analyses in this climatically sensitive region.

Marine geodesy a multipurpose approach to solve oceanic problems. [including submersible navigation under iced seas, demarcation and determination of boundaries in deep ocean, tsunamis, and ecology

NASA Technical Reports Server (NTRS)

Saxena, N.

1974-01-01

Various current and future problem areas of marine geodesy are identified. These oceanic problem areas are highly diversified and include submersible navigation under ice seas, demarcation and determination of boundaries in deep ocean, tsunamis, ecology, etc., etc. Their achieved as well as desired positional accuracy estimates, based upon publications and discussions, are also given. A multipurpose approach to solve these problems is described. An optimum configuration of an ocean-bottom control-net unit is provided.

Deep-Sea Bioluminescence Blooms after Dense Water Formation at the Ocean Surface

PubMed Central

Tamburini, Christian; Canals, Miquel; Durrieu de Madron, Xavier; Houpert, Loïc; Lefèvre, Dominique; Martini, Séverine; D'Ortenzio, Fabrizio; Robert, Anne; Testor, Pierre; Aguilar, Juan Antonio; Samarai, Imen Al; Albert, Arnaud; André, Michel; Anghinolfi, Marco; Anton, Gisela; Anvar, Shebli; Ardid, Miguel; Jesus, Ana Carolina Assis; Astraatmadja, Tri L.; Aubert, Jean-Jacques; Baret, Bruny; Basa, Stéphane; Bertin, Vincent; Biagi, Simone; Bigi, Armando; Bigongiari, Ciro; Bogazzi, Claudio; Bou-Cabo, Manuel; Bouhou, Boutayeb; Bouwhuis, Mieke C.; Brunner, Jurgen; Busto, José; Camarena, Francisco; Capone, Antonio; Cârloganu, Christina; Carminati, Giada; Carr, John; Cecchini, Stefano; Charif, Ziad; Charvis, Philippe; Chiarusi, Tommaso; Circella, Marco; Coniglione, Rosa; Costantini, Heide; Coyle, Paschal; Curtil, Christian; Decowski, Patrick; Dekeyser, Ivan; Deschamps, Anne; Donzaud, Corinne; Dornic, Damien; Dorosti, Hasankiadeh Q.; Drouhin, Doriane; Eberl, Thomas; Emanuele, Umberto; Ernenwein, Jean-Pierre; Escoffier, Stéphanie; Fermani, Paolo; Ferri, Marcelino; Flaminio, Vincenzo; Folger, Florian; Fritsch, Ulf; Fuda, Jean-Luc; Galatà, Salvatore; Gay, Pascal; Giacomelli, Giorgio; Giordano, Valentina; Gómez-González, Juan-Pablo; Graf, Kay; Guillard, Goulven; Halladjian, Garadeb; Hallewell, Gregory; van Haren, Hans; Hartman, Joris; Heijboer, Aart J.; Hello, Yann; Hernández-Rey, Juan Jose; Herold, Bjoern; Hößl, Jurgen; Hsu, Ching-Cheng; de Jong, Marteen; Kadler, Matthias; Kalekin, Oleg; Kappes, Alexander; Katz, Uli; Kavatsyuk, Oksana; Kooijman, Paul; Kopper, Claudio; Kouchner, Antoine; Kreykenbohm, Ingo; Kulikovskiy, Vladimir; Lahmann, Robert; Lamare, Patrick; Larosa, Giuseppina; Lattuada, Dario; Lim, Gordon; Presti, Domenico Lo; Loehner, Herbert; Loucatos, Sotiris; Mangano, Salvatore; Marcelin, Michel; Margiotta, Annarita; Martinez-Mora, Juan Antonio; Meli, Athina; Montaruli, Teresa; Motz, Holger; Neff, Max; Nezri, Emma nuel; Palioselitis, Dimitris; Păvălaş, Gabriela E.; Payet, Kevin; Payre, Patrice; Petrovic, Jelena; Piattelli, Paolo; Picot-Clemente, Nicolas; Popa, Vlad; Pradier, Thierry; Presani, Eleonora; Racca, Chantal; Reed, Corey; Riccobene, Giorgio; Richardt, Carsten; Richter, Roland; Rivière, Colas; Roensch, Kathrin; Rostovtsev, Andrei; Ruiz-Rivas, Joaquin; Rujoiu, Marius; Russo, Valerio G.; Salesa, Francisco; Sánchez-Losa, Augustin; Sapienza, Piera; Schöck, Friederike; Schuller, Jean-Pierre; Schussler, Fabian; Shanidze, Rezo; Simeone, Francesco; Spies, Andreas; Spurio, Maurizio; Steijger, Jos J. M.; Stolarczyk, Thierry; Taiuti, Mauro G. F.; Toscano, Simona; Vallage, Bertrand; Van Elewyck, Véronique; Vannoni, Giulia; Vecchi, Manuela; Vernin, Pascal; Wijnker, Guus; Wilms, Jorn; de Wolf, Els; Yepes, Harold; Zaborov, Dmitry; De Dios Zornoza, Juan; Zúñiga, Juan

2013-01-01

The deep ocean is the largest and least known ecosystem on Earth. It hosts numerous pelagic organisms, most of which are able to emit light. Here we present a unique data set consisting of a 2.5-year long record of light emission by deep-sea pelagic organisms, measured from December 2007 to June 2010 at the ANTARES underwater neutrino telescope in the deep NW Mediterranean Sea, jointly with synchronous hydrological records. This is the longest continuous time-series of deep-sea bioluminescence ever recorded. Our record reveals several weeks long, seasonal bioluminescence blooms with light intensity up to two orders of magnitude higher than background values, which correlate to changes in the properties of deep waters. Such changes are triggered by the winter cooling and evaporation experienced by the upper ocean layer in the Gulf of Lion that leads to the formation and subsequent sinking of dense water through a process known as “open-sea convection”. It episodically renews the deep water of the study area and conveys fresh organic matter that fuels the deep ecosystems. Luminous bacteria most likely are the main contributors to the observed deep-sea bioluminescence blooms. Our observations demonstrate a consistent and rapid connection between deep open-sea convection and bathypelagic biological activity, as expressed by bioluminescence. In a setting where dense water formation events are likely to decline under global warming scenarios enhancing ocean stratification, in situ observatories become essential as environmental sentinels for the monitoring and understanding of deep-sea ecosystem shifts. PMID:23874425

Cold pool organization and the merging of convective updrafts in a Large Eddy Simulation

NASA Astrophysics Data System (ADS)

Glenn, I. B.; Krueger, S. K.

2016-12-01

Cold pool organization is a process that accelerates the transition from shallow to deep cumulus convection, and leads to higher deep convective cloud top heights. The mechanism by which cold pool organization enhances convection remains not well understood, but the basic idea is that since precipitation evaporation and a low equivalent potential temperature in the mid-troposphere lead to strong cold pools, the net cold pool effect can be accounted for in a cumulus parameterization as a relationship involving those factors. Understanding the actual physical mechanism at work will help quantify the strength of the relationship between cold pools and enhanced deep convection. One proposed mechanism of enhancement is that cold pool organization leads to reduced distances between updrafts, creating a local environment more conducive to convection as updrafts entrain parcels of air recently detrained by their neighbors. We take this hypothesis one step further and propose that convective updrafts actually merge, not just exchange recently processed air. Because entrainment and detrainment around an updraft draws nearby air in or pushes it out, respectively, they act like dynamic flow sources and sinks, drawing each other in or pushing each other away. The acceleration is proportional to the inverse square of the distance between two updrafts, so a small reduction in distance can make a big difference in the rate of merging. We have shown in previous research how merging can be seen as collisions between different updraft air parcels using Lagrangian Parcel Trajectories (LPTs) released in a Large Eddy Simulation (LES) during a period with organized deep convection. Now we use a Eulerian frame of reference to examine the updraft merging process during the transition from shallow to organized deep convection. We use a case based on the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) for our LES. We directly measure the rate of entrainment and the properties of the entrained air for all convective updrafts in the simulation. We use a tracking algorithm to define merging between convective updrafts. We will show the rate of merging as the transition between shallow and deep convection occurs and the different distributions of entrainment rate and ultimate detrainment height of merged and non-merged updrafts.

Southern Ocean Circulation: a High Resolution Examination of the Last Deglaciation from Deep-Sea Corals

NASA Astrophysics Data System (ADS)

Robinson, L. F.; Li, T.; Chen, T.; Burke, A.; Pegrum Haram, A.; Stewart, J.; Rae, J. W. B.; van de Flierdt, T.; Struve, T.; Wilson, D. J.

2017-12-01

Two decades ago it was first noted that the skeletal remains of deep-sea corals had the potential to provide absolutely dated archives of past ocean conditions. In the intervening twenty years this field has developed to the point where strategic collections and high throughput dating techniques now allow high resolution, well dated records of past deep sea behaviour to be produced. Likewise, efforts to improve understanding of biomineralisation and growth rates are leading to refinements in proxy tools useful for examining circulation, nutrient and carbon cycling, temperature and weathering processes. Deep-sea corals are particularly valuable archives in high latitude regions where radiocarbon-based age models are susceptible to large changes in surface reservoir ages. In this presentation we show new high resolution multiproxy records of the Southern Ocean (Drake Passage) made on U-Th dated corals spanning the last glacial cycle. With more than seventeen hundred reconnaissance ages, and around 200 precise isotope dilution U-Th ages, subtle changes in ocean behaviour can be identified during times of abrupt climate change. The geochemical signature of corals from the deepest sites, closest to modern day Lower Circumpolar Deep Waters, typically show a gradual shift from glacial to Holocene values during deglaciation, likely related to ventilation of the deep ocean. By contrast for the samples collected shallower in the water column (within sites currently bathed by Upper Circumpolar Deep Waters and Antarctic Intermediate and Mode Waters) the evidence points to a more complicated picture. Vertical zonation in the geochemical data suggests that periods of stratification are interspersed with mixing events within the upper 1500m of the water column. At the same time comparison to U-Th dated records from the low latitude Pacific and Atlantic points to an important role for the Southern Ocean in feeding the intermediate waters of both ocean basins throughout the deglaciation.

Combined ocean acidification and low temperature stressors cause coral mortality

NASA Astrophysics Data System (ADS)

Kavousi, Javid; Parkinson, John Everett; Nakamura, Takashi

2016-09-01

Oceans are predicted to become more acidic and experience more temperature variability—both hot and cold—as climate changes. Ocean acidification negatively impacts reef-building corals, especially when interacting with other stressors such as elevated temperature. However, the effects of combined acidification and low temperature stress have yet to be assessed. Here, we exposed nubbins of the scleractinian coral Montipora digitata to ecologically relevant acidic, cold, or combined stress for 2 weeks. Coral nubbins exhibited 100% survival in isolated acidic and cold treatments, but ~30% mortality under combined conditions. These results provide further evidence that coupled stressors have an interactive effect on coral physiology, and reveal that corals in colder environments are also susceptible to the deleterious impacts of coupled ocean acidification and thermal stress.

A two-dimensional ocean model for long-term climatic simulations: Stability and coupling to atmospheric and sea ice models

NASA Astrophysics Data System (ADS)

Harvey, L. D. Danny

1992-06-01

A two-dimensional (latitude-depth) deep ocean model is presented which is coupled to a sea ice model and an Energy Balance Climate Model (EBCM), the latter having land-sea and surface-air resolution. The processes which occur in the ocean model are thermohaline overturning driven by the horizontal density gradient, shallow wind-driven overturning cells, convective overturning, and vertical and horizontal diffusion of heat and salt. The density field is determined from the temperature and salinity fields using a nonlinear equation of state. Mixed layer salinity is affected by evaporation, precipitation, runoff from continents, and sea ice freezing and melting, as well as by advective, convective, and diffusive exchanges with the deep ocean. The ocean model is first tested in an uncoupled mode, in which hemispherically symmetric mixed layer temperature and salinity, or salinity flux, are specified as upper boundary conditions. An experiment performed with previous models is repeated in which a mixed layer salinity perturbation is introduced in the polar half of one hemisphere after switching from a fixed salinity to a fixed salinity flux boundary condition. For small values of the vertical diffusion coefficient KV, the model undergoes self-sustained oscillations with a period of about 1500 years. With larger values of KV, the model locks into either an asymmetric mode with a single overturning cell spanning both hemispheres, or a symmetric quiescent state with downwelling near the equator, upwelling at high latitudes, and a warm deep ocean (depending on the value of KV). When the ocean model is forced with observed mixed layer temperature and salinity, no oscillations occur. The model successfully simulates the very weak meridional overturning and strong Antarctic Circumpolar Current at the latitudes of the Drake Passage. The coupled EBCM-deep ocean model displays internal oscillations with a period of 3000 years if the ocean fraction is uniform with latitude and KV and the horizontal diffusion coefficient in the mixed layer are not too large. Globally averaged atmospheric temperature changes of 2 K are driven by oscillations in the heat flux into or out of the deep ocean, with the sudden onset of a heat flux out of the deep ocean associated with the rapid onset of thermohaline overturning after a quiescent period, and the sudden onset of a heat flux into the deep ocean associated with the collapse of thermohaline overturning. When the coupled model is run with prescribed parameters (such as land-sea fraction and precipitation) varying with latitude based on observations, the model does not oscillate and produces a reasonable deep ocean temperature field but a completely unrealistic salinity field. Resetting the mixed layer salinity to observations on each time step (equivalent to the "flux correction" method used in atmosphere-ocean general circulation models) is sufficient to give a realistic salinity field throughout the ocean depth, but dramatically alters the flow field and associated heat transport. Although the model is highly idealized, the finding that the maximum perturbation in globally averaged heat flux from the deep ocean to the surface over a 100-year period is 1.4 W m-2 suggests that effect of continuing greenhouse gas increases, which could result in a heating perturbation of 10 W m-2 by the end of the next century, will swamp possible surface heating perturbations due to changes in oceanic circulation. On the other hand, the extreme sensitivity of the oceanic flow field to variations in precipitation and evaporation suggests that it will not be possible to produce accurate projections of regional climatic change in the near term, if at all.

Recent distribution of lead in the Indian Ocean reflects the impact of regional emissions.

PubMed

Echegoyen, Yolanda; Boyle, Edward A; Lee, Jong-Mi; Gamo, Toshitaka; Obata, Hajime; Norisuye, Kazuhiro

2014-10-28

Humans have injected lead (Pb) massively into the earth surface environment in a temporally and spatially evolving pattern. A significant fraction is transported by the atmosphere into the surface ocean where we can observe its transport by ocean currents and sinking particles. This study of the Indian Ocean documents high Pb concentrations in the northern and tropical surface waters and extremely low Pb levels in the deep water. North of 20°S, dissolved Pb concentrations decrease from 42 to 82 pmol/kg in surface waters to 1.5-3.3 pmol/kg in deep waters. South of 20°S, surface water Pb concentrations decrease from 21 pmol/kg at 31°S to 7 pmol/kg at 62°S. This surface Pb concentration gradient reflects a southward decrease in anthropogenic Pb emissions. The upper waters of the north and central Indian Ocean have high Pb concentrations resulting from recent regional rapid industrialization and a late phase-out of leaded gasoline, and these concentrations are now higher than currently seen in the central North Pacific and North Atlantic oceans. The Antarctic sector of the Indian Ocean shows very low concentrations due to limited regional anthropogenic Pb emissions, high scavenging rates, and rapid vertical mixing, but Pb still occurs at higher levels than would have existed centuries ago. Penetration of Pb into the northern and central Indian Ocean thermocline waters is minimized by limited ventilation. Pb concentrations in the deep Indian Ocean are comparable to the other oceans at the same latitude, and deep waters of the central Indian Ocean match the lowest observed oceanic Pb concentrations.

Glacial ocean circulation and stratification explained by reduced atmospheric temperature

NASA Astrophysics Data System (ADS)

Jansen, Malte F.

2017-01-01

Earth’s climate has undergone dramatic shifts between glacial and interglacial time periods, with high-latitude temperature changes on the order of 5-10 °C. These climatic shifts have been associated with major rearrangements in the deep ocean circulation and stratification, which have likely played an important role in the observed atmospheric carbon dioxide swings by affecting the partitioning of carbon between the atmosphere and the ocean. The mechanisms by which the deep ocean circulation changed, however, are still unclear and represent a major challenge to our understanding of glacial climates. This study shows that various inferred changes in the deep ocean circulation and stratification between glacial and interglacial climates can be interpreted as a direct consequence of atmospheric temperature differences. Colder atmospheric temperatures lead to increased sea ice cover and formation rate around Antarctica. The associated enhanced brine rejection leads to a strongly increased deep ocean stratification, consistent with high abyssal salinities inferred for the last glacial maximum. The increased stratification goes together with a weakening and shoaling of the interhemispheric overturning circulation, again consistent with proxy evidence for the last glacial. The shallower interhemispheric overturning circulation makes room for slowly moving water of Antarctic origin, which explains the observed middepth radiocarbon age maximum and may play an important role in ocean carbon storage.

Glacial ocean circulation and stratification explained by reduced atmospheric temperature

PubMed Central

Jansen, Malte F.

2017-01-01

Earth’s climate has undergone dramatic shifts between glacial and interglacial time periods, with high-latitude temperature changes on the order of 5–10 °C. These climatic shifts have been associated with major rearrangements in the deep ocean circulation and stratification, which have likely played an important role in the observed atmospheric carbon dioxide swings by affecting the partitioning of carbon between the atmosphere and the ocean. The mechanisms by which the deep ocean circulation changed, however, are still unclear and represent a major challenge to our understanding of glacial climates. This study shows that various inferred changes in the deep ocean circulation and stratification between glacial and interglacial climates can be interpreted as a direct consequence of atmospheric temperature differences. Colder atmospheric temperatures lead to increased sea ice cover and formation rate around Antarctica. The associated enhanced brine rejection leads to a strongly increased deep ocean stratification, consistent with high abyssal salinities inferred for the last glacial maximum. The increased stratification goes together with a weakening and shoaling of the interhemispheric overturning circulation, again consistent with proxy evidence for the last glacial. The shallower interhemispheric overturning circulation makes room for slowly moving water of Antarctic origin, which explains the observed middepth radiocarbon age maximum and may play an important role in ocean carbon storage. PMID:27994158

NOAA Propagation Database Value in Tsunami Forecast Guidance

NASA Astrophysics Data System (ADS)

Eble, M. C.; Wright, L. M.

2016-02-01

The National Oceanic and Atmospheric Administration (NOAA) Center for Tsunami Research (NCTR) has developed a tsunami forecasting capability that combines a graphical user interface with data ingestion and numerical models to produce estimates of tsunami wave arrival times, amplitudes, current or water flow rates, and flooding at specific coastal communities. The capability integrates several key components: deep-ocean observations of tsunamis in real-time, a basin-wide pre-computed propagation database of water level and flow velocities based on potential pre-defined seismic unit sources, an inversion or fitting algorithm to refine the tsunami source based on the observations during an event, and tsunami forecast models. As tsunami waves propagate across the ocean, observations from the deep ocean are automatically ingested into the application in real-time to better define the source of the tsunami itself. Since passage of tsunami waves over a deep ocean reporting site is not immediate, we explore the value of the NOAA propagation database in providing placeholder forecasts in advance of deep ocean observations. The propagation database consists of water elevations and flow velocities pre-computed for 50 x 100 [km] unit sources in a continuous series along all known ocean subduction zones. The 2011 Japan Tohoku tsunami is presented as the case study

Glacial ocean circulation and stratification explained by reduced atmospheric temperature.

PubMed

Jansen, Malte F

2017-01-03

Earth's climate has undergone dramatic shifts between glacial and interglacial time periods, with high-latitude temperature changes on the order of 5-10 °C. These climatic shifts have been associated with major rearrangements in the deep ocean circulation and stratification, which have likely played an important role in the observed atmospheric carbon dioxide swings by affecting the partitioning of carbon between the atmosphere and the ocean. The mechanisms by which the deep ocean circulation changed, however, are still unclear and represent a major challenge to our understanding of glacial climates. This study shows that various inferred changes in the deep ocean circulation and stratification between glacial and interglacial climates can be interpreted as a direct consequence of atmospheric temperature differences. Colder atmospheric temperatures lead to increased sea ice cover and formation rate around Antarctica. The associated enhanced brine rejection leads to a strongly increased deep ocean stratification, consistent with high abyssal salinities inferred for the last glacial maximum. The increased stratification goes together with a weakening and shoaling of the interhemispheric overturning circulation, again consistent with proxy evidence for the last glacial. The shallower interhemispheric overturning circulation makes room for slowly moving water of Antarctic origin, which explains the observed middepth radiocarbon age maximum and may play an important role in ocean carbon storage.

Fate of copper complexes in hydrothermally altered deep-sea sediments from the Central Indian Ocean Basin.

PubMed

Chakraborty, Parthasarathi; Sander, Sylvia G; Jayachandran, Saranya; Nath, B Nagender; Nagaraju, G; Chennuri, Kartheek; Vudamala, Krushna; Lathika, N; Mascarenhas-Pereira, Maria Brenda L

2014-11-01

The current study aims to understand the speciation and fate of Cu complexes in hydrothermally altered sediments from the Central Indian Ocean Basin and assess the probable impacts of deep-sea mining on speciation of Cu complexes and assess the Cu flux from this sediment to the water column in this area. This study suggests that most of the Cu was strongly associated with different binding sites in Fe-oxide phases of the hydrothermally altered sediments with stabilities higher than that of Cu-EDTA complexes. The speciation of Cu indicates that hydrothermally influenced deep-sea sediments from Central Indian Ocean Basin may not significantly contribute to the global Cu flux. However, increasing lability of Cu-sediment complexes with increasing depth of sediment may increase bioavailability and Cu flux to the global ocean during deep-sea mining. Copyright © 2014 Elsevier Ltd. All rights reserved.

Modelled ocean changes at the Plio-Pleistocene transition driven by Antarctic ice advance

PubMed Central

Hill, Daniel J.; Bolton, Kevin P.; Haywood, Alan M.

2017-01-01

The Earth underwent a major transition from the warm climates of the Pliocene to the Pleistocene ice ages between 3.2 and 2.6 million years ago. The intensification of Northern Hemisphere Glaciation is the most obvious result of the Plio-Pleistocene transition. However, recent data show that the ocean also underwent a significant change, with the convergence of deep water mass properties in the North Pacific and North Atlantic Ocean. Here we show that the lack of coastal ice in the Pacific sector of Antarctica leads to major reductions in Pacific Ocean overturning and the loss of the modern North Pacific Deep Water (NPDW) mass in climate models of the warmest periods of the Pliocene. These results potentially explain the convergence of global deep water mass properties at the Plio-Pleistocene transition, as Circumpolar Deep Water (CDW) became the common source. PMID:28252023

Dynamics of the global meridional ice flow of Europa's icy shell

NASA Astrophysics Data System (ADS)

Ashkenazy, Yosef; Sayag, Roiy; Tziperman, Eli

2018-01-01

Europa is one of the most probable places in the solar system to find extra-terrestrial life1,2, motivating the study of its deep ( 100 km) ocean3-6 and thick icy shell3,7-11. The chaotic terrain patterns on Europa's surface12-15 have been associated with vertical convective motions within the ice8,10. Horizontal gradients of ice thickness16,17 are expected due to the large equator-to-pole gradient of surface temperature and can drive a global horizontal ice flow, yet such a flow and its observable implications have not been studied. We present a global ice flow model for Europa composed of warm, soft ice flowing beneath a cold brittle rigid ice crust3. The model is coupled to an underlying (diffusive) ocean and includes the effect of tidal heating and convection within the ice. We show that Europa's ice can flow meridionally due to pressure gradients associated with equator-to-pole ice thickness differences, which can be up to a few km and can be reduced both by ice flow and due to ocean heat transport. The ice thickness and meridional flow direction depend on whether the ice convects or not; multiple (convecting and non-convecting) equilibria are found. Measurements of the ice thickness and surface temperature from future Europa missions18,19 can be used with our model to deduce whether Europa's icy shell convects and to constrain the effectiveness of ocean heat transport.

Glendonites in Neoproterozoic low-latitude, interglacial, sedimentary rocks, northwest Canada: Insights into the Cryogenian ocean and Precambrian cold-water carbonates

NASA Astrophysics Data System (ADS)

James, Noel P.; Narbonne, Guy M.; Dalrymple, Robert W.; Kurtis Kyser, T.

2005-01-01

Stellate crystals of ferroan dolomite in neritic siliciclastic and carbonate sedimentary rocks between Sturtian and Marinoan glaciations in the Mackenzie Mountains are interpreted as replaced glendonites. These pseudomorphs after ikaite indicate that shallow seawater at that time was near freezing. Stromatolites verify that paleoenvironments were in the photic zone and physical sedimentary structures such as hummocky cross-bedding confirm that the seafloor was repeatedly disturbed by storms. Glendonites within these low-latitude, continental shelf to coastal sedimentary deposits imply that global ocean water during much of Cryogenian time was likely very cold. Such an ocean would easily have cooled to yield widespread sea ice and, through positive feedback, growth of low-latitude continental glaciers. In this situation gas hydrates could have formed in shallow-water, cold shelf sediment, but would have been particularly sensitive to destabilization as a result of sea-level change. Co-occurrence of pisolites and glendonites in these rocks additionally implies that some ooids and pisoids might have been, unlike Phanerozoic equivalents, characteristic of cold-water sediments.

Variations in radiolarian assemblages in the Japan Sea since the Last Glacial Period: implications for paleoceanography Zhi Dong12, Xuefa Shi2, Xinqing Zou1, Jianjun Zou2, Muhong Chen3, Qiang Zhang3, Chendong Ge1,Yanguang Liu21. Nanjing University,China 2. First Institute of Oceanography, China 3. South China Sea Institute of Oceanology, China

NASA Astrophysics Data System (ADS)

Dong, Z.; Shi, X.; Zou, X.; Zou, J. J.; Chen, M.; Zhang, Q.; Ge, C.; Liu, Y.

