Geoengineering impact of open ocean dissolution of olivine on atmospheric CO2, surface ocean pH and marine biology

NASA Astrophysics Data System (ADS)

Köhler, Peter; Abrams, Jesse F.; Völker, Christoph; Hauck, Judith; Wolf-Gladrow, Dieter A.

2013-03-01

Ongoing global warming induced by anthropogenic emissions has opened the debate as to whether geoengineering is a ‘quick fix’ option. Here we analyse the intended and unintended effects of one specific geoengineering approach, which is enhanced weathering via the open ocean dissolution of the silicate-containing mineral olivine. This approach would not only reduce atmospheric CO2 and oppose surface ocean acidification, but would also impact on marine biology. If dissolved in the surface ocean, olivine sequesters 0.28 g carbon per g of olivine dissolved, similar to land-based enhanced weathering. Silicic acid input, a byproduct of the olivine dissolution, alters marine biology because silicate is in certain areas the limiting nutrient for diatoms. As a consequence, our model predicts a shift in phytoplankton species composition towards diatoms, altering the biological carbon pumps. Enhanced olivine dissolution, both on land and in the ocean, therefore needs to be considered as ocean fertilization. From dissolution kinetics we calculate that only olivine particles with a grain size of the order of 1 μm sink slowly enough to enable a nearly complete dissolution. The energy consumption for grinding to this small size might reduce the carbon sequestration efficiency by ˜30%.

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.

Reviews and Syntheses: Ocean acidification and its potential impacts on marine ecosystems

NASA Astrophysics Data System (ADS)

Mostofa, Khan M. G.; Liu, Cong-Qiang; Zhai, WeiDong; Minella, Marco; Vione, Davide; Gao, Kunshan; Minakata, Daisuke; Arakaki, Takemitsu; Yoshioka, Takahito; Hayakawa, Kazuhide; Konohira, Eiichi; Tanoue, Eiichiro; Akhand, Anirban; Chanda, Abhra; Wang, Baoli; Sakugawa, Hiroshi

2016-03-01

Ocean acidification, a complex phenomenon that lowers seawater pH, is the net outcome of several contributions. They include the dissolution of increasing atmospheric CO2 that adds up with dissolved inorganic carbon (dissolved CO2, H2CO3, HCO3-, and CO32-) generated upon mineralization of primary producers (PP) and dissolved organic matter (DOM). The aquatic processes leading to inorganic carbon are substantially affected by increased DOM and nutrients via terrestrial runoff, acidic rainfall, increased PP and algal blooms, nitrification, denitrification, sulfate reduction, global warming (GW), and by atmospheric CO2 itself through enhanced photosynthesis. They are consecutively associated with enhanced ocean acidification, hypoxia in acidified deeper seawater, pathogens, algal toxins, oxidative stress by reactive oxygen species, and thermal stress caused by longer stratification periods as an effect of GW. We discuss the mechanistic insights into the aforementioned processes and pH changes, with particular focus on processes taking place with different timescales (including the diurnal one) in surface and subsurface seawater. This review also discusses these collective influences to assess their potential detrimental effects to marine organisms, and of ecosystem processes and services. Our review of the effects operating in synergy with ocean acidification will provide a broad insight into the potential impact of acidification itself on biological processes. The foreseen danger to marine organisms by acidification is in fact expected to be amplified by several concurrent and interacting phenomena.

Reviews and Syntheses: Ocean acidification and its potential impacts on marine ecosystems

NASA Astrophysics Data System (ADS)

Mostofa, K. M. G.; Liu, C.-Q.; Zhai, W. D.; Minella, M.; Vione, D.; Gao, K.; Minakata, D.; Arakaki, T.; Yoshioka, T.; Hayakawa, K.; Konohira, E.; Tanoue, E.; Akhand, A.; Chanda, A.; Wang, B.; Sakugawa, H.

2015-07-01

Ocean acidification, a complex phenomenon that lowers seawater pH, is the net outcome of several contributions. They include the dissolution of increasing atmospheric CO2 that adds up with dissolved inorganic carbon (dissolved CO2, H2CO3, HCO3-, and CO32-) generated upon mineralization of primary producers (PP) and dissolved organic matter (DOM). The aquatic processes leading to inorganic carbon are substantially affected by increased DOM and nutrients via terrestrial runoff, acidic rainfall, increased PP and algal blooms, nitrification, denitrification, sulfate reduction, global warming (GW), and by atmospheric CO2 itself through enhanced photosynthesis. They are consecutively associated with enhanced ocean acidification, hypoxia in acidified deeper seawater, pathogens, algal toxins, oxidative stress by reactive oxygen species, and thermal stress caused by longer stratification periods as an effect of GW. We discuss the mechanistic insights into the aforementioned processes and pH changes, with particular focus on processes taking place with different time scales (including the diurnal one) in surface and subsurface seawater. This review also discusses these collective influences to assess their potential detrimental effects to marine organisms, and of ecosystem processes and services. Our review of the effects operating in synergy with ocean acidification will provide a broad insight into the potential impact of acidification itself on biological processes. The foreseen danger to marine organisms by acidification is in fact expected to be amplified by several concurrent and interacting phenomena.

Fluxes of dissolved methane from the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard

NASA Astrophysics Data System (ADS)

Graves, Carolyn; Steinle, Lea; Niemann, Helge; Rehder, Gregor; Fisher, Rebecca; Lowry, Dave; Connelly, Doug; James, Rachael

2015-04-01

Seepage of methane from seafloor sediments offshore Svalbard may partly be driven by destabilization of gas hydrates as a result of bottom water warming. As the world's oceans are expected to continue to warm, in particular in the Arctic, destabilization of hydrate may become an important source of methane to ocean bottom waters and potentially to the overlying atmosphere where it contributes to further warming. In order to quantify the fate of methane from seafloor seeps, we have determined the distribution of dissolved methane in the water column on the upper slope and shelf offshore western Svalbard during three research cruises with RRS James Clark Ross (JR253) in 2011 and R/V Maria S. Merian (MSM21/4) and Heincke (HE387) in 2012. Combining discrete depth profile methane concentration data and surface seawater concentrations from an equilibrator-online system with oxidation rate measurements and atmospheric methane observations allows insight into the fate of methane input from the seafloor, and evaluation of the potential contributions of other methane sources. A simple box model considering oxidation and horizontal and vertical mixing indicates that the majority of seep methane is oxidized at depth. A plume of high methane concentrations is expected to persist more than 100 km downstream of the seepage area in the rapid barotropic West Spitsbergen Current, which flows northward towards the Arctic Ocean. We calculate that the diffusive sea-air flux of methane is largest on the shallow shelf, reaching 36 μmol m-2 day-1. Over the entire western Svalbard region there is a persistent, but small, source of methane from surface seawater to the overlying atmosphere. Measurements of the atmospheric methane carbon isotope signature indicate that the seafloor seeps do not make a significant contribution to atmospheric methane in this region, which is consistent with earlier studies. Observations downstream of the seepage region are necessary to further constrain potential for transport of previously hydrate-bound methane to the atmosphere, which would require a mechanism for enhanced vertical mixing of dissolved methane from bottom waters into the surface mixed layer.

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.

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.

Implementation of methane cycling for deep-time global warming simulations with the DCESS Earth system model (version 1.2)

NASA Astrophysics Data System (ADS)

Shaffer, Gary; Fernández Villanueva, Esteban; Rondanelli, Roberto; Olaf Pepke Pedersen, Jens; Malskær Olsen, Steffen; Huber, Matthew

2017-11-01

Geological records reveal a number of ancient, large and rapid negative excursions of the carbon-13 isotope. Such excursions can only be explained by massive injections of depleted carbon to the Earth system over a short duration. These injections may have forced strong global warming events, sometimes accompanied by mass extinctions such as the Triassic-Jurassic and end-Permian extinctions 201 and 252 million years ago, respectively. In many cases, evidence points to methane as the dominant form of injected carbon, whether as thermogenic methane formed by magma intrusions through overlying carbon-rich sediment or from warming-induced dissociation of methane hydrate, a solid compound of methane and water found in ocean sediments. As a consequence of the ubiquity and importance of methane in major Earth events, Earth system models for addressing such events should include a comprehensive treatment of methane cycling but such a treatment has often been lacking. Here we implement methane cycling in the Danish Center for Earth System Science (DCESS) model, a simplified but well-tested Earth system model of intermediate complexity. We use a generic methane input function that allows variation in input type, size, timescale and ocean-atmosphere partition. To be able to treat such massive inputs more correctly, we extend the model to deal with ocean suboxic/anoxic conditions and with radiative forcing and methane lifetimes appropriate for high atmospheric methane concentrations. With this new model version, we carried out an extensive set of simulations for methane inputs of various sizes, timescales and ocean-atmosphere partitions to probe model behavior. We find that larger methane inputs over shorter timescales with more methane dissolving in the ocean lead to ever-increasing ocean anoxia with consequences for ocean life and global carbon cycling. Greater methane input directly to the atmosphere leads to more warming and, for example, greater carbon dioxide release from land soils. Analysis of synthetic sediment cores from the simulations provides guidelines for the interpretation of real sediment cores spanning the warming events. With this improved DCESS model version and paleo-reconstructions, we are now better armed to gauge the amounts, types, timescales and locations of methane injections driving specific, observed deep-time, global warming events.

Canary in the coal mine: Historical oxygen decline in the Gulf of St. Lawrence due to large scale climate changes

NASA Astrophysics Data System (ADS)

Claret, M.; Galbraith, E. D.; Palter, J. B.; Gilbert, D.; Bianchi, D.; Dunne, J. P.

2016-02-01

The regional signature of anthropogenic climate change on the atmosphere and upper ocean is often difficult to discern from observational timeseries, dominated as they are by decadal climate variability. Here we argue that a long-term decline of dissolved oxygen concentrations observed in the Gulf of S. Lawrence (GoSL) is consistent with anthropogenic climate change. Oxygen concentrations in the GoSL have declined markedly since 1930 due primarily to an increase of oxygen-poor North Atlantic Central Waters relative to Labrador Current Waters (Gilbert et al. 2005). We compare these observations to a climate warming simulation using a very high-resolution global coupled ocean-atmospheric climate model. The numerical model (CM2.6), developed by the Geophysical Fluid Dynamics Laboratory, is strongly eddying and includes a biogeochemical module with dissolved oxygen. The warming scenario shows that oxygen in the GoSL decreases and it is associated to changes in western boundary currents and wind patterns in the North Atlantic. We speculate that the large-scale changes behind the simulated decrease in GoSL oxygen have also been at play in the real world over the past century, although they are difficult to resolve in noisy atmospheric data.

Sensitivity of Ocean Chemistry and Oxygen Change to the Uncertainty in Climate Change

NASA Astrophysics Data System (ADS)

Cao, L.; Wang, S.; Zheng, M.; Zhang, H.

2014-12-01

With increasing atmospheric CO2 and climate change, global ocean is undergoing substantial physical and biogeochemical changes. In particular, changes in ocean oxygen and carbonate chemistry have great implication for marine biota. There is considerable uncertainty in the projections of future climate change, and it is unclear how the uncertainty in climate change would affect the projection of ocean oxygen and carbonate chemistry. To examine the effect of climate change on ocean oxygen and carbonate chemistry, we used an Earth system model of intermediate complexity to perform simulations that are driven by atmospheric CO2 concentration pathway of RCP 8.5 with climate sensitivity varying from 0.0°C to 4.5 °C. Climate change affects carbonate chemistry and oxygen mainly through its impact on ocean temperature, ocean ventilation, and concentration of dissolved inorganic carbon and alkalinity. Our simulations show that climate change mitigates the decrease of carbonate ions at the ocean surface but has negligible effect on surface ocean pH. Averaged over the whole ocean, climate change acts to decrease oxygen concentration but mitigates the CO2-induced reduction of carbonate ion and pH. In our simulations, by year 2500, every degree increase of climate sensitivity warms the ocean by 0.8 °C and reduces ocean-mean dissolved oxygen concentration by 5.0%. Meanwhile, every degree increase of climate sensitivity buffers CO2-induced reduction in ocean-mean carbonate ion concentration and pH by 3.4% and 0.02 units, respectively. Our study demonstrates different sensitivities of ocean temperature, carbonate chemistry, and oxygen, in terms of both the sign and magnitude, to the amount of climate change, which have great implications for understanding the response of ocean biota to climate change.

Evaluating the Impact of Changes in Oceanic Dissolved Oxygen on Marine Nitrous Oxide

NASA Astrophysics Data System (ADS)

Suntharalingam, Parvadha; Buitenhuis, Erik; Schmidtko, Sunke; Andrews, Oliver; LeQuere, Corinne

2013-04-01

Emissions of the greenhouse gas nitrous-oxide (N2O) from oceanic oxygen minimum zones (OMZs) in the Equatorial Pacific and Northwest Indian Ocean are believed to provide a significant portion of the global oceanic flux to the atmosphere. Mechanisms of marine N2O production and consumption in these regions display significant sensitivity to ambient oxygen, with high yields at low oxygen levels (O2 < 50 micromol/L), and N2O depletion via denitrification in anoxic zones. These OMZ regions display large gradients in sub-surface N2O, and high rates of N2O turnover that far exceed those observed in the open ocean. Recent studies have suggested that possible expansion of oceanic OMZs in a warming climate, could lead to significant changes in N2O emissions from these zones. In this analysis we employ a global ocean biogeochemistry model (NEMO-PlankTOM), which includes representation of the marine N2O cycle, to explore the impact of changes in dissolved oxygen on the ocean-atmosphere N2O flux. We focus on the period 1960-2000, and evaluate the impact of estimated changes in ocean oxygen from two alternative sources : (a) the observationally-based upper-ocean oxygen distributions and trends of Stramma et al. [2012]; (b) simulated oxygen distributions and temporal variations from a set of CMIP5 Earth System models. We will inter-compare the oceanic N2O estimates derived from these alternative scenarios of ocean de-oxygenation. We will also discuss the implications of our results for the ability to reliably predict changes in N2O emissions under potential expansion of oceanic OMZs, particularly in view of the recently noted discrepancies between observed and modeled trends in oceanic oxygen by Stramma et al. [2012].

Mechanisms and detectability of oxygen depletion in the North Atlantic

NASA Astrophysics Data System (ADS)

Tjiputra, J. F.; Goris, N.; Lauvset, S. K.; Schwinger, J.

2016-12-01

Dissolved oxygen is a key tracer in models used to represent the tight interaction between ocean biogeochemical cycle and circulation. Future ocean warming and stratification are projected, leading to a reduced oxygen concentration. Reduction in export production, in contrast, is projected to increase subsurface concentration by lowering the oxygen consumption during organic matter remineralization. In this exercise, we use a suite of CMIP5 models to study the oxygen evolution under the RCP8.5 scenario focusing on the North Atlantic, a region of rapid and steady circulation change. Most models agree with a large reduction in the deep North Atlantic (north of 40N), whereas an increase is projected in the upper subtropical ocean region. We attribute the former to weakening of the net primary production due to stronger stratification and the latter to less air-sea oxygen flux owing to less ventilation. The models also show that interior oxygen could provide earlier indicator of climate change than surface tracers. Sustained observation of oxygen is therefore crucial to reaffirm the ongoing circulation change due to global warming.

Assessing the potential impacts of declining Arctic sea ice cover on the photochemical degradation of dissolved organic matter in the Chukchi and Beaufort Seas

NASA Astrophysics Data System (ADS)

Logvinova, Christie L.; Frey, Karen E.; Mann, Paul J.; Stubbins, Aron; Spencer, Robert G. M.

2015-11-01

A warming and shifting climate in the Arctic has led to significant declines in sea ice over the last several decades. Although these changes in sea ice cover are well documented, large uncertainties remain in how associated increases in solar radiation transmitted to the underlying ocean water column will impact heating, biological, and biogeochemical processes in the Arctic Ocean. In this study, six under-ice marine, two ice-free marine, and two ice-free terrestrially influenced water samples were irradiated using a solar simulator for 72 h (representing ~10 days of ambient sunlight) to investigate dissolved organic matter (DOM) dynamics from the Chukchi and Beaufort Seas. Solar irradiation caused chromophoric DOM (CDOM) light absorption at 254 nm to decrease by 48 to 63%. An overall loss in total DOM fluorescence intensity was also observed at the end of all experiments, and each of six components identified by parallel factor (PARAFAC) analysis was shown to be photoreactive in at least one experiment. Fluorescent DOM (FDOM) also indicated that the majority of DOM in under-ice and ice-free marine waters was likely algal-derived. Measurable changes in dissolved organic carbon (DOC) were only observed for sites influenced by riverine runoff. Losses of CDOM absorbance at shorter wavelengths suggest that the beneficial UV protection currently received by marine organisms may decline with the increased light transmittance associated with sea ice melt ponding and overall reductions of sea ice. Our FDOM analyses demonstrate that DOM irrespective of source was susceptible to photobleaching. Additionally, our findings suggest that photodegradation of CDOM in under-ice waters is not currently a significant source of carbon dioxide (CO2) (i.e., we did not observe systematic DOC loss). However, increases in primary production and terrestrial freshwater export expected under future climate change scenarios may cause an increase in CDOM quantity and shift in quality throughout Arctic Ocean surface waters. As Arctic temperatures continue to warm and summer sea ice further declines, examination of the resulting enhanced photodegradation processes and their impacts on the interplay between primary production, carbon cycling, and surface ocean heating processes will be paramount.

Simulated Hothouse Climate at the P-Tr and implications for the mass extinction (Invited)

NASA Astrophysics Data System (ADS)

Winguth, A. M.; Winguth, C.

2013-12-01

The Permian-Triassic Boundary (P-Tr, ~251.5 Ma) marks the largest mass extinction of the Phanerozoic, with a reduction of marine family diversity of 60% and an extinction of marine organisms of 90%, and is characterized by large oscillatory excursions of carbon isotopes, wide-spread anoxia and extreme sea surface temperatures, reaching over 40 C in the equatorial Tethys. Anthropogenic emissions from fossil fuel burning over the next centuries will probably lead to a transition into a hothouse world with an ice-free climate analog to that at the P-Tr. The P-Tr global warming has been linked to greenhouse emissions from the Siberian Traps and associated coal-bed intrusions and likely led to severe environmental consequences, such as a decline in the dissolved oxygen concentration and marine productivity. In order to understand these changes, the pole-to-equator heat transport and feedbacks in the climate system have been explored with climate simulations, temperature reconstructions, climate-sensitive sediments, and the distribution of biomes. The response of the ocean circulation to a perturbation of ~4,900 PgC, comparable to the total Earth's fossil fuel inventory, leads to a global temperature increase by 3-4 C and an increase in ocean stratification. The pole-to-equator gradient changes remain small, because an ice-free world already existed during the Late Permian, with an atmospheric CO2 concentration of ~4x the preindustrial value, prior to the carbon pulse. However, the climatic changes might have been amplified by feedback processes. The greenhouse-induced warming could have led to a weakening of the Hadley cell and an associated decrease in the trade winds and equatorial primary productivity. A decline of cloud condensation nuclei due to these changes would lead to reduction of the cloud optical depth, particularly in high latitudes. Results from a climate simulation with reduced optical depth suggest a polar warming of ~5-7 C and a reduction of the pole-to-equator temperature gradient by 2-4 C, an increase in ocean stratification, a decline in marine productivity, and widespread low-oxygen concentrations throughout the Late Permian/Early Triassic deep sea. The recently observed rise in present-day deep-sea temperatures, slowdown of the overturning circulation, and decline in dissolved oxygen in the North Pacific and Equatorial Pacific could be the first signs of a transition to a more stratified ocean with lower dissolved oxygen concentrations in the deep water.

Enceladus and Europa: How Does Hydrothermal Activity Begin at the Surface?

NASA Technical Reports Server (NTRS)

Matson, D. L.; Castillo-Rogez, J. C.; Johnson, T. V.; Lunine, J. I.; Davies, A. G.

2011-01-01

The question of how the surface hydrothermal activity (e.g., eruptive plumes and heat flow) is initiated can be addressed within the frame-work of our "Perrier Ocean" model. This model delivers the necessary heat and chemicals to support the heat flow and plumes observed by Cassini in Enceladus' South Polar Region. The model employs closed-loop circulation of water from a sub-surface ocean. The ocean is the main reservoir of heat and chemicals, including dissolved gases. As ocean water moves up toward the surface, pressure is re-duced and gases exsolve forming bubbles. This bub-bly mixture is less dense than the icy crust and the buoyant ocean-water mixture rises toward the surface. Near the surface, heat and chemicals, including some volatiles, are delivered to the chambers in which plumes form and also to shallow reservoirs that keep the surface ice "warm". (Plume operations, per se, are as described by Schmidt et al. and Postberg et al. and are adopted by us.) After transferring heat, the water cools, bubbles contract and dissolve, and the mixture is now relatively dense. It descends through cracks in the crust and returns to the ocean. Once the closed-loop circulation has started it is self-sustaining. Loss of water via the erupting plumes is relatively negligible compared to the amount needed to maintain the heat flow.We note that the activity described herein for the the "Perrier-Ocean" model could, a priori, apply to all small icy bodies that sheltered an interior ocean at some point in their history.

Effects of ocean acidification, warming and melting of sea ice on aragonite saturation of the Canada Basin surface water

NASA Astrophysics Data System (ADS)

Yamamoto-Kawai, M.; McLaughlin, F. A.; Carmack, E. C.

2011-02-01

In 2008, surface waters in the Canada Basin of the Arctic Ocean were found to be undersaturated with respect to aragonite. This is associated with recent extensive melting of sea ice in this region, as well as elevated sea surface temperature and atmospheric CO2 concentrations. We have estimated the relative contribution of each of these controlling factors to the calcium carbonate saturation state (Ω) from observations of dissolved inorganic carbon, total alkalinity and oxygen isotope ratio. Results indicate that the increase in atmospheric CO2 has lowered surface Ω by ˜0.3 in the Canada Basin since the preindustrial period. Recent melting of sea ice has further lowered mean Ω by 0.4, and of this, half was due to dilution of surface water and half was due to the change in air-sea disequilibrium state. Surface water warming has generally counteracted the mean decrease in Ω by 0.1.

Exploring the reversibility of marine climate change impacts in temperature overshoot scenarios

NASA Astrophysics Data System (ADS)

Zickfeld, K.; Li, X.; Tokarska, K.; Kohfeld, K. E.

2017-12-01

Artificial carbon dioxide removal (CDR) from the atmosphere has been proposed as a measure for mitigating climate change and restoring the climate system to a `safe' state after overshoot. Previous studies have demonstrated that the changes in surface air temperature due to anthropogenic CO2 emissions can be reversed through CDR, while some oceanic properties, for example thermosteric sea level rise, show a delay in their response to CDR. This research aims to investigate the reversibility of changes in ocean conditions after implementation of CDR with a focus on ocean biogeochemical properties. To achieve this, we analyze climate model simulations based on two sets of emission scenarios. We first use RCP2.6 and its extension until year 2300 as the reference scenario and design several temperature and cumulative CO2 emissions "overshoot" scenarios based on other RCPs, which represents cases with less ambitious mitigation policies in the near term that temporarily exceed the 2 °C target adopted by the Paris Agreement. In addition, we use a set of emission scenarios with a reference scenario limiting warming to 1.5°C in the long term and two overshoot scenarios. The University of Victoria Earth System Climate Model (UVic ESCM), a climate model of intermediate complexity, is forced with these emission scenarios. We compare the response of select ocean variables (seawater temperature, pH, dissolved oxygen) in the overshoot scenarios to that in the respective reference scenario at the time the same amount of cumulative emissions is achieved. Our results suggest that the overshoot and subsequent return to a reference CO2 cumulative emissions level would leave substantial impacts on the marine environment. Although the changes in global mean sea surface variables (temperature, pH and dissolved oxygen) are largely reversible, global mean ocean temperature, dissolved oxygen and pH differ significantly from those in the reference scenario. Large ocean areas exhibit temperature increase and pH and dissolved oxygen decrease relative to the reference scenario without cumulative CO2 emissions overshoot. Furthermore, our results show that the higher the level of overshoot, the lower the reversibility of changes in the marine environment.

Acidification at the Surface in the East Sea: A Coupled Climate-carbon Cycle Model Study

NASA Astrophysics Data System (ADS)

Park, Young-Gyu; Seol, Kyung-Hee; Boo, Kyung-On; Lee, Johan; Cho, Chunho; Byun, Young-Hwa; Seo, Seongbong

2018-05-01

This modeling study investigates the impacts of increasing atmospheric CO2 concentration on acidification in the East Sea. A historical simulation for the past three decades (1980 to 2010) was performed using the Hadley Centre Global Environmental Model (version 2), a coupled climate model with atmospheric, terrestrial and ocean cycles. As the atmospheric CO2 concentration increased, acidification progressed in the surface waters of the marginal sea. The acidification was similar in magnitude to observations and models of acidification in the global ocean. However, in the global ocean, the acidification appears to be due to increased in-situ oceanic CO2 uptake, whereas local processes had stronger effects in the East Sea. pH was lowered by surface warming and by the influx of water with higher dissolved inorganic carbon (DIC) from the northwestern Pacific. Due to the enhanced advection of DIC, the partial pressure of CO2 increased faster than in the overlying air; consequently, the in-situ oceanic uptake of CO2 decreased.

Gas hydrate dissociation off Svalbard induced by isostatic rebound rather than global warming.

PubMed

Wallmann, Klaus; Riedel, M; Hong, W L; Patton, H; Hubbard, A; Pape, T; Hsu, C W; Schmidt, C; Johnson, J E; Torres, M E; Andreassen, K; Berndt, C; Bohrmann, G

2018-01-08

Methane seepage from the upper continental slopes of Western Svalbard has previously been attributed to gas hydrate dissociation induced by anthropogenic warming of ambient bottom waters. Here we show that sediment cores drilled off Prins Karls Foreland contain freshwater from dissociating hydrates. However, our modeling indicates that the observed pore water freshening began around 8 ka BP when the rate of isostatic uplift outpaced eustatic sea-level rise. The resultant local shallowing and lowering of hydrostatic pressure forced gas hydrate dissociation and dissolved chloride depletions consistent with our geochemical analysis. Hence, we propose that hydrate dissociation was triggered by postglacial isostatic rebound rather than anthropogenic warming. Furthermore, we show that methane fluxes from dissociating hydrates were considerably smaller than present methane seepage rates implying that gas hydrates were not a major source of methane to the oceans, but rather acted as a dynamic seal, regulating methane release from deep geological reservoirs.

Sensitivity of ocean acidification and oxygen to the uncertainty in climate change

NASA Astrophysics Data System (ADS)

Cao, Long; Wang, Shuangjing; Zheng, Meidi; Zhang, Han

2014-05-01

Due to increasing atmospheric CO2 concentrations and associated climate change, the global ocean is undergoing substantial physical and biogeochemical changes. Among these, changes in ocean oxygen and carbonate chemistry have great implication for marine biota. There is considerable uncertainty in the projections of future climate change, and it is unclear how the uncertainty in climate change would also affect the projection of oxygen and carbonate chemistry. To investigate this issue, we use an Earth system model of intermediate complexity to perform a set of simulations, including that which involves no radiative effect of atmospheric CO2 and those which involve CO2-induced climate change with climate sensitivity varying from 0.5 °C to 4.5 °C. Atmospheric CO2 concentration is prescribed to follow RCP 8.5 pathway and its extensions. Climate change affects carbonate chemistry and oxygen mainly through its impact on ocean temperature, ocean ventilation, and concentration of dissolved inorganic carbon and alkalinity. It is found that climate change mitigates the decrease of carbonate ions at the ocean surface but has negligible effect on surface ocean pH. Averaged over the whole ocean, climate change acts to decrease oxygen concentration but mitigates the CO2-induced reduction of carbonate ion and pH. In our simulations, by year 2500, every degree increase of climate sensitivity warms the ocean by 0.8 °C and reduces ocean-mean dissolved oxygen concentration by 5.0%. Meanwhile, every degree increase of climate sensitivity buffers CO2-induced reduction in ocean-mean carbonate ion concentration and pH by 3.4% and 0.02 units, respectively. Our study demonstrates different sensitivities of ocean temperature, carbonate chemistry, and oxygen, in terms of both the sign and magnitude to the amount of climate change, which have great implications for understanding the response of ocean biota to climate change.