2017-12-01

Japan Sea is a marginal sea located on the rim of the western Pacific, connecting with the open ocean via key straits with sill depths of less than 130 m, whichis close to the maximum drop of sea level during the Last Glacial Maximum (LGM). Tsushima Strait connects modern JS with neighboring seas and Tsushima Warm Current (TWC), the only warm current flowing into the JS, reaches the northern JS where the cold saline deep wate is formed. Previous studies show that only northern Tsugaru Strait was opened during the last deglaciation, indicating different pattern of water mass exchange between JS and adjacent seas. Few paleoceanographic reconstructions in the southern JS are available to reconstruct the history of inflow of the TWC and deep ventilation. Radiolaria comprises shallow to deep water dwellers, sensitive response to changes in sea water physical and chemical states. It is well known for being preserved in the deep-sea sediments of the North Pacific. In order to decipher the changes of paleoceanography in the JS, here we investigate SST, SSS, deep ventilation using radiolarian assemblages recorded in core KCES1 recovered from the Ulleung Basin. We identified total 108 taxa which have been counted and divided into three categories: TWC, low-salinity and deep water taxa. Changes in radiolaria reveal that the paleoceanographic conditions has changed drastically during the last glacial period. The dominance of low-salinitytaxa indicates low SSS in JS during LGM. For older interval (24-46 ka), low-salinity taxa and TWC taxa could be identified, suggesting both East China Sea Coastal Water, whose volume is higher than Holocene, and TWC flow into the JS. The TWC taxa start to increase at 19 ka, also indicated by negative excursion of TOC δ13C due to the re-open of the Tsushima Strait, coincident with the 19 ka-MWP. The increasing abundance of low-salinity taxa during the B/A warm period, indicated an enhanced influence of river discharge forced by EASM. The enhanced deep ventilation occurred abruptly at 17 ka, caused by the sink of cold and saline water into the deep during the HS 1. While between 13 and 12 ka, high abundance of C.davisiana, one of the dominant species of deep water, inferring the strongest ventilation corresponding to the YD-like event. High abundance of TWC taxa shows the TWC re-enters into the JS during 9-7 ka.

The addition of hydrodynamic variables to predictive cold water coral habitat modeling: The Bari Canyon case-study, southwestern Adriatic Sea

NASA Astrophysics Data System (ADS)

Foglini, Federica; Bargain, Annaëlle; Angeletti, Lorenzo; Bonaldo, Davide; Carniel, Sandro; Taviani, Marco

2017-04-01

Predictive habitat modeling is gaining momentum because of its usefulness to recognize potential distributional patterns of ecosystems thus facilitating their proper governance when required, as it is for instance the case of the Marine Strategy Framework Directive (MSFD). This holds particularly true for the deep-sea in front of its overwhelming areal extent on a global scale and intrinsic technological difficulties (with related costs) for its direct exploration. Cold Water Corals (CWC) is one emblematic, virtually cosmopolitan, ecosystem in the deep, that is under international attention because of its multifaceted ecological importance. CWC is currently represented in the Mediterranean basin by habitats engineered by the arborescent scleractinians Madrepora oculata and Lophelia pertusa associated with a number of other benthic invertebrates. One major CWC hotspot located on the southwestern Adriatic margin, the Bari Canyon cold water coral province, has been targeted for producing habitat suitability maps. Initially the evaluation of the theoretical distribution of CWC in this area has been based upon visual observations, mainly extracted from geo-referenced underwater ROV imagery, coupled with the eco-geographic information derived from bathymetry. This approach relies upon the compilation and comparison of presence-only models (MaxEnt and ENFA), but also presence-absence model (GLMs). However, the pivotal role played by oceanographic factors has been soon added in order to achieve more robust predictive models. In fact, the Bari Canyon CWC province is situated on the main path of the North Adriatic Dense Water cascading, and hypothesized to be sensitive to hydrological factors. Accordingly, the statistical models to assess potential habitat extent have been implemented using hydrodynamic fields provided by ROMS for ocean currents, coupled with SWAN within the COAWST modelling system to account for wave-current interactions. The integration of results is beneficial to the production of more sophisticated habitat suitability maps.

The giant cold-water coral mound as a nested microbial/metazoan system: physical, chemical, biological and geological picture (ESF EuroDiversity MiCROSYSTEMS)

NASA Astrophysics Data System (ADS)

Henriet, J. P.; Microsystems Team

2009-04-01

The MiCROSYSTEMS project under the ESF EUROCORES EuroDiversity scheme is a holistic and multi-scale approach in studying microbial diversity and functionality in a nested microbial/metazoan system, which thrives in deep waters: the giant cold-water coral mound. Studies on prolific cold-water coral sites have been carried out from the canyons of the Bay of Biscay to the fjords of the Norwegian margin, while the Pen Duick carbonate mound province off Morocco developed into a joint natural lab for studying in particular the impact of biogeochemical and microbial processes on modern sedimentary diagenesis within the reef sediments, in complement to the studies on I0DP Exp. 307 cores (Challenger Mound, off Ireland). Major outcomes of this research can be summarized as follows. • IODP Exp. 307 on Challenger Mound had revealed a significant prokaryotic community both within and beneath the carbonate mound. MiCROSYSTEMS unveils a remarkable degree of compartmentalization in such community from the seawater, the coral skeleton surface and mucus to the reef sediments. The occurrence of such multiple and distinct microbial compartments associated with cold-water coral ecosystems promotes opportunities for microbial diversity in the deep ocean. • New cases of co-habitation of cold-water corals and giant deep-water oysters were discovered in the Bay of Biscay, which add a new facet of macrofaunal diversity to cold-water coral reef systems. • The discovery of giant, ancient coral graveyards on the Moroccan mounds not only fuels the debate about natural versus anthropogenic mass extinction, but these open frameworks simultaneously invite for the study of bio-erosion and early diagenesis, in particular organo-mineralization, and of the possible role and significance of these thick, solid rubble patches in 3D mound-building and consolidation. • The assessment of the carbonate budget of a modern cold-water coral mound (Challenger Mound) reveals that only 33 to 40 wt % of carbonate is derived from corals and suggests a selective enrichment of the hemipelagic carbonate fraction, compared to adjacent sediment drift deposits. • The detection of allochthonous fluids, in particular brines, in the pore space of the surficial mound sediments on the Pen Duick Escarpment hints towards the presence of salt deposits deep underneath, and simultaneously provides the first direct evidence of advective fluid transfer from the deep, throughout the mound substrate and the full mound height. Potential stratigraphic pathways leading from the deeper basinal realms directly to the mound setting have been imaged in a spectacular way through high-resolution pseudo-3D seismic imaging. Geophysical signatures of free gas accumulations have been detected a few hundreds of meters below the mound base, but low concentrations of methane and the absence of lipid biomarkers from methane-dependent prokaryotes suggest low fluxes of methane-derived carbon and thus very small rates of anaerobic oxidation of methane (AOM) in the immediate mound subsurface. Local changes in the sediment biogeochemistry are most likely dictated by slow diffusive fluid transfer, operating in a heterogeneous way in the subsurface. • Cultivation experiments with sediments from microbially active mound zones have allowed to study microbially induced carbonate precipitation and provide a tool for the interpretation of carbonate mineralogy. The development and operation of a continuous high-pressure bioreactor (100 bars) allows to simulate in an ex situ mode the impact of environmental parameter changes onto the functioning of relevant microbial communities. • The detected influx of sulfate in mound sediments implies that bacterial sulfate reduction can be the dominant anaerobic carbon mineralization process. Groundwater flow modeling suggests that currents impinging on the escarpment and the flanks of an exposed mound can account for a significant influx and transport of sulfate through convective fluid transfer within the mound sediments. Oceanic currents consequently provide not only a major control on the external flux of nutrients to the mound-building communities, but they also potentially drive internal flow in the mound. The extant hydrodynamic climate of the mound setting is documented through long-term lander deployments and CTD stations: the current records reveal a significant tidal and seasonal variability. The past environmental record over the last 400 ka is documented in a most comprehensive sedimentary archive, sampled with long cores at the foot of the Pen Duick Escarpment during the MD169 ‘MiCROSYSTEMS' cruise in July 2008. • MiCROSYSTEMS has significantly contributed to the successful submission of IODP proposal 673-Full, which should (i) document the whole-mound architecture and the mound setting on Pen Duick Escarpment as well as a most comprehensive stratigraphic record on a reference site at the foot of the escarpment, (ii) reveal the full spatial pattern in microbial diversity, activity and functionality throughout the mound and underneath, and (iii) unravel the plumbing system of a mound and the dynamic interaction between advective, convective and diffusive transfers of organic and inorganic compounds, which impact on biogeochemical equilibria, microbial activity and early diagenetic processes.

The importance of habitat and life history to extinction risk in sharks, skates, rays and chimaeras

PubMed Central

García, Verónica B; Lucifora, Luis O; Myers, Ransom A

2007-01-01

We compared life-history traits and extinction risk of chondrichthyans (sharks, rays and chimaeras), a group of high conservation concern, from the three major marine habitats (continental shelves, open ocean and deep sea), controlling for phylogenetic correlation. Deep-water chondrichthyans had a higher age at maturity and longevity, and a lower growth completion rate than shallow-water species. The average fishing mortality needed to drive a deep-water chondrichthyan species to extinction (Fextinct) was 38–58% of that estimated for oceanic and continental shelf species, respectively. Mean values of Fextinct were 0.149, 0.250 and 0.368 for deep-water, oceanic and continental shelf species, respectively. Reproductive mode was an important determinant of extinction risk, while body size had a weak effect on extinction risk. As extinction risk was highly correlated with phylogeny, the loss of species will be accompanied by a loss of phylogenetic diversity. Conservation priority should not be restricted to large species, as is usually suggested, since many small species, like those inhabiting the deep ocean, are also highly vulnerable to extinction. Fishing mortality of deep-water chondrichthyans already exploited should be minimized, and new deep-water fisheries affecting chondrichthyans should be prevented. PMID:17956843

Observation of water mass characteristics in the southwestern Mariana Trench

NASA Astrophysics Data System (ADS)

Xu, H.; Xie, Q.; Hong, B.

2016-12-01

The identification of large water mass characteristic can help oceanographer to better understand the oceanic circulation structures and other physical processes in open oceans. In current stage, the water mass characteristics were recognized well by extensive observation in the upper ocean, however, it was rarely studied in deep oceans, especially for deep trench with > 6000 m depth. In this study, we use observed data collected by CTDs during several surveys to investigate the water mass physical characteristic and transport in the world deepest trench, `Challenger Deep', in the southwestern Mariana Trench. The preliminary results show complex vertical structures of water mass in this trench. From surface to 4500 m, the water masses are occupied by typical tropical surface water, NPTUW, NPMW, NPIW and NPDW. Under 4500m, the water mass shows mixing characteristics of NPDW and AABW, which indicate AABW can be transported by form the deep ocean of the South Ocean to Northwestern Pacific and it can affect local water mass characteristics. The baroclinic geostrophic current calculated from the CTDs data shows the westerly transport of water mass can reach about 1.0 SV in the trench which is close to previous results.

Cross-frontal cold jets near Iceland: In-water, satellite infrared, and Geosat altimeter data

NASA Astrophysics Data System (ADS)

Scott, John C.; McDowall, Anne L.

1990-10-01

This paper reports detailed in-water observations and satellite infrared images which are approximately coincident with a single Geosat altimeter track across the Iceland-Faeroes Frontal Zone. The ARE thermistor chain covered the upper 300 m of the ocean along the track, and the first two of a long sequence of NOAA satellite infrared images were obtained, all within 24 hours of the Geosat overpass. The data are interpreted as showing cold cross-frontal jets related to the formation of cold eddies south of the main frontal boundary. Implications for the use of altimetry for ocean monitoring are considered.

The Discovery of New Deep-Sea Hydrothermal Vent Communities in the Southern Ocean and Implications for Biogeography

PubMed Central

Rogers, Alex D.; Tyler, Paul A.; Connelly, Douglas P.; Copley, Jon T.; James, Rachael; Larter, Robert D.; Linse, Katrin; Mills, Rachel A.; Garabato, Alfredo Naveira; Pancost, Richard D.; Pearce, David A.; Polunin, Nicholas V. C.; German, Christopher R.; Shank, Timothy; Boersch-Supan, Philipp H.; Alker, Belinda J.; Aquilina, Alfred; Bennett, Sarah A.; Clarke, Andrew; Dinley, Robert J. J.; Graham, Alastair G. C.; Green, Darryl R. H.; Hawkes, Jeffrey A.; Hepburn, Laura; Hilario, Ana; Huvenne, Veerle A. I.; Marsh, Leigh; Ramirez-Llodra, Eva; Reid, William D. K.; Roterman, Christopher N.; Sweeting, Christopher J.; Thatje, Sven; Zwirglmaier, Katrin

2012-01-01

Since the first discovery of deep-sea hydrothermal vents along the Galápagos Rift in 1977, numerous vent sites and endemic faunal assemblages have been found along mid-ocean ridges and back-arc basins at low to mid latitudes. These discoveries have suggested the existence of separate biogeographic provinces in the Atlantic and the North West Pacific, the existence of a province including the South West Pacific and Indian Ocean, and a separation of the North East Pacific, North East Pacific Rise, and South East Pacific Rise. The Southern Ocean is known to be a region of high deep-sea species diversity and centre of origin for the global deep-sea fauna. It has also been proposed as a gateway connecting hydrothermal vents in different oceans but is little explored because of extreme conditions. Since 2009 we have explored two segments of the East Scotia Ridge (ESR) in the Southern Ocean using a remotely operated vehicle. In each segment we located deep-sea hydrothermal vents hosting high-temperature black smokers up to 382.8°C and diffuse venting. The chemosynthetic ecosystems hosted by these vents are dominated by a new yeti crab (Kiwa n. sp.), stalked barnacles, limpets, peltospiroid gastropods, anemones, and a predatory sea star. Taxa abundant in vent ecosystems in other oceans, including polychaete worms (Siboglinidae), bathymodiolid mussels, and alvinocaridid shrimps, are absent from the ESR vents. These groups, except the Siboglinidae, possess planktotrophic larvae, rare in Antarctic marine invertebrates, suggesting that the environmental conditions of the Southern Ocean may act as a dispersal filter for vent taxa. Evidence from the distinctive fauna, the unique community structure, and multivariate analyses suggest that the Antarctic vent ecosystems represent a new vent biogeographic province. However, multivariate analyses of species present at the ESR and at other deep-sea hydrothermal vents globally indicate that vent biogeography is more complex than previously recognised. PMID:22235194

Abrupt pre-Bølling-Allerød warming and circulation changes in the deep ocean.

PubMed

Thiagarajan, Nivedita; Subhas, Adam V; Southon, John R; Eiler, John M; Adkins, Jess F

2014-07-03

Several large and rapid changes in atmospheric temperature and the partial pressure of carbon dioxide in the atmosphere--probably linked to changes in deep ocean circulation--occurred during the last deglaciation. The abrupt temperature rise in the Northern Hemisphere and the restart of the Atlantic meridional overturning circulation at the start of the Bølling-Allerød interstadial, 14,700 years ago, are among the most dramatic deglacial events, but their underlying physical causes are not known. Here we show that the release of heat from warm waters in the deep North Atlantic Ocean probably triggered the Bølling-Allerød warming and reinvigoration of the Atlantic meridional overturning circulation. Our results are based on coupled radiocarbon and uranium-series dates, along with clumped isotope temperature estimates, from water column profiles of fossil deep-sea corals in a limited area of the western North Atlantic. We find that during Heinrich stadial 1 (the cool period immediately before the Bølling-Allerød interstadial), the deep ocean was about three degrees Celsius warmer than shallower waters above. This reversal of the ocean's usual thermal stratification pre-dates the Bølling-Allerød warming and must have been associated with increased salinity at depth to preserve the static stability of the water column. The depleted radiocarbon content of the warm and salty water mass implies a long-term disconnect from rapid surface exchanges, and, although uncertainties remain, is most consistent with a Southern Ocean source. The Heinrich stadial 1 ocean profile is distinct from the modern water column, that for the Last Glacial Maximum and that for the Younger Dryas, suggesting that the patterns we observe are a unique feature of the deglacial climate system. Our observations indicate that the deep ocean influenced dramatic Northern Hemisphere warming by storing heat at depth that preconditioned the system for a subsequent abrupt overturning event during the Bølling-Allerød interstadial.

Subsurface Hybrid Power Options for Oil & Gas Production at Deep Ocean Sites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farmer, J C; Haut, R; Jahn, G

2010-02-19

An investment in deep-sea (deep-ocean) hybrid power systems may enable certain off-shore oil and gas exploration and production. Advanced deep-ocean drilling and production operations, locally powered, may provide commercial access to oil and gas reserves otherwise inaccessible. Further, subsea generation of electrical power has the potential of featuring a low carbon output resulting in improved environmental conditions. Such technology therefore, enhances the energy security of the United States in a green and environmentally friendly manner. The objective of this study is to evaluate alternatives and recommend equipment to develop into hybrid energy conversion and storage systems for deep ocean operations.more » Such power systems will be located on the ocean floor and will be used to power offshore oil and gas exploration and production operations. Such power systems will be located on the oceans floor, and will be used to supply oil and gas exploration activities, as well as drilling operations required to harvest petroleum reserves. The following conceptual hybrid systems have been identified as candidates for powering sub-surface oil and gas production operations: (1) PWR = Pressurized-Water Nuclear Reactor + Lead-Acid Battery; (2) FC1 = Line for Surface O{sub 2} + Well Head Gas + Reformer + PEMFC + Lead-Acid & Li-Ion Batteries; (3) FC2 = Stored O2 + Well Head Gas + Reformer + Fuel Cell + Lead-Acid & Li-Ion Batteries; (4) SV1 = Submersible Vehicle + Stored O{sub 2} + Fuel Cell + Lead-Acid & Li-Ion Batteries; (5) SV2 = Submersible Vehicle + Stored O{sub 2} + Engine or Turbine + Lead-Acid & Li-Ion Batteries; (6) SV3 = Submersible Vehicle + Charge at Docking Station + ZEBRA & Li-Ion Batteries; (7) PWR TEG = PWR + Thermoelectric Generator + Lead-Acid Battery; (8) WELL TEG = Thermoelectric Generator + Well Head Waste Heat + Lead-Acid Battery; (9) GRID = Ocean Floor Electrical Grid + Lead-Acid Battery; and (10) DOC = Deep Ocean Current + Lead-Acid Battery.« less

Spontaneous abrupt climate change due to an atmospheric blocking-sea-ice-ocean feedback in an unforced climate model simulation.

PubMed

Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A; Livina, Valerie

2013-12-03

Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70 °N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change.

Spontaneous abrupt climate change due to an atmospheric blocking–sea-ice–ocean feedback in an unforced climate model simulation

PubMed Central

Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A.; Livina, Valerie

2013-01-01

Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70°N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change. PMID:24248352

The Recent Atlantic Cold Anomaly: Causes, Consequences, and Related Phenomena

NASA Astrophysics Data System (ADS)

Josey, Simon A.; Hirschi, Joel J.-M.; Sinha, Bablu; Duchez, Aurélie; Grist, Jeremy P.; Marsh, Robert

2018-01-01

Cold ocean temperature anomalies have been observed in the mid- to high-latitude North Atlantic on interannual to centennial timescales. Most notably, a large region of persistently low surface temperatures accompanied by a sharp reduction in ocean heat content was evident in the subpolar gyre from the winter of 2013-2014 to 2016, and the presence of this feature at a time of pervasive warming elsewhere has stimulated considerable debate. Here, we review the role of air-sea interaction and ocean processes in generating this cold anomaly and place it in a longer-term context. We also discuss the potential impacts of surface temperature anomalies for the atmosphere, including the North Atlantic Oscillation and European heat waves; contrast the behavior of the Atlantic with the extreme warm surface event that occurred in the North Pacific over a similar timescale; and consider the possibility that these events represent a response to a change in atmospheric planetary wave forcing.

Ubiquitous healthy diatoms in the deep sea confirms deep carbon injection by the biological pump

NASA Astrophysics Data System (ADS)

Agustí, Susana; González-Gordillo, Jose I.; Vaqué, Dolors; Estrada, Marta; Cerezo, Maria I.; Salazar, Guillem; Gasol, Josep M.; Duarte, Carlos M.

2016-04-01

The role of the ocean as a sink for CO2 is partially dependent on the downward transport of phytoplankton cells packaged within fast-sinking particles. However, whether such fast-sinking mechanisms deliver fresh organic carbon down to the deep bathypelagic sea and whether this mechanism is prevalent across the ocean awaits confirmation. Photosynthetic plankton, directly responsible for trapping CO2 in organic form in the surface layer, are a key constituent of the flux of sinking particles and are assumed to die and become detritus upon leaving the photic layer. Research in the 1960-70's reported the occasional presence of well-preserved phytoplankton cells in the deep ocean, but these observations, which could signal at rapid sinking rates, were considered anecdotal. Using new developments we tested the presence of healthy phytoplankton cells in the deep sea (2000 to 4000 m depth) along the Malaspina 2010 Circumnavigation Expedition, a global expedition sampling the bathypelagic zone of the Atlantic, Indian and Pacific Oceans. In particular, we used a new microplankton sampling device, the Bottle-Net, 16S rDNA sequences, flow cytometric counts, vital stains and experiments to explore the abundance and health status of photosynthetic plankton cells between 2,000 and 4,000 m depth along the Circumnavigation track. We described the community of microplankton (> 20μm) found at the deep ocean (2000-4000 m depth), surprisingly dominated by phytoplankton, and within this, by diatoms. Moreover, we report the ubiquitous presence of healthy photosynthetic cells, dominated by diatoms, down to 4,000 m in the deep dark sea. Decay experiments with surface phytoplankton suggested that the large proportion (18%) of healthy photosynthetic cells observed, on average, in the dark ocean, requires transport times from few days to few weeks, corresponding to sinking rates of 124 to 732 m d-1, comparable to those of fast sinking aggregates and faecal pellets. These results confirm the expectation that fast-sinking mechanisms inject fresh organic carbon into the deep-sea and that this is a prevalent process operating across the global oligotrophic ocean.

Adapting to the Deep Sea: A Fun Activity with Bioluminescence

ERIC Educational Resources Information Center

Rife, Gwynne

2006-01-01

Over the past decade, much has been learned about the ocean's secrets and especially about the creatures of the deep sea. The deepest parts of the oceans are currently the focus of many new discoveries in both the physical and biological sciences. Middle school students find the deep sea fascinating and especially seem to enjoy its mysterious and…

Genomes of Novel Microbial Lineages Assembled from the Sub-Ice Waters of Lake Baikal

PubMed Central

Cabello-Yeves, Pedro J.; Zemskaya, Tamara I.; Rosselli, Riccardo; Coutinho, Felipe H.; Zakharenko, Alexandra S.; Blinov, Vadim V.

2017-01-01

ABSTRACT We present a metagenomic study of Lake Baikal (East Siberia). Two samples obtained from the water column under the ice cover (5 and 20 m deep) in March 2016 have been deep sequenced and the reads assembled to generate metagenome-assembled genomes (MAGs) that are representative of the microbes living in this special environment. Compared with freshwater bodies studied around the world, Lake Baikal had an unusually high fraction of Verrucomicrobia. Other groups, such as Actinobacteria and Proteobacteria, were in proportions similar to those found in other lakes. The genomes (and probably cells) tended to be small, presumably reflecting the extremely oligotrophic and cold prevalent conditions. Baikal microbes are novel lineages recruiting very little from other water bodies and are distantly related to other freshwater microbes. Despite their novelty, they showed the closest relationship to genomes discovered by similar approaches from other freshwater lakes and reservoirs. Some of them were particularly similar to MAGs from the Baltic Sea, which, although it is brackish, connected to the ocean, and much more eutrophic, has similar climatological conditions. Many of the microbes contained rhodopsin genes, indicating that, in spite of the decreased light penetration allowed by the thick ice/snow cover, photoheterotrophy could be widespread in the water column, either because enough light penetrates or because the microbes are already adapted to the summer ice-less conditions. We have found a freshwater SAR11 subtype I/II representative showing striking synteny with Pelagibacter ubique strains, as well as a phage infecting the widespread freshwater bacterium Polynucleobacter. IMPORTANCE Despite the increasing number of metagenomic studies on different freshwater bodies, there is still a missing component in oligotrophic cold lakes suffering from long seasonal frozen cycles. Here, we describe microbial genomes from metagenomic assemblies that appear in the upper water column of Lake Baikal, the largest and deepest freshwater body on Earth. This lake is frozen from January to May, which generates conditions that include an inverted temperature gradient (colder up), decrease in light penetration due to ice, and, especially, snow cover, and oligotrophic conditions more similar to the open-ocean and high-altitude lakes than to other freshwater or brackish systems. As could be expected, most reconstructed genomes are novel lineages distantly related to others in cold environments, like the Baltic Sea and other freshwater lakes. Among them, there was a broad set of streamlined microbes with small genomes/intergenic spacers, including a new nonmarine Pelagibacter-like (subtype I/II) genome. PMID:29079621

Genomes of Novel Microbial Lineages Assembled from the Sub-Ice Waters of Lake Baikal.