Changes in Ocean Heat, Carbon Content, and Ventilation: A Review of the First Decade of GO-SHIP Global Repeat Hydrography.

PubMed

Talley, L D; Feely, R A; Sloyan, B M; Wanninkhof, R; Baringer, M O; Bullister, J L; Carlson, C A; Doney, S C; Fine, R A; Firing, E; Gruber, N; Hansell, D A; Ishii, M; Johnson, G C; Katsumata, K; Key, R M; Kramp, M; Langdon, C; Macdonald, A M; Mathis, J T; McDonagh, E L; Mecking, S; Millero, F J; Mordy, C W; Nakano, T; Sabine, C L; Smethie, W M; Swift, J H; Tanhua, T; Thurnherr, A M; Warner, M J; Zhang, J-Z

2016-01-01

Global ship-based programs, with highly accurate, full water column physical and biogeochemical observations repeated decadally since the 1970s, provide a crucial resource for documenting ocean change. The ocean, a central component of Earth's climate system, is taking up most of Earth's excess anthropogenic heat, with about 19% of this excess in the abyssal ocean beneath 2,000 m, dominated by Southern Ocean warming. The ocean also has taken up about 27% of anthropogenic carbon, resulting in acidification of the upper ocean. Increased stratification has resulted in a decline in oxygen and increase in nutrients in the Northern Hemisphere thermocline and an expansion of tropical oxygen minimum zones. Southern Hemisphere thermocline oxygen increased in the 2000s owing to stronger wind forcing and ventilation. The most recent decade of global hydrography has mapped dissolved organic carbon, a large, bioactive reservoir, for the first time and quantified its contribution to export production (∼20%) and deep-ocean oxygen utilization. Ship-based measurements also show that vertical diffusivity increases from a minimum in the thermocline to a maximum within the bottom 1,500 m, shifting our physical paradigm of the ocean's overturning circulation.

Geochemistry and Flux of Terrigenous Dissolved Organic Matter to the Arctic Ocean

NASA Astrophysics Data System (ADS)

Spencer, R. G.; Mann, P. J.; Hernes, P. J.; Tank, S. E.; Striegl, R. G.; Dyda, R. Y.; Peterson, B. J.; McClelland, J. W.; Holmes, R. M.

2011-12-01

Rivers draining into the Arctic Ocean exhibit high concentrations of terrigenous dissolved organic carbon (DOC) and recent studies indicate that DOC export is changing due to climatic warming and alteration in permafrost condition. The fate of exported DOC in the Arctic Ocean is of key importance for understanding the regional carbon cycle and remains a point of discussion in the literature. As part of the Arctic Great Rivers Observatory (Arctic-GRO) project, samples were collected for DOC, chromophoric dissolved organic matter (CDOM) and lignin phenols from the Ob', Yenisey, Lena, Kolyma, Mackenzie and Yukon rivers in 2009 - 2010. DOC and lignin concentrations were elevated during the spring freshet and measurements related to DOC composition indicated an increasing contribution from terrestrial vascular plant sources at this time of year (e.g. lignin carbon-normalized yield, CDOM spectral slope, SUVA254, humic-like fluorescence). CDOM absorption was found to correlate strongly with both DOC (r2=0.83) and lignin concentration (r2=0.92) across the major arctic rivers. Utilizing these relationships we modeled loads for DOC and lignin export from high-resolution CDOM measurements (daily across the freshet) to derive improved flux estimates, particularly from the dynamic spring discharge maxima period when the majority of DOC and lignin export occurs. The new load estimates for DOC and lignin are higher than previous evaluations, emphasizing that if these are more representative of current arctic riverine export, terrigenous DOC is transiting through the Arctic Ocean at a faster rate than previously thought. It is apparent that higher resolution sampling of arctic rivers is exceptionally valuable with respect to deriving accurate fluxes and we highlight the potential of CDOM in this role for future studies and the applicability of in-situ CDOM sensors.

Multicentury changes in ocean and land contributions to the climate-carbon feedback

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

Randerson, J. T.; Lindsay, K.; Munoz, E.

Improved constraints on carbon cycle responses to climate change are needed to inform mitigation policy, yet our understanding of how these responses may evolve after 2100 remains highly uncertain. Using the Community Earth System Model (v1.0), we quantified climate-carbon feedbacks from 1850 to 2300 for the Representative Concentration Pathway 8.5 and its extension. In three simulations, land and ocean biogeochemical processes experienced the same trajectory of increasing atmospheric CO 2. Each simulation had a different degree of radiative coupling for CO 2 and other greenhouse gases and aerosols, enabling diagnosis of feedbacks. In a fully coupled simulation, global mean surfacemore » air temperature increased by 9.3 K from 1850 to 2300, with 4.4 K of this warming occurring after 2100. Excluding CO 2, warming from other greenhouse gases and aerosols was 1.6 K by 2300, near a 2 K target needed to avoid dangerous anthropogenic interference with the climate system. Ocean contributions to the climate-carbon feedback increased considerably over time and exceeded contributions from land after 2100. The sensitivity of ocean carbon to climate change was found to be proportional to changes in ocean heat content, as a consequence of this heat modifying transport pathways for anthropogenic CO 2 inflow and solubility of dissolved inorganic carbon. By 2300, climate change reduced cumulative ocean uptake by 330 Pg C, from 1410 Pg C to 1080 Pg C. Land fluxes similarly diverged over time, with climate change reducing stocks by 232 Pg C. Regional influence of climate change on carbon stocks was largest in the North Atlantic Ocean and tropical forests of South America. Our analysis suggests that after 2100, oceans may become as important as terrestrial ecosystems in regulating the magnitude of the climate-carbon feedback.« less

Multicentury changes in ocean and land contributions to the climate-carbon feedback

NASA Astrophysics Data System (ADS)

Randerson, J. T.; Lindsay, K.; Munoz, E.; Fu, W.; Moore, J. K.; Hoffman, F. M.; Mahowald, N. M.; Doney, S. C.

2015-06-01

Improved constraints on carbon cycle responses to climate change are needed to inform mitigation policy, yet our understanding of how these responses may evolve after 2100 remains highly uncertain. Using the Community Earth System Model (v1.0), we quantified climate-carbon feedbacks from 1850 to 2300 for the Representative Concentration Pathway 8.5 and its extension. In three simulations, land and ocean biogeochemical processes experienced the same trajectory of increasing atmospheric CO2. Each simulation had a different degree of radiative coupling for CO2 and other greenhouse gases and aerosols, enabling diagnosis of feedbacks. In a fully coupled simulation, global mean surface air temperature increased by 9.3 K from 1850 to 2300, with 4.4 K of this warming occurring after 2100. Excluding CO2, warming from other greenhouse gases and aerosols was 1.6 K by 2300, near a 2 K target needed to avoid dangerous anthropogenic interference with the climate system. Ocean contributions to the climate-carbon feedback increased considerably over time and exceeded contributions from land after 2100. The sensitivity of ocean carbon to climate change was found to be proportional to changes in ocean heat content, as a consequence of this heat modifying transport pathways for anthropogenic CO2 inflow and solubility of dissolved inorganic carbon. By 2300, climate change reduced cumulative ocean uptake by 330 Pg C, from 1410 Pg C to 1080 Pg C. Land fluxes similarly diverged over time, with climate change reducing stocks by 232 Pg C. Regional influence of climate change on carbon stocks was largest in the North Atlantic Ocean and tropical forests of South America. Our analysis suggests that after 2100, oceans may become as important as terrestrial ecosystems in regulating the magnitude of the climate-carbon feedback.

The marine diatom and diazotroph under future climate: Role of Iron

NASA Astrophysics Data System (ADS)

Li, Xuefeng; Fonseca-batista, Debany; Brouwers, Julie; Roevros, Nathalie; Dehairs, Frank; Chou, Lei

2016-04-01

Diatoms constitute a major group of phytoplankton, accounting for one quarter of the world's net primary productivity. Diazotrophs provide the largest input of new nitrogen (N) to the ocean and control the marine N budgets. It has been shown that iron (Fe) can be the limiting factor for diatom growth, in particular, in the HNLC (High Nutrient Low Chlorophyll) regions. This trace element can also govern the development of marine diazotrophs due to the high Fe demand necessary for biological N2 fixation. Iron plays thus an essential role in governing the marine primary productivity and the efficiency of biological carbon pump. Ocean systems are undergoing continuous modifications at varying rates and magnitudes as a result of changing climate. The objectives of our research is to evaluate 1) how climate change (dust deposition, ocean warming and acidification) can affect Fe biogeochemistry and the growth of diatoms and diazotrophs, and 2) the role of Fe in the control of biological N2 fixation under future climate scenarios. Laboratory culture experiments using Chaetoceros socialis were examined at two temperatures (13°C and 18°C) and two CO2 conditions (400 μatm and 800 μatm). The present study demonstrates clearly the influence of ocean acidification on the release of Fe upon dust deposition. It also shows that dust particles could provide a readily utilizable source of Fe and other macronutrients (dissolved phosphate and silicate) for phytoplankton growth. Elevated pCO2 concentrations may have adverse impact on the diatom growth; seawater warming may cause poleward shifts in the biogeographic distribution of diatoms. The impact of Fe on the natural N2 fixation was tested via field incubation experiments using natureal phytoplankton assemblage in the Bay of Biscay and along the Iberian Margin. N2 fixation rates in oligotrophic waters were greatly stimulated through the addition of dissolved Fe compared to the control, demonstrating the limitation of N2 fixation by Fe. Numerous factors can affect the extent of N2 fixation, but a better understanding of the major controlling factors is highly required. Semi-continuous dilution culture experiments were conducted on Trichodesmium IMS-101 under future high pCO2 and warming seawater conditions. Additionally, special attention has been given to studying the effects of mineral dust deposition which is believed to promote N2 fixation through increasing Fe availability.

Modeling the Oxygen Cycle in the Equatorial Pacific: Regulation of Physical and Biogeochemical Processes

NASA Astrophysics Data System (ADS)

Wang, X.; Murtugudde, R. G.; Zhang, D.

2016-12-01

Photosynthesis and respiration are important processes in all ecosystems on the Earth, in which carbon and oxygen are the two main elements. However, the oxygen cycle has received much less attention (relative to the carbon cycle) despite its big role in the earth system. Oxygen is a sensitive indicator of physical and biogeochemical processes in the ocean thus a key parameter for understanding the ocean's ecosystem and biogeochemistry. The Oxygen-Minimum-Zone (OMZ), often seen below 200 m, is a profound feature in the world oceans. There has been evidence of OMZ expansion over the past few decades in the tropical oceans. Climate models project that there would be a continued decline in dissolved oxygen (DO) and an expansion of the tropical OMZs under future warming conditions, which is of great concern because of the implications for marine organisms. We employ a validated three-dimensional model that simulates physical transport (circulation and vertical mixing), biological processes (O2 production and consumption) and ocean-atmosphere O2 exchange to quantify various sources and sinks of DO over 1980-2015. We show how we use observational data to improve our model simulation. Then we assess the spatial and temporal variability in simulated DO in the tropical Pacific Ocean, and explore the impacts of physical and biogeochemical processes on the DO dynamics, with a focus on the MOZ. Our analyses indicate that DO in the OMZ has a positive relationship with the 13ºC isotherm depth and a negative relationship with the concentration of dissolved organic material.

Expanded oxygen minimum zones during the late Paleocene-early Eocene: Hints from multiproxy comparison and ocean modeling

NASA Astrophysics Data System (ADS)

Zhou, X.; Thomas, E.; Winguth, A. M. E.; Ridgwell, A.; Scher, H.; Hoogakker, B. A. A.; Rickaby, R. E. M.; Lu, Z.

2016-12-01

Anthropogenic warming could well drive depletion of oceanic oxygen in the future. Important insight into the relationship between deoxygenation and warming can be gleaned from the geological record, but evidence is limited because few ocean oxygenation records are available for past greenhouse climate conditions. We use I/Ca in benthic foraminifera to reconstruct late Paleocene through early Eocene bottom and pore water redox conditions in the South Atlantic and Southern Indian Oceans and compare our results with those derived from Mn speciation and the Ce anomaly in fish teeth. We conclude that waters with lower oxygen concentrations were widespread at intermediate depths (1.5-2 km), whereas bottom waters were more oxygenated at the deepest site, in the Southeast Atlantic Ocean (>3 km). Epifaunal benthic foraminiferal I/Ca values were higher in the late Paleocene, especially at low-oxygen sites, than at well-oxygenated modern sites, indicating higher seawater total iodine concentrations in the late Paleocene than today. The proxy-based bottom water oxygenation pattern agrees with the site-to-site O2 gradient as simulated in a comprehensive climate model (Community Climate System Model Version 3), but the simulated absolute dissolved O2 values are low (< 35 µmol/kg), while higher O2 values ( 60-100 µmol/kg) were obtained in an Earth system model (Grid ENabled Integrated Earth system model). Multiproxy data together with improvements in boundary conditions and model parameterization are necessary if the details of past oceanographic oxygenation are to be resolved.

Effects of Southern Hemispheric Wind Changes on Global Oxygen and the Pacific Oxygen Minimum Zone

NASA Astrophysics Data System (ADS)

Getzlaff, J.; Dietze, H.; Oschlies, A.

2016-02-01

We use a coupled ocean biogeochemistry-circulation model to compare the impact of changes in southern hemispheric winds with that of warming induced buoyancy fluxes on dissolved oxygen. Changes in the southern hemispheric wind fields, which are in line with an observed shift of the southern annual mode, are a combination of a strengthening and poleward shift of the southern westerlies. We differentiate between effects caused by a strengthening of the westerlies and effects of a southward shift of the westerlies that is accompanied by a poleward expansion of the tropical trade winds. Our results confirm that the Southern Ocean plays an important role for the marine oxygen supply: a strengthening of the southern westerlies, that leads to an increase of the water formation rates of the oxygen rich deep and intermediate water masses, can counteract part of the warming-induced decline in marine oxygen levels. The wind driven intensification of the Southern Ocean meridional overturning circulation drives an increase of the global oxygen supply. Furthermore the results show that the shift of the boundary between westerlies and trades results in an increase of subantarctic mode water and an anti-correlated decrease of deep water formation and reduces the oceanic oxygen supply. In addition we find that the increased meridional extension of the southern trade winds, results in a strengthening and southward shift of the subtropical wind stress curl. This alters the subtropical gyre circulation (intensification and southward shift) and with it decreases the water mass transport into the oxygen minimum zone. In a business-as-usual CO2 emission scenario, the poleward shift of the trade-to-westerlies boundary is as important for the future evolution of the suboxic volume as direct warming-induced changes.