PubMed

Cabello-Yeves, Pedro J; Zemskaya, Tamara I; Rosselli, Riccardo; Coutinho, Felipe H; Zakharenko, Alexandra S; Blinov, Vadim V; Rodriguez-Valera, Francisco

2018-01-01

We present a metagenomic study of Lake Baikal (East Siberia). Two samples obtained from the water column under the ice cover (5 and 20 m deep) in March 2016 have been deep sequenced and the reads assembled to generate metagenome-assembled genomes (MAGs) that are representative of the microbes living in this special environment. Compared with freshwater bodies studied around the world, Lake Baikal had an unusually high fraction of Verrucomicrobia Other groups, such as Actinobacteria and Proteobacteria , were in proportions similar to those found in other lakes. The genomes (and probably cells) tended to be small, presumably reflecting the extremely oligotrophic and cold prevalent conditions. Baikal microbes are novel lineages recruiting very little from other water bodies and are distantly related to other freshwater microbes. Despite their novelty, they showed the closest relationship to genomes discovered by similar approaches from other freshwater lakes and reservoirs. Some of them were particularly similar to MAGs from the Baltic Sea, which, although it is brackish, connected to the ocean, and much more eutrophic, has similar climatological conditions. Many of the microbes contained rhodopsin genes, indicating that, in spite of the decreased light penetration allowed by the thick ice/snow cover, photoheterotrophy could be widespread in the water column, either because enough light penetrates or because the microbes are already adapted to the summer ice-less conditions. We have found a freshwater SAR11 subtype I/II representative showing striking synteny with Pelagibacter ubique strains, as well as a phage infecting the widespread freshwater bacterium Polynucleobacter IMPORTANCE Despite the increasing number of metagenomic studies on different freshwater bodies, there is still a missing component in oligotrophic cold lakes suffering from long seasonal frozen cycles. Here, we describe microbial genomes from metagenomic assemblies that appear in the upper water column of Lake Baikal, the largest and deepest freshwater body on Earth. This lake is frozen from January to May, which generates conditions that include an inverted temperature gradient (colder up), decrease in light penetration due to ice, and, especially, snow cover, and oligotrophic conditions more similar to the open-ocean and high-altitude lakes than to other freshwater or brackish systems. As could be expected, most reconstructed genomes are novel lineages distantly related to others in cold environments, like the Baltic Sea and other freshwater lakes. Among them, there was a broad set of streamlined microbes with small genomes/intergenic spacers, including a new nonmarine Pelagibacter -like (subtype I/II) genome. Copyright © 2017 American Society for Microbiology.

Arctic Ocean Model Intercomparison Using Sound Speed

NASA Astrophysics Data System (ADS)

Dukhovskoy, D. S.; Johnson, M. A.

2002-05-01

The monthly and annual means from three Arctic ocean - sea ice climate model simulations are compared for the period 1979-1997. Sound speed is used to integrate model outputs of temperature and salinity along a section between Barrow and Franz Josef Land. A statistical approach is used to test for differences among the three models for two basic data subsets. We integrated and then analyzed an upper layer between 2 m - 50 m, and also a deep layer from 500 m to the bottom. The deep layer is characterized by low time-variability. No high-frequency signals appear in the deep layer having been filtered out in the upper layer. There is no seasonal signal in the deep layer and the monthly means insignificantly oscillate about the long-period mean. For the deep ocean the long-period mean can be considered quasi-constant, at least within the 19 year period of our analysis. Thus we assumed that the deep ocean would be the best choice for comparing the means of the model outputs. The upper (mixed) layer was chosen to contrast the deep layer dynamics. There are distinct seasonal and interannual signals in the sound speed time series in this layer. The mixed layer is a major link in the ocean - air interaction mechanism. Thus, different mean states of the upper layer in the models might cause different responses in other components of the Arctic climate system. The upper layer also strongly reflects any differences in atmosphere forcing. To compare data from the three models we have used a one-way t-test for the population mean, the Wilcoxon one-sample signed-rank test (when the requirement of normality of tested data is violated), and one-way ANOVA method and F-test to verify our hypothesis that the model outputs have the same mean sound speed. The different statistical approaches have shown that all models have different mean characteristics of the deep and upper layers of the Arctic Ocean.

Trace element evidence for abrupt changes in deep South Atlantic Ocean nutrient and carbonate chemistry across the Mid-Pleistocene Transition

NASA Astrophysics Data System (ADS)

Farmer, J. R.; Hoenisch, B.; Haynes, L.; Kroon, D.; Bell, D. B.; Jung, S.; Seguí, M. J.; Raymo, M. E.; Goldstein, S. L.; Pena, L. D.

2016-12-01

Pleistocene glaciations underwent a profound transition from lower amplitude 40 kyr cycles to high amplitude 100 kyr cycles between 1.2 and 0.8 Ma, an interval termed the Mid-Pleistocene Transition (MPT). While the underlying causes of the MPT are uncertain, previous studies show quasi-contemporaneous reductions in North Atlantic Deep Water (NADW) export1 and glacial atmospheric pCO22 around 0.9 Ma. Although this suggests a possible role for enhanced deep-ocean carbon storage in amplifying climate change across the MPT, few direct records of deep ocean carbonate chemistry exist for this interval to test this hypothesis. Here we present South Atlantic benthic foraminiferal B/Ca and Cd/Ca records from International Ocean Discovery Program Sites 1088, 1264 and 1267 (2.1 to 4.3 km water depth) as part of a larger study of Atlantic-wide changes in deep ocean chemistry and circulation spanning the MPT. Results show an abrupt 15-20% decrease in benthic B/Ca and 40-50% increase in Cd/Ca at 4.3 km depth (Site 1267) between 1.0 and 0.9 Ma. Site 1088, which at 2.1 km depth is sensitive to input of southern-sourced Upper Circumpolar Deep Water, shows a prolonged 25% decrease in B/Ca and 50% increase in Cd/Ca from 1.0 to 0.6 Ma. In contrast, at Site 1264 ( 2.5 km depth within the core of modern NADW) B/Ca and Cd/Ca changes across the MPT are more modest (-5% and +10%, respectively). These observations reflect on the accumulation of regenerated carbon and nutrients in the deep South Atlantic, and varying contributions of northern- and southern-sourced watermasses to each core site. Implications for deep-ocean carbon storage and forcing of the MPT will be discussed. 1Pena, L. and Goldstein, S. (2014), Science 345, 318 2Hönisch, B. et al. (2009), Science 324, 1551

Effects of Cold Therapy on Pain and Breathing Exercises Among Median Sternotomy Patients.

PubMed

Zencir, Gülbanu; Eser, Ismet

2016-12-01

The most painful activities during the days following cardiac surgery are coughing and deep breathing exercises. Cold therapy is an effective nonpharmacological method that decreases the pain during coughing and mobilization. In this study, the effects of cold therapy on pain and breathing exercises among patients with median sternotomy following cardiac surgery were investigated in a randomized crossover clinical trial. Data were collected from patients with median sternotomy (N = 34) in the first two postoperative days. Because of the crossover design of the study, each patient was taken as a simultaneous control. Gel pack application was used as the cold therapy. Patients underwent four episodes of deep breathing and coughing exercises using an incentive spirometer (volumetric). Patients were evaluated according to the visual analogue scale for pain intensity before and after deep breathing and coughing exercise sessions. The pain score was 3.44 ± 2.45 at baseline for deep breathing and coughing exercises on the first day. The reported postoperative pain in the gel-pack group was not significantly different before and after the deep breathing and coughing exercises, but it significantly increased in the no-gel-pack group (p < .001). Although the interaction between the treatment and time was significant (partial eta-squared: .09), the gel-pack group had a lower change in average pain levels. This interaction was not significant in terms of spirometric values. In conclusion, cold therapy had a positive effect on pain management in the early period of post-cardiac surgery but was not effective for the pain associated with breathing exercises. Copyright © 2016 American Society for Pain Management Nursing. Published by Elsevier Inc. All rights reserved.

46 CFR 180.202 - Survival craft-vessels operating on oceans routes.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 7 2012-10-01 2012-10-01 false Survival craft-vessels operating on oceans routes. 180... § 180.202 Survival craft—vessels operating on oceans routes. (a) Each vessel certificated to operate on an oceans route in cold water must either: (1) Be provided with inflatable buoyant apparatus of an...

46 CFR 117.202 - Survival craft-vessels operating on oceans routes.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 4 2013-10-01 2013-10-01 false Survival craft-vessels operating on oceans routes. 117... operating on oceans routes. (a) Except as allowed by paragraph (b) of this section, each vessel certificated to operate on an oceans route in cold water must be provided with inflatable liferafts of an...

46 CFR 117.202 - Survival craft-vessels operating on oceans routes.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 4 2014-10-01 2014-10-01 false Survival craft-vessels operating on oceans routes. 117... operating on oceans routes. (a) Except as allowed by paragraph (b) of this section, each vessel certificated to operate on an oceans route in cold water must be provided with inflatable liferafts of an...

46 CFR 180.202 - Survival craft-vessels operating on oceans routes.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 7 2010-10-01 2010-10-01 false Survival craft-vessels operating on oceans routes. 180... § 180.202 Survival craft—vessels operating on oceans routes. (a) Each vessel certificated to operate on an oceans route in cold water must either: (1) Be provided with inflatable buoyant apparatus of an...

46 CFR 180.202 - Survival craft-vessels operating on oceans routes.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Survival craft-vessels operating on oceans routes. 180... § 180.202 Survival craft—vessels operating on oceans routes. (a) Each vessel certificated to operate on an oceans route in cold water must either: (1) Be provided with inflatable buoyant apparatus of an...

46 CFR 180.202 - Survival craft-vessels operating on oceans routes.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Survival craft-vessels operating on oceans routes. 180... § 180.202 Survival craft—vessels operating on oceans routes. (a) Each vessel certificated to operate on an oceans route in cold water must either: (1) Be provided with inflatable buoyant apparatus of an...

46 CFR 117.202 - Survival craft-vessels operating on oceans routes.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 4 2012-10-01 2012-10-01 false Survival craft-vessels operating on oceans routes. 117... operating on oceans routes. (a) Except as allowed by paragraph (b) of this section, each vessel certificated to operate on an oceans route in cold water must be provided with inflatable liferafts of an...

46 CFR 180.202 - Survival craft-vessels operating on oceans routes.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 7 2014-10-01 2014-10-01 false Survival craft-vessels operating on oceans routes. 180... § 180.202 Survival craft—vessels operating on oceans routes. (a) Each vessel certificated to operate on an oceans route in cold water must either: (1) Be provided with inflatable buoyant apparatus of an...

46 CFR 117.202 - Survival craft-vessels operating on oceans routes.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 4 2011-10-01 2011-10-01 false Survival craft-vessels operating on oceans routes. 117... operating on oceans routes. (a) Except as allowed by paragraph (b) of this section, each vessel certificated to operate on an oceans route in cold water must be provided with inflatable liferafts of an...

46 CFR 117.202 - Survival craft-vessels operating on oceans routes.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 4 2010-10-01 2010-10-01 false Survival craft-vessels operating on oceans routes. 117... operating on oceans routes. (a) Except as allowed by paragraph (b) of this section, each vessel certificated to operate on an oceans route in cold water must be provided with inflatable liferafts of an...

An alternative model for CaCO3 over-shooting during the PETM: Biological carbonate compensation

NASA Astrophysics Data System (ADS)

Luo, Yiming; Boudreau, Bernard P.; Dickens, Gerald R.; Sluijs, Appy; Middelburg, Jack J.

2016-11-01

Decreased CaCO3 content of deep-sea sediments argues for rapid and massive acidification of the oceans during the Paleocene-Eocene Thermal Maximum (PETM, ∼56 Ma BP). In the course of the subsequent recovery from this acidification, sediment CaCO3 content came to exceed pre-PETM levels, known as over-shooting. Past studies have largely attributed the latter to increased alkalinity input to the oceans via enhanced weathering, but this ignores potentially important biological factors. We successfully reproduce the CaCO3 records from Walvis Ridge in the Atlantic Ocean, including over-shooting, using a biogeochemical box model. Replication of the CaCO3 records required: 1) introduction of a maximum of ∼6500 GtC of CO2 directly into deep-ocean waters or ∼8000 GtC into the atmosphere, 2) limited deep-water exchange between the Indo-Atlantic and Pacific oceans, 3) the disappearance of sediment bioturbation during a portion of the PETM, and 4) most central to this study, a ∼50% reduction in net CaCO3 production, during acidification. In our simulations, over-shooting is an emergent property, generated at constant alkalinity input (no weathering feedback) as a consequence of attenuated CaCO3 productivity. This occurs because lower net CaCO3 production from surface waters allows alkalinity to build-up in the deep oceans (alkalinization), thus promoting deep-water super-saturation. Restoration of CaCO3 productivity later in the PETM, particularly in the Indo-Atlantic Ocean, leads to greater accumulation of CaCO3, ergo over-shooting, which returns the ocean to pre-PETM conditions over a time scale greater than 200 ka.

Understanding the effect of an excessive cold tongue bias on projecting the tropical Pacific SST warming pattern in CMIP5 models

NASA Astrophysics Data System (ADS)

Ying, Jun; Huang, Ping; Lian, Tao; Tan, Hongjian

2018-05-01

An excessive cold tongue is a common bias among current climate models, and considered an important source of bias in projections of tropical Pacific climate change under global warming. Specifically, the excessive cold tongue bias is closely related to the tropical Pacific SST warming (TPSW) pattern. In this study, we reveal that two processes are the critical mechanisms by which the excessive cold tongue bias influences the projection of the TPSW pattern, based on 32 models from phase 5 of Coupled Model Intercomparison Projection (CMIP5). On the one hand, by assuming that the shortwave (SW) radiation to SST feedback is linearly correlated to the cold tongue SST, the excessive cold tongue bias can induce an overly weak negative SW-SST feedback in the central Pacific, which can lead to a positive SST warming bias in the central to western Pacific (around 150°E-140°W). Moreover, the overly weak local atmospheric dynamics response to SST is a key process of the overly weak SW-SST feedback, compared with the cloud response to atmospheric dynamics and the SW radiation response to cloud. On the other hand, the overly strong ocean zonal overturning circulation associated with the excessive cold tongue bias results in an overestimation of the ocean dynamical thermostat effect, with enhanced ocean stratification under global warming, leading to a negative SST warming bias in the central and eastern Pacific (around 170°W-120°W). These two processes jointly form a positive SST warming bias in the western Pacific, contributing to a La Niña-like warming bias. Therefore, we suggest a more realistic climatological cold tongue SST is needed for a more reliable projection of the TPSW pattern.

Late Miocene - Pliocene Evolution of the Pacific Warm Pool and Cold Tongue: Implications for El Niño

NASA Astrophysics Data System (ADS)

Zhang, Y.; Pagani, M.

2011-12-01

The Western Pacific Warm Pool of the tropical Pacific Ocean retains the largest and warmest sea surface water body on Earth, while the eastern equatorial Pacific is characterized by strong upwelling of cold, nutrient-rich deep waters, termed the Pacific cold tongue. Evolution of the Pacific warm pool and cold tongue are important because they control the circum-Pacific climate and impact the globe via El Niño - Southern Oscillation (ENSO) teleconnections. Sea surface temperature (SST) reconstructions using a single site from the warm pool (ODP 806) and two sites from the cold tongue (ODP 846, 847) suggest that the temperature of the warm pool was "stable" throughout the Plio-Pleistocene, whereas the cold tongue was much warmer in the Pliocene and subsequently cooled. The absence of an east-west Pacific temperature gradient during the early Pliocene is the basis for the "permanent El Niño" hypothesis. However, annually-resolved fossil coral and evaporite records found 3-7 years climate variability during the Pliocene warm period and late Miocene, challenging a "permanent" or invariant climate state. Here we present a multi-proxy (TEX86, UK37, Mg/Ca), multi-site reconstruction of the late Miocene - Pliocene (ca. 12 Ma - 3 Ma) SST in the Pacific warm pool (ODP 806, ODP 769 in the Sulu Sea, ODP 1143 in the South China Sea) and the cold tongue (ODP 850, 849, 846). Our results show that the cold tongue was even warmer in the late Miocene than the Pliocene, and that the warm pool cooled 2-3°C from the late Miocene into the Pliocene - in contrast to the invariant character previously assumed. Temperature comparison between different sites suggests that the warm pool may have expanded in size in the late Miocene. Although eastern and western ends of the tropical Pacific were warmer, a persistent, but low east-west temperature gradient (~3°C) is apparent. This agrees with recent studies which have shown ENSO-related frequency of climate change in the late Miocene and early Pliocene.

Primary producing prokaryotic communities of brine, interface and seawater above the halocline of deep anoxic lake L'Atalante, Eastern Mediterranean Sea.

PubMed

Yakimov, Michail M; La Cono, Violetta; Denaro, Renata; D'Auria, Giuseppe; Decembrini, Franco; Timmis, Kenneth N; Golyshin, Peter N; Giuliano, Laura

2007-12-01

Meso- and bathypelagic ecosystems represent the most common marine ecological niche on Earth and contain complex communities of microorganisms that are for the most part ecophysiologically poorly characterized. Gradients of physico-chemical factors (for example, depth-related gradients of light, temperature, salinity, nutrients and pressure) constitute major forces shaping ecosystems at activity 'hot spots' on the ocean floor, such as hydrothermal vents, cold seepages and mud volcanoes and hypersaline lakes, though the relationships between community composition, activities and environmental parameters remain largely elusive. We report here results of a detailed study of primary producing microbial communities in the deep Eastern Mediterranean Sea. The brine column of the deep anoxic hypersaline brine lake, L'Atalante, the overlying water column and the brine-seawater interface, were characterized physico- and geochemically, and microbiologically, in terms of their microbial community compositions, functional gene distributions and [(14)C]bicarbonate assimilation activities. The depth distribution of genes encoding the crenarchaeal ammonia monooxygenase alpha subunit (amoA), and the bacterial ribulose-1,5-biphosphate carboxylase/oxygenase large subunit (RuBisCO), was found to coincide with two different types of chemoautotrophy. Meso- and bathypelagic microbial communities were enriched in ammonia-oxidizing Crenarchaeota, whereas the autotrophic community at the oxic/anoxic interface of L'Atalante lake was dominated by Epsilonproteobacteria and sulfur-oxidizing Gammaproteobacteria. These autotrophic microbes are thus the basis of the food webs populating these deep-sea ecosystems.

New insights on the propagation of the Near Inertial Waves (NIW) governing the bottom dynamic of the Western Ionian Sea (Eastern Mediterranean Sea).

NASA Astrophysics Data System (ADS)

Lo Bue, N.; Artale, V.; Marullo, S.; Marinaro, G.; Embriaco, D.; Favali, P.; Beranzoli, L.

2017-12-01

The past general idea that the ocean-deep circulation is in quasi-stationary motion, has conditioned the observations of deep layers for a long time, excluding them from the majority of the surveys around the ocean world and influencing studies on the deep ocean processes. After the pioneering work of Munk (1966) highlighting the importance of bottom mixing processes, an underestimation of these issue has continued to persist for decades, due also to the difficulty to make reliable observations in the abyssal layers. The real awareness about the unsteady state of the abyssal layers has only risen recently and encourages us to wonder how the deep mechanisms can induce an internal instability and, consequently, affect the ocean circulation. The NIWs are characterized by a frequency near the inertial frequency f and can be generated by a variety of mechanisms, including wind, nonlinear interactions wave-shear flow and wave-topography, and geostrophic adjustments. NIWs represent one of the main high-frequency variabilities in the ocean, and they contain around half the kinetic energy observed in the oceans (Simmons et al. 2012) appearing as a prominent peak rising well above the Garrett & Munk (1975) continuum internal wave spectrum. As such, they upset the mixing processes in the upper ocean and they can interact strongly with mesoscale and sub-mesoscale motions. Likewise, NIWs likely affect the mixing of the deep ocean in ways that are just beginning to be understood. The analysis carried out on yearly time series collected by the bottom observatory SN1, the Western Ionian node of EMSO (European Multidisciplinary Seafloor and water column Observatory) Research Infrastructure, provides new important understanding on the role of the NIWs in the abyssal ocean. Also, this analysis is very useful to shed light on the possible mechanism that can trigger deep processes such as the abyssal vortex chains found by Rubino et al. (2012) in the Ionian abyssal plain of the Eastern Mediterranean (EM) basin. Finally, spectral analysis, including the Singular Spectrum Analysis (SSA) and Wavelet, allow us to explain how the NIWs can contributes to activate and increase the mixing in the bottom layers with significant impact on overall abyssal and deep circulation at local and regional scale (Mediterranean Sea).

The Combined Effect of Cold and Moisture on Manual Performance.

PubMed

Ray, Matthew; Sanli, Elizabeth; Brown, Robert; Ennis, Kerri Ann; Carnahan, Heather

2018-02-01

Objective The aim of this study was to investigate the combined effect of cold and moisture on manual performance and tactile sensitivity. Background People working in the ocean environment often perform manual work in cold and wet conditions. Although the independent effects of cold and moisture on hand function are known, their combined effect has not been investigated. Method Participants completed sensory (Touch-Test, two-point discrimination) and motor (Purdue Pegboard, Grooved Pegboard, reef knot untying) tests in the following conditions: dry hand, wet hand, cold hand, and cold and wet hand. Results For the Purdue Pegboard and knot untying tasks, the greatest decrement in performance was observed in the cold-and-wet-hand condition, whereas the decrements seen in the cold-hand and wet-hand conditions were similar. In the Grooved Pegboard task, the performance decrements exhibited in the cold-and-wet-hand condition and the cold-hand condition were similar, whereas no decrement was observed in the wet-hand condition. Tactile sensitivity was reduced in the cold conditions for the Touch-Test but not the two-point discrimination test. The combined effect of cold and moisture led to the largest performance decrements except when intrinsic object properties helped with grasp maintenance. The independent effects of cold and moisture on manual performance were comparable. Application Tools and equipment for use in the cold ocean environment should be designed to minimize the effects of cold and moisture on manual performance by including object properties that enhance grasp maintenance and minimize the fine-dexterity requirements.

Mooring Measurements of the Abyssal Circulations in the Western Pacific Ocean

NASA Astrophysics Data System (ADS)

Wang, J.; Wang, F.

2016-12-01

A scientific observing network in the western tropical Pacific has initially been established by the Institute of Oceanology, Chinese Academy of Sciences (IOCAS). Using fifteen moorings that gives unprecedented measurements in the intermediate and abyssal layers, we present multi-timescale variations of the deep ocean circulations prior to and during 2015 El Niño event. The deep ocean velocities increase equatorward with high standard deviation and nearly zero mean. The deep ocean currents mainly flow in meridional direction in the central Philippine Basin, and are dominated by a series of alternating westward and eastward zonal jets in the Caroline Basin. The currents in the deep channel connecting the East and West Mariana Basins mainly flow southeastward. Seasonal variation is only present in the deep jets in the Caroline Basin, associating with vertical propagating annual Rossby wave. The high-frequency flow bands are dominated by diurnal, and semi-diurnal tidal currents, and near-inertial currents. The rough topography has a strong influence on the abyssal circulations, including the intensifications in velocity and internal tidal energy, and the formation of upwelling flow.

Boldness in a deep sea hermit crab to simulated tactile predator attacks is unaffected by ocean acidification

NASA Astrophysics Data System (ADS)

Kim, Tae Won; Barry, James P.

2016-09-01

Despite rapidly growing interest in the effects of ocean acidification on marine animals, the ability of deep-sea animals to acclimate or adapt to reduced pH conditions has received little attention. Deep-sea species are generally thought to be less tolerant of environmental variation than shallow-living species because they inhabit relatively stable conditions for nearly all environmental parameters. To explore whether deep-sea hermit crabs ( Pagurus tanneri) can acclimate to ocean acidification over several weeks, we compared behavioral "boldness," measured as time taken to re-emerge from shells after a simulated predatory attack by a toy octopus, under ambient (pH ˜7.6) and expected future (pH ˜7.1) conditions. The boldness measure for crab behavioral responses did not differ between different pH treatments, suggesting that future deep-sea acidification would not influence anti-predatory behavior. However, we did not examine the effects of olfactory cues released by predators that may affect hermit crab behavior and could be influenced by changes in the ocean carbonate system driven by increasing CO2 levels.

Deep seafloor arrivals in long range ocean acoustic propagation.

PubMed

Stephen, Ralph A; Bolmer, S Thompson; Udovydchenkov, Ilya A; Worcester, Peter F; Dzieciuch, Matthew A; Andrew, Rex K; Mercer, James A; Colosi, John A; Howe, Bruce M

2013-10-01

Ocean bottom seismometer observations at 5000 m depth during the long-range ocean acoustic propagation experiment in the North Pacific in 2004 show robust, coherent, late arrivals that are not readily explained by ocean acoustic propagation models. These "deep seafloor" arrivals are the largest amplitude arrivals on the vertical particle velocity channel for ranges from 500 to 3200 km. The travel times for six (of 16 observed) deep seafloor arrivals correspond to the sea surface reflection of an out-of-plane diffraction from a seamount that protrudes to about 4100 m depth and is about 18 km from the receivers. This out-of-plane bottom-diffracted surface-reflected energy is observed on the deep vertical line array about 35 dB below the peak amplitude arrivals and was previously misinterpreted as in-plane bottom-reflected surface-reflected energy. The structure of these arrivals from 500 to 3200 km range is remarkably robust. The bottom-diffracted surface-reflected mechanism provides a means for acoustic signals and noise from distant sources to appear with significant strength on the deep seafloor.

Order-picking in deep cold--physiological responses of younger and older females. Part 1: heart rate.