Effects of ocean warming and acidification on survival, growth and skeletal development in the early benthic juvenile sea urchin (Heliocidaris erythrogramma).

PubMed

Wolfe, Kennedy; Dworjanyn, Symon A; Byrne, Maria

2013-09-01

Co-occurring ocean warming, acidification and reduced carbonate mineral saturation have significant impacts on marine biota, especially calcifying organisms. The effects of these stressors on development and calcification in newly metamorphosed juveniles (ca. 0.5 mm test diameter) of the intertidal sea urchin Heliocidaris erythrogramma, an ecologically important species in temperate Australia, were investigated in context with present and projected future conditions. Habitat temperature and pH/pCO2 were documented to place experiments in a biologically and ecologically relevant context. These parameters fluctuated diurnally up to 10 °C and 0.45 pH units. The juveniles were exposed to three temperature (21, 23 and 25 °C) and four pH (8.1, 7.8, 7.6 and 7.4) treatments in all combinations, representing ambient sea surface conditions (21 °C, pH 8.1; pCO2 397; ΩCa 4.7; ΩAr 3.1), near-future projected change (+2-4 °C, -0.3-0.5 pH units; pCO2 400-1820; ΩCa 5.0-1.6; ΩAr 3.3-1.1), and extreme conditions experienced at low tide (+4 °C, -0.3-0.7 pH units; pCO2 2850-2967; ΩCa 1.1-1.0; ΩAr 0.7-0.6). The lowest pH treatment (pH 7.4) was used to assess tolerance levels. Juvenile survival and test growth were resilient to current and near-future warming and acidification. Spine development, however, was negatively affected by near-future increased temperature (+2-4 °C) and extreme acidification (pH 7.4), with a complex interaction between stressors. Near-future warming was the more significant stressor. Spine tips were dissolved in the pH 7.4 treatments. Adaptation to fluctuating temperature-pH conditions in the intertidal may convey resilience to juvenile H. erythrogramma to changing ocean conditions, however, ocean warming and acidification may shift baseline intertidal temperature and pH/pCO2 to levels that exceed tolerance limits. © 2013 John Wiley & Sons Ltd.

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.

Interactive effects of temperature, food and skeletal mineralogy mediate biological responses to ocean acidification in a widely distributed bryozoan.

PubMed

Swezey, Daniel S; Bean, Jessica R; Ninokawa, Aaron T; Hill, Tessa M; Gaylord, Brian; Sanford, Eric

2017-04-26

Marine invertebrates with skeletons made of high-magnesium calcite may be especially susceptible to ocean acidification (OA) due to the elevated solubility of this form of calcium carbonate. However, skeletal composition can vary plastically within some species, and it is largely unknown how concurrent changes in multiple oceanographic parameters will interact to affect skeletal mineralogy, growth and vulnerability to future OA. We explored these interactive effects by culturing genetic clones of the bryozoan Jellyella tuberculata (formerly Membranipora tuberculata ) under factorial combinations of dissolved carbon dioxide (CO 2 ), temperature and food concentrations. High CO 2 and cold temperature induced degeneration of zooids in colonies. However, colonies still maintained high growth efficiencies under these adverse conditions, indicating a compensatory trade-off whereby colonies degenerate more zooids under stress, redirecting energy to the growth and maintenance of new zooids. Low-food concentration and elevated temperatures also had interactive effects on skeletal mineralogy, resulting in skeletal calcite with higher concentrations of magnesium, which readily dissolved under high CO 2 For taxa that weakly regulate skeletal magnesium concentration, skeletal dissolution may be a more widespread phenomenon than is currently documented and is a growing concern as oceans continue to warm and acidify. © 2017 The Author(s).

Interactive effects of temperature, food and skeletal mineralogy mediate biological responses to ocean acidification in a widely distributed bryozoan

PubMed Central

Bean, Jessica R.; Ninokawa, Aaron T.; Hill, Tessa M.; Gaylord, Brian; Sanford, Eric

2017-01-01

Marine invertebrates with skeletons made of high-magnesium calcite may be especially susceptible to ocean acidification (OA) due to the elevated solubility of this form of calcium carbonate. However, skeletal composition can vary plastically within some species, and it is largely unknown how concurrent changes in multiple oceanographic parameters will interact to affect skeletal mineralogy, growth and vulnerability to future OA. We explored these interactive effects by culturing genetic clones of the bryozoan Jellyella tuberculata (formerly Membranipora tuberculata) under factorial combinations of dissolved carbon dioxide (CO2), temperature and food concentrations. High CO2 and cold temperature induced degeneration of zooids in colonies. However, colonies still maintained high growth efficiencies under these adverse conditions, indicating a compensatory trade-off whereby colonies degenerate more zooids under stress, redirecting energy to the growth and maintenance of new zooids. Low-food concentration and elevated temperatures also had interactive effects on skeletal mineralogy, resulting in skeletal calcite with higher concentrations of magnesium, which readily dissolved under high CO2. For taxa that weakly regulate skeletal magnesium concentration, skeletal dissolution may be a more widespread phenomenon than is currently documented and is a growing concern as oceans continue to warm and acidify. PMID:28424343

AccuRT: A versatile tool for radiative transfer simulations in the coupled atmosphere-ocean system

NASA Astrophysics Data System (ADS)

Hamre, Børge; Stamnes, Snorre; Stamnes, Knut; Stamnes, Jakob

2017-02-01

Reliable, accurate, and efficient modeling of the transport of electromagnetic radiation in turbid media has important applications in the study of the Earth's climate by remote sensing. For example, such modeling is needed to develop forward-inverse methods used to quantify types and concentrations of aerosol and cloud particles in the atmosphere, the dissolved organic and particulate biogeochemical matter in lakes, rivers, coastal, and open-ocean waters. It is also needed to simulate the performance of remote sensing detectors deployed on aircraft, balloons, and satellites as well as radiometric detectors deployed on buoys, gliders and other aquatic observing systems. Accurate radiative transfer modeling is also required to compute irradiances and scalar irradiances that are used to compute warming/cooling and photolysis rates in the atmosphere and primary production and warming/cooling rates in the water column. AccuRT is a radiative transfer model for the coupled atmosphere-water system that is designed to be a versatile tool for researchers in the ocean optics and remote sensing communities. It addresses the needs of researchers interested in analyzing irradiance and radiance measurements in the field and laboratory as well as those interested in making simulations of the top-of-the-atmosphere radiance in support of remote sensing algorithm development.

High colored dissolved organic matter (CDOM) absorption in surface waters of the central-eastern Arctic Ocean: Implications for biogeochemistry and ocean color algorithms

PubMed Central

Rabe, Benjamin; Peeken, Ilka; Bracher, Astrid

2018-01-01

As consequences of global warming sea-ice shrinking, permafrost thawing and changes in fresh water and terrestrial material export have already been reported in the Arctic environment. These processes impact light penetration and primary production. To reach a better understanding of the current status and to provide accurate forecasts Arctic biogeochemical and physical parameters need to be extensively monitored. In this sense, bio-optical properties are useful to be measured due to the applicability of optical instrumentation to autonomous platforms, including satellites. This study characterizes the non-water absorbers and their coupling to hydrographic conditions in the poorly sampled surface waters of the central and eastern Arctic Ocean. Over the entire sampled area colored dissolved organic matter (CDOM) dominates the light absorption in surface waters. The distribution of CDOM, phytoplankton and non-algal particles absorption reproduces the hydrographic variability in this region of the Arctic Ocean which suggests a subdivision into five major bio-optical provinces: Laptev Sea Shelf, Laptev Sea, Central Arctic/Transpolar Drift, Beaufort Gyre and Eurasian/Nansen Basin. Evaluating ocean color algorithms commonly applied in the Arctic Ocean shows that global and regionally tuned empirical algorithms provide poor chlorophyll-a (Chl-a) estimates. The semi-analytical algorithms Generalized Inherent Optical Property model (GIOP) and Garver-Siegel-Maritorena (GSM), on the other hand, provide robust estimates of Chl-a and absorption of colored matter. Applying GSM with modifications proposed for the western Arctic Ocean produced reliable information on the absorption by colored matter, and specifically by CDOM. These findings highlight that only semi-analytical ocean color algorithms are able to identify with low uncertainty the distribution of the different optical water constituents in these high CDOM absorbing waters. In addition, a clustering of the Arctic Ocean into bio-optical provinces will help to develop and then select province-specific ocean color algorithms. PMID:29304182

High colored dissolved organic matter (CDOM) absorption in surface waters of the central-eastern Arctic Ocean: Implications for biogeochemistry and ocean color algorithms.

PubMed

Gonçalves-Araujo, Rafael; Rabe, Benjamin; Peeken, Ilka; Bracher, Astrid

2018-01-01

As consequences of global warming sea-ice shrinking, permafrost thawing and changes in fresh water and terrestrial material export have already been reported in the Arctic environment. These processes impact light penetration and primary production. To reach a better understanding of the current status and to provide accurate forecasts Arctic biogeochemical and physical parameters need to be extensively monitored. In this sense, bio-optical properties are useful to be measured due to the applicability of optical instrumentation to autonomous platforms, including satellites. This study characterizes the non-water absorbers and their coupling to hydrographic conditions in the poorly sampled surface waters of the central and eastern Arctic Ocean. Over the entire sampled area colored dissolved organic matter (CDOM) dominates the light absorption in surface waters. The distribution of CDOM, phytoplankton and non-algal particles absorption reproduces the hydrographic variability in this region of the Arctic Ocean which suggests a subdivision into five major bio-optical provinces: Laptev Sea Shelf, Laptev Sea, Central Arctic/Transpolar Drift, Beaufort Gyre and Eurasian/Nansen Basin. Evaluating ocean color algorithms commonly applied in the Arctic Ocean shows that global and regionally tuned empirical algorithms provide poor chlorophyll-a (Chl-a) estimates. The semi-analytical algorithms Generalized Inherent Optical Property model (GIOP) and Garver-Siegel-Maritorena (GSM), on the other hand, provide robust estimates of Chl-a and absorption of colored matter. Applying GSM with modifications proposed for the western Arctic Ocean produced reliable information on the absorption by colored matter, and specifically by CDOM. These findings highlight that only semi-analytical ocean color algorithms are able to identify with low uncertainty the distribution of the different optical water constituents in these high CDOM absorbing waters. In addition, a clustering of the Arctic Ocean into bio-optical provinces will help to develop and then select province-specific ocean color algorithms.

Environmental forcing of nitrogen fixation in the eastern tropical and sub-tropical North Atlantic Ocean.

PubMed

Rijkenberg, Micha J A; Langlois, Rebecca J; Mills, Matthew M; Patey, Matthew D; Hill, Polly G; Nielsdóttir, Maria C; Compton, Tanya J; Laroche, Julie; Achterberg, Eric P

2011-01-01

During the winter of 2006 we measured nifH gene abundances, dinitrogen (N(2)) fixation rates and carbon fixation rates in the eastern tropical and sub-tropical North Atlantic Ocean. The dominant diazotrophic phylotypes were filamentous cyanobacteria, which may include Trichodesmium and Katagnymene, with up to 10(6) L(-1)nifH gene copies, unicellular group A cyanobacteria with up to 10(5) L(-1)nifH gene copies and gamma A proteobacteria with up to 10(4) L(-1)nifH gene copies. N(2) fixation rates were low and ranged between 0.032-1.28 nmol N L(-1) d(-1) with a mean of 0.30 ± 0.29 nmol N L(-1) d(-1) (1σ, n = 65). CO(2)-fixation rates, representing primary production, appeared to be nitrogen limited as suggested by low dissolved inorganic nitrogen to phosphate ratios (DIN:DIP) of about 2 ± 3.2 in surface waters. Nevertheless, N(2) fixation rates contributed only 0.55 ± 0.87% (range 0.03-5.24%) of the N required for primary production. Boosted regression trees analysis (BRT) showed that the distribution of the gamma A proteobacteria and filamentous cyanobacteria nifH genes was mainly predicted by the distribution of Prochlorococcus, Synechococcus, picoeukaryotes and heterotrophic bacteria. In addition, BRT indicated that multiple a-biotic environmental variables including nutrients DIN, dissolved organic nitrogen (DON) and DIP, trace metals like dissolved aluminum (DAl), as a proxy of dust inputs, dissolved iron (DFe) and Fe-binding ligands as well as oxygen and temperature influenced N(2) fixation rates and the distribution of the dominant diazotrophic phylotypes. Our results suggest that lower predicted oxygen concentrations and higher temperatures due to climate warming may increase N(2) fixation rates. However, the balance between a decreased supply of DIP and DFe from deep waters as a result of more pronounced stratification and an enhanced supply of these nutrients with a predicted increase in deposition of Saharan dust may ultimately determine the consequences of climate warming for N(2) fixation in the North Atlantic.

Zooplankton Gut Passage Mobilizes Lithogenic Iron for Ocean Productivity.

PubMed

Schmidt, Katrin; Schlosser, Christian; Atkinson, Angus; Fielding, Sophie; Venables, Hugh J; Waluda, Claire M; Achterberg, Eric P

2016-10-10

Iron is an essential nutrient for phytoplankton, but low concentrations limit primary production and associated atmospheric carbon drawdown in large parts of the world's oceans [1, 2]. Lithogenic particles deriving from aeolian dust deposition, glacial runoff, or river discharges can form an important source if the attached iron becomes dissolved and therefore bioavailable [3-5]. Acidic digestion by zooplankton is a potential mechanism for iron mobilization [6], but evidence is lacking. Here we show that Antarctic krill sampled near glacial outlets at the island of South Georgia (Southern Ocean) ingest large amounts of lithogenic particles and contain 3-fold higher iron concentrations in their muscle than specimens from offshore, which confirms mineral dissolution in their guts. About 90% of the lithogenic and biogenic iron ingested by krill is passed into their fecal pellets, which contain ∼5-fold higher proportions of labile (reactive) iron than intact diatoms. The mobilized iron can be released in dissolved form directly from krill or via multiple pathways involving microbes, other zooplankton, and krill predators. This can deliver substantial amounts of bioavailable iron and contribute to the fertilization of coastal waters and the ocean beyond. In line with our findings, phytoplankton blooms downstream of South Georgia are more intensive and longer lasting during years with high krill abundance on-shelf. Thus, krill crop phytoplankton but boost new production via their nutrient supply. Understanding and quantifying iron mobilization by zooplankton is essential to predict ocean productivity in a warming climate where lithogenic iron inputs from deserts, glaciers, and rivers are increasing [7-10]. Copyright © 2016 Elsevier Ltd. All rights reserved.