PubMed

Kluth, Karsten; Baldus, Sandra; Strasser, Helmut

2012-01-01

The sales figures of chilled and frozen food have been rising steadily over the years. Naturally, this has also led to an increase in the number of jobs related to these goods. While these workplaces are becoming more and more important there are, nevertheless, only a few investigations into the effects of working in deep cold on humans. Order-picking in a cold environment represents a high workload. Especially working at -24°C with wearing heavy cold protective clothing leads to explicitly higher strain. Since performance decreases with age, varying physical strain between younger and older employees can hypothetically be expected. In order to quantify the physiological responses to working in the cold, 15 subjects of two female age groups, each, (20- to 35-year-olds and 40- to 65-year-olds) were asked to carry out whole working day tasks in a chill room (+3°) and in a cold store (-24°C). Simultaneously, heart rate and other physiological relevant parameters were measured.

Variability of neodymium isotopes associated with planktonic foraminifera in the Pacific Ocean during the Holocene and Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Hu, Rong; Piotrowski, Alexander M.; Bostock, Helen C.; Crowhurst, Simon; Rennie, Victoria

2016-08-01

The deep Pacific Ocean holds the largest oceanic reservoir of carbon which may interchange with the atmosphere on climatologically important timescales. The circulation of the deep Pacific during the Last Glacial Maximum (LGM), however, is not well understood. Neodymium (Nd) isotopes of ferromanganese oxide coatings precipitated on planktonic foraminifera are a valuable proxy for deep ocean water mass reconstruction in paleoceanography. In this study, we present Nd isotope compositions (εNd) of planktonic foraminifera for the Holocene and the LGM obtained from 55 new sites widely distributed in the Pacific Ocean. The Holocene planktonic foraminiferal εNd results agree with the proximal seawater data, indicating that they provide a reliable record of modern bottom water Nd isotopes in the deep Pacific. There is a good correlation between foraminiferal εNd and seawater phosphate concentrations (R2 = 0.80), but poorer correlation with silicate (R2 = 0.37). Our interpretation is that the radiogenic Nd isotope is added to the deep open Pacific through particle release from the upper ocean during deep water mass advection and aging. The data thus also imply the Nd isotopes in the Pacific are not likely to be controlled by silicate cycling. In the North Pacific, the glacial Nd isotopic compositions are similar to the Holocene values, indicating that the Nd isotope composition of North Pacific Deep Water (NPDW) remained constant (-3.5 to -4). During the LGM, the southwest Pacific cores throughout the water column show higher εNd corroborating previous studies which suggested a reduced inflow of North Atlantic Deep Water to the Pacific. However, the western equatorial Pacific deep water does not record a corresponding radiogenic excursion, implying reduced radiogenic boundary inputs during the LGM probably due to a shorter duration of seawater-particle interaction in a stronger glacial deep boundary current. A significant negative glacial εNd excursion is evident in mid-depth (1-2 km) cores of the eastern equatorial Pacific (EEP) which may suggest a stronger influence of NPDW return flow to the core sites and decreased local input in the EEP. Taken together, our Nd records do not support a dynamically slower glacial Pacific overturning circulation, and imply that the increased carbon inventory of Pacific deep water might be due to poor high latitude air-sea exchange and increased biological pump efficiency in glacial times.

Deep Water Ocean Acoustics

DTIC Science & Technology

2015-04-15

0 A S S PROGRESS REPORT NO. QSR-14C0172-0CEAN ACOUSTICS-033115 Contract No. N00014-14-C-0172 Office of Naval Research Task Reporting: Deep ...AND SUBTITLE Deep Water Ocean Acoustics 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e...298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 Cost Summary OASIS, INC. JOB STATUS RB’ORT 1172 DEEP WATER ACOUSTICS FOP. 9/27f13-316/16

Extracerebral deep-body cold sensitivity in the Pekin duck.

PubMed

Inomoto, T; Simon, E

1981-09-01

Pekin ducks, in which cerebral cold sensitivity is negligible, were submitted to general body cooling at warm, thermoneutral, and cold ambient temperature (Ta) with an intestinal thermode. In some animals, hypothermia was enhanced by additional hypothalamic cooling that suppressed cold defense. In other animals, the spinal cord was cooled, either selectively or during intestinal cooling. From core temperature (Tc) and metabolic heat production (M) an overall cold sensitivity of about -5 to -6 W . kg-1 . degrees C-1 was determined at thermoneutrality. Maximum M amounted to four to five times the resting M of 3.8 W . kg-1 and was attained when Tc fell by 2.5 degrees C or more. In the cold, threshold Tc for the activation of M was elevated; overall cold sensitivity remained constant. In the warmth, threshold Tc was lowered; overall cold sensitivity was reduced, if mean skin temperature (Tsk) remained at aout 39 degrees C or higher. Spinal cold sensitivity amounted to about -0.25 W . kg-1 . degrees C-1 at normal Tc and thermoneutral and warm Ta; it increased to aout -0.50 W . kg-1 . degrees C-1 in the cold and during hypothermia. Peripheral cold sensitivity was estimated from Tsk and M as -0.4 to -0.8 W . kg-1 . degrees C-1. It is concluded that overall cold sensitivity in ducks mainly depends on deep-body temperature sensors outside of the central nervous system.

Dive Europa: a search-for-life initiative.

PubMed

Naganuma, T; Uematsu, H

1998-06-01

Liquid water, underwater volcanoes and possibly life forms have been suggested to be present beneath the estimated 10 km-thick ice shell of Europa the Jovian satellite J2. Europa's possible ocean is estimated to be 100-200km deep. Despite the great depth of the Europa's ocean, hydrostatic pressure at the seafloor would be 130-260 MPa, corresponding to 13-26 km depth of a theoretical Earth's ocean. The hydrostatic pressure is not beyond the edge of existing deep-sea technology. Here we propose exploration of Europa's deep-sea by the use of current technologies, taking a symbolic example of a deep submergence vehicle Shinkai 6500 which dives to a depth of 6.5 km deep (50 km depth of Europa's ocean). Shinkai 6500 is embarkable in the payload bay of the Space Shuttles in terms of size and weight for the transportation to a Low Earth Orbit (LEO). Secondary boost is needed for interplanetary flight from the LEO. On-orbit assembly of the secondary booster is a technological challenge. The International Space Station (ISS) and ISS-related technologies will facilitate the secondary boost. Also, ice shell drilling is a challenge and is needed before the dive into Europa's ocean. These challenges should be overcome during a certain leading time for matured experience in the ISS operation.

Dynamics of Oceanic Motions

DTIC Science & Technology

1997-09-30

research is multiscale , interdisciplinary and generic. The methods are applicable to an arbitrary region of the coastal and/or deep ocean and across the...dynamics. OBJECTIVES General objectives are: (I) To determine for the coastal and/or coupled deep ocean the multiscale processes which occur: i) in...Straits and the eastern basin; iii) extension and application of our balance of terms scheme (EVA) to multiscale , interdisciplinary fields with data

Active Pacific meridional overturning circulation (PMOC) during the warm Pliocene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burls, Natalie J.; Fedorov, Alexey V.; Sigman, Daniel M.

An essential element of modern ocean circulation and climate is the Atlantic meridional overturning circulation (AMOC), which includes deep-water formation in the subarctic North Atlantic. However, a comparable overturning circulation is absent in the Pacific, theworld’s largest ocean,where relatively fresh surface waters inhibitNorth Pacific deep convection. We present complementary measurement and modeling evidence that the warm, ~400–ppmv (parts per million by volume) CO 2 world of the Pliocene supported subarctic North Pacific deep-water formation and a Pacific meridional overturning circulation (PMOC) cell. In Pliocene subarctic North Pacific sediments, we report orbitally paced maxima in calcium carbonate accumulation rate, with accompanyingmore » pigment and total organic carbon measurements supporting deep-ocean ventilation-driven preservation as their cause. Together with high accumulation rates of biogenic opal, these findings require vigorous bidirectional communication between surface waters and interior waters down to ~3 km in the western subarctic North Pacific, implying deep convection. Redoxsensitive trace metal data provide further evidence of higher Pliocene deep-ocean ventilation before the 2.73-Ma (million years) transition. This observational analysis is supported by climate modeling results, demonstrating that atmospheric moisture transport changes, in response to the reduced meridional sea surface temperature gradients of the Pliocene, were capable of eroding the halocline, leading to deep-water formation in the western subarctic Pacific and a strong PMOC. This second Northern Hemisphere overturning cell has important implications for heat transport, the ocean/atmosphere cycle of carbon, and potentially the equilibrium response of the Pacific to global warming.« less

Active Pacific meridional overturning circulation (PMOC) during the warm Pliocene

PubMed Central

Burls, Natalie J.; Fedorov, Alexey V.; Sigman, Daniel M.; Jaccard, Samuel L.; Tiedemann, Ralf; Haug, Gerald H.

2017-01-01

An essential element of modern ocean circulation and climate is the Atlantic meridional overturning circulation (AMOC), which includes deep-water formation in the subarctic North Atlantic. However, a comparable overturning circulation is absent in the Pacific, the world’s largest ocean, where relatively fresh surface waters inhibit North Pacific deep convection. We present complementary measurement and modeling evidence that the warm, ~400–ppmv (parts per million by volume) CO2 world of the Pliocene supported subarctic North Pacific deep-water formation and a Pacific meridional overturning circulation (PMOC) cell. In Pliocene subarctic North Pacific sediments, we report orbitally paced maxima in calcium carbonate accumulation rate, with accompanying pigment and total organic carbon measurements supporting deep-ocean ventilation-driven preservation as their cause. Together with high accumulation rates of biogenic opal, these findings require vigorous bidirectional communication between surface waters and interior waters down to ~3 km in the western subarctic North Pacific, implying deep convection. Redox-sensitive trace metal data provide further evidence of higher Pliocene deep-ocean ventilation before the 2.73-Ma (million years) transition. This observational analysis is supported by climate modeling results, demonstrating that atmospheric moisture transport changes, in response to the reduced meridional sea surface temperature gradients of the Pliocene, were capable of eroding the halocline, leading to deep-water formation in the western subarctic Pacific and a strong PMOC. This second Northern Hemisphere overturning cell has important implications for heat transport, the ocean/atmosphere cycle of carbon, and potentially the equilibrium response of the Pacific to global warming. PMID:28924606

Active Pacific meridional overturning circulation (PMOC) during the warm Pliocene

DOE PAGES

Burls, Natalie J.; Fedorov, Alexey V.; Sigman, Daniel M.; ...

2017-09-13

An essential element of modern ocean circulation and climate is the Atlantic meridional overturning circulation (AMOC), which includes deep-water formation in the subarctic North Atlantic. However, a comparable overturning circulation is absent in the Pacific, theworld’s largest ocean,where relatively fresh surface waters inhibitNorth Pacific deep convection. We present complementary measurement and modeling evidence that the warm, ~400–ppmv (parts per million by volume) CO 2 world of the Pliocene supported subarctic North Pacific deep-water formation and a Pacific meridional overturning circulation (PMOC) cell. In Pliocene subarctic North Pacific sediments, we report orbitally paced maxima in calcium carbonate accumulation rate, with accompanyingmore » pigment and total organic carbon measurements supporting deep-ocean ventilation-driven preservation as their cause. Together with high accumulation rates of biogenic opal, these findings require vigorous bidirectional communication between surface waters and interior waters down to ~3 km in the western subarctic North Pacific, implying deep convection. Redoxsensitive trace metal data provide further evidence of higher Pliocene deep-ocean ventilation before the 2.73-Ma (million years) transition. This observational analysis is supported by climate modeling results, demonstrating that atmospheric moisture transport changes, in response to the reduced meridional sea surface temperature gradients of the Pliocene, were capable of eroding the halocline, leading to deep-water formation in the western subarctic Pacific and a strong PMOC. This second Northern Hemisphere overturning cell has important implications for heat transport, the ocean/atmosphere cycle of carbon, and potentially the equilibrium response of the Pacific to global warming.« less

Trophic ecology of two cold-water coral species from the Mediterranean Sea revealed by lipid biomarkers and compound-specific isotope analyses

NASA Astrophysics Data System (ADS)

Naumann, Malik S.; Tolosa, Imma; Taviani, Marco; Grover, Renaud; Ferrier-Pagès, Christine

2015-12-01

Scleractinian cold-water corals (CWC) act as key ecosystem engineers in deep-sea reef environments worldwide. However, our current understanding of their trophic ecology is still limited, particularly in understudied temperate oceanic regions such as the Mediterranean Sea. Hence, this study investigated the trophic ecology of the CWC Desmophyllum dianthus and Madrepora oculata by employing lipid biomarker techniques and compound-specific isotope analyses on coral tissues, suspended particulate organic matter (sPOM), and surface sediment sampled in a Mediterranean CWC habitat. CWC exhibited high contents of poly- and monounsaturated fatty acids (FA) (≥49 and 32 % of FA, respectively) and cholesterol (≥67 % of sterols), while sPOM and sediment samples were enriched in saturated FA (≥44 % of FA) and sitosterol (≥35 % of sterols). CWC contained some rare very long-chained polyunsaturated FA (>C22) and ergosterol absent in sPOM and sediment samples. Our results indicate that Mediterranean CWC mainly consume living food items, rather than detrital sPOM or resuspended sediment, and provide evidence for preferred feeding on omnivorous and carnivorous zooplankton. Overall, these findings provide new insights to the trophic ecology of two common CWC from the Mediterranean Sea.

Resilience of cold-water scleractinian corals to ocean acidification: Boron isotopic systematics of pH and saturation state up-regulation

NASA Astrophysics Data System (ADS)

McCulloch, Malcolm; Trotter, Julie; Montagna, Paolo; Falter, Jim; Dunbar, Robert; Freiwald, André; Försterra, Günter; López Correa, Matthias; Maier, Cornelia; Rüggeberg, Andres; Taviani, Marco

2012-06-01

The boron isotope systematics has been determined for azooxanthellate scleractinian corals from a wide range of both deep-sea and shallow-water environments. The aragonitic coral species, Caryophyllia smithii, Desmophyllum dianthus, Enallopsammia rostrata, Lophelia pertusa, and Madrepora oculata, are all found to have relatively high δ11B compositions ranging from 23.2‰ to 28.7‰. These values lie substantially above the pH-dependent inorganic seawater borate equilibrium curve, indicative of strong up-regulation of pH of the internal calcifying fluid (pHcf), being elevated by ˜0.6-0.8 units (ΔpH) relative to ambient seawater. In contrast, the deep-sea calcitic coral Corallium sp. has a significantly lower δ11B composition of 15.5‰, with a corresponding lower ΔpH value of ˜0.3 units, reflecting the importance of mineralogical control on biological pH up-regulation. The solitary coral D. dianthus was sampled over a wide range of seawater pHT and shows an approximate linear correlation with ΔpHDesmo = 6.43 - 0.71pHT (r2 = 0.79). An improved correlation is however found with the closely related parameter of seawater aragonite saturation state, where ΔpHDesmo = 1.09 - 0.14Ωarag (r2 = 0.95), indicating the important control that carbonate saturation state has on calcification. The ability to up-regulate internal pHcf, and consequently Ωcf, of the calcifying fluid is therefore a process present in both azooxanthellate and zooxanthellate aragonitic corals, and is attributed to the action of Ca2+-ATPase in modulating the proton gradient between seawater and the site of calcification. These findings also show that the boron isotopic compositions (δ11Bcarb) of aragonitic corals are highly systematic and consistent with direct uptake of the borate species within the biologically controlled extracellular calcifying medium. We also show that the relatively strong up-regulation of pH and consequent elevation of the internal carbonate saturation state (Ωcf ˜8.5 to ˜13) at the site of calcification by cold-water corals, facilitates calcification at or in some cases below the aragonite saturation horizon, providing a greater ability to adapt to the already low and now decreasing carbonate ion concentrations. Although providing greater resilience to the effects of ocean acidification and enhancing rates of calcification with increasing temperature, the process of internal pHcf up-regulation has an associated energetic cost, and therefore growth-rate cost, of ˜10% per 0.1 pH unit decrease in seawater pHT. Furthermore, as the aragonite saturation horizon shoals with rapidly increasing pCO2 and Ωarag < 1, increased dissolution of the exposed skeleton will ultimately limit their survival in the deep oceans.

The Once and Future Battles of Thor and the Midgard Serpent (or the Southern Ocean's Role in Climate)

NASA Astrophysics Data System (ADS)

Russell, J. L.

2017-12-01

Floats deployed by oceanographers are giving us all ringside seats to the epic battle between the wind and the deep ocean around Antarctica which will determine the rate of global atmospheric warming over the next century. The poleward-shift and intensification of the Southern Hemisphere westerly winds has been shown to maintain the connection between the surface ocean and the atmosphere with the deep ocean even as the surface ocean warms. This "doorway" allows the vast deep ocean reservoir to play a significant role in the transient global climate response to increasing atmospheric greenhouse gases. Coupled climate and earth system models at low and high resolution all simulate poleward-shifted and intensified Southern Hemisphere surface westerly winds when subjected to an atmospheric carbon dioxide doubling. Comparisons of these simulations reveal how stratification, resolution and eddies affect the transient global climate response to increasing atmospheric greenhouse gases - and our collective fate.

Diversity of deep-water cetaceans in relation to temperature: implications for ocean warming.

PubMed

Whitehead, Hal; McGill, Brian; Worm, Boris

2008-11-01

Understanding the effects of natural environmental variation on biodiversity can help predict response to future anthropogenic change. Here we analyse a large, long-term data set of sightings of deep-water cetaceans from the Atlantic, Pacific and Indian Oceans. Seasonal and geographic changes in the diversity of these genera are well predicted by a convex function of sea-surface temperature peaking at c. 21 degrees C. Thus, diversity is highest at intermediate latitudes - an emerging general pattern for the pelagic ocean. When applied to a range of Intergovernmental Panel on Climate Change global change scenarios, the predicted response is a decline of cetacean diversity across the tropics and increases at higher latitudes. This suggests that deep-water oceanic communities that dominate > 60% of the planet's surface may reorganize in response to ocean warming, with low-latitude losses of diversity and resilience.

A constant flux of diverse thermophilic bacteria into the cold Arctic seabed.

PubMed

Hubert, Casey; Loy, Alexander; Nickel, Maren; Arnosti, Carol; Baranyi, Christian; Brüchert, Volker; Ferdelman, Timothy; Finster, Kai; Christensen, Flemming Mønsted; Rosa de Rezende, Júlia; Vandieken, Verona; Jørgensen, Bo Barker

2009-09-18

Microorganisms have been repeatedly discovered in environments that do not support their metabolic activity. Identifying and quantifying these misplaced organisms can reveal dispersal mechanisms that shape natural microbial diversity. Using endospore germination experiments, we estimated a stable supply of thermophilic bacteria into permanently cold Arctic marine sediment at a rate exceeding 10(8) spores per square meter per year. These metabolically and phylogenetically diverse Firmicutes show no detectable activity at cold in situ temperatures but rapidly mineralize organic matter by hydrolysis, fermentation, and sulfate reduction upon induction at 50 degrees C. The closest relatives to these bacteria come from warm subsurface petroleum reservoir and ocean crust ecosystems, suggesting that seabed fluid flow from these environments is delivering thermophiles to the cold ocean. These transport pathways may broadly influence microbial community composition in the marine environment.

A CloudSat-CALIPSO View of Cloud and Precipitation Properties Across Cold Fronts over the Global Oceans

NASA Technical Reports Server (NTRS)

Naud, Catherine M.; Posselt, Derek J.; van den Heever, Susan C.

2015-01-01

The distribution of cloud and precipitation properties across oceanic extratropical cyclone cold fronts is examined using four years of combined CloudSat radar and CALIPSO lidar retrievals. The global annual mean cloud and precipitation distributions show that low-level clouds are ubiquitous in the post frontal zone while higher-level cloud frequency and precipitation peak in the warm sector along the surface front. Increases in temperature and moisture within the cold front region are associated with larger high-level but lower mid-/low level cloud frequencies and precipitation decreases in the cold sector. This behavior seems to be related to a shift from stratiform to convective clouds and precipitation. Stronger ascent in the warm conveyor belt tends to enhance cloudiness and precipitation across the cold front. A strong temperature contrast between the warm and cold sectors also encourages greater post-cold-frontal cloud occurrence. While the seasonal contrasts in environmental temperature, moisture, and ascent strength are enough to explain most of the variations in cloud and precipitation across cold fronts in both hemispheres, they do not fully explain the differences between Northern and Southern Hemisphere cold fronts. These differences are better explained when the impact of the contrast in temperature across the cold front is also considered. In addition, these large-scale parameters do not explain the relatively large frequency in springtime post frontal precipitation.

Oceanic Uptake of Oxygen During Deep Convection Events Through Diffusive and Bubble-Mediated Gas Exchange

NASA Astrophysics Data System (ADS)

Sun, Daoxun; Ito, Takamitsu; Bracco, Annalisa

2017-10-01

The concentration of dissolved oxygen (O2) plays fundamental roles in diverse chemical and biological processes throughout the oceans. The balance between the physical supply and the biological consumption controls the O2 level of the interior ocean, and the O2 supply to the deep waters can only occur through deep convection in the polar oceans. We develop a theoretical framework describing the oceanic O2 uptake during open-ocean deep convection events and test it against a suite of numerical sensitivity experiments. Our framework allows for two predictions, confirmed by the numerical simulations. First, both the duration and the intensity of the wintertime cooling contribute to the total O2 uptake for a given buoyancy loss. Stronger cooling leads to deeper convection and the oxygenation can reach down to deeper depths. Longer duration of the cooling period increases the total amount of O2 uptake over the convective season. Second, the bubble-mediated influx of O2 tends to weaken the diffusive influx by shifting the air-sea disequilibrium of O2 toward supersaturation. The degree of compensation between the diffusive and bubble-mediated gas exchange depends on the dimensionless number measuring the relative strength of oceanic vertical mixing and the gas transfer velocity. Strong convective mixing, which may occur under strong cooling, reduces the degree of compensation so that the two components of gas exchange together drive exceptionally strong oceanic O2 uptake.

North Atlantic Deep Water Production during the Last Glacial Maximum

PubMed Central

Howe, Jacob N. W.; Piotrowski, Alexander M.; Noble, Taryn L.; Mulitza, Stefan; Chiessi, Cristiano M.; Bayon, Germain

2016-01-01

Changes in deep ocean ventilation are commonly invoked as the primary cause of lower glacial atmospheric CO2. The water mass structure of the glacial deep Atlantic Ocean and the mechanism by which it may have sequestered carbon remain elusive. Here we present neodymium isotope measurements from cores throughout the Atlantic that reveal glacial–interglacial changes in water mass distributions. These results demonstrate the sustained production of North Atlantic Deep Water under glacial conditions, indicating that southern-sourced waters were not as spatially extensive during the Last Glacial Maximum as previously believed. We demonstrate that the depleted glacial δ13C values in the deep Atlantic Ocean cannot be explained solely by water mass source changes. A greater amount of respired carbon, therefore, must have been stored in the abyssal Atlantic during the Last Glacial Maximum. We infer that this was achieved by a sluggish deep overturning cell, comprised of well-mixed northern- and southern-sourced waters. PMID:27256826

Hydrogen peroxide in deep waters from the Mediterranean Sea, South Atlantic and South Pacific Oceans

NASA Astrophysics Data System (ADS)

Hopwood, Mark J.; Rapp, Insa; Schlosser, Christian; Achterberg, Eric P.

2017-03-01

Hydrogen peroxide (H2O2) is present ubiquitously in marine surface waters where it is a reactive intermediate in the cycling of many trace elements. Photochemical processes are considered the dominant natural H2O2 source, yet cannot explain nanomolar H2O2 concentrations below the photic zone. Here, we determined the concentration of H2O2 in full depth profiles across three ocean basins (Mediterranean Sea, South Atlantic and South Pacific Oceans). To determine the accuracy of H2O2 measurements in the deep ocean we also re-assessed the contribution of interfering species to ‘apparent H2O2’, as analysed by the luminol based chemiluminescence technique. Within the vicinity of coastal oxygen minimum zones, accurate measurement of H2O2 was not possible due to interference from Fe(II). Offshore, in deep (>1000 m) waters H2O2 concentrations ranged from 0.25 ± 0.27 nM (Mediterranean, Balearics-Algeria) to 2.9 ± 2.2 nM (Mediterranean, Corsica-France). Our results indicate that a dark, pelagic H2O2 production mechanism must occur throughout the deep ocean. A bacterial source of H2O2 is the most likely origin and we show that this source is likely sufficient to account for all of the observed H2O2 in the deep ocean.

Hydrogen peroxide in deep waters from the Mediterranean Sea, South Atlantic and South Pacific Oceans

PubMed Central

Hopwood, Mark J.; Rapp, Insa; Schlosser, Christian; Achterberg, Eric P.

2017-01-01

Hydrogen peroxide (H2O2) is present ubiquitously in marine surface waters where it is a reactive intermediate in the cycling of many trace elements. Photochemical processes are considered the dominant natural H2O2 source, yet cannot explain nanomolar H2O2 concentrations below the photic zone. Here, we determined the concentration of H2O2 in full depth profiles across three ocean basins (Mediterranean Sea, South Atlantic and South Pacific Oceans). To determine the accuracy of H2O2 measurements in the deep ocean we also re-assessed the contribution of interfering species to ‘apparent H2O2’, as analysed by the luminol based chemiluminescence technique. Within the vicinity of coastal oxygen minimum zones, accurate measurement of H2O2 was not possible due to interference from Fe(II). Offshore, in deep (>1000 m) waters H2O2 concentrations ranged from 0.25 ± 0.27 nM (Mediterranean, Balearics-Algeria) to 2.9 ± 2.2 nM (Mediterranean, Corsica-France). Our results indicate that a dark, pelagic H2O2 production mechanism must occur throughout the deep ocean. A bacterial source of H2O2 is the most likely origin and we show that this source is likely sufficient to account for all of the observed H2O2 in the deep ocean. PMID:28266529

From aerosol-limited to invigoration of warm convective clouds.