Widespread methane seepage along the continental margin off Svalbard - from Bjørnøya to Kongsfjorden

PubMed Central

Mau, S.; Römer, M.; Torres, M. E.; Bussmann, I.; Pape, T.; Damm, E.; Geprägs, P.; Wintersteller, P.; Hsu, C.-W.; Loher, M.; Bohrmann, G.

2017-01-01

Numerous articles have recently reported on gas seepage offshore Svalbard, because the gas emission from these Arctic sediments was thought to result from gas hydrate dissociation, possibly triggered by anthropogenic ocean warming. We report on findings of a much broader seepage area, extending from 74° to 79°, where more than a thousand gas discharge sites were imaged as acoustic flares. The gas discharge occurs in water depths at and shallower than the upper edge of the gas hydrate stability zone and generates a dissolved methane plume that is hundreds of kilometer in length. Data collected in the summer of 2015 revealed that 0.02–7.7% of the dissolved methane was aerobically oxidized by microbes and a minor fraction (0.07%) was transferred to the atmosphere during periods of low wind speeds. Most flares were detected in the vicinity of the Hornsund Fracture Zone, leading us to postulate that the gas ascends along this fracture zone. The methane discharges on bathymetric highs characterized by sonic hard grounds, whereas glaciomarine and Holocene sediments in the troughs apparently limit seepage. The large scale seepage reported here is not caused by anthropogenic warming. PMID:28230189

Marine cycling of the climate relevant trace gases carbonyl sulfide (OCS) and carbon disulfide (CS2) in the Peruvian upwelling regime

NASA Astrophysics Data System (ADS)

Lennartz, Sinikka; von Hobe, Marc; Booge, Dennis; Gonçalves-Araujo, Rafael; Bracher, Astrid; Röttgers, Rüdiger; Ksionzek, Kerstin B.; Koch, Boris P.; Fischer, Tim; Bittig, Henry; Quack, Birgit; Krüger, Kirstin; Marandino, Christa A.

2017-04-01

The ocean is a major source for the climate relevant trace gases carbonyl sulfide (OCS) and carbon disulfide (CS2). While the greenhouse gas CS2 quickly oxidizes to OCS in the atmosphere, the atmospheric lifetime of OCS of 2-7 years leads to an accumulation of this gas and makes it the most abundant reduced sulfur compound in the atmosphere. OCS has a counteracting effect on the climate: in the troposphere, it acts as a greenhouse gas causing warming, whereas it also sustains the stratospheric aerosol layer, and thus increases Earth's albedo causing cooling. To better constrain the important oceanic source of these trace gases, the marine cycling needs to be well understood and quantified. For OCS, the production and consumption processes are identified, but photoproduction and light-independent production rates remain to be quantified across different regions. In contrast, the processes that influence the oceanic cycling of CS2 are less well understood. Here we present new data from a cruise to the Peruvian upwelling regime and relate measurements of OCS and CS2 to key parameters, such as dissolved organic sulfur, chromophoric and fluorescent dissolved organic matter. We use a 1D water column model to further constrain their production and degradation rates. A focus is set on the influence of oxygen on the marine cycling of these two gases in oxygen depleted zones in the ocean, which are expected to expand in the future.

Snowball Earth prevention by dissolved organic carbon remineralization.

PubMed

Peltier, W Richard; Liu, Yonggang; Crowley, John W

2007-12-06

The 'snowball Earth' hypothesis posits the occurrence of a sequence of glaciations in the Earth's history sufficiently deep that photosynthetic activity was essentially arrested. Because the time interval during which these events are believed to have occurred immediately preceded the Cambrian explosion of life, the issue as to whether such snowball states actually developed has important implications for our understanding of evolutionary biology. Here we couple an explicit model of the Neoproterozoic carbon cycle to a model of the physical climate system. We show that the drawdown of atmospheric oxygen into the ocean, as surface temperatures decline, operates so as to increase the rate of remineralization of a massive pool of dissolved organic carbon. This leads directly to an increase of atmospheric carbon dioxide, enhanced greenhouse warming of the surface of the Earth, and the prevention of a snowball state.

Assessing the role of solar radiation in heating, photosynthesis, and photo-oxidation in upper Arctic Ocean waters via autonomous buoys

NASA Astrophysics Data System (ADS)

Hill, V. J.; Steele, M.; Light, B.

2016-02-01

As part of the Arctic Observing Network, a new ice-tethered buoy has been developed for monitoring the role of sunlight in regulating ocean temperature, phytoplankton growth, and carbon cycling. A 20 or 50 m string (depending on local bathymetry) supports sensors both within and below the ice for the hourly measurement of downwelling irradiance, temperature, Chlorophyll a, light backscattering, and dissolved organic material (DOM). Two buoys were deployed in March 2014 and two in March 2015. Because the buoys are engineered to survive melting out of first year ice, they have successfully provided complete seasonal records of water column warming, phytoplankton abundance and photo-oxidation patterns in the Pacific Arctic Region. The data collected will be used to determine whether reduced ice extent and thinner ice are driving increases in under ice warming, accelerating bottom ice ablation, increasing available photosynthetic radiation to support large under ice blooms, and to quantify photo-oxidation of the DOM pool. Observations so far have revealed strong under ice daily warming as high as ±0.5 °C driven by local solar radiation. Water column absorption was dominated by colored dissolved organic material which served to trap solar radiation in the upper water column. Chlorophyll concentrations observed in June and July indicated high phytoplankton abundance beneath the ice. Light intensity at this time was not sufficient to support growth rates high enough to produce the 8 to 10 mg m-3 of chlorophyll observed. We hypothesize that phytoplankton were advected under the ice from the ice edge. However, once there phytoplankton were able to sustain low growth rates leading to nutrient limitation before open water status was reached. Strong daily cycles of photo-oxidation have also been observed in the late summer that indicate the fast cycling of highly labile DOM in the open waters of the Pacific Arctic Region.

Abrupt termination of Marine Isotope Stage 16 (Termination VII) at 631.5 ka in Santa Barbara Basin, Californi

USGS Publications Warehouse

Dean, Walter E.; Kennett, James P.; Behl, Richard J.; Nicholson, Craig; Sorlien, Christopher C.

2015-01-01

The Marine Isotope Stage 16–15 boundary (Termination VII) is the first deglacial warming step of the late Quaternary following the mid-Pleistocene transition (MPT), when 41 kyr climatic cycles shifted to strong 100 kyr cycles. The detailed structure of this important climatic event has remained unknown until now. Core MV0508-19JPC from Santa Barbara Basin, California, contains a decadal-scale climatic and geochemical sediment record of 4000 years duration that includes the early part of this deglacial episode. This record reveals that the climatic shift during the early deglacial occurred rapidly (<700 years), in a progression of three abrupt warming steps. The onset of Marine Isotope Stage (MIS) 15 was remarkably abrupt with 4–5°C sea surface warming in ~50 years. The deglacial sequence contains the well-dated Lava Creek tephra (631.3 ± 4 ka) from Yellowstone Caldera used to date the onset of Termination VII at 631.5 ka. The late MIS 16 and early MIS 15 interval exhibits multiple decadal-scale negative excursions in δ13C of planktic foraminifera, likely the result of repeated discharges of methane from methane hydrates associated with both ocean warming and low sea level. A warm interstadial that interrupts late MIS 16 is marked by elevated concentrations of redox-sensitive elements indicating sulfidic, oxygen-deficient bottom and pore-waters, and elevated concentrations of total organic carbon and Cd, reflecting increased surface productivity. Unlike younger sediments on the California margin, these indicators of increased productivity and low dissolved oxygen do not consistently correspond with each other or with preserved laminations, possibly reflecting instability of a still evolving ocean-atmosphere system following the MPT.

The Response of a Branch of Puget Sound, Washington to the 2014 North Pacific Warm Anomaly

NASA Astrophysics Data System (ADS)

Mickett, J.; Newton, J.; Devol, A.; Krembs, C.; Ruef, W.

2016-02-01

The flow of the unprecedentedly-warm upper-ocean North Pacific "Blob" water into Puget Sound, Washington, caused local extreme water property anomalies that extended from the arrival of the water inshore in the fall of 2014 through 2015. Here we report on moored and seaplane observations from Hood Canal, a branch of Puget Sound, where temperature was more than 2σ above climatology for much of the year with maximum temperature anomalies at depth and at the surface +2.5 °C and +7 °C respectively. The low density of the oceanic warm "Blob" water resulted in weak deep water flushing in Hood Canal in the fall of 2014, which combined with a lack of wintertime flushing to result in anomalously-low dissolved oxygen (DO) concentrations at depth. Late-summer 2015 DO values were the lowest in a decade of mooring observations and more than 2σ below climatology. The anomalously low density of the deep basin water allowed a very early onset of the annually-occurring, late-summer intrusion, which first entered Hood Canal at the end of July compared to the usual arrival in early to mid-September. In late August this intrusion conspired with an early fall storm to lift the very low DO deep water to surface at the south end of Hood Canal, causing a significant fish kill event.

Towards an assessment of riverine dissolved organic carbon in surface waters of the western Arctic Ocean based on remote sensing and biogeochemical modeling

NASA Astrophysics Data System (ADS)

Le Fouest, Vincent; Matsuoka, Atsushi; Manizza, Manfredi; Shernetsky, Mona; Tremblay, Bruno; Babin, Marcel

2018-03-01

Future climate warming of the Arctic could potentially enhance the load of terrigenous dissolved organic carbon (tDOC) of Arctic rivers due to increased carbon mobilization within watersheds. A greater flux of tDOC might impact the biogeochemical processes of the coastal Arctic Ocean (AO) and ultimately its capacity to absorb atmospheric CO2. In this study, we show that sea-surface tDOC concentrations simulated by a physical-biogeochemical coupled model in the Canadian Beaufort Sea for 2003-2011 compare favorably with estimates retrieved by satellite imagery. Our results suggest that, over spring-summer, tDOC of riverine origin contributes to 35 % of primary production and that an equivalent of ˜ 10 % of tDOC is exported westwards with the potential of fueling the biological production of the eastern Alaskan nearshore waters. The combination of model and satellite data provides promising results to extend this work to the entire AO so as to quantify, in conjunction with in situ data, the expected changes in tDOC fluxes and their potential impact on the AO biogeochemistry at basin scale.

Physicochemical Constraints on the Distribution of Benthic Foraminiferal Cell Morphology in the Modern Ocean

NASA Astrophysics Data System (ADS)

Keating-Bitonti, C.; Payne, J.

2016-02-01

Patterns in the sizes and shapes of marine organisms often occur across latitude and water depth gradients as a function of metabolic constraints dictated by the physical environment. However, the environmental factors that maintain these gradients in morphology remain incompletely understood because several oceanographic variables of biological importance are intimately correlated, such as temperature, dissolved oxygen concentration, particulate organic carbon (POC) flux, and carbonate saturation. Benthic foraminifera, a diverse group of single-celled protists that occur in nearly all marine environments, provide an ideal opportunity to test statistically among the various hypothesized environmental controls on cell morphology. Here, we use over 7,000 occurrences of 541 species of recent benthic foraminifera that span more than 60 degrees of latitude and 1,600 meters of water depth around the North American continental margin to assess the relative contributions of temperature, oxygen availability, carbonate saturation, and POC flux on their size and volume-to-surface area ratio in the modern ocean. Seawater temperature and dissolved oxygen concentrations best predict both measures of benthic foraminiferal cell morphology from the North American continental margin. These same variables also explain morphological variations from the Pacific continental margin in isolation, but dissolved oxygen is absent from the best model for the Atlantic. Because our results concur with predictions from first principles of cell physiology, we interpret these findings to reflect the physiological selective pressures on cell morphology as determined by the physical environment. Moreover, these findings suggest that warming waters and the expansion of hypoxic zones associated with anthropogenic-induced climate change are more likely to impact benthic foraminiferal communities than changes in primary productivity or ocean acidification.

Effects of a controlled freeze-thaw event on dissolved and colloidal soil organic matter.

PubMed

Kim, Eun-Ah; Lee, Ha Kyung; Choi, Jung Hyun

2017-01-01

This study investigated the effects of the freezing and thawing that accompany the warming process on the composition of the soil organic matter in the dissolved and colloidal fractions. Temperate soil samples were incubated in a refrigerator at 2 °C for 4 weeks and compared with those frozen at -20 °C in the second week followed by thawing at 2 °C to study a freeze-thaw effect with minimal effect from the thawing temperature. The freeze-thaw group was compared with those incubated at 25 °C in the last week to investigate a warming effect after thawing. Thawing at 2 °C after freezing at -20 °C increased the dissolved organic carbon (DOC), but decreased colloidal Ca. The subsequent warming condition greatly increased both DOC and colloidal Ca. The colloidal organic carbon (COC) and dissolved Ca showed rather subtle changes in response to the freeze-thaw and warming treatments compared to the changes in DOC and colloidal Ca. The fluorescence excitation-emission matrix (EEM) and Fourier transformation-infrared spectrometry (FT-IR) results showed that the freeze-thaw and warming treatments gave the opposite effects on the compositions of dissolved humic-like substances, polysaccharides or silicates, and aliphatic alcohols. A principal component analysis (PCA) with the DOC, fluorescence EEM, and FT-IR spectra produced two principal components that successfully distinguished the effects of the freeze-thaw and warming treatments. Due to the contrasting effects of the freeze-thaw and warming treatments, the overall effects of freeze-thaw events in nature on the dissolved and colloidal soil organic matter could vary depending on the thawing temperature.

Dissolved Organic Matter Land-Ocean Linkages in the Arctic

NASA Astrophysics Data System (ADS)

Mann, P. J.; Spencer, R. M.; Hernes, P. J.; Tank, S. E.; Striegl, R.; Dyda, R. Y.; Peterson, B. J.; McClelland, J. W.; Holmes, R. M.