PubMed

Koren, Ilan; Dagan, Guy; Altaratz, Orit

2014-06-06

Among all cloud-aerosol interactions, the invigoration effect is the most elusive. Most of the studies that do suggest this effect link it to deep convective clouds with a warm base and cold top. Here, we provide evidence from observations and numerical modeling of a dramatic aerosol effect on warm clouds. We propose that convective-cloud invigoration by aerosols can be viewed as an extension of the concept of aerosol-limited clouds, where cloud development is limited by the availability of cloud-condensation nuclei. A transition from pristine to slightly polluted atmosphere yields estimated negative forcing of ~15 watts per square meter (cooling), suggesting that a substantial part of this anthropogenic forcing over the oceans occurred at the beginning of the industrial era, when the marine atmosphere experienced such transformation. Copyright © 2014, American Association for the Advancement of Science.

Using Ocean Exploration in the Atlantic Canyons to Advance Conversations about Transatlantic Ocean Literacy

NASA Astrophysics Data System (ADS)

Keener, P.; Tuddenham, P. T.; Bishop, T.

2016-02-01

The National Oceanic and Atmospheric Administration (NOAA) Ship Okeanos Explorer spent the 2013 field season exploring a wide variety of seafloor features and biological communities in and between largely unexplored canyons in the Northeast Atlantic Ocean, revealing hot spots for biodiversity and providing new information about how these canyons change over time. During the expeditions, an interdisciplinary team of scientists from dozens of institutions and multiple sectors together with ocean educators and the public were able to observe via telepresence the deep Atlantic using NOAA's new remotely-operated vehicle Deep Discoverer. In a collaboration between the NOAA Office of Ocean Exploration and Research and The College of Exploration, along with partners in Canada and the European Union (EU), key exploration findings from the NOAA Ship Okeanos Explorer 2013 field season were designed into an online workshop in which 640 educators, scientists, government representatives, policy makers, and other interested stakeholders representing 40 states within the U.S. and 29 countries participated. The five-week long online offering, titled Deepwater Explorations in the North Atlantic Onboard the NOAA Ship Okeanos Explorer…Online Conversations to Advance Transatlantic Ocean Literacy, built upon the telepresence experience and served as a foundation for extending conversations begun approximately a year earlier on transatlantic ocean literacy, as called for in The Galway Statement. Scientific experts from the U.S., Canada, and the EU provided keynote addresses on deep-sea corals, methane seeps, deep-water canyons, seamounts, and biological diversity in this important area of our "shared Atlantic Ocean." This session will socialize key findings of the workshop based on an evaluation conducted at the conclusion of the workshop and offers insight into how online learning communities can advance ocean literacy and scientific understanding in support of The Galway Statement.

Global Ocean Vertical Velocity From a Dynamically Consistent Ocean State Estimate

NASA Astrophysics Data System (ADS)

Liang, Xinfeng; Spall, Michael; Wunsch, Carl

2017-10-01

Estimates of the global ocean vertical velocities (Eulerian, eddy-induced, and residual) from a dynamically consistent and data-constrained ocean state estimate are presented and analyzed. Conventional patterns of vertical velocity, Ekman pumping, appear in the upper ocean, with topographic dominance at depth. Intense and vertically coherent upwelling and downwelling occur in the Southern Ocean, which are likely due to the interaction of the Antarctic Circumpolar Current and large-scale topographic features and are generally canceled out in the conventional zonally averaged results. These "elevators" at high latitudes connect the upper to the deep and abyssal oceans and working together with isopycnal mixing are likely a mechanism, in addition to the formation of deep and abyssal waters, for fast responses of the deep and abyssal oceans to the changing climate. Also, Eulerian and parameterized eddy-induced components are of opposite signs in numerous regions around the global ocean, particularly in the ocean interior away from surface and bottom. Nevertheless, residual vertical velocity is primarily determined by the Eulerian component, and related to winds and large-scale topographic features. The current estimates of vertical velocities can serve as a useful reference for investigating the vertical exchange of ocean properties and tracers, and its complex spatial structure ultimately permits regional tests of basic oceanographic concepts such as Sverdrup balance and coastal upwelling/downwelling.

Iron defecation by sperm whales stimulates carbon export in the Southern Ocean

PubMed Central

Lavery, Trish J.; Roudnew, Ben; Gill, Peter; Seymour, Justin; Seuront, Laurent; Johnson, Genevieve; Mitchell, James G.; Smetacek, Victor

2010-01-01

The iron-limited Southern Ocean plays an important role in regulating atmospheric CO2 levels. Marine mammal respiration has been proposed to decrease the efficiency of the Southern Ocean biological pump by returning photosynthetically fixed carbon to the atmosphere. Here, we show that by consuming prey at depth and defecating iron-rich liquid faeces into the photic zone, sperm whales (Physeter macrocephalus) instead stimulate new primary production and carbon export to the deep ocean. We estimate that Southern Ocean sperm whales defecate 50 tonnes of iron into the photic zone each year. Molar ratios of Cexport ∶Feadded determined during natural ocean fertilization events are used to estimate the amount of carbon exported to the deep ocean in response to the iron defecated by sperm whales. We find that Southern Ocean sperm whales stimulate the export of 4 × 105 tonnes of carbon per year to the deep ocean and respire only 2 × 105 tonnes of carbon per year. By enhancing new primary production, the populations of 12 000 sperm whales in the Southern Ocean act as a carbon sink, removing 2 × 105 tonnes more carbon from the atmosphere than they add during respiration. The ability of the Southern Ocean to act as a carbon sink may have been diminished by large-scale removal of sperm whales during industrial whaling. PMID:20554546

Dissipation in the deep interiors of Ganymede and Europa

NASA Astrophysics Data System (ADS)

Hussmann, Hauke; Shoji, Daigo; Steinbruegge, Gregor; Stark, Alexander; Sohl, Frank

2017-04-01

Jupiter's satellites are subject to strong tidal forces which result in variations of the gravitational potential and deformations of the satellites' surfaces on the diurnal tidal cycle. Tidal flexing in the deep interiors can be a significant heat source for the satellites' thermal-orbital evolution. Whereas typical structure models of Europa consist of a core, a silicate mantle, an ocean and an outer ice-I shell [1], pressures inside Ganymede are sufficient for high-pressure ice phases to occur between the silicate mantle and the ocean [2]. With current data it is unknown whether the deep interiors (i.e., Europa's silicate shell and Ganymede's silicate mantle and/or high-pressure ice layer) are dissipative. Other possibilities would be that the dissipation rates are in general very low (unlikely at least for Europa due to recent observations) or that dissipative processes are mainly occurring in the ice-I shell and/or ocean. Thus, for evaluations of the heating state of these satellites, it is important to measure the magnitude of the interior dissipation. However, observation of the interior layers such as high-pressure ice layers is more challenging than that of the surface ice-I layer. Here we suggest a method to constrain the dissipation states of the deep interiors of Ganymede and Europa by altimetry and gravity measurements from an orbiting or multi-flyby spacecraft. Tidal variations are generally described by the Love numbers k2 and h2 for the tide-induced potential variation due to internal mass redistribution and the radial surface displacement, respectively. The phase-lags of these complex numbers contain information about the rheological and dissipative states of the satellites. For the satellites we assume a decoupling of the outer ice-shell from the deep interior by a liquid subsurface water ocean. We show that, in this case, the phase-lag difference between the lags of k2 and h2 can provide information on the rheological and thermal state of the deep interiors if the viscosities of the deeper layers are small (the phase-lag difference is almost independent of the dissipation in the surface layer). In case of Ganymede, phase-lag differences can reach values of a few degrees for high-pressure ice viscosities of 1e13-1e14 Pa s (around the lower boundary at its melting temperature) and would indicate a highly dissipative state of the deep interior. In this case, in contrast to the phase lags itself, the phase-lag difference is dominated by dissipation in the high-pressure ice layer rather than dissipation within the ice-I shell. These phase lags would be detectable from spacecraft in orbit around the satellite [3]. For Europa the phase-lag difference could reach values exceeding 20 deg if the silicate mantle contains melt and phase-lag measurements could help distinguish between (1) a hot dissipative (melt-containing) silicate mantle which would in thermal equilibrium correspond to a very thin outer ice-I shell and (2) a cold deep interior implying that dissipation would mainly occur in a thick (several tens of km) outer ice-I shell. These measurements are highly relevant for ESA's Jupiter Icy Moons Explorer (JUICE) and NASA's Europa Multiple Flyby Mission, both targeted for the Jupiter system. References: [1] Schubert, G., F. Sohl and H. Hussmann 2009. Interior of Europa. In: Europa, (R.T. Pappalardo, W.B. McKinnon, K. Khurana, Eds.), University of Arizona Press, pp. 353 - 368. [2] Schubert G., J. D. Anderson, T. Spohn, and W. B. McKinnon 2004. Interior composition, structure, and dynamics of the Galilean satellites. In: F. Bagenal, T. E. Dowling, and W. B. McKinnon (eds.) Jupiter. The Planet, Satellites, and Magnetosphere, pp. 281-306. Cambridge University Press. [3] Hussmann, H., D. Shoji, G. Steinbrügge, A. Stark, F. Sohl 2016. Constraints on dissipation in the deep interiors of Ganymede and Europa from tidal phase-lags. Cel. Mech. Dyn. Astr. 126, 131 - 144.

Antarctic ice sheet discharge driven by atmosphere-ocean feedbacks at the Last Glacial Termination.

PubMed

Fogwill, C J; Turney, C S M; Golledge, N R; Etheridge, D M; Rubino, M; Thornton, D P; Baker, A; Woodward, J; Winter, K; van Ommen, T D; Moy, A D; Curran, M A J; Davies, S M; Weber, M E; Bird, M I; Munksgaard, N C; Menviel, L; Rootes, C M; Ellis, B; Millman, H; Vohra, J; Rivera, A; Cooper, A

2017-01-05

Reconstructing the dynamic response of the Antarctic ice sheets to warming during the Last Glacial Termination (LGT; 18,000-11,650 yrs ago) allows us to disentangle ice-climate feedbacks that are key to improving future projections. Whilst the sequence of events during this period is reasonably well-known, relatively poor chronological control has precluded precise alignment of ice, atmospheric and marine records, making it difficult to assess relationships between Antarctic ice-sheet (AIS) dynamics, climate change and sea level. Here we present results from a highly-resolved 'horizontal ice core' from the Weddell Sea Embayment, which records millennial-scale AIS dynamics across this extensive region. Counterintuitively, we find AIS mass-loss across the full duration of the Antarctic Cold Reversal (ACR; 14,600-12,700 yrs ago), with stabilisation during the subsequent millennia of atmospheric warming. Earth-system and ice-sheet modelling suggests these contrasting trends were likely Antarctic-wide, sustained by feedbacks amplified by the delivery of Circumpolar Deep Water onto the continental shelf. Given the anti-phase relationship between inter-hemispheric climate trends across the LGT our findings demonstrate that Southern Ocean-AIS feedbacks were controlled by global atmospheric teleconnections. With increasing stratification of the Southern Ocean and intensification of mid-latitude westerly winds today, such teleconnections could amplify AIS mass loss and accelerate global sea-level rise.

Validation of an intermediate-complexity model for simulating marine biogeochemistry under anoxic conditions in the modern Black Sea

NASA Astrophysics Data System (ADS)

Romaniello, Stephen J.; Derry, Louis A.

2010-08-01

We test the ability of a new 1-D intermediate-complexity box model (ICBM) that includes process-based C, N, P, O, and S biogeochemistry to simulate profiles and fluxes of biogeochemically reactive species across a wide range of ocean redox states. The ICBM was developed to simulate whole ocean processes for paleoceanographic applications and has been tested with data from the modern global ocean. Here we adapt the circulation submodel of the ICBM to simulate water mass exchange and eddy diffusion processes in the Black Sea but make only very minor changes to the biogeochemical submodel. We force the model with estimated natural and anthropogenic inputs of tracers and nutrients to the Black Sea and compare the results of the simulations to modern observations. Ventilation of the Black Sea is modeled by depth-dependent entrainment of Cold Intermediate Layer water into Bosphorus plume water and subsequent intrusion into deep layers. The simulated profiles of circulation tracers θ, salinity, CFC-12, and radiocarbon agree well with available data, suggesting that the model does a reasonable job of representing physical exchange. Vertical profiles of biogeochemically active components are in good overall agreement with observations. The lack of trace metal (Mn and Fe) cycling in the model results in some discrepancies between the simulated profiles and observation across the suboxic zone; however, the overall redox balance is not sensitive to this difference. We compare modeled basin-wide biogeochemical fluxes to available estimates, but in a number of cases uncertainties in modern budgets limit our ability to test the model rigorously. In agreement with earlier work we find that fixed N losses via thiodenitrification are likely a major pathway in the Black Sea N cycle. Overall, the same biogeochemical submodel used to simulate the modern global ocean appears to perform well in simulating Black Sea processes without requiring significant modification. The ability of a single model to perform across a wide range of redox states is an important prerequisite for applying the ICBM to deep time paleoceanographic problems. The model source code is available as MATLAB™ 7 m-files provided as auxiliary material.

ASW Research at WHOI and SIO

DTIC Science & Technology

2016-06-07

North Pacific targeting ocean-acoustic bottom interaction, deep seafloor arri vals and bottom diffracted surface refl ected acoustic paths. We...These arrivals were named Deep Sea Floor Arrivals (DSF As). SIO (Worcester) and WHOI (Kemp) provided the near-seafloor DVLA. The OBSJP (Ocean...Andrew, R. K. , Mercer, J . A. , Colosi, J. A. , and Howe, B. M. (2012). "Analysis of Deep Seafloor Arrivals Observed on NPAL04," WHO! Technical Report

Spatial and temporal scales of sea ice protists and phytoplankton distribution from the gateway Fram Strait into the Central Arctic Ocean

NASA Astrophysics Data System (ADS)

Peeken, I.; Hardge, K.; Krumpen, T.; Metfies, K.; Nöthig, E. M.; Rabe, B.; von Appen, W. J.; Vernet, M.

2016-02-01

The Arctic Ocean is currently one of the key regions where the effect of climate change is most pronounced. Sea ice is an important interface in this region by representing a unique habitat for many organisms. Massive reduction of sea ice thickness and extent, which have been recorded over the last twenty years, is anticipated to cause large cascading changes in the entire Arctic ecosystem. Most sea ice is formed on the Eurasian shelves and transported via the Transpolardrift to the western Fram Strait and out of the Arctic Ocean with the cold East Greenland Current (EGC). Warm Atlantic water enters the Arctic Ocean with the West Spitsbergen Current (WSC) via eastern Fram Strait. Here, we focus on the spatial spreading of protists from the Atlantic water masses, and their occurrences over the deep basins of the Central Arctic and the relationship amongst them in water and sea ice. Communities were analyzed by using pigments, flow cytometer and ARISA fingerprints during several cruises with the RV Polarstern to the Fram Strait, the Greenland Sea and the Central Arctic Ocean. By comparing these data sets we are able to demonstrate that the origin of the studied sea ice floes is more important for the biodiversity found in the sea ice communities then the respective underlying water mass. In contrast, biodiversity in the water column is mainly governed by the occurring water masses and the presence or absence of sea ice. However, overall the development of standing stocks in both biomes was governed by the availability of nutrients. To get a temporal perspective of the recent results, the study will be embedded in a long-term data set of phytoplankton biomass obtained during several cruises over the last twenty years.

The Equatorial Pacific Cold Tongue Simulated by IPCC AR4 Coupled GCMs: Upper Ocean Heat Budget and Feedback Analysis

DTIC Science & Technology

2012-05-15

ET AL .: THE PACIFIC COLD TONGUE BIAS ANALYSIS C05024 circulation, which intensifies the surface easterly winds over the Pacific Basin, further...productivity, and in carbon cycling since it is the major oceanic source of C02 for the atmosphere [Field et al , 1998; Calvo et al , 2011]. Large SST anomalies...used for climate predictions and projec- tions [Neelin et al , 1992; Mechoso et al , 1995; Delecluse et al , 1998; Laufet al , 2001; Davey

Deep Bering Sea Circulation and Variability, 2001-2016, From Argo Data

NASA Astrophysics Data System (ADS)

Johnson, Gregory C.; Stabeno, Phyllis J.

2017-12-01

The mean structure, seasonal cycle, and interannual variability of temperature and salinity are analyzed in the deep Bering Sea basin using Argo profile data collected from 2001 to 2016. Gyre transports are estimated using geostrophic stream function maps of Argo profile data referenced to a 1,000 dbar nondivergent absolute velocity stream function mapped from Argo parking pressure displacement data. Relatively warm and salty water from the North Pacific enters the basin through the Near Strait and passages between Aleutian Islands to the east. This water then flows in a cyclonic (counterclockwise) direction around the region, cooling (and freshening) along its path. Aleutian North Slope Current transports from 0 to 1,890 dbar are estimated at 3-6 Sverdrups (1 Sv = 106 m3 s-1) eastward, feeding into the northwestward Bering Slope Current with transports of mostly 5-6 Sv. The Kamchatka Current has transports of ˜6 Sv north of Shirshov Ridge, increasing to 14-16 Sv south of the ridge, where it is augmented by westward flow from Near Strait. Temperature exhibits strong interannual variations in the upper ocean, with warm periods in 2004-2005 and 2015-2016, and cold periods around 2009 and 2012. In contrast, upper ocean salinity generally decreases from 2001 to 2016. As a result of this salinity decrease, the density of the subsurface temperature minimum decreased over this time period, despite more interannual variability in the minimum temperature value. The subsurface temperature maximum also exhibits interannual variability, but with values generally warmer than those previously reported for the 1970s and 1980s.

North Pacific Mesoscale Coupled Air-Ocean Simulations Compared with Observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koracin, Darko; Cerovecki, Ivana; Vellore, Ramesh

2013-04-11

Executive summary The main objective of the study was to investigate atmospheric and ocean interaction processes in the western Pacific and, in particular, effects of significant ocean heat loss in the Kuroshio and Kuroshio Extension regions on the lower and upper atmosphere. It is yet to be determined how significant are these processes are on climate scales. The understanding of these processes led us also to development of the methodology of coupling the Weather and Research Forecasting model with the Parallel Ocean Program model for western Pacific regional weather and climate simulations. We tested NCAR-developed research software Coupler 7 formore » coupling of the WRF and POP models and assessed its usability for regional-scale applications. We completed test simulations using the Coupler 7 framework, but implemented a standard WRF model code with options for both one- and two-way mode coupling. This type of coupling will allow us to seamlessly incorporate new WRF updates and versions in the future. We also performed a long-term WRF simulation (15 years) covering the entire North Pacific as well as high-resolution simulations of a case study which included extreme ocean heat losses in the Kuroshio and Kuroshio Extension regions. Since the extreme ocean heat loss occurs during winter cold air outbreaks (CAO), we simulated and analyzed a case study of a severe CAO event in January 2000 in detail. We found that the ocean heat loss induced by CAOs is amplified by additional advection from mesocyclones forming on the southern part of the Japan Sea. Large scale synoptic patterns with anomalously strong anticyclone over Siberia and Mongolia, deep Aleutian Low, and the Pacific subtropical ridge are a crucial setup for the CAO. It was found that the onset of the CAO is related to the breaking of atmospheric Rossby waves and vertical transport of vorticity that facilitates meridional advection. The study also indicates that intrinsic parameterization of the surface fluxes within the WRF model needs more evaluation and analysis.« less

Seasonal sea surface cooling in the equatorial Pacific cold tongue controlled by ocean mixing.

PubMed

Moum, James N; Perlin, Alexander; Nash, Jonathan D; McPhaden, Michael J

2013-08-01

Sea surface temperature (SST) is a critical control on the atmosphere, and numerical models of atmosphere-ocean circulation emphasize its accurate prediction. Yet many models demonstrate large, systematic biases in simulated SST in the equatorial 'cold tongues' (expansive regions of net heat uptake from the atmosphere) of the Atlantic and Pacific oceans, particularly with regard to a central but little-understood feature of tropical oceans: a strong seasonal cycle. The biases may be related to the inability of models to constrain turbulent mixing realistically, given that turbulent mixing, combined with seasonal variations in atmospheric heating, determines SST. In temperate oceans, the seasonal SST cycle is clearly related to varying solar heating; in the tropics, however, SSTs vary seasonally in the absence of similar variations in solar inputs. Turbulent mixing has long been a likely explanation, but firm, long-term observational evidence has been absent. Here we show the existence of a distinctive seasonal cycle of subsurface cooling via mixing in the equatorial Pacific cold tongue, using multi-year measurements of turbulence in the ocean. In boreal spring, SST rises by 2 kelvin when heating of the upper ocean by the atmosphere exceeds cooling by mixing from below. In boreal summer, SST decreases because cooling from below exceeds heating from above. When the effects of lateral advection are considered, the magnitude of summer cooling via mixing (4 kelvin per month) is equivalent to that required to counter the heating terms. These results provide quantitative assessment of how mixing varies on timescales longer than a few weeks, clearly showing its controlling influence on seasonal cooling of SST in a critical oceanic regime.

On the coevolution of Ediacaran oceans and animals

PubMed Central

Shen, Yanan; Zhang, Tonggang; Hoffman, Paul F.

2008-01-01

Fe speciation and S-isotope of pyrite data from the terminal Proterozoic Sheepbed Formation in Canada and Doushantuo Formation in China reveal that ocean deep waters were anoxic after the global glaciations (snowball Earth) ending 635 million years ago, but that marine sulfate concentrations and inferentially atmospheric oxygen levels were higher than before the glaciations. This supports a long-postulated link between oxygen levels and the emergence of eumetazoa. Subsequent ventilation of the deep ocean, inferred from shifts in Fe speciation in Newfoundland (previously published data) and western Canada (this report), paved the way for Ediacaran macrobiota to colonize the deep seafloors. PMID:18469138

DeepSAGE Based Differential Gene Expression Analysis under Cold and Freeze Stress in Seabuckthorn (Hippophae rhamnoides L.)

PubMed Central

Chaudhary, Saurabh; Sharma, Prakash C.

2015-01-01

Seabuckthorn (Hippophae rhamnoides L.), an important plant species of Indian Himalayas, is well known for its immense medicinal and nutritional value. The plant has the ability to sustain growth in harsh environments of extreme temperatures, drought and salinity. We employed DeepSAGE, a tag based approach, to identify differentially expressed genes under cold and freeze stress in seabuckthorn. In total 36.2 million raw tags including 13.9 million distinct tags were generated using Illumina sequencing platform for three leaf tissue libraries including control (CON), cold stress (CS) and freeze stress (FS). After discarding low quality tags, 35.5 million clean tags including 7 million distinct clean tags were obtained. In all, 11922 differentially expressed genes (DEGs) including 6539 up regulated and 5383 down regulated genes were identified in three comparative setups i.e. CON vs CS, CON vs FS and CS vs FS. Gene ontology and KEGG pathway analysis were performed to assign gene ontology term to DEGs and ascertain their biological functions. DEGs were mapped back to our existing seabuckthorn transcriptome assembly comprising of 88,297 putative unigenes leading to the identification of 428 cold and freeze stress responsive genes. Expression of randomly selected 22 DEGs was validated using qRT-PCR that further supported our DeepSAGE results. The present study provided a comprehensive view of global gene expression profile of seabuckthorn under cold and freeze stresses. The DeepSAGE data could also serve as a valuable resource for further functional genomics studies aiming selection of candidate genes for development of abiotic stress tolerant transgenic plants. PMID:25803684

DeepSAGE based differential gene expression analysis under cold and freeze stress in seabuckthorn (Hippophae rhamnoides L.).

PubMed

Chaudhary, Saurabh; Sharma, Prakash C

2015-01-01

Seabuckthorn (Hippophae rhamnoides L.), an important plant species of Indian Himalayas, is well known for its immense medicinal and nutritional value. The plant has the ability to sustain growth in harsh environments of extreme temperatures, drought and salinity. We employed DeepSAGE, a tag based approach, to identify differentially expressed genes under cold and freeze stress in seabuckthorn. In total 36.2 million raw tags including 13.9 million distinct tags were generated using Illumina sequencing platform for three leaf tissue libraries including control (CON), cold stress (CS) and freeze stress (FS). After discarding low quality tags, 35.5 million clean tags including 7 million distinct clean tags were obtained. In all, 11922 differentially expressed genes (DEGs) including 6539 up regulated and 5383 down regulated genes were identified in three comparative setups i.e. CON vs CS, CON vs FS and CS vs FS. Gene ontology and KEGG pathway analysis were performed to assign gene ontology term to DEGs and ascertain their biological functions. DEGs were mapped back to our existing seabuckthorn transcriptome assembly comprising of 88,297 putative unigenes leading to the identification of 428 cold and freeze stress responsive genes. Expression of randomly selected 22 DEGs was validated using qRT-PCR that further supported our DeepSAGE results. The present study provided a comprehensive view of global gene expression profile of seabuckthorn under cold and freeze stresses. The DeepSAGE data could also serve as a valuable resource for further functional genomics studies aiming selection of candidate genes for development of abiotic stress tolerant transgenic plants.

The Role of Model Complexity in Determining Patterns of Chlorophyll Variability in the Coastal Northwest North Atlantic

NASA Astrophysics Data System (ADS)

Kuhn, A. M.; Fennel, K.; Bianucci, L.