2012-04-01

Rivers draining into the Arctic Ocean exhibit high concentrations of terrigenous dissolved organic carbon (DOC), and recent studies indicate that DOC export is changing due to climatic warming and alteration in permafrost condition. The fate of exported DOC in the Arctic Ocean is important for understanding the regional carbon cycle and remains a point of discussion in the literature. As part of the NSF funded Arctic Great Rivers Observatory (Arctic-GRO) project, samples were collected for DOC, chromophoric and fluorescent dissolved organic matter (CDOM & FDOM) and lignin phenols from the Ob', Yenisey, Lena, Kolyma, Mackenzie and Yukon rivers in 2009 - 2010. DOC and lignin concentrations were elevated during the spring freshet and measurements related to DOC composition indicated an increasing contribution from terrestrial vascular plant sources at this time of year (e.g. lignin carbon-normalized yield, CDOM spectral slope, SUVA254, humic-like fluorescence). CDOM absorption was found to correlate strongly with both DOC (r2=0.83) and lignin concentration (r2=0.92) across the major arctic rivers. Lignin composition was also successfully modeled using FDOM measurements decomposed using PARAFAC analysis. Utilizing these relationships we modeled loads for DOC and lignin export from high-resolution CDOM measurements (daily across the freshet) to derive improved flux estimates, particularly from the dynamic spring discharge maxima period when the majority of DOC and lignin export occurs. The new load estimates for DOC and lignin are higher than previous evaluations, emphasizing that if these are more representative of current arctic riverine export, terrigenous DOC is transiting through the Arctic Ocean at a faster rate than previously thought. It is apparent that higher resolution sampling of arctic rivers is exceptionally valuable with respect to deriving accurate fluxes and we highlight the potential of CDOM in this role for future studies and the applicability of in-situ CDOM sensors.

Emerging climate change signals in the interior ocean oxygen content

NASA Astrophysics Data System (ADS)

Tjiputra, Jerry; Goris, Nadine; Schwinger, Jörg; Lauvset, Siv

2017-04-01

Earth System Models (ESMs) indicate that human-induced climate change will introduce spatially heterogeneous modifications of dissolved oxygen in the North Atlantic. In the upper ocean, an increase (decrease) is predicted at low (high) latitude. Oxygen increase is driven by a reduction of the oxygen consumption for biological remineralization while warming-induced reduction in air-sea fluxes and increase in remineralization due to weaker overturning circulation lead to the projected decrease. In the interior ocean, modifications in the apparent oxygen utilization (AOU) dominate the overall oxygen changes. Moreover, for the southern subpolar gyre, both observations and model hindcast indicate a close relationship between interior ocean oxygen and the subpolar gyre index. Over the 21st century, all ESMs consistently project a steady weakening of this index and consequently the oxygen. Our finding shows that climate change-induced oxygen depletion in the interior has likely occurred and can already be detected. Nevertheless, considering the observational uncertainties, we show that in the proximity of southern subpolar gyre the projected interior trend is sufficiently large enough for early detection.

Black Carbon in Estuarine and Coastal Ocean Dissolved Organic Matter

NASA Technical Reports Server (NTRS)

Mannino, Antonio; Harvey, H. Rodger

2003-01-01

Analysis of high-molecular-weight dissolved organic matter (DOM) from two estuaries in the northwest Atlantic Ocean reveals that black carbon (BC) is a significant component of previously uncharacterized DOM, suggesting that river-estuary systems are important exporters of recalcitrant dissolved organic carbon to the ocean.

Biological responses of the marine diatom Chaetoceros socialis to changing environmental conditions: A laboratory experiment

PubMed Central

Roevros, Nathalie; Dehairs, Frank; Chou, Lei

2017-01-01

Diatoms constitute a major group of phytoplankton, accounting for ~20% of the world’s primary production. It has been shown that iron (Fe) can be the limiting factor for phytoplankton growth, in particular, in the HNLC (High Nutrient Low Chlorophyll) regions. Iron plays thus an essential role in governing the marine primary productivity and the efficiency of biological carbon pump. Oceanic systems are undergoing continuous modifications at varying rates and magnitudes as a result of changing climate. The objective of our research is to evaluate how changing environmental conditions (dust deposition, ocean warming and acidification) can affect marine Fe biogeochemistry and diatom growth. Laboratory culture experiments using a marine diatom Chaetoceros socialis were conducted at two temperatures (13°C and 18°C) and under two pCO2 (carbon dioxide partial pressure) (400 μatm and 800 μatm) conditions. The present study clearly highlights the effect of ocean acidification on enhancing the release of Fe upon dust deposition. Our results also confirm that being a potential source of Fe, dust provides in addition a readily utilizable source of macronutrients such as dissolved phosphate (PO4) and silicate (DSi). However, elevated atmospheric CO2 concentrations may also have an adverse impact on diatom growth, causing a decrease in cell size and possible further changes in phytoplankton composition. Meanwhile, ocean warming may lead to the reduction of diatom production and cell size, inducing poleward shifts in the biogeographic distribution of diatoms. The changing climate has thus a significant implication for ocean phytoplankton growth, cell size and primary productivity, phytoplankton distribution and community composition, and carbon (C), nitrogen (N), phosphorus (P), silicon (Si) and Fe biogeochemical cycles in various ways. PMID:29190826

Impact of global warming and rising CO2 levels on coral reef fishes: what hope for the future?

PubMed

Munday, Philip L; McCormick, Mark I; Nilsson, Göran E

2012-11-15

Average sea-surface temperature and the amount of CO(2) dissolved in the ocean are rising as a result of increasing concentrations of atmospheric CO(2). Many coral reef fishes appear to be living close to their thermal optimum, and for some of them, even relatively moderate increases in temperature (2-4°C) lead to significant reductions in aerobic scope. Reduced aerobic capacity could affect population sustainability because less energy can be devoted to feeding and reproduction. Coral reef fishes seem to have limited capacity to acclimate to elevated temperature as adults, but recent research shows that developmental and transgenerational plasticity occur, which might enable some species to adjust to rising ocean temperatures. Predicted increases in P(CO(2)), and associated ocean acidification, can also influence the aerobic scope of coral reef fishes, although there is considerable interspecific variation, with some species exhibiting a decline and others an increase in aerobic scope at near-future CO(2) levels. As with thermal effects, there are transgenerational changes in response to elevated CO(2) that could mitigate impacts of high CO(2) on the growth and survival of reef fishes. An unexpected discovery is that elevated CO(2) has a dramatic effect on a wide range of behaviours and sensory responses of reef fishes, with consequences for the timing of settlement, habitat selection, predator avoidance and individual fitness. The underlying physiological mechanism appears to be the interference of acid-base regulatory processes with brain neurotransmitter function. Differences in the sensitivity of species and populations to global warming and rising CO(2) have been identified that will lead to changes in fish community structure as the oceans warm and becomes more acidic; however, the prospect for acclimation and adaptation of populations to these threats also needs to be considered. Ultimately, it will be the capacity for species to adjust to environmental change over coming decades that will determine the impact of climate change on marine ecosystems.

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.

Sea surface height evidence for long-term warming effects of tropical cyclones on the ocean.

PubMed

Mei, Wei; Primeau, François; McWilliams, James C; Pasquero, Claudia

2013-09-17

Tropical cyclones have been hypothesized to influence climate by pumping heat into the ocean, but a direct measure of this warming effect is still lacking. We quantified cyclone-induced ocean warming by directly monitoring the thermal expansion of water in the wake of cyclones, using satellite-based sea surface height data that provide a unique way of tracking the changes in ocean heat content on seasonal and longer timescales. We find that the long-term effect of cyclones is to warm the ocean at a rate of 0.32 ± 0.15 PW between 1993 and 2009, i.e., ∼23 times more efficiently per unit area than the background equatorial warming, making cyclones potentially important modulators of the climate by affecting heat transport in the ocean-atmosphere system. Furthermore, our analysis reveals that the rate of warming increases with cyclone intensity. This, together with a predicted shift in the distribution of cyclones toward higher intensities as climate warms, suggests the ocean will get even warmer, possibly leading to a positive feedback.

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

PubMed

Resing, Joseph A; Sedwick, Peter N; German, Christopher R; Jenkins, William J; Moffett, James W; Sohst, Bettina M; Tagliabue, Alessandro

2015-07-09

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

Understanding and Improving Ocean Mixing Parameterizations for modeling Climate Change

NASA Astrophysics Data System (ADS)

Howard, A. M.; Fells, J.; Clarke, J.; Cheng, Y.; Canuto, V.; Dubovikov, M. S.

2017-12-01

Climate is vital. Earth is only habitable due to the atmosphere&oceans' distribution of energy. Our Greenhouse Gas emissions shift overall the balance between absorbed and emitted radiation causing Global Warming. How much of these emissions are stored in the ocean vs. entering the atmosphere to cause warming and how the extra heat is distributed depends on atmosphere&ocean dynamics, which we must understand to know risks of both progressive Climate Change and Climate Variability which affect us all in many ways including extreme weather, floods, droughts, sea-level rise and ecosystem disruption. Citizens must be informed to make decisions such as "business as usual" vs. mitigating emissions to avert catastrophe. Simulations of Climate Change provide needed knowledge but in turn need reliable parameterizations of key physical processes, including ocean mixing, which greatly impacts transport&storage of heat and dissolved CO2. The turbulence group at NASA-GISS seeks to use physical theory to improve parameterizations of ocean mixing, including smallscale convective, shear driven, double diffusive, internal wave and tidal driven vertical mixing, as well as mixing by submesoscale eddies, and lateral mixing along isopycnals by mesoscale eddies. Medgar Evers undergraduates aid NASA research while learning climate science and developing computer&math skills. We write our own programs in MATLAB and FORTRAN to visualize and process output of ocean simulations including producing statistics to help judge impacts of different parameterizations on fidelity in reproducing realistic temperatures&salinities, diffusivities and turbulent power. The results can help upgrade the parameterizations. Students are introduced to complex system modeling and gain deeper appreciation of climate science and programming skills, while furthering climate science. We are incorporating climate projects into the Medgar Evers college curriculum. The PI is both a member of the turbulence group at NASA-GISS and an associate professor at Medgar Evers College of CUNY, an urban minority serving institution in central Brooklyn. Supported by NSF Award AGS-1359293 And NASA Award NNX17AC81G.

The Role of Ocean Dynamical Thermostat in Delaying the El Niño–Like Response over the Equatorial Pacific to Climate Warming

DOE PAGES

Luo, Yiyong; Lu, Jian; Liu, Fukai; ...

2017-03-27

The role of the ocean dynamics in the response of the equatorial Pacific Ocean to climate warming is investigated using both an atmosphere-ocean coupled climate system and its ocean component. Results show that the initial response (fast pattern) to an uniform heating imposed on to the ocean is a warming centered to the west of the dateline owing to the conventional ocean dynamical thermostat (ODT) mechanism in the eastern equatorial Pacific-a cooling effect arising from the up-gradient upwelling. In time, the warming pattern gradually propagates eastward, becoming more El Niño-like (slow pattern). The transition from the fast to the slowmore » patterns is likely resulted from i) the gradual warming of the equatorial thermocline temperature, which is associated with the arrival of the relatively warmer extratropical waters advected along the subsurface branch of the subtropical cells (STC) and ii) the reduction of the STC strength itself. A mixed layer heat budget analysis finds that it is the total ocean dynamical effect rather than the conventional ODT that holds the key for understanding the pattern of the SST in the equatorial Pacific and that the surface heat flux works mainly to compensate the ocean dynamics. Further passive tracer experiments with the ocean component of the coupled system verify the role of the ocean dynamical processes in initiating a La Niña-like SST warming and in setting the pace of the transition to an El Niño-like warming and identify an oceanic origin for the slow eastern Pacific warming independent of the weakening trade wind.« less

The Role of Ocean Dynamical Thermostat in Delaying the El Niño–Like Response over the Equatorial Pacific to Climate Warming

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

Luo, Yiyong; Lu, Jian; Liu, Fukai

The role of the ocean dynamics in the response of the equatorial Pacific Ocean to climate warming is investigated using both an atmosphere-ocean coupled climate system and its ocean component. Results show that the initial response (fast pattern) to an uniform heating imposed on to the ocean is a warming centered to the west of the dateline owing to the conventional ocean dynamical thermostat (ODT) mechanism in the eastern equatorial Pacific-a cooling effect arising from the up-gradient upwelling. In time, the warming pattern gradually propagates eastward, becoming more El Niño-like (slow pattern). The transition from the fast to the slowmore » patterns is likely resulted from i) the gradual warming of the equatorial thermocline temperature, which is associated with the arrival of the relatively warmer extratropical waters advected along the subsurface branch of the subtropical cells (STC) and ii) the reduction of the STC strength itself. A mixed layer heat budget analysis finds that it is the total ocean dynamical effect rather than the conventional ODT that holds the key for understanding the pattern of the SST in the equatorial Pacific and that the surface heat flux works mainly to compensate the ocean dynamics. Further passive tracer experiments with the ocean component of the coupled system verify the role of the ocean dynamical processes in initiating a La Niña-like SST warming and in setting the pace of the transition to an El Niño-like warming and identify an oceanic origin for the slow eastern Pacific warming independent of the weakening trade wind.« less

Widespread methane seepage along the continental margin off Svalbard - from Bjørnøya to Kongsfjorden

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

Mau, S.; Romer, M.; Torres, M. E.

Numerous articles have recently reported on gas seepage offshore Svalbard, because the gas emission from these Arctic sediments was thought to result from gas hydrate dissociation, possibly triggered by anthropogenic ocean warming. We report on findings of a much broader seepage area, extending from 74° to 79°, where more than a thousand gas discharge sites were imaged as acoustic flares. The gas discharge occurs in water depths at and shallower than the upper edge of the gas hydrate stability zone and generates a dissolved methane plume that is hundreds of kilometer in length. Data collected in the summer of 2015more » revealed that 0.02–7.7% of the dissolved methane was aerobically oxidized by microbes and a minor fraction (0.07%) was transferred to the atmosphere during periods of low wind speeds. Most flares were detected in the vicinity of the Hornsund Fracture Zone, leading us to postulate that the gas ascends along this fracture zone. The methane discharges on bathymetric highs characterized by sonic hard grounds, whereas glaciomarine and Holocene sediments in the troughs apparently limit seepage. The large scale seepage reported here is not caused by anthropogenic warming.« less

Widespread methane seepage along the continental margin off Svalbard - from Bjørnøya to Kongsfjorden

DOE PAGES

Mau, S.; Romer, M.; Torres, M. E.; ...

2017-02-23

Numerous articles have recently reported on gas seepage offshore Svalbard, because the gas emission from these Arctic sediments was thought to result from gas hydrate dissociation, possibly triggered by anthropogenic ocean warming. We report on findings of a much broader seepage area, extending from 74° to 79°, where more than a thousand gas discharge sites were imaged as acoustic flares. The gas discharge occurs in water depths at and shallower than the upper edge of the gas hydrate stability zone and generates a dissolved methane plume that is hundreds of kilometer in length. Data collected in the summer of 2015more » revealed that 0.02–7.7% of the dissolved methane was aerobically oxidized by microbes and a minor fraction (0.07%) was transferred to the atmosphere during periods of low wind speeds. Most flares were detected in the vicinity of the Hornsund Fracture Zone, leading us to postulate that the gas ascends along this fracture zone. The methane discharges on bathymetric highs characterized by sonic hard grounds, whereas glaciomarine and Holocene sediments in the troughs apparently limit seepage. The large scale seepage reported here is not caused by anthropogenic warming.« less

Impacts of Polar Changes on the UV-induced Mineralization of Terrigenous Dissolved Organic Matter.

PubMed

Sulzberger, Barbara; Arey, J Samuel

2016-07-05

Local climates in the Northern and Southern Hemisphere are influenced by Arctic Amplification and by interactions of the Antarctic ozone hole with climate change, respectively. Polar changes may affect hydroclimatic conditions in temperate regions, for example, by increasing the length and intensity of precipitation events at Northern Hemisphere midlatitudes. Additionally, global warming has led to the thawing of ancient permafrost soils, particularly in Arctic regions, due to Arctic Amplification. Both heavy precipitation events and thawing of permafrost are increasing the net transfer of terrestrially derived dissolved organic matter (DOM) from land to surface waters. In aquatic ecosystems, UV-induced oxidation of terrigenous DOM (tDOM) produces atmospheric CO2 and this process is one of several mechanisms by which natural organic matter in aquatic and soil environments may play an important role in climate feedbacks. The Arctic is particularly affected by these processes: for example, melting of Arctic sea ice allows solar UV radiation to penetrate into the ice-free Arctic Ocean and to cause photochemical reactions that result in bleaching and mineralization of tDOM. Open questions, in addition to those shown in the Graphical Abstract, remain regarding the resulting contributions of tDOM photomineralization to CO2 production and global warming.

Calcification rates of the Caribbean reef-building coral Siderastrea siderea adversely affected by both seawater warming and CO2-induced ocean acidification

NASA Astrophysics Data System (ADS)

Horvath, K. M.; Connolly, B. D.; Westfield, I. T.; Chow, E.; Castillo, K. D.; Ries, J. B.

2013-05-01

The Intergovernmental Panel on Climate Change (IPCC) predicts that atmospheric pCO2 will increase to ca. 550-950 ppm by the end of the century, primarily due to the anthropogenic combustion of fossil fuels, deforestation, and cement production. This is predicted to cause SST to increase by 1-3 °C and seawater pH to decrease by 0.1-0.3 units. Laboratory studies have shown that warming depresses calcification rates of scleractinian corals and that acidification yields mixed effects on coral calcification. With both warming and ocean acidification predicted for the next century, we must constrain the interactive effects of these two CO2-induced stressors on scleractinian coral calcification. Here, we present the results of experiments designed to assess the response of the scleractinian coral Siderastrea siderea to both ocean warming and acidification. Coral fragments (12/tank) were reared for 60 days under three temperatures (25.1± 0.02 °C, 28.0± 0.02 °C, 31.8± 0.02 °C) at near modern pCO2 (436 ± 7) and near the highest IPCC estimate for atmospheric pCO2 for the year 2100 AD (883 ± 16). Each temperature and pCO2 treatment was executed in triplicate and contained similarly sized S. Siderea fragments obtained from the same suite of coral colonies equitably distributed amongst the nearshore, backreef, and forereef zones of the Mesoamerican Barrier Reef System off the coast of southern Belize. Individual coral fragments were hand fed Artemia sp. to satiation twice weekly. Weekly seawater samples (250 ml) were collected and analyzed for dissolved inorganic carbon via coulometry and total alkalinity via closed-cell potentiometric titration. Seawater pCO2, pH, carbonate ion concentration, bicarbonate ion concentration, aqueous CO2, and aragonite saturation state (ΩA) were calculated with the program CO2SYS. Under near-modern atmospheric pCO2 of ca. 436 ± 7 ppm, seawater warming from 25 to 28 to 32°C caused coral calcification rates (estimated from change in buoyant weight) to decrease nearly linearly. Under the high-pCO2 treatment, warming exerted a parabolic effect on calcification rate, i.e., calcification rate increased from 25 to 28 °C and then declined from 28 to 32 ° C. Under each of the three temperature treatments, increasing atmospheric pCO2 cause calcification rates to significantly decline (p < 0.006). These findings reveal that for the range of atmospheric pCO2 and seawater temperatures predicted by the IPCC for the end of this century, seawater warming is predicted to have the more negative impact on calcification rates of the coral S. siderea. Nevertheless, these experiments reveal that the effect of the predicted CO2-induced ocean acidification may be severe and, perhaps most importantly, that it is the combination of ocean warming and acidification that yields the least favorable outcome for calcification by this coral species.

Trends in continental temperature and humidity directly linked to ocean warming.

PubMed

Byrne, Michael P; O'Gorman, Paul A

2018-05-08

In recent decades, the land surface has warmed substantially more than the ocean surface, and relative humidity has fallen over land. Amplified warming and declining relative humidity over land are also dominant features of future climate projections, with implications for climate-change impacts. An emerging body of research has shown how constraints from atmospheric dynamics and moisture budgets are important for projected future land-ocean contrasts, but these ideas have not been used to investigate temperature and humidity records over recent decades. Here we show how both the temperature and humidity changes observed over land between 1979 and 2016 are linked to warming over neighboring oceans. A simple analytical theory, based on atmospheric dynamics and moisture transport, predicts equal changes in moist static energy over land and ocean and equal fractional changes in specific humidity over land and ocean. The theory is shown to be consistent with the observed trends in land temperature and humidity given the warming over ocean. Amplified land warming is needed for the increase in moist static energy over drier land to match that over ocean, and land relative humidity decreases because land specific humidity is linked via moisture transport to the weaker warming over ocean. However, there is considerable variability about the best-fit trend in land relative humidity that requires further investigation and which may be related to factors such as changes in atmospheric circulations and land-surface properties.

Autumn photoproduction of carbon monoxide in Jiaozhou Bay, China

NASA Astrophysics Data System (ADS)

Ren, Chunyan; Yang, Guipeng; Lu, Xiaolan

2014-06-01

Carbon monoxide (CO) plays a significant role in global warming and atmospheric chemistry. Global oceans are net natural sources of atmospheric CO. CO at surface ocean is primarily produced from the photochemical degradation of chromophoric dissolved organic matter (CDOM). In this study, the effects of photobleaching, temperature and the origin (terrestrial or marine) of CDOM on the apparent quantum yields (AQY) of CO were studied for seawater samples collected from Jiaozhou Bay. Our results demonstrat that photobleaching, temperature and the origin of CDOM strongly affected the efficiency of CO photoproduction. The concentration, absorbance and fluorescence of CDOM exponentially decreased with increasing light dose. Terrestrial riverine organic matter could be more prone to photodegradation than the marine algae-derived one. The relationships between CO AQY and the dissolved organic carbon-specific absorption coefficient at 254 nm for the photobleaching study were nonlinear, whereas those of the original samples were strongly linear. This suggests that: 1) terrestrial riverine CDOM was more efficient than marine algae-derived CDOM for CO photoproduction; 2) aromatic and olefinic moieties of the CDOM pool were affected more strongly by degradation processes than by aliphatic ones. Water temperature and the origin of CDOM strongly affected the efficiency of CO photoproduction. The photoproduction rate of CO in autumn was estimated to be 31.98 μmol m-2 d-1 and the total DOC photomineralization was equivalent to 3.25%-6.35% of primary production in Jiaozhou Bay. Our results indicate that CO photochemistry in coastal areas is important for oceanic carbon cycle.

Sea surface height evidence for long-term warming effects of tropical cyclones on the ocean

PubMed Central

Mei, Wei; Primeau, François; McWilliams, James C.; Pasquero, Claudia

2013-01-01

Tropical cyclones have been hypothesized to influence climate by pumping heat into the ocean, but a direct measure of this warming effect is still lacking. We quantified cyclone-induced ocean warming by directly monitoring the thermal expansion of water in the wake of cyclones, using satellite-based sea surface height data that provide a unique way of tracking the changes in ocean heat content on seasonal and longer timescales. We find that the long-term effect of cyclones is to warm the ocean at a rate of 0.32 ± 0.15 PW between 1993 and 2009, i.e., ∼23 times more efficiently per unit area than the background equatorial warming, making cyclones potentially important modulators of the climate by affecting heat transport in the ocean–atmosphere system. Furthermore, our analysis reveals that the rate of warming increases with cyclone intensity. This, together with a predicted shift in the distribution of cyclones toward higher intensities as climate warms, suggests the ocean will get even warmer, possibly leading to a positive feedback. PMID:23922393

Enhanced CO2 uptake at a shallow Arctic Ocean seep field overwhelms the positive warming potential of emitted methane.

PubMed

Pohlman, John W; Greinert, Jens; Ruppel, Carolyn; Silyakova, Anna; Vielstädte, Lisa; Casso, Michael; Mienert, Jürgen; Bünz, Stefan

2017-05-23

Continued warming of the Arctic Ocean in coming decades is projected to trigger the release of teragrams (1 Tg = 10 6 tons) of methane from thawing subsea permafrost on shallow continental shelves and dissociation of methane hydrate on upper continental slopes. On the shallow shelves (<100 m water depth), methane released from the seafloor may reach the atmosphere and potentially amplify global warming. On the other hand, biological uptake of carbon dioxide (CO 2 ) has the potential to offset the positive warming potential of emitted methane, a process that has not received detailed consideration for these settings. Continuous sea-air gas flux data collected over a shallow ebullitive methane seep field on the Svalbard margin reveal atmospheric CO 2 uptake rates (-33,300 ± 7,900 μmol m -2 ⋅d -1 ) twice that of surrounding waters and ∼1,900 times greater than the diffusive sea-air methane efflux (17.3 ± 4.8 μmol m -2 ⋅d -1 ). The negative radiative forcing expected from this CO 2 uptake is up to 231 times greater than the positive radiative forcing from the methane emissions. Surface water characteristics (e.g., high dissolved oxygen, high pH, and enrichment of 13 C in CO 2 ) indicate that upwelling of cold, nutrient-rich water from near the seafloor accompanies methane emissions and stimulates CO 2 consumption by photosynthesizing phytoplankton. These findings challenge the widely held perception that areas characterized by shallow-water methane seeps and/or strongly elevated sea-air methane flux always increase the global atmospheric greenhouse gas burden.

Enhanced CO2 uptake at a shallow Arctic Ocean seep field overwhelms the positive warming potential of emitted methane

PubMed Central

Greinert, Jens; Silyakova, Anna; Vielstädte, Lisa; Casso, Michael; Mienert, Jürgen; Bünz, Stefan

2017-01-01

Continued warming of the Arctic Ocean in coming decades is projected to trigger the release of teragrams (1 Tg = 106 tons) of methane from thawing subsea permafrost on shallow continental shelves and dissociation of methane hydrate on upper continental slopes. On the shallow shelves (<100 m water depth), methane released from the seafloor may reach the atmosphere and potentially amplify global warming. On the other hand, biological uptake of carbon dioxide (CO2) has the potential to offset the positive warming potential of emitted methane, a process that has not received detailed consideration for these settings. Continuous sea−air gas flux data collected over a shallow ebullitive methane seep field on the Svalbard margin reveal atmospheric CO2 uptake rates (−33,300 ± 7,900 μmol m−2⋅d−1) twice that of surrounding waters and ∼1,900 times greater than the diffusive sea−air methane efflux (17.3 ± 4.8 μmol m−2⋅d−1). The negative radiative forcing expected from this CO2 uptake is up to 231 times greater than the positive radiative forcing from the methane emissions. Surface water characteristics (e.g., high dissolved oxygen, high pH, and enrichment of 13C in CO2) indicate that upwelling of cold, nutrient-rich water from near the seafloor accompanies methane emissions and stimulates CO2 consumption by photosynthesizing phytoplankton. These findings challenge the widely held perception that areas characterized by shallow-water methane seeps and/or strongly elevated sea−air methane flux always increase the global atmospheric greenhouse gas burden. PMID:28484018

Decadal evolution of the surface energy budget during the fast warming and global warming hiatus periods in the ERA-interim

NASA Astrophysics Data System (ADS)

Hu, Xiaoming; Sejas, Sergio A.; Cai, Ming; Taylor, Patrick C.; Deng, Yi; Yang, Song

2018-05-01

The global-mean surface temperature has experienced a rapid warming from the 1980s to early-2000s but a muted warming since, referred to as the global warming hiatus in the literature. Decadal changes in deep ocean heat uptake are thought to primarily account for the rapid warming and subsequent slowdown. Here, we examine the role of ocean heat uptake in establishing the fast warming and warming hiatus periods in the ERA-Interim through a decomposition of the global-mean surface energy budget. We find the increase of carbon dioxide alone yields a nearly steady increase of the downward longwave radiation at the surface from the 1980s to the present, but neither accounts for the fast warming nor warming hiatus periods. During the global warming hiatus period, the transfer of latent heat energy from the ocean to atmosphere increases and the total downward radiative energy flux to the surface decreases due to a reduction of solar absorption caused primarily by an increase of clouds. The reduction of radiative energy into the ocean and the surface latent heat flux increase cause the ocean heat uptake to decrease and thus contribute to the slowdown of the global-mean surface warming. Our analysis also finds that in addition to a reduction of deep ocean heat uptake, the fast warming period is also driven by enhanced solar absorption due predominantly to a decrease of clouds and by enhanced longwave absorption mainly attributed to the air temperature feedback.