2016-02-01

A key feature of the North Atlantic Ocean's biological dynamics is the annual phytoplankton spring bloom. In the region comprising the continental shelf and adjacent deep ocean of the northwest North Atlantic, we identified two patterns of bloom development: 1) locations with cold temperatures and deep winter mixed layers, where the spring bloom peaks around April and the annual chlorophyll cycle has a large amplitude, and 2) locations with warmer temperatures and shallow winter mixed layers, where the spring bloom peaks earlier in the year, sometimes indiscernible from the fall bloom. These patterns result from a combination of limiting environmental factors and interactions among planktonic groups with different optimal requirements. Simple models that represent the ecosystem with a single phytoplankton (P) and a single zooplankton (Z) group are challenged to reproduce these ecological interactions. Here we investigate the effect that added complexity has on determining spatio-temporal chlorophyll. We compare two ecosystem models, one that contains one P and one Z group, and one with two P and three Z groups. We consider three types of changes in complexity: 1) added dependencies among variables (e.g., temperature dependent rates), 2) modified structural pathways, and 3) added pathways. Subsets of the most sensitive parameters are optimized in each model to replicate observations in the region. For computational efficiency, the parameter optimization is performed using 1D surrogates of a 3D model. We evaluate how model complexity affects model skill, and whether the optimized parameter sets found for each model modify the interpretation of ecosystem functioning. Spatial differences in the parameter sets that best represent different areas hint at the existence of different ecological communities or at physical-biological interactions that are not represented in the simplest model. Our methodology emphasizes the combined use of observations, 1D models to help identifying patterns, and 3D models able to simulate the environment modre realistically, as a means to acquire predictive understanding of the ocean's ecology.

Deglacial and Holocene sea-ice variability north of Iceland and response to ocean circulation changes

NASA Astrophysics Data System (ADS)

Xiao, Xiaotong; Zhao, Meixun; Knudsen, Karen Luise; Sha, Longbin; Eiríksson, Jón; Gudmundsdóttir, Esther; Jiang, Hui; Guo, Zhigang

2017-08-01

Sea-ice conditions on the North Icelandic shelf constitute a key component for the study of the climatic gradients between the Arctic and the North Atlantic Oceans at the Polar Front between the cold East Icelandic Current delivering Polar surface water and the relatively warm Irminger Current derived from the North Atlantic Current. The variability of sea ice contributes to heat reduction (albedo) and gas exchange between the ocean and the atmosphere, and further affects the deep-water formation. However, lack of long-term and high-resolution sea-ice records in the region hinders the understanding of palaeoceanographic change mechanisms during the last glacial-interglacial cycle. Here, we present a sea-ice record back to 15 ka (cal. ka BP) based on the sea-ice biomarker IP25, phytoplankton biomarker brassicasterol and terrestrial biomarker long-chain n-alkanols in piston core MD99-2272 from the North Icelandic shelf. During the Bølling/Allerød (14.7-12.9 ka), the North Icelandic shelf was characterized by extensive spring sea-ice cover linked to reduced flow of warm Atlantic Water and dominant Polar water influence, as well as strong meltwater input in the area. This pattern showed an anti-phase relationship with the ice-free/less ice conditions in marginal areas of the eastern Nordic Seas, where the Atlantic Water inflow was strong, and contributed to an enhanced deep-water formation. Prolonged sea-ice cover with occasional occurrence of seasonal sea ice prevailed during the Younger Dryas (12.9-11.7 ka) interrupted by a brief interval of enhanced Irminger Current and deposition of the Vedde Ash, as opposed to abruptly increased sea-ice conditions in the eastern Nordic Seas. The seasonal sea ice decreased gradually from the Younger Dryas to the onset of the Holocene corresponding to increasing insolation. Ice-free conditions and sea surface warming were observed for the Early Holocene, followed by expansion of sea ice during the Mid-Holocene.

Analysis of the environmental issues concerning the deployment of an OTEC power plant in Martinique.

PubMed

Devault, Damien A; Péné-Annette, Anne

2017-11-01

Ocean thermal energy conversion (OTEC) is a form of power generation, which exploits the temperature difference between warm surface seawater and cold deep seawater. Suitable conditions for OTEC occur in deep warm seas, especially the Caribbean, the Red Sea and parts of the Indo-Pacific Ocean. The continuous power provided by this renewable power source makes a useful contribution to a renewable energy mix because of the intermittence of the other major renewable power sources, i.e. solar or wind power. Industrial-scale OTEC power plants have simply not been built. However, recent innovations and greater political awareness of power transition to renewable energy sources have strengthened the support for such power plants and, after preliminary studies in the Reunion Island (Indian Ocean), the Martinique Island (West Indies) has been selected for the development of the first full-size OTEC power plant in the world, to be a showcase for testing and demonstration. An OTEC plant, even if the energy produced is cheap, calls for high initial capital investment. However, this technology is of interest mainly in tropical areas where funding is limited. The cost of innovations to create an operational OTEC plant has to be amortized, and this technology remains expensive. This paper will discuss the heuristic, technical and socio-economic limits and consequences of deploying an OTEC plant in Martinique to highlight respectively the impact of the OTEC plant on the environment the impact of the environment on the OTEC plant. After defining OTEC, we will describe the different constraints relating to the setting up of the first operational-scale plant worldwide. This includes the investigations performed (reporting declassified data), the political context and the local acceptance of the project. We will then provide an overview of the processes involved in the OTEC plant and discuss the feasibility of future OTEC installations. We will also list the extensive marine investigations required prior to installation and the dangers of setting up OTEC plants in inappropriate locations.

Downscaling ocean conditions with application to the Gulf of Maine, Scotian Shelf and adjacent deep ocean

NASA Astrophysics Data System (ADS)

Katavouta, Anna; Thompson, Keith

2017-04-01

A high resolution regional model (1/36 degree) of the Gulf of Maine, Scotian Shelf and adjacent deep ocean (GoMSS) is developed to downscale ocean conditions from an existing global operational system. First, predictions from the regional GoMSS model in a one-way nesting set up are evaluated using observations from multiple sources including satellite-borne sensors of surface temperature and sea level, CTDs, Argo floats and moored current meters. It is shown that on the shelf, the regional model predicts more realistic fields than the global system because it has higher resolution and includes tides that are absent from the global system. However, in deep water the regional model misplaces deep ocean eddies and meanders associated with the Gulf Stream. This is because of unrealistic internally generated variability (associated with the one-way nesting set up) that leads to decoupling of the regional model from the global system in the deep water. To overcome this problem, the large scales (length scales > 90 km) of the regional model are spectrally nudged towards the global system fields. This leads to more realistic predictions off the shelf. Wavenumber spectra show that even though spectral nudging constrains the large scales, it does not suppress the variability on small scales; on the contrary, it favours the formation of eddies with length scales below the cut-off wavelength of the spectral nudging.

Long-Term, Deep Ocean Test of Concrete Spherical Structures - Results after 13 Years.

DTIC Science & Technology

1985-07-01

corrosion of reinforcing steel are problems, even though the concrete becomes saturated with seawater. Uncoated concrete has a very low rate of permeation... concrete matrix nor corrosion of reinforcing steel are problems, even though the concrete becomes saturated with seawater. Uncoated concrete I has a...which concrete protects the steel against corrosion in the deep ocean environ- ment. The ocean depth range for the spheres corresponds to predicled

Earthquakes drive large-scale submarine canyon development and sediment supply to deep-ocean basins

PubMed Central

Mountjoy, Joshu J.; Howarth, Jamie D.; Orpin, Alan R.; Barnes, Philip M.; Bowden, David A.; Rowden, Ashley A.; Schimel, Alexandre C. G.; Holden, Caroline; Horgan, Huw J.; Nodder, Scott D.; Patton, Jason R.; Lamarche, Geoffroy; Gerstenberger, Matthew; Micallef, Aaron; Pallentin, Arne; Kane, Tim

2018-01-01

Although the global flux of sediment and carbon from land to the coastal ocean is well known, the volume of material that reaches the deep ocean—the ultimate sink—and the mechanisms by which it is transferred are poorly documented. Using a globally unique data set of repeat seafloor measurements and samples, we show that the moment magnitude (Mw) 7.8 November 2016 Kaikōura earthquake (New Zealand) triggered widespread landslides in a submarine canyon, causing a powerful “canyon flushing” event and turbidity current that traveled >680 km along one of the world’s longest deep-sea channels. These observations provide the first quantification of seafloor landscape change and large-scale sediment transport associated with an earthquake-triggered full canyon flushing event. The calculated interevent time of ~140 years indicates a canyon incision rate of 40 mm year−1, substantially higher than that of most terrestrial rivers, while synchronously transferring large volumes of sediment [850 metric megatons (Mt)] and organic carbon (7 Mt) to the deep ocean. These observations demonstrate that earthquake-triggered canyon flushing is a primary driver of submarine canyon development and material transfer from active continental margins to the deep ocean. PMID:29546245

A window on the deep ocean: The special value of ocean bottom pressure for monitoring the large-scale, deep-ocean circulation

NASA Astrophysics Data System (ADS)

Hughes, Chris W.; Williams, Joanne; Blaker, Adam; Coward, Andrew; Stepanov, Vladimir

2018-02-01

We show how, by focusing on bottom pressure measurements particularly on the global continental slope, it is possible to avoid the "fog" of mesoscale variability which dominates most observables in the deep ocean. This makes it possible to monitor those aspects of the ocean circulation which are most important for global scale ocean variability and climate. We therefore argue that such measurements should be considered an important future component of the Global Ocean Observing System, to complement the present open-ocean and coastal elements. Our conclusions are founded on both theoretical arguments, and diagnostics from a fine-resolution ocean model that has realistic amplitudes and spectra of mesoscale variability. These show that boundary pressure variations are coherent over along-slope distances of tens of thousands of kilometres, for several vertical modes. We illustrate the value of this in the model Atlantic, by determining the time for boundary and equatorial waves to complete a circuit of the northern basin (115 and 205 days for the first and second vertical modes), showing how the boundary features compare with basin-scale theoretical models, and demonstrating the ability to monitor the meridional overturning circulation using these boundary measurements. Finally, we discuss applicability to the real ocean and make recommendations on how to make such measurements without contamination from instrumental drift.

Brine/Rock Interaction in Deep Oceanic Layered Gabbros: Petrological Evidence from Cl-Rich Amphibole, High-Temperature Hydrothermal Veins, and Experiments

NASA Astrophysics Data System (ADS)

Currin Sala, A. M.; Koepke, J.; Almeev, R. R.; Teagle, D. A. H.; Zihlmann, B.; Wolff, P. E.

2017-12-01

Evidence of high temperature brine/rock interaction is found in hydrothermal veins and dykelets that cross-cut layered olivine gabbros in the deep palaeocrust of the Sumail Ophiolite, Sultanate of Oman. Here we present petrological and geochemical data from these samples, and an experimental attempt to simulate brine/gabbro interaction using externally heated cold seal pressure vessels. The studied natural veins and dykelets contain pargasite, hornblende, actinolite, and Cl-rich pargasite with up to 5 wt% Cl, showing a range of formation conditions from magmatic to metamorphic (hydrothermal) and thus a complex history of brine/rock interaction. In addition, the isotopic study of the radiogenic 87/86Sr and stable 18O in different amphibole types provide an estimate for the extent of seawater influence as alteration agent in the veins of the studied samples. Experiments performed at 750 °C and 200 MPa with different starting materials (chlorine-free amphibole, olivine gabbro powder) and 20 wt% NaCl aqueous brine, illustrate the process by which gabbro-hosted amphibole-rich veins evolve at subsolidus temperatures in the presence of a seawater-derived fluid. Our results demonstrate a decrease in olivine, plagioclase and magnetite content in favour of hastingsite, pargasite and magnesiohornblende, a decrease of IVAl and Ti in the starting amphibole, and an increase in Cl in amphibole, up to 0.2 Cl wt%. Our experiments show the change of magmatic pargasite towards more magnesium and silica-rich end members with results comparable to mildly chlorine-rich pargasites and hornblendes found in the natural samples studied. However, the experimental setup also presents limitations in the attainment of very high-chlorine amphibole (up to 5 wt%). Our analytical and experimental results provide further evidence for the existence of a hydrothermal cooling system in the deep oceanic crust.

Bottom Interaction in Ocean Acoustic Propagation

DTIC Science & Technology

2014-09-30

deep seafloor (greater than the critical depth). What is the relationship between the seismic (ground motion) noise on the seafloor and the acoustic...ocean bottom seismometers (OBSs), but were very weak on the deep vertical line array (Deep VLA), located above 750 m from the seafloor. Stephen et al...was carried out in April-May 2011 near the location of the PhilSea10 Distributed Vertical Line Array (DVLA) (Stephen et al., 2011). The second

Bottom Interaction in Ocean Acoustic Propagation

DTIC Science & Technology

2015-09-30

the deep seafloor (greater than the critical depth). What is the relationship between the seismic (ground motion) noise on the seafloor and the...ocean bottom seismometers (OBSs), but were very weak on the deep vertical line array (Deep VLA), located above 750 m from the seafloor. Stephen et...carried out in April-May 2011 near the location of the PhilSea10 Distributed Vertical Line Array (DVLA) (Stephen et al., 2011). The second experiment

On the Land-Ocean Contrast of Tropical Convection and Microphysics Statistics Derived from TRMM Satellite Signals and Global Storm-Resolving Models

NASA Technical Reports Server (NTRS)

Matsui, Toshihisa; Chern, Jiun-Dar; Tao, Wei-Kuo; Lang, Stephen E.; Satoh, Masaki; Hashino, Tempei; Kubota, Takuji

2016-01-01

A 14-year climatology of Tropical Rainfall Measuring Mission (TRMM) collocated multi-sensor signal statistics reveal a distinct land-ocean contrast as well as geographical variability of precipitation type, intensity, and microphysics. Microphysics information inferred from the TRMM precipitation radar and Microwave Imager (TMI) show a large land-ocean contrast for the deep category, suggesting continental convective vigor. Over land, TRMM shows higher echo-top heights and larger maximum echoes, suggesting taller storms and more intense precipitation, as well as larger microwave scattering, suggesting the presence of morelarger frozen convective hydrometeors. This strong land-ocean contrast in deep convection is invariant over seasonal and multi-year time-scales. Consequently, relatively short-term simulations from two global storm-resolving models can be evaluated in terms of their land-ocean statistics using the TRMM Triple-sensor Three-step Evaluation via a satellite simulator. The models evaluated are the NASA Multi-scale Modeling Framework (MMF) and the Non-hydrostatic Icosahedral Cloud Atmospheric Model (NICAM). While both simulations can represent convective land-ocean contrasts in warm precipitation to some extent, near-surface conditions over land are relatively moisture in NICAM than MMF, which appears to be the key driver in the divergent warm precipitation results between the two models. Both the MMF and NICAM produced similar frequencies of large CAPE between land and ocean. The dry MMF boundary layer enhanced microwave scattering signals over land, but only NICAM had an enhanced deep convection frequency over land. Neither model could reproduce a realistic land-ocean contrast in in deep convective precipitation microphysics. A realistic contrast between land and ocean remains an issue in global storm-resolving modeling.

Site Management and Monitoring Plan (SMMP) for the Mouth of Columbia River- Deep and Shallow Water Ocean Dredged Material Disposal Sites, OR/WA

EPA Pesticide Factsheets

This SMMP is intended to provide management and monitoring strategies for disposal in the Mouth of Columbia River- Deep and Shallow Ocean Dredged Material Disposal Sites on the border of Oregon and Washington.

Tidal Energy Available for Deep Ocean Mixing: Bounds from Altimetry Data

NASA Technical Reports Server (NTRS)

Egbert, Gary D.; Ray, Richard D.

1999-01-01

Maintenance of the large-scale thermohaline circulation has long presented a problem to oceanographers. Observed mixing rates in the pelagic ocean are an order of magnitude too small to balance the rate at which dense bottom water is created at high latitudes. Recent observational and theoretical work suggests that much of this mixing may occur in hot spots near areas of rough topography (e.g., mid-ocean ridges and island arcs). Barotropic tidal currents provide a very plausible source of energy to maintain these mixing processes. Topex/Poseidon (T/P) satellite altimetry data have made precise mapping of open ocean tidal elevations possible for the first time. We can thus obtain empirical, spatially localized, estimates of barotropic tidal dissipation. These provide an upper bound on the amount of tidal energy that is dissipated in the deep ocean, and hence is available for deep mixing. We will present and compare maps of open ocean tidal energy flux divergence, and estimates of tidal energy flux into shallow seas, derived from T/P altimetry data using both formal data assimilation methods and empirical approaches. With the data assimilation methods we can place formal error bars on the fluxes. Our results show that 20-25% of tidal energy dissipation occurs outside of the shallow seas, the traditional sink for tidal energy. This suggests that up to 1 TW of energy may be available from the tides (lunar and solar) for mixing the deep ocean. The dissipation indeed appears to be concentrated over areas of rough topography.

Tidal Energy Available for Deep Ocean Mixing: Bounds From Altimetry Data

NASA Technical Reports Server (NTRS)

Egbert, Gary D.; Ray, Richard D.

1999-01-01

Maintenance of the large-scale thermohaline circulation has long presented a problem to oceanographers. Observed mixing rates in the pelagic ocean are an order of magnitude too small to balance the rate at which dense bottom water is created at high latitudes. Recent observational and theoretical work suggests that much of this mixing may occur in hot spots near areas of rough topography (e.g., mid-ocean ridges and island arcs). Barotropic tidal currents provide a very plausible source of energy to maintain these mixing processes. Topex/Poseidon satellite altimetry data have made precise mapping of open ocean tidal elevations possible for the first time. We can thus obtain empirical, spatially localized, estimates of barotropic tidal dissipation. These provide an upper bound on the amount of tidal energy that is dissipated in the deep ocean, and hence is available for deep mixing. We will present and compare maps of open ocean tidal energy flux divergence, and estimates of tidal energy flux into shallow seas, derived from T/P altimetry data using both formal data assimilation methods and empirical approaches. With the data assimilation methods we can place formal error bars on the fluxes. Our results show that 20-25% of tidal energy dissipation occurs outside of the shallow seas, the traditional sink for tidal energy. This suggests that up to 1 TW of energy may be available from the tides (lunar and solar) for mixing the deep ocean. The dissipation indeed appears to be concentrated over areas of rough topography.

Tidal Energy Available for Deep Ocean Mixing: Bounds from Altimetry Data

NASA Technical Reports Server (NTRS)

Ray, Richard D.; Egbert, Gary D.

1999-01-01

Maintenance of the large-scale thermohaline circulation has long presented an interesting problem. Observed mixing rates in the pelagic ocean are an order of magnitude too small to balance the rate at which dense bottom water is created at high latitudes. Recent observational and theoretical work suggests that much of this mixing may occur in hot spots near areas of rough topography (e.g., mid-ocean ridges and island arcs). Barotropic tidal currents provide a very plausible source of energy to maintain these mixing processes. Topex/Poseidon satellite altimetry data have made precise mapping of open ocean tidal elevations possible for the first time. We can thus obtain empirical, spatially localized, estimates of barotropic tidal dissipation. These provide an upper bound on the amount of tidal energy that is dissipated in the deep ocean, and hence is available for deep mixing. We will present and compare maps of open ocean tidal energy flux divergence, and estimates of tidal energy flux into shallow seas, derived from T/P altimetry data using both formal data assimilation methods and empirical approaches. With the data assimilation methods we can place formal error bars on the fluxes. Our results show that 20-25% of tidal energy dissipation occurs outside of the shallow seas, the traditional sink for tidal energy. This suggests that up to 1 TW of energy may be available from the tides (lunar and solar) for mixing the deep ocean. The dissipation indeed appears to be concentrated over areas of rough topography.

Glacial greenhouse-gas fluctuations controlled by ocean circulation changes.

PubMed

Schmittner, Andreas; Galbraith, Eric D

2008-11-20

Earth's climate and the concentrations of the atmospheric greenhouse gases carbon dioxide (CO(2)) and nitrous oxide (N(2)O) varied strongly on millennial timescales during past glacial periods. Large and rapid warming events in Greenland and the North Atlantic were followed by more gradual cooling, and are highly correlated with fluctuations of N(2)O as recorded in ice cores. Antarctic temperature variations, on the other hand, were smaller and more gradual, showed warming during the Greenland cold phase and cooling while the North Atlantic was warm, and were highly correlated with fluctuations in CO(2). Abrupt changes in the Atlantic meridional overturning circulation (AMOC) have often been invoked to explain the physical characteristics of these Dansgaard-Oeschger climate oscillations, but the mechanisms for the greenhouse-gas variations and their linkage to the AMOC have remained unclear. Here we present simulations with a coupled model of glacial climate and biogeochemical cycles, forced only with changes in the AMOC. The model simultaneously reproduces characteristic features of the Dansgaard-Oeschger temperature, as well as CO(2) and N(2)O fluctuations. Despite significant changes in the land carbon inventory, CO(2) variations on millennial timescales are dominated by slow changes in the deep ocean inventory of biologically sequestered carbon and are correlated with Antarctic temperature and Southern Ocean stratification. In contrast, N(2)O co-varies more rapidly with Greenland temperatures owing to fast adjustments of the thermocline oxygen budget. These results suggest that ocean circulation changes were the primary mechanism that drove glacial CO(2) and N(2)O fluctuations on millennial timescales.

Development of continental margins of the Atlantic Ocean and successive breakup of the Pangaea-3 supercontinent

NASA Astrophysics Data System (ADS)

Melankholina, E. N.; Sushchevskaya, N. M.

2017-01-01

Comparative tectonic analysis of passive margins of the Atlantic Ocean has been performed. Tectonotypes of both volcanic and nonvolcanic margins are described, and their comparison with other passive Atlantic margins is given. The structural features of margins, peculiarities of magmatism, its sources and reasons for geochemical enrichment of melts are discussed. The important role of melting of the continental lithosphere in the development of magmatism is demonstrated. Enriched EM I and EM II sources are determined for the lower parts of the volcanic section, and a depleted or poorly enriched source is determined for the upper parts of the volcanic section based on isotope data. The conclusions of the paper relate to tectonic settings of the initial occurrence of magmatism and rifting and breakup during the period of opening of the Mesozoic Ocean. It was found out that breakup and magmatism at proximal margins led only to insignificant structural transformations and reduction of the thickness of the ancient continental crust, while very important magmatic events happened later in the distal zone. New growth of magmatic crust at the stage of continental breakup is determined as a typical feature of distal zones of the margins under study. The relationship of development of margins with the impact of deep plumes as the source of magmatic material or a heat source only is discussed. Progradation of the zone of extension and breakup into the areas of cold lithosphere of the Atlantic and the formation of a single tectonomagmatic system of the ocean are under consideration.

Global diversity and biogeography of deep-sea pelagic prokaryotes.

PubMed

Salazar, Guillem; Cornejo-Castillo, Francisco M; Benítez-Barrios, Verónica; Fraile-Nuez, Eugenio; Álvarez-Salgado, X Antón; Duarte, Carlos M; Gasol, Josep M; Acinas, Silvia G

2016-03-01

The deep-sea is the largest biome of the biosphere, and contains more than half of the whole ocean's microbes. Uncovering their general patterns of diversity and community structure at a global scale remains a great challenge, as only fragmentary information of deep-sea microbial diversity exists based on regional-scale studies. Here we report the first globally comprehensive survey of the prokaryotic communities inhabiting the bathypelagic ocean using high-throughput sequencing of the 16S rRNA gene. This work identifies the dominant prokaryotes in the pelagic deep ocean and reveals that 50% of the operational taxonomic units (OTUs) belong to previously unknown prokaryotic taxa, most of which are rare and appear in just a few samples. We show that whereas the local richness of communities is comparable to that observed in previous regional studies, the global pool of prokaryotic taxa detected is modest (~3600 OTUs), as a high proportion of OTUs are shared among samples. The water masses appear to act as clear drivers of the geographical distribution of both particle-attached and free-living prokaryotes. In addition, we show that the deep-oceanic basins in which the bathypelagic realm is divided contain different particle-attached (but not free-living) microbial communities. The combination of the aging of the water masses and a lack of complete dispersal are identified as the main drivers for this biogeographical pattern. All together, we identify the potential of the deep ocean as a reservoir of still unknown biological diversity with a higher degree of spatial complexity than hitherto considered.

Global diversity and biogeography of deep-sea pelagic prokaryotes

PubMed Central

Salazar, Guillem; Cornejo-Castillo, Francisco M; Benítez-Barrios, Verónica; Fraile-Nuez, Eugenio; Álvarez-Salgado, X Antón; Duarte, Carlos M; Gasol, Josep M; Acinas, Silvia G

2016-01-01

The deep-sea is the largest biome of the biosphere, and contains more than half of the whole ocean's microbes. Uncovering their general patterns of diversity and community structure at a global scale remains a great challenge, as only fragmentary information of deep-sea microbial diversity exists based on regional-scale studies. Here we report the first globally comprehensive survey of the prokaryotic communities inhabiting the bathypelagic ocean using high-throughput sequencing of the 16S rRNA gene. This work identifies the dominant prokaryotes in the pelagic deep ocean and reveals that 50% of the operational taxonomic units (OTUs) belong to previously unknown prokaryotic taxa, most of which are rare and appear in just a few samples. We show that whereas the local richness of communities is comparable to that observed in previous regional studies, the global pool of prokaryotic taxa detected is modest (~3600 OTUs), as a high proportion of OTUs are shared among samples. The water masses appear to act as clear drivers of the geographical distribution of both particle-attached and free-living prokaryotes. In addition, we show that the deep-oceanic basins in which the bathypelagic realm is divided contain different particle-attached (but not free-living) microbial communities. The combination of the aging of the water masses and a lack of complete dispersal are identified as the main drivers for this biogeographical pattern. All together, we identify the potential of the deep ocean as a reservoir of still unknown biological diversity with a higher degree of spatial complexity than hitherto considered. PMID:26251871

Tracking ocean heat uptake during the surface warming hiatus

DOE PAGES

Liu, Wei; Xie, Shang -Ping; Lu, Jian

2016-03-30

Ocean heat uptake is observed to penetrate deep during the recent hiatus1,2,3 of global warming in the Atlantic and Southern Ocean. This has been suggested to indicate that the two regions are the driver of the surface warming hiatus4. We show that the deep heat penetration in the Atlantic and Southern Ocean is not unique to the hiatus but common to the past four decades including the 1970s-90s epoch of accelerated surface warming. Our analyses of a large ensemble simulation5 confirm the deep heat penetration in the Atlantic and Southern Ocean in ensemble members with or without surface warming hiatusmore » in the early 21th century. During the past four decades, the global ocean heat content (OHC) of upper 1500m is dominated by a warming trend, and the depth of anthropogenic heat penetration merely reflects the depth of the mean meridional overturning circulation in the basin. Furthermore, the heat penetration depth is not a valid basis to infer the hiatus mechanism.« less

Tracking ocean heat uptake during the surface warming hiatus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Wei; Xie, Shang -Ping; Lu, Jian

Ocean heat uptake is observed to penetrate deep during the recent hiatus1,2,3 of global warming in the Atlantic and Southern Ocean. This has been suggested to indicate that the two regions are the driver of the surface warming hiatus4. We show that the deep heat penetration in the Atlantic and Southern Ocean is not unique to the hiatus but common to the past four decades including the 1970s-90s epoch of accelerated surface warming. Our analyses of a large ensemble simulation5 confirm the deep heat penetration in the Atlantic and Southern Ocean in ensemble members with or without surface warming hiatusmore » in the early 21th century. During the past four decades, the global ocean heat content (OHC) of upper 1500m is dominated by a warming trend, and the depth of anthropogenic heat penetration merely reflects the depth of the mean meridional overturning circulation in the basin. Furthermore, the heat penetration depth is not a valid basis to infer the hiatus mechanism.« less

Deep ocean nutrients imply large latitudinal variation in particle transfer efficiency.

PubMed

Weber, Thomas; Cram, Jacob A; Leung, Shirley W; DeVries, Timothy; Deutsch, Curtis

2016-08-02

The "transfer efficiency" of sinking organic particles through the mesopelagic zone and into the deep ocean is a critical determinant of the atmosphere-ocean partition of carbon dioxide (CO2). Our ability to detect large-scale spatial variations in transfer efficiency is limited by the scarcity and uncertainties of particle flux data. Here we reconstruct deep ocean particle fluxes by diagnosing the rate of nutrient accumulation along transport pathways in a data-constrained ocean circulation model. Combined with estimates of organic matter export from the surface, these diagnosed fluxes reveal a global pattern of transfer efficiency to 1,000 m that is high (∼25%) at high latitudes and low (∼5%) in subtropical gyres, with intermediate values in the tropics. This pattern is well correlated with spatial variations in phytoplankton community structure and the export of ballast minerals, which control the size and density of sinking particles. These findings accentuate the importance of high-latitude oceans in sequestering carbon over long timescales, and highlight potential impacts on remineralization depth as phytoplankton communities respond to a warming climate.

Deep ocean nutrients imply large latitudinal variation in particle transfer efficiency

PubMed Central

Weber, Thomas; Cram, Jacob A.; Leung, Shirley W.; DeVries, Timothy; Deutsch, Curtis

2016-01-01

The “transfer efficiency” of sinking organic particles through the mesopelagic zone and into the deep ocean is a critical determinant of the atmosphere−ocean partition of carbon dioxide (CO2). Our ability to detect large-scale spatial variations in transfer efficiency is limited by the scarcity and uncertainties of particle flux data. Here we reconstruct deep ocean particle fluxes by diagnosing the rate of nutrient accumulation along transport pathways in a data-constrained ocean circulation model. Combined with estimates of organic matter export from the surface, these diagnosed fluxes reveal a global pattern of transfer efficiency to 1,000 m that is high (∼25%) at high latitudes and low (∼5%) in subtropical gyres, with intermediate values in the tropics. This pattern is well correlated with spatial variations in phytoplankton community structure and the export of ballast minerals, which control the size and density of sinking particles. These findings accentuate the importance of high-latitude oceans in sequestering carbon over long timescales, and highlight potential impacts on remineralization depth as phytoplankton communities respond to a warming climate. PMID:27457946

Deep ocean nutrients imply large latitudinal variation in particle transfer efficiency

NASA Astrophysics Data System (ADS)

Weber, Thomas; Cram, Jacob A.; Leung, Shirley W.; DeVries, Timothy; Deutsch, Curtis

2016-08-01

The “transfer efficiency” of sinking organic particles through the mesopelagic zone and into the deep ocean is a critical determinant of the atmosphere-ocean partition of carbon dioxide (CO2). Our ability to detect large-scale spatial variations in transfer efficiency is limited by the scarcity and uncertainties of particle flux data. Here we reconstruct deep ocean particle fluxes by diagnosing the rate of nutrient accumulation along transport pathways in a data-constrained ocean circulation model. Combined with estimates of organic matter export from the surface, these diagnosed fluxes reveal a global pattern of transfer efficiency to 1,000 m that is high (˜25%) at high latitudes and low (˜5%) in subtropical gyres, with intermediate values in the tropics. This pattern is well correlated with spatial variations in phytoplankton community structure and the export of ballast minerals, which control the size and density of sinking particles. These findings accentuate the importance of high-latitude oceans in sequestering carbon over long timescales, and highlight potential impacts on remineralization depth as phytoplankton communities respond to a warming climate.

Colonization of the deep sea by fishes

PubMed Central

Priede, I G; Froese, R

2013-01-01

Analysis of maximum depth of occurrence of 11 952 marine fish species shows a global decrease in species number (N) with depth (x; m): log10N = −0·000422x + 3·610000 (r2 = 0·948). The rate of decrease is close to global estimates for change in pelagic and benthic biomass with depth (−0·000430), indicating that species richness of fishes may be limited by food energy availability in the deep sea. The slopes for the Classes Myxini (−0·000488) and Actinopterygii (−0·000413) follow this trend but Chondrichthyes decrease more rapidly (−0·000731) implying deficiency in ability to colonize the deep sea. Maximum depths attained are 2743, 4156 and 8370 m for Myxini, Chondrichthyes and Actinopterygii, respectively. Endemic species occur in abundance at 7–7800 m depth in hadal trenches but appear to be absent from the deepest parts of the oceans, >9000 m deep. There have been six global oceanic anoxic events (OAE) since the origin of the major fish taxa in the Devonian c. 400 million years ago (mya). Colonization of the deep sea has taken place largely since the most recent OAE in the Cretaceous 94 mya when the Atlantic Ocean opened up. Patterns of global oceanic circulation oxygenating the deep ocean basins became established coinciding with a period of teleost diversification and appearance of the Acanthopterygii. Within the Actinopterygii, there is a trend for greater invasion of the deep sea by the lower taxa in accordance with the Andriashev paradigm. Here, 31 deep-sea families of Actinopterygii were identified with mean maximum depth >1000 m and with >10 species. Those with most of their constituent species living shallower than 1000 m are proposed as invasive, with extinctions in the deep being continuously balanced by export of species from shallow seas. Specialized families with most species deeper than 1000 m are termed deep-sea endemics in this study; these appear to persist in the deep by virtue of global distribution enabling recovery from regional extinctions. Deep-sea invasive families such as Ophidiidae and Liparidae make the greatest contribution to fish fauna at depths >6000 m. PMID:24298950

Spatial and vertical gradients in the stable carbon isotope composition of Lower Circumpolar Deep Water over the last 900 thousand years

NASA Astrophysics Data System (ADS)

Williams, T.; Hillenbrand, C. D.; Piotrowski, A. M.; Smith, J.; Hodell, D. A.; Frederichs, T.; Allen, C. S.

2014-12-01

Changes in stable carbon isotopes (δ13C) recorded in benthic foraminiferal calcite reflect that of the dissolved inorganic carbon (DIC) of ambient seawater, and thus are used to reconstruct past changes in water mass mixing. Records of benthic foraminiferal δ13C from the Atlantic Ocean have revealed the development of a sharp vertical δ13C gradient between 2300-2500m water depth during successive glacial periods throughout the Late Quaternary, with extremely negative δ13C values recorded below this depth. It had been hypothesised that this gradient resulted from an increased stratification of water masses within the glacial Atlantic Ocean, and that these extreme δ13C values originated in the Southern Ocean. However the mechanisms behind the formation of this gradient and extreme δ13C depletion have remained unclear. This is in part due to the poor preservation of calcareous microfossils in the corrosive waters below 2500-3000m found in the Southern Ocean, which hampers our understanding of this key region. Here we present a unique new δ13C deep water record measured on benthic foraminifera (Cibicidoides spp.) from a sediment core recovered from 2100m water depth in the Amundsen Sea, south-eastern Pacific sector of the Southern Ocean. The site is bathed in Lower Circumpolar Deep Water (LCDW) today, and combined palaeomagnetic and oxygen isotope stratigraphy show that the sediments continuously span at least the last 890 ka. A comparison of this new δ13C data with other LCDW records from ODP Sites 1089/1090 in the South Atlantic and ODP Site 1123 in the Southwest Pacific demonstrate a clear spatial gradient in circum-Antarctic LCDW during glacial periods. The pool of extremely depleted glacial deep marine δ13C is restricted to the Atlantic Sector of the Southern Ocean, with increasingly positive δ13C values found in the Southwest Pacific and the south-eastern Pacific sector of the Southern Ocean. This implies that the δ13C depletion in the deep glacial Atlantic was sourced in the Atlantic sector of the Southern Ocean, and remained limited to this sector. This finding indicates either increased supply of relatively more positive δ13C deep waters or increased vertical mixing in the Indian and Pacific sectors of the glacial Southern Ocean.

Asynchronous warming and δ18O evolution of deep Atlantic water masses during the last deglaciation

NASA Astrophysics Data System (ADS)

Zhang, J.; Liu, Z.; Brady, E. C.; Oppo, D.; Clark, P. U.; Jahn, A.; Marcott, S. A.; Lindsay, K. T.

2017-12-01

The large-scale reorganization of deep-ocean circulation in the Atlantic involving changes in North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) played a critical role in regulating hemispheric and global climate during the last deglaciation. However, changes in the relative contributions of NADW and AABW and their properties are poorly constrained by marine records, including δ18O of benthic foraminiferal calcite (δ18Oc). Here we use an isotope-enabled ocean general circulation model with realistic geometry and forcing conditions to simulate the deglacial water mass and δ18O evolution. Model results suggest that in response to North Atlantic freshwater forcing during the early phase of the last deglaciation, NADW nearly collapses while AABW mildly weakens. Rather than reflecting changes in NADW or AABW properties due to freshwater input as suggested previously, the observed phasing difference of deep δ18Oc likely reflects early warming of the deep northern North Atlantic by 1.4°C while deep Southern Ocean temperature remains largely unchanged. We propose a thermodynamic mechanism to explain the early warming in the North Atlantic, featuring a strong mid-depth warming and enhanced downward heat flux via vertical mixing. Our results emphasize that the way ocean circulation affects heat, a dynamic tracer, is considerably different than how it affects passive tracers like δ18O, and call for caution when inferring water mass changes from δ18Oc records while assuming uniform changes in deep temperatures.

Asynchronous warming and δ18O evolution of deep Atlantic water masses during the last deglaciation

NASA Astrophysics Data System (ADS)

Zhang, Jiaxu; Liu, Zhengyu; Brady, Esther C.; Oppo, Delia W.; Clark, Peter U.; Jahn, Alexandra; Marcott, Shaun A.; Lindsay, Keith

2017-10-01

The large-scale reorganization of deep ocean circulation in the Atlantic involving changes in North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) played a critical role in regulating hemispheric and global climate during the last deglaciation. However, changes in the relative contributions of NADW and AABW and their properties are poorly constrained by marine records, including δ18O of benthic foraminiferal calcite (δ18Oc). Here, we use an isotope-enabled ocean general circulation model with realistic geometry and forcing conditions to simulate the deglacial water mass and δ18O evolution. Model results suggest that, in response to North Atlantic freshwater forcing during the early phase of the last deglaciation, NADW nearly collapses, while AABW mildly weakens. Rather than reflecting changes in NADW or AABW properties caused by freshwater input as suggested previously, the observed phasing difference of deep δ18Oc likely reflects early warming of the deep northern North Atlantic by ˜1.4 °C, while deep Southern Ocean temperature remains largely unchanged. We propose a thermodynamic mechanism to explain the early warming in the North Atlantic, featuring a strong middepth warming and enhanced downward heat flux via vertical mixing. Our results emphasize that the way that ocean circulation affects heat, a dynamic tracer, is considerably different from how it affects passive tracers, like δ18O, and call for caution when inferring water mass changes from δ18Oc records while assuming uniform changes in deep temperatures.

Sediments and fossiliferous rocks from the eastern side of the Tongue of the Ocean, Bahamas

USGS Publications Warehouse

Gibson, T.G.; Schlee, J.

1967-01-01

In August 1966, two dives were made with the deep-diving submersible Alvin along the eastern side of the Tongue of the Ocean to sample the rock and sediment. Physiographically, the area is marked by steep slopes of silty carbonate sediment and precipitous rock cliffs dusted by carbonate debris. Three rocks, obtained from the lower and middle side of the canyon (914-1676 m depth), are late Miocene-early Pliocene to late Pleistocene-Recent in age; all are deep-water pelagic limestones. They show (i) that the Tongue of the Ocean has been a deep-water area at least back into the Miocene, and (ii) that much shallow-water detritus has been swept off neighbouring banks to be incorporated with the deep-water fauna in the sediment. ?? 1967 Pergamon Press Ltd.

A unified spectral,parameterization for wave breaking: from the deep ocean to the surf zone

NASA Astrophysics Data System (ADS)

Filipot, J.

2010-12-01

A new wave-breaking dissipation parameterization designed for spectral wave models is presented. It combines wave breaking basic physical quantities, namely, the breaking probability and the dissipation rate per unit area. The energy lost by waves is fi[|#12#|]rst calculated in the physical space before being distributed over the relevant spectral components. This parameterization allows a seamless numerical model from the deep ocean into the surf zone. This transition from deep to shallow water is made possible by a dissipation rate per unit area of breaking waves that varies with the wave height, wavelength and water depth.The parameterization is further tested in the WAVEWATCH III TM code, from the global ocean to the beach scale. Model errors are smaller than with most specialized deep or shallow water parameterizations.

Extraterrestrial demise of banded iron formations 1.85 billion years ago

USGS Publications Warehouse

Slack, J.F.; Cannon, W.F.

2009-01-01

In the Lake Superior region of North America, deposition of most banded iron formations (BIFs) ended abruptly 1.85 Ga ago, coincident with the oceanic impact of the giant Sudbury extraterrestrial bolide. We propose a new model in which this impact produced global mixing of shallow oxic and deep anoxic waters of the Paleoproterozoic ocean, creating a suboxic redox state for deep seawater. This suboxic state, characterized by only small concentrations of dissolved O2 (???1 ??M), prevented transport of hydrothermally derived Fe(II) from the deep ocean to continental-margin settings, ending an ???1.1 billion-year-long period of episodic BIF mineralization. The model is supported by the nature of Precambrian deep-water exhalative chemical sediments, which changed from predominantly sulfide facies prior to ca. 1.85 Ga to mainly oxide facies thereafter. ?? 2009 Geological Society of America.

Ocean Thermal Energy.

ERIC Educational Resources Information Center

Berkovsky, Boris

1987-01-01

Describes Ocean Thermal Energy Conservation (OTEC) as a method for exploiting the temperature difference between warm surface waters of the sea and its cold depths. Argues for full-scale demonstrations of the technique for producing energy for coastal regions. (TW)

Fronts and frontogenesis as revealed by high time resolution data

NASA Technical Reports Server (NTRS)

Frank, A. E.; Barber, D. A.

1977-01-01

Upper air sounding are used to examine a cold front of average intensity. Vertical cross sections of potential temperature and wind, and horizontal analyses were compared and adjusted for consistency. These analyses were then used to study the evolution of the front, found to consist of a complex system of fronts occurring at all levels of the troposphere. Low level fronts were strongest at the surface and rapidly weakened with height. Fronts in the midddle troposphere were much more intense. The warm air ahead of the fronts was nearly barotropic, while the cold air behind was baroclinic through deep layers. A deep mixed layer was observed to grow in this cold air.

Comparison of Deep-Water Viromes from the Atlantic Ocean and the Mediterranean Sea

PubMed Central

Winter, Christian; Garcia, Juan A. L.; Weinbauer, Markus G.; DuBow, Michael S.; Herndl, Gerhard J.

2014-01-01

The aim of this study was to compare the composition of two deep-sea viral communities obtained from the Romanche Fracture Zone in the Atlantic Ocean (collected at 5200 m depth) and the southwest Mediterranean Sea (from 2400 m depth) using a pyro-sequencing approach. The results are based on 18.7% and 6.9% of the sequences obtained from the Atlantic Ocean and the Mediterranean Sea, respectively, with hits to genomes in the non-redundant viral RefSeq database. The identifiable richness and relative abundance in both viromes were dominated by archaeal and bacterial viruses accounting for 92.3% of the relative abundance in the Atlantic Ocean and for 83.6% in the Mediterranean Sea. Despite characteristic differences in hydrographic features between the sampling sites in the Atlantic Ocean and the Mediterranean Sea, 440 virus genomes were found in both viromes. An additional 431 virus genomes were identified in the Atlantic Ocean and 75 virus genomes were only found in the Mediterranean Sea. The results indicate that the rather contrasting deep-sea environments of the Atlantic Ocean and the Mediterranean Sea share a common core set of virus types constituting the majority of both virus communities in terms of relative abundance (Atlantic Ocean: 81.4%; Mediterranean Sea: 88.7%). PMID:24959907

Relationships between the Raindrop Size Distribution and Properties of the Environment and Clouds Inferred from TRMM

NASA Technical Reports Server (NTRS)

Munchak, Stephen Joseph; Kummerow, Christian; Elsaesser, Gregory

2013-01-01

Variability in the raindrop sized distribution (DSD) has long been recognized as a source of uncertainty in relationships between radar reflectivity Z and rain rate R. In this study, we analyze DSD retrievals from two years of data gathered by the Tropical Rainfall Measuring Mission (TRMM) satellite and processed with a combined radar-radiometer retrieval algorithm over the global oceans equatorward of 35?. Numerous variables describing properties of each reflectivity profile, large-scale organization, and the background environment are examined for relationships to the reflectivity-normalized median drop diameter, epsilonDSD. In general, we find that higher freezing levels and relative humidities are associated with smaller epsilonDSD. Within a given environment, the mesoscale organization of precipitation and the vertical profile of reflectivity are associated with DSD characteristics. In the tropics, the smallest epsilonDSD values are found in large but shallow convective systems, where warm rain formation processes are thought to be predominant, whereas larger sizes are found in the stratiform regions of organized deep convection. In the extratropics, the largest epsilonDSD values are found in the scattered convection that occurs when cold, dry continental air moves over the much warmer ocean after the passage of a cold front. The geographical distribution of the retrieved DSDs is consistent with many of the observed regional Z-R relationships found in the literature as well as discrepancies between the TRMM radar-only and radiometer-only precipitation products. In particular, mid-latitude and tropical regions near land tend to have larger drops for a given reflectivity, whereas the smallest drops are found in the eastern Pacific Intertropical Convergence Zone.

Cold cratonic roots and thermal blankets: How continents affect mantle convection

USGS Publications Warehouse

Trubitsyn, V.P.; Mooney, W.D.; Abbott, D.H.

2003-01-01

Two-dimensional convection models with moving continents show that continents profoundly affect the pattern of mantle convection. If the continents are wider than the wavelength of the convection cells (???3000 km, the thickness of the mantle), they cause neighboring deep mantle thermal upwellings to coalesce into a single focused upwelling. This focused upwelling zone will have a potential temperature anomaly of about 200??C, much higher than the 100??C temperature anomaly of upwelling zones generated beneath typical oceanic lithosphere. Extensive high-temperature melts (including flood basalts and late potassic granites) will be produced, and the excess temperature anomaly will induce continental uplift (as revealed in sea level changes) and the eventual breakup of the supercontinent. The mantle thermal anomaly will persist for several hundred million years after such a breakup. In contrast, small continental blocks (<1000 km diameter) do not induce focused mantle upwelling zones. Instead, small continental blocks are dragged to mantle downwelling zones, where they spend most of their time, and will migrate laterally with the downwelling. As a result of sitting over relatively cold mantle (downwellings), small continental blocks are favored to keep their cratonic roots. This may explain the long-term survival of small cratonic blocks (e.g., the Yilgarn and Pilbara cratons of western Australia, and the West African craton). The optimum size for long-term stability of a continental block is <3000 km. These results show that continents profoundly affect the pattern of mantle convection. These effects are illustrated in terms of the timing and history of supercontinent breakup, the production of high-temperature melts, and sea level changes. Such two-dimensional calculations can be further refined and tested by three-dimensional numerical simulations of mantle convection with moving continental and oceanic plates.

Relative risk assessment of cruise ships biosolids disposal alternatives.

PubMed

Avellaneda, Pedro M; Englehardt, James D; Olascoaga, Josefina; Babcock, Elizabeth A; Brand, Larry; Lirman, Diego; Rogge, Wolfgang F; Solo-Gabriele, Helena; Tchobanoglous, George

2011-10-01

A relative risk assessment of biosolids disposal alternatives for cruise ships is presented in this paper. The area of study encompasses islands and marine waters of the Caribbean Sea. The objective was to evaluate relative human health and ecological risks of (a) dewatering/incineration, (b) landing the solids for disposal, considering that in some countries land-disposed solids might be discharged in the near-shore environment untreated, and (c) deep ocean disposal. Input to the Bayesian assessment consisted of professional judgment based on available literature and modeling information, data on constituent concentrations in cruise ship biosolids, and simulations of constituent concentrations in Caribbean waters assuming ocean disposal. Results indicate that human health and ecological risks associated with land disposal and shallow ocean disposal are higher than those of the deep ocean disposal and incineration. For incineration, predicted ecological impacts were lower relative to deep ocean disposal before considering potential impacts of carbon emissions. Copyright © 2011 Elsevier Ltd. All rights reserved.

Major hydrogeochemical processes in the two reservoirs of the Yangbajing geothermal field, Tibet, China

NASA Astrophysics Data System (ADS)

Guo, Qinghai; Wang, Yanxin; Liu, Wei

2007-10-01

The Yangbajing geothermal field with the highest reservoir temperature in China is located about 90 km northwest to Lhasa City, capital of Tibet, where high temperature geothermal fluids occur both in shallow and deep reservoirs. The geophysical survey by the INDEPTH (International Deep Profiling of Tibet and the Himalayas) project group proved the existence of magmatic heat source at Yangbajing. In the study area, the hydrochemistry of cold surface waters and groundwaters and that of thermal groundwaters from both reservoirs are distinctively different. However, analysis of the relationship between enthalpy values and Cl concentrations of cold groundwaters and geothermal fluids indicates that the geothermal fluids from the shallow reservoir were formed as a result of mixing of cold groundwaters with geothermal fluids from the deep reservoir. In other words, the geothermal fluids from the deep reservoir flowed upwards into the shallow reservoir where it was diluted by the shallow cold groundwaters to form the shallow geothermal fluids with much lower temperature. A binary mixing model with two endmembers (the cold groundwaters and the deep geothermal fluids) was proposed and the mixing ratios for the geothermal fluid from each shallow well were estimated. Using the mixing ratios, the concentrations of some constituents in shallow geothermal fluids, such as As, B, SiO 2, SO 42- and F, were calculated and their differences with the actual concentrations were estimated. The results show that the differences between estimated and actual concentrations of As and B are small (the average absolute values being only 1.9% and 7.9%, respectively), whereas those of SiO 2, SO 42- and F are much bigger, indicating that other hydrogeochemical processes are responsible for the concentrations of these constituents. It is postulated that SiO 2 precipitation due to water temperature decrease, H 2S oxidation and ion exchange between OH - in geothermal waters and exchangeable F - in fluoride bearing silicate minerals during the geothermal fluid upflow might be the causes for the observed concentration differences.

Deepwater Program: Lophelia II, continuing ecological research on deep-sea corals and deep-reef habitats in the Gulf of Mexico

USGS Publications Warehouse

Demopoulos, Amanda W.J.; Ross, Steve W.; Kellogg, Christina A.; Morrison, Cheryl L.; Nizinski, Martha S.; Prouty, Nancy G.; Bourque, Jill R.; Galkiewicz, Julie P.; Gray, Michael A.; Springmann, Marcus J.; Coykendall, D. Katharine; Miller, Andrew; Rhode, Mike; Quattrini, Andrea; Ames, Cheryl L.; Brooke, Sandra D.; McClain Counts, Jennifer; Roark, E. Brendan; Buster, Noreen A.; Phillips, Ryan M.; Frometa, Janessy

2017-12-11

The deep sea is a rich environment composed of diverse habitat types. While deep-sea coral habitats have been discovered within each ocean basin, knowledge about the ecology of these habitats and associated inhabitants continues to grow. This report presents information and results from the Lophelia II project that examined deep-sea coral habitats in the Gulf of Mexico. The Lophelia II project focused on Lophelia pertusa habitats along the continental slope, at depths ranging from 300 to 1,000 meters. The chapters are authored by several scientists from the U.S. Geological Survey, National Oceanic and Atmospheric Administration, University of North Carolina Wilmington, and Florida State University who examined the community ecology (from microbes to fishes), deep-sea coral age, growth, and reproduction, and population connectivity of deep-sea corals and inhabitants. Data from these studies are presented in the chapters and appendixes of the report as well as in journal publications. This study was conducted by the Ecosystems Mission Area of the U.S. Geological Survey to meet information needs identified by the Bureau of Ocean Energy Management.

SEASAT economic assessment. Volume 4: Ocean mining case study and generalization. [economic benefits of SEASAT satellites for mineral exploration

NASA Technical Reports Server (NTRS)

1975-01-01

The results of a study of the weather sensitive features of near shore and deep water ocean mining industries are described. Problems with the evaluation of economic benefits for the deep water ocean mining industry are attributed to the relative immaturity and highly proprietary nature of the industry. Case studies on the gold industry, diamond industry, tin industry and sand and gravel industry are cited.

Constraints on ocean circulation at the Paleocene-Eocene Thermal Maximum from neodymium isotopes

NASA Astrophysics Data System (ADS)

Abbott, April N.; Haley, Brian A.; Tripati, Aradhna K.; Frank, Martin

2016-04-01

Global warming during the Paleocene-Eocene Thermal Maximum (PETM) ˜ 55 million years ago (Ma) coincided with a massive release of carbon to the ocean-atmosphere system, as indicated by carbon isotopic data. Previous studies have argued for a role of changing ocean circulation, possibly as a trigger or response to climatic changes. We use neodymium (Nd) isotopic data to reconstruct short high-resolution records of deep-water circulation across the PETM. These records are derived by reductively leaching sediments from seven globally distributed sites to reconstruct past deep-ocean circulation across the PETM. The Nd data for the leachates are interpreted to be consistent with previous studies that have used fish teeth Nd isotopes and benthic foraminiferal δ13C to constrain regions of convection. There is some evidence from combining Nd isotope and δ13C records that the three major ocean basins may not have had substantial exchanges of deep waters. If the isotopic data are interpreted within this framework, then the observed pattern may be explained if the strength of overturning in each basin varied distinctly over the PETM, resulting in differences in deep-water aging gradients between basins. Results are consistent with published interpretations from proxy data and model simulations that suggest modulation of overturning circulation had an important role for initiation and recovery of the ocean-atmosphere system associated with the PETM.

DeepSurveyCam--A Deep Ocean Optical Mapping System.

PubMed

Kwasnitschka, Tom; Köser, Kevin; Sticklus, Jan; Rothenbeck, Marcel; Weiß, Tim; Wenzlaff, Emanuel; Schoening, Timm; Triebe, Lars; Steinführer, Anja; Devey, Colin; Greinert, Jens

2016-01-28

Underwater photogrammetry and in particular systematic visual surveys of the deep sea are by far less developed than similar techniques on land or in space. The main challenges are the rough conditions with extremely high pressure, the accessibility of target areas (container and ship deployment of robust sensors, then diving for hours to the ocean floor), and the limitations of localization technologies (no GPS). The absence of natural light complicates energy budget considerations for deep diving flash-equipped drones. Refraction effects influence geometric image formation considerations with respect to field of view and focus, while attenuation and scattering degrade the radiometric image quality and limit the effective visibility. As an improvement on the stated issues, we present an AUV-based optical system intended for autonomous visual mapping of large areas of the seafloor (square kilometers) in up to 6000 m water depth. We compare it to existing systems and discuss tradeoffs such as resolution vs. mapped area and show results from a recent deployment with 90,000 mapped square meters of deep ocean floor.

Novel microbial assemblages inhabiting crustal fluids within mid-ocean ridge flank subsurface basalt

PubMed Central

Jungbluth, Sean P; Bowers, Robert M; Lin, Huei-Ting; Cowen, James P; Rappé, Michael S

2016-01-01

Although little is known regarding microbial life within our planet's rock-hosted deep subseafloor biosphere, boreholes drilled through deep ocean sediment and into the underlying basaltic crust provide invaluable windows of access that have been used previously to document the presence of microorganisms within fluids percolating through the deep ocean crust. In this study, the analysis of 1.7 million small subunit ribosomal RNA genes amplified and sequenced from marine sediment, bottom seawater and basalt-hosted deep subseafloor fluids that span multiple years and locations on the Juan de Fuca Ridge flank was used to quantitatively delineate a subseafloor microbiome comprised of distinct bacteria and archaea. Hot, anoxic crustal fluids tapped by newly installed seafloor sampling observatories at boreholes U1362A and U1362B contained abundant bacterial lineages of phylogenetically unique Nitrospirae, Aminicenantes, Calescamantes and Chloroflexi. Although less abundant, the domain Archaea was dominated by unique, uncultivated lineages of marine benthic group E, the Terrestrial Hot Spring Crenarchaeotic Group, the Bathyarchaeota and relatives of cultivated, sulfate-reducing Archaeoglobi. Consistent with recent geochemical measurements and bioenergetic predictions, the potential importance of methane cycling and sulfate reduction were imprinted within the basalt-hosted deep subseafloor crustal fluid microbial community. This unique window of access to the deep ocean subsurface basement reveals a microbial landscape that exhibits previously undetected spatial heterogeneity. PMID:26872042

A Survey of Precipitation-Induced Atmospheric Cold Pools over Oceans and Their Interactions with the Larger-Scale Environment

NASA Astrophysics Data System (ADS)

Zuidema, Paquita; Torri, Giuseppe; Muller, Caroline; Chandra, Arunchandra

2017-11-01

Pools of air cooled by partial rain evaporation span up to several hundreds of kilometers in nature and typically last less than 1 day, ultimately losing their identity to the large-scale flow. These fundamentally differ in character from the radiatively-driven dry pools defining convective aggregation. Advancement in remote sensing and in computer capabilities has promoted exploration of how precipitation-induced cold pool processes modify the convective spectrum and life cycle. This contribution surveys current understanding of such cold pools over the tropical and subtropical oceans. In shallow convection with low rain rates, the cold pools moisten, preserving the near-surface equivalent potential temperature or increasing it if the surface moisture fluxes cannot ventilate beyond the new surface layer; both conditions indicate downdraft origin air from within the boundary layer. When rain rates exceed ˜ 2 mm h^{-1}, convective-scale downdrafts can bring down drier air of lower equivalent potential temperature from above the boundary layer. The resulting density currents facilitate the lifting of locally thermodynamically favorable air and can impose an arc-shaped mesoscale cloud organization. This organization allows clouds capable of reaching 4-5 km within otherwise dry environments. These are more commonly observed in the northern hemisphere trade wind regime, where the flow to the intertropical convergence zone is unimpeded by the equator. Their near-surface air properties share much with those shown from cold pools sampled in the equatorial Indian Ocean. Cold pools are most effective at influencing the mesoscale organization when the atmosphere is moist in the lower free troposphere and dry above, suggesting an optimal range of water vapor paths. Outstanding questions on the relationship between cold pools, their accompanying moisture distribution and cloud cover are detailed further. Near-surface water vapor rings are documented in one model inside but near the cold pool edge; these are not consistent with observations, but do improve with smaller horizontal grid spacings.

A Survey of Precipitation-Induced Atmospheric Cold Pools over Oceans and Their Interactions with the Larger-Scale Environment

NASA Astrophysics Data System (ADS)

Zuidema, Paquita; Torri, Giuseppe; Muller, Caroline; Chandra, Arunchandra

Pools of air cooled by partial rain evaporation span up to several hundreds of kilometers in nature and typically last less than 1 day, ultimately losing their identity to the large-scale flow. These fundamentally differ in character from the radiatively-driven dry pools defining convective aggregation. Advancement in remote sensing and in computer capabilities has promoted exploration of how precipitation-induced cold pool processes modify the convective spectrum and life cycle. This contribution surveys current understanding of such cold pools over the tropical and subtropical oceans. In shallow convection with low rain rates, the cold pools moisten, preserving the near-surface equivalent potential temperature or increasing it if the surface moisture fluxes cannot ventilate beyond the new surface layer; both conditions indicate downdraft origin air from within the boundary layer. When rain rates exceed 2 mm h-1, convective-scale downdrafts can bring down drier air of lower equivalent potential temperature from above the boundary layer. The resulting density currents facilitate the lifting of locally thermodynamically favorable air and can impose an arc-shaped mesoscale cloud organization. This organization allows clouds capable of reaching 4-5 km within otherwise dry environments. These are more commonly observed in the northern hemisphere trade wind regime, where the flow to the intertropical convergence zone is unimpeded by the equator. Their near-surface air properties share much with those shown from cold pools sampled in the equatorial Indian Ocean. Cold pools are most effective at influencing the mesoscale organization when the atmosphere is moist in the lower free troposphere and dry above, suggesting an optimal range of water vapor paths. Outstanding questions on the relationship between cold pools, their accompanying moisture distribution and cloud cover are detailed further. Near-surface water vapor rings are documented in one model inside but near the cold pool edge; these are not consistent with observations, but do improve with smaller horizontal grid spacings.

Emergence of the continents

NASA Technical Reports Server (NTRS)

Frey, H.

1978-01-01

If early degassing of the Earth produced a global ocean several km deep overlying a global sialic crust, then late heavy bombardment of that crust by basin forming impacting bodies would have produced topography such that by 4 billion years ago dry continential landmasses would stand above sea level. From extrapolation of lunar crater statistics, at least 50% of an original global crust on the earth would have been converted into basins averaging 4 km deep after isostatic adjustment. These basins formed the sink into which such a global ocean would drain. If the ocean was initially 2 km deep, then approximately 50% of the early Earth would have stood above sea level when the late heavy bombardment came to a close.

Deep Convective Cloud Top Heights and Their Thermodynamic Control During CRYSTAL-FACE

NASA Technical Reports Server (NTRS)

Sherwood, Steven C.; Minnis, Patrick; McGill, Matthew

2004-01-01

Infrared (11 micron) radiances from GOES-8 and local radiosonde profiles, collected during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) in July 2002, are used to assess the vertical distribution of Florida-area deep convective cloud top height and test predictions as to its variation based on parcel theory. The highest infrared tops (Z(sub 11)) reached approximately to the cold point, though there is at least a 1-km uncertainty due to unknown cloud-environment temperature differences. Since lidar shows that visible 'tops' are 1 km or more above Z(sub 11), visible cloud tops frequently penetrated the lapse-rate tropopause (approx. 15 km). Further, since lofted ice content may be present up to approx. 1 km above the visible tops, lofting of moisture through the mean cold point (15.4 km) was probably common. Morning clouds, and those near Key West, rarely penetrated the tropopause. Non-entraining parcel theory (i.e., CAPE) does not successfully explain either of these results, but can explain some of the day-to-day variations in cloud top height over the peninsula. Further, moisture variations above the boundary layer account for most of the day-today variability not explained by CAPE, especially over the oceans. In all locations, a 20% increase in mean mixing ratio between 750 and 500 hPa was associated with about 1 km deeper maximum cloud penetration relative to the neutral level. These results suggest that parcel theory may be useful for predicting changes in cumulus cloud height over time, but that parcel entrainment must be taken into account even for the tallest clouds. Accordingly, relative humidity above the boundary layer may exert some control on the height of the tropical troposphere.

Seismic and Thermal Structure of the Arctic Lithosphere, From Waveform Tomography and Thermodynamic Modelling

NASA Astrophysics Data System (ADS)

Lebedev, S.; Schaeffer, A. J.; Fullea, J.; Pease, V.

2015-12-01

Thermal structure of the lithosphere is reflected in the values of seismic velocities within it. Our new tomographic models of the crust and upper mantle of the Arctic are constrained by an unprecedentedly large global waveform dataset and provide substantially improved resolution, compared to previous models. The new tomography reveals lateral variations in the temperature and thickness of the lithosphere and defines deep boundaries between tectonic blocks with different lithospheric properties and age. The shape and evolution of the geotherm beneath a tectonic unit depends on both crustal and mantle-lithosphere structure beneath it: the lithospheric thickness and its changes with time (these determine the supply of heat from the deep Earth), the crustal thickness and heat production (the supply of heat from within the crust), and the thickness and thermal conductivity of the sedimentary cover (the insulation). Detailed thermal structure of the basins can be modelled by combining seismic velocities from tomography with data on the crustal structure and heat production, in the framework of computational petrological modelling. The most prominent lateral contrasts across the Arctic are between the cold, thick lithospheres of the cratons (in North America, Greenland and Eurasia) and the warmer, non-cratonic blocks. The lithosphere of the Canada Basin is cold and thick, similar to old oceanic lithosphere elsewhere around the world; its thermal structure offers evidence on its lithospheric age and formation mechanism. At 150-250 km depth, the central Arctic region shows a moderate low-velocity anomaly, cooler than that beneath Iceland and N Atlantic. An extension of N Atlantic low-velocity anomaly into the Arctic through the Fram Strait may indicate an influx of N Atlantic asthenosphere under the currently opening Eurasia Basin.

46 CFR 180.200 - Survival craft-general.

Code of Federal Regulations, 2014 CFR

2014-10-01

... in Table 180.200(c). Table 180.200(c) Route Survival craft requirements Oceans (a) cold water 1—100...(b). Coastwise (a) wood vsls in cold water. (i) 67% IBA—§ 180.204(a)(1). (ii) w/subdivision—100% LF... 20 miles from a harbor of safe refuge) (a) wood vsls in cold water.(i) 67% IBA—§ 180.205(a)(1). (ii...

IOCCG Report Number 16, 2015 Ocean Colour Remote Sensing in Polar Seas . Chapter 2; The Polar Environment: Sun, Clouds, and Ice

NASA Technical Reports Server (NTRS)

Comiso, Josefino C.; Perovich, Don; Stamnes, Knut; Stuart, Venetia (Editor)

2015-01-01

The polar regions are places of extremes. There are months when the regions are enveloped in unending darkness, and months when they are in continuous daylight. During the daylight months the sun is low on the horizon and often obscured by clouds. In the dark winter months temperatures are brutally cold, and high winds and blowing snow are common. Even in summer, temperatures seldom rise above 0degC. The cold winter temperatures cause the ocean to freeze, forming sea ice. This sea ice cover acts as a barrier limiting the transfer of heat, moisture, and momentum between the atmosphere and the ocean. It also greatly complicates the optical signature of the surface. Taken together, these factors make the polar regions a highly challenging environment for optical remote sensing of the ocean.

Thermodynamic Controls on Deep Convection in the Tropics: Observations and Applications to Modeling

NASA Astrophysics Data System (ADS)

Schiro, Kathleen Anne

Constraining precipitation processes in climate models with observations is crucial to accurately simulating current climate and reducing uncertainties in future projections. This work presents robust relationships between tropical deep convection, column-integrated water vapor (CWV), and other thermodynamic quantities analyzed with data from the DOE Atmospheric Radiation Measurement (ARM) Mobile Facility in Manacapuru, Brazil as part of the GOAmazon campaign and are directly compared to such relationships at DOE ARM sites in the tropical western Pacific. A robust relationship between CWV and precipitation, as explained by variability in lower tropospheric humidity, exists just as strongly in a tropical continental region as it does in a tropical oceanic region. Given sufficient mixing in the lower troposphere, higher CWV generally results in greater plume buoyancies through a deep convective layer. Although sensitivity of convection to other controls is suggested, such as microphysical processes and dynamical lifting mechanisms, the increase in buoyancy with CWV is consistent with the sharp increase in precipitation observed. Entraining plume buoyancy calculations confirm that CWV is a good proxy for the conditional instability of the environment, yet differences in convective onset as a function of CWV exist over land and ocean, as well as seasonally and diurnally over land. This is largely due to variability in the contribution of lower tropospheric humidity to the total column moisture. Over land, the relationship between deep convection and lower free tropospheric moisture is robust across all seasons and times of day, whereas the relation to boundary layer moisture is robust for the daytime only. Using S-Band radar, these transition statistics are examined separately for unorganized and mesoscale-organized convection, which exhibit sharp increases in probability of occurrence with increasing moisture throughout the column, particularly in the lower free troposphere. An observational basis for an integrated buoyancy measure from a single plume buoyancy formulation that provides a strong relation to precipitation can be useful for constraining convective parameterizations. A mixing scheme corresponding to deep inflow of environmental air into a plume that grows with height provides a weighting of boundary layer and free tropospheric air that yields buoyancies consistent with the observed onset of deep convection across seasons and times of day, across land and ocean sites, and for all convection types. This provides a substantial improvement relative to more traditional constant mixing assumptions, and a dramatic improvement relative to no mixing. Furthermore, it provides relationships that are as strong or stronger for mesoscale-organized convection as for unorganized convection. Downdrafts and their associated parameters are poorly constrained in models, as physical and microphysical processes of leading order importance are difficult to observe with sufficient frequency for development of robust statistics. Downdrafts and cold pool characteristics for mesoscale convective systems (MCSs) and isolated, unorganized deep precipitating convection in the Amazon are composited and both exhibit similar signatures in wind speed, surface fluxes, surface equivalent potential temperature (theta e) and precipitation. For both MCSs and unorganized convection, downdrafts associated with the strongest modifications to surface thermodynamics have increasing probability of occurrence with decreasing height through the lowest 4 km and show similar mean downdraft magnitudes with height. If theta e is approximately conserved following descent, a large fraction of the air reaching the surface likely originates at altitudes in the lowest 2 km. Mixing computations suggest that, on average, air originating at heights greater than 3 km would require substantial mixing, particularly in the case of isolated cells, to match the observed cold pool thetae . Statistics from two years of surface meteorological data at the GOAmazon site and 15 years of data at the DOE ARM site on Manus Island in the tropical western Pacific show that Deltathetae conditioned on precipitation levels off with increasing precipitation rate, bounded by the maximum difference between surface thetae and its minimum in the profile aloft. Robustness of these statistics observed across scales and regions suggests their potential use as model diagnostic tools for the improvement of downdraft parameterizations in climate models.

North Atlantic variability and its links to European climate over the last 3000 years.

PubMed

Moffa-Sánchez, Paola; Hall, Ian R

2017-11-23

The subpolar North Atlantic is a key location for the Earth's climate system. In the Labrador Sea, intense winter air-sea heat exchange drives the formation of deep waters and the surface circulation of warm waters around the subpolar gyre. This process therefore has the ability to modulate the oceanic northward heat transport. Recent studies reveal decadal variability in the formation of Labrador Sea Water. Yet, crucially, its longer-term history and links with European climate remain limited. Here we present new decadally resolved marine proxy reconstructions, which suggest weakened Labrador Sea Water formation and gyre strength with similar timing to the centennial cold periods recorded in terrestrial climate archives and historical records over the last 3000 years. These new data support that subpolar North Atlantic circulation changes, likely forced by increased southward flow of Arctic waters, contributed to modulating the climate of Europe with important societal impacts as revealed in European history.

The biogeochemistry of anchialine caves: Progress and possibilities

USGS Publications Warehouse

Pohlman, John W.

2011-01-01

Recent investigations of anchialine caves and sinkholes have identified complex food webs dependent on detrital and, in some cases, chemosynthetically produced organic matter. Chemosynthetic microbes in anchialine systems obtain energy from reduced compounds produced during organic matter degradation (e.g., sulfide, ammonium, and methane), similar to what occurs in deep ocean cold seeps and mud volcanoes, but distinct from dominant processes operating at hydrothermal vents and sulfurous mineral caves where the primary energy source is mantle derived. This review includes case studies from both anchialine and non-anchialine habitats, where evidence for in situ chemosynthetic production of organic matter and its subsequent transfer to higher trophic level metazoans is documented. The energy sources and pathways identified are synthesized to develop conceptual models for elemental cycles and energy cascades that occur within oligotrophic and eutrophic anchialine caves. Strategies and techniques for testing the hypothesis of chemosynthesis as an active process in anchialine caves are also suggested.

Habituation of the metabolic and ventilatory responses to cold-water immersion in humans.

PubMed

Tipton, Michael J; Wakabayashi, Hitoshi; Barwood, Martin J; Eglin, Clare M; Mekjavic, Igor B; Taylor, Nigel A S

2013-01-01

An experiment was undertaken to answer long-standing questions concerning the nature of metabolic habituation in repeatedly cooled humans. It was hypothesised that repeated skin and deep-body cooling would produce such a habituation that would be specific to the magnitude of the cooling experienced, and that skin cooling alone would dampen the cold-shock but not the metabolic response to cold-water immersion. Twenty-one male participants were divided into three groups, each of which completed two experimental immersions in 12°C water, lasting until either rectal temperature fell to 35°C or 90min had elapsed. Between these two immersions, the control group avoided cold exposures, whilst two experimental groups completed five additional immersions (12°C). One experimental group repeatedly immersed for 45min in average, resulting in deep-body (1.18°C) and skin temperature reductions. The immersions in the second experimental group were designed to result only in skin temperature reductions, and lasted only 5min. Only the deep-body cooling group displayed a significantly blunted metabolic response during the second experimental immersion until rectal temperature decreased by 1.18°C, but no habituation was observed when they were cooled further. The skin cooling group showed a significant habituation in the ventilatory response during the initial 5min of the second experimental immersion, but no alteration in the metabolic response. It is concluded that repeated falls of skin and deep-body temperature can habituate the metabolic response, which shows tissue temperature specificity. However, skin temperature cooling only will lower the cold-shock response, but appears not to elicit an alteration in the metabolic response. Copyright © 2012 Elsevier Ltd. All rights reserved.

Biogeochemistry and geomicrobiology of cold-water coral carbonate mounds - lessons learned from IODP Expedition 307

NASA Astrophysics Data System (ADS)

Ferdelman, Timothy; Wehrmann, Laura; Mangelsdorf, Kai; Kano, Akihiro; Williams, Trevor; Jean-Pierre, Henriet

2010-05-01

Large mound structures associated with cold-water coral ecosystems commonly occur on the slopes of continental margins, for instance, west of Ireland in the Porcupine Seabight, the Gulf of Cadiz or the Straits of Florida. In the Porcupine Seabight over 1500 mounds of up to 5 km in diameter and 250 m height lie at water depths of 600 to 900 m. The cold-water coral reef ecosystems associated with these structures are considered to be "hotspots" of organic carbon mineralization and microbial systems. To establish a depositional and biogeochemical/diagenetic model for cold-water carbonate mounds, Challenger Mound and adjacent continental slope sites were drilled in May 2005 during IODP Expedition 307. One major objective was to test whether deep sub-surface hydrocarbon flow and enhanced microbial activity within the mound structure was important in producing and stabilizing these sedimentary structures. Drilling results showed that the Challenger mound succession (IODP Site U1317) is 130 to 150 meters thick, and mainly consists of floatstone and rudstone facies formed of fine sediments and cold-water branching corals. Pronounced recurring cycles on the scales of several meters are recognized in carbonate content (up to 70% carbonate) and color reflectance, and are probably associated with Pleistocene glacial-interglacial cycles. A role for methane seepage and subsequent anaerobic oxidation was discounted both as a hard-round substrate for mound initiation and as a principal source of carbonate within the mound succession. A broad sulfate-methane transition (approximately 50 m thick)within the Miocene sediments suggested that the zone of anaerobic oxidation of methane principally occurs below the moundbase. In the mound sediments, interstitial water profiles of sulfate, alkalinity, Mg, and Sr suggested a tight coupling between carbonate diagenesis and low rates of microbial sulfate reduction. Overall organic carbon mineralization within cold-water coral mound appeared to be dominated by low rates of iron- and sulfate-reduction that occur in discrete layers within the mound. This was consistent with distributions of total cell-counts, acetate turnover (Webster et al. 2009) and hydrogenase activity (Soffiento et al. 2009). However, biomarker lipid distributions suggested that the Miocene sediments underlying the mound, into which sulfate is diffusing, as well as the sediments from the non-cold water coral reference site (U1318) contain higher abundances of living microbes. The results obtained from Expedition 307 are consistent with a picture emerging from other biogeochemical studies of cold-water coral mound and reef sites. Unless impacted by some external forcing (e.g. fluid flow or erosion event), the microbial activity in the underlying cold-water coral mound sediments is largely decoupled from the highly diverse, active surface ecosystem. References: Soffiento B, Spivack AJ, Smith DC, and D'Hondt S (2009) Hydrogenase activity in deeply buried sediments of the Arctic and North Atlantic Oceans. Geomicro. J. 26: 537-545. Webster, G, Blazejak A, Cragg BA, Schippers A, Sass H, Rinna J, Tang X, Mathes F, Ferdelman TG., Fry JC, Weightman AJ, and Parkes RJ. 2009. Subsurface microbiology and biogeochemistry of a deep, cold-water carbonate mound from the Porcupine Seabight (IODP Expediton 307). Env. Microbiol., 11, 239-257, doi:10.1111/j.1462-2920.01759.x.

Downscaling ocean conditions with application to the Gulf of Maine, Scotian Shelf and adjacent deep ocean

NASA Astrophysics Data System (ADS)

Katavouta, Anna; Thompson, Keith R.

2016-08-01

The overall goal is to downscale ocean conditions predicted by an existing global prediction system and evaluate the results using observations from the Gulf of Maine, Scotian Shelf and adjacent deep ocean. The first step is to develop a one-way nested regional model and evaluate its predictions using observations from multiple sources including satellite-borne sensors of surface temperature and sea level, CTDs, Argo floats and moored current meters. It is shown that the regional model predicts more realistic fields than the global system on the shelf because it has higher resolution and includes tides that are absent from the global system. However, in deep water the regional model misplaces deep ocean eddies and meanders associated with the Gulf Stream. This is not because the regional model's dynamics are flawed but rather is the result of internally generated variability in deep water that leads to decoupling of the regional model from the global system. To overcome this problem, the next step is to spectrally nudge the regional model to the large scales (length scales > 90 km) of the global system. It is shown this leads to more realistic predictions off the shelf. Wavenumber spectra show that even though spectral nudging constrains the large scales, it does not suppress the variability on small scales; on the contrary, it favours the formation of eddies with length scales below the cutoff wavelength of the spectral nudging.