Under-ice turbulent microstructure and upper ocean vertical fluxes in the Makarov and Eurasian basins, Arctic Ocean, during late spring and late summer / autumn in 2015

NASA Astrophysics Data System (ADS)

Rabe, Benjamin; Janout, Markus; Graupner, Rainer; Hoelemann, Jens; Hampe, Hendrik; Hoppmann, Mario; Horn, Myriel; Juhls, Bennet; Korhonen, Meri; Nikolopoulos, Anna; Pisarev, Sergey; Randelhoff, Achim; Savy, Jean-Philippe; Villacieros Robineau, Nicolas

2017-04-01

The Arctic Ocean is generally assumed to be fairly quiescent when compared to many other oceans. The sea-ice cover, a strong halocline and a shallow, cold mixed-layer prevents much of the ocean to be affected by atmospheric conditions and properties of the ocean mixed-layer. In turn, the mixed-layer and the sea-ice is largely isolated from the warm layer of Atlantic origin below by the lower halocline. Yet, the content of heat, freshwater and biologically important nutrients differs strongly between these different layers. Hence, it is crucial to be able to estimate vertical fluxes of salt, heat and nutrients to understand variability in the upper Arctic Ocean and the sea-ice, including the ecosystem. Yet, it is difficult to obtain direct flux measurements, and estimates are sparse. We present several sets of under-ice turbulent microstructure profiles in the Eurasian and Makarov Basin of the Arctic Ocean from two expeditions, in 2015. These cover melt during late spring north of Svalbard and freeze-up during late summer / autumn across the Eurasian and Makarov basins. Our results are presented against a background of the anomalously warm atmospheric conditions during summer 2015 followed by unusually low temperatures in September. 4 - 24 h averages of the measurements generally show elevated dissipation rates at the base of the mixed-layer. We found highest levels of dissipation near the Eurasian continental slope and smaller peaks in the profiles where Bering Sea Summer Water (sBSW) lead to additional stratification within the upper halocline in the Makarov Basin. The elevated levels of dissipation associated with sBSW and the base of the mixed-layer were associated with the relatively low levels of vertical eddy diffusivity. We discuss these findings in the light of the anomalous conditions in the upper ocean, sea-ice and the atmosphere during 2015 and present estimates of vertical fluxes of heat, salt and other dissolved substances measured in water samples.

Determination and impact of surface radiative processes for TOGA COARE

NASA Technical Reports Server (NTRS)

Curry, Judith A.; Ackerman, Thomas; Rossow, William B.; Webster, Peter J.

1991-01-01

Experiments using atmospheric general circulation models have shown that the atmospheric circulation is very sensitive to small changes in sea surface temperature in the tropical western Pacific Ocean warm pool region. The mutual sensitivity of the ocean and the atmosphere in the warm pool region places stringent requirements on models of the coupled ocean atmosphere system. At present, the situation is such that diagnostic studies using available data sets have been unable to balance the surface energy budget in the warm pool region to better than 50 to 80 W/sq m. The Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean Atmosphere Response Experiment (COARE) is an observation and modelling program that aims specifically at the elucidation of the physical process which determine the mean and transient state of the warm pool region and the manner in which the warm pool interacts with the global ocean and atmosphere. This project focuses on one very important aspect of the ocean atmosphere interface component of TOGA COARE, namely the temporal and spatial variability of surface radiative fluxes in the warm pool region.

Methane hydrate-bearing seeps as a source of aged dissolved organic carbon to the oceans

USGS Publications Warehouse

Pohlman, J.W.; Bauer, J.E.; Waite, W.F.; Osburn, C.L.; Chapman, N.R.

2011-01-01

Marine sediments contain about 500-10,000 Gt of methane carbon, primarily in gas hydrate. This reservoir is comparable in size to the amount of organic carbon in land biota, terrestrial soils, the atmosphere and sea water combined, but it releases relatively little methane to the ocean and atmosphere. Sedimentary microbes convert most of the dissolved methane to carbon dioxide. Here we show that a significant additional product associated with microbial methane consumption is methane-derived dissolved organic carbon. We use ??14 C and ??13 C measurements and isotopic mass-balance calculations to evaluate the contribution of methane-derived carbon to seawater dissolved organic carbon overlying gas hydrate-bearing seeps in the northeastern Pacific Ocean. We show that carbon derived from fossil methane accounts for up to 28% of the dissolved organic carbon. This methane-derived material is much older, and more depleted in 13 C, than background dissolved organic carbon. We suggest that fossil methane-derived carbon may contribute significantly to the estimated 4,000-6,000 year age of dissolved organic carbon in the deep ocean, and provide reduced organic matter and energy to deep-ocean microbial communities. ?? 2011 Macmillan Publishers Limited. All rights reserved.

The Response of the North Atlantic Bloom to NAO Forcing

NASA Technical Reports Server (NTRS)

Mizoguchi, Ken-Ichi; Worthen, Denise L.; Hakkinen, Sirpa; Gregg, Watson W.

2004-01-01

Results from the climatologically forced coupled ice/ocean/biogeochemical model that covers the Arctic and North Atlantic Oceans are presented and compared to the chlorophyll fields of satellite-derived ocean color measurements. Biogeochemical processes in the model are determined from the interactions among four phytoplankton functional groups (diatoms, chlorophytes, cyanobacteria and coccolithophores) and four nutrients (nitrate, ammonium, silicate and dissolved iron). The model simulates the general large-scale pattern in April, May and June, when compared to both satellite-derived and in situ observations. The subpolar North Atlantic was cool in the 1980s and warm in the latter 1990s, corresponding to the CZCS and SeaWiFS satellite observing periods, respectively. The oceanographic conditions during these periods resemble the typical subpolar upper ocean response to the NAO+ and NAO-phases, respectively. Thus, we use the atmospheric forcing composites from the two NAO phases to simulate the variability of the mid-ocean bloom during the satellite observing periods. The model results show that when the subpolar North Atlantic is cool, the NAO+ case, more nutrients are available in early spring than when the North Atlantic is warm, the NAO-case. However, the NAO+ simulation produces a later bloom than the NAO-simulation. This difference in the bloom times is also identified in SeaWiFS and CZCS satellite measurements. In the model results, we can trace the difference to the early diatom bloom due to a warmer upper ocean. The higher nutrient abundance in the NAO+ case did not provide larger total production than in the NAO- case, instead the two cases had a comparable area averaged amplitude. This leads us to conclude that in the subpolar North Atlantic, the timing of the spring phytoplankton bloom depends on surface temperature and the magnitude of the bloom is not significantly impacted by the nutrient abundance.

Intraseasonal sea surface warming in the western Indian Ocean by oceanic equatorial Rossby waves

NASA Astrophysics Data System (ADS)

Rydbeck, Adam V.; Jensen, Tommy G.; Nyadjro, Ebenezer S.

2017-05-01

A novel process is identified whereby equatorial Rossby (ER) waves maintain warm sea surface temperature (SST) anomalies against cooling by processes related to atmospheric convection in the western Indian Ocean. As downwelling ER waves enter the western Indian Ocean, SST anomalies of +0.15°C develop near 60°E. These SST anomalies are hypothesized to stimulate convective onset of the Madden-Julian Oscillation. The upper ocean warming that manifests in response to downwelling ER waves is examined in a mixed layer heat budget using observational and reanalysis products, respectively. In the heat budget, horizontal advection is the leading contributor to warming, in part due to an equatorial westward jet of 80 cm s-1 associated with downwelling ER waves. When anomalous currents associated with ER waves are removed in the budget, the warm intraseasonal temperature anomaly in the western Indian Ocean is eliminated in observations and reduced by 55% in reanalysis.

Southern Ocean warming due to human influence

NASA Astrophysics Data System (ADS)

Fyfe, John C.

2006-10-01

I show that the latest series of climate models reproduce the observed mid-depth Southern Ocean warming since the 1950s if they include time-varying changes in anthropogenic greenhouse gases, sulphate aerosols and volcanic aerosols in the Earth's atmosphere. The remarkable agreement between observations and state-of-the art climate models suggests significant human influence on Southern Ocean temperatures. I also show that climate models that do not include volcanic aerosols produce mid-depth Southern Ocean warming that is nearly double that produced by climate models that do include volcanic aerosols. This implies that the full effect of human-induced warming of the Southern Ocean may yet to be realized.

Early onset of industrial-era warming across the oceans and continents.

PubMed

Abram, Nerilie J; McGregor, Helen V; Tierney, Jessica E; Evans, Michael N; McKay, Nicholas P; Kaufman, Darrell S

2016-08-25

The evolution of industrial-era warming across the continents and oceans provides a context for future climate change and is important for determining climate sensitivity and the processes that control regional warming. Here we use post-ad 1500 palaeoclimate records to show that sustained industrial-era warming of the tropical oceans first developed during the mid-nineteenth century and was nearly synchronous with Northern Hemisphere continental warming. The early onset of sustained, significant warming in palaeoclimate records and model simulations suggests that greenhouse forcing of industrial-era warming commenced as early as the mid-nineteenth century and included an enhanced equatorial ocean response mechanism. The development of Southern Hemisphere warming is delayed in reconstructions, but this apparent delay is not reproduced in climate simulations. Our findings imply that instrumental records are too short to comprehensively assess anthropogenic climate change and that, in some regions, about 180 years of industrial-era warming has already caused surface temperatures to emerge above pre-industrial values, even when taking natural variability into account.

Detecting anthropogenic climate forcing in the ocean

NASA Astrophysics Data System (ADS)

Wijffels, S. A.

2016-12-01

Owing to its immense heat capacity, the global ocean is the fly-wheel of the climate system, absorbing, redistributing and storing heat on long timescales and over great distances. Of the extra heat trapped in the Earth System due to rising greenhouse gases, over 90% is being stored in the global oceans. Tracking this warming has been challenging due to past changes in the coverage and technology used in past ocean observations. Here, I'll review progress in estimating past warming rates and patterns. The warming of Earth's surface is also driving changes in the global hydrological cycle, which also intimately involves the oceans. Global ocean salinity changes reveal another footprint of a warming Earth. Some simple model runs that give insight into observed subsurface changes will also be described, along with an update on current warming rates and patterns as tracked by the global Argo programme. The prospects for the next advances in broadscale ocean monitoring will also be discussed.

Dissolved organic matter (DOM) in pore water of Arctic Ocean sediments: linking DOM molecular composition with microbial community structure

NASA Astrophysics Data System (ADS)

Rossel, P. E.; Bienhold, C.; Boetius, A.; Dittmar, T.

2016-02-01

Marine organic matter (OM) that sinks from surface waters to the seafloor is the energy and carbon source for benthic communities. These communities produce dissolved organic matter (DOM) in the process of remineralization, enriching the sediment porewater with fresh DOM compounds. In the Arctic Ocean, primary production is limited by nutrients and light and is thus strongly influenced by sea ice cover. Ice cover is expected to further decrease due to global warming, which may have important consequences for primary production and the quantity and quality of OM exported to the seafloor. This study focused on: 1) the molecular composition of the DOM in sediment pore waters of the deep Eurasian Arctic basins, 2) whether there is any relation between Arctic Ocean ice cover and DOM composition and 3) whether the DOM composition correlates with microbial community structure. Molecular data, obtained via 15 Tesla Fourier transform ion cyclotron resonance mass spectrometry, were statistically correlated with environmental parameters. The productive ice margin stations showed higher abundances of molecular formulae of peptides, unsaturated aliphatics and saturated fatty acids. This molecular trend is indicative of fresh OM and phytodetritus deposition, compared to the northernmost, ice-covered stations which had stronger aromatic signals. Benthic bacterial community structure, as assessed with the fingerprinting method ARISA, was significantly correlated with DOM molecular composition. Further analyses using Illumina next-generation sequencing will enable the taxonomic identification of specific bacterial groups and their interdependence with DOM compounds. This study contributes to the understanding of the coupling between Arctic Ocean productivity and its depositional regime, and provides first insights into potential links between microbial community structure and DOM molecular composition in Arctic sediments

The effects of elevated temperature and dissolved ρCO2 on a marine foundation species.

PubMed

Speights, Cori J; Silliman, Brian R; McCoy, Michael W

2017-06-01

Understanding how climate change and other environmental stressors will affect species is a fundamental concern of modern ecology. Indeed, numerous studies have documented how climate stressors affect species distributions and population persistence. However, relatively few studies have investigated how multiple climate stressors might affect species. In this study, we investigate the impacts of how two climate change factors affect an important foundation species. Specifically, we tested how ocean acidification from dissolution of CO 2 and increased sea surface temperatures affect multiple characteristics of juvenile eastern oysters ( Crassostrea virginica ). We found strong impacts of each stressor, but no interaction between the two. Simulated warming to mimic heat stressed summers reduced oyster growth, survival, and filtration rates. Additionally, we found that CO 2 -induced acidification reduced strength of oyster shells, which could potentially facilitate crab predation. As past studies have detected few impacts of these stressors on adult oysters, these results indicate that early life stages of calcareous marine organisms may be more susceptible to effects of ocean acidification and global warming. Overall, these data show that predicted changes in temperature and CO 2 can differentially influence direct effects on individual species, which could have important implications for the nature of their trophic interactions.

Coherent Multidecadal Atmospheric and Oceanic Variability in the North Atlantic: Blocking Corresponds with Warm Subpolar Ocean

NASA Technical Reports Server (NTRS)

Hakkinen, Sirpa M.; Rhines, P. B.; Worthen, D. L.

2012-01-01

Winters with frequent atmospheric blocking, in a band of latitudes from Greenland to Western Europe, are found to persist over several decades and correspond to a warm North Atlantic Ocean. This is evident in atmospheric reanalysis data, both modern and for the full 20th century. Blocking is approximately in phase with Atlantic multidecadal ocean variability (AMV). Wintertime atmospheric blocking involves a highly distorted jetstream, isolating large regions of air from the westerly circulation. It influences the ocean through windstress-curl and associated air/sea heat flux. While blocking is a relatively high-frequency phenomenon, it is strongly modulated over decadal timescales. The blocked regime (weaker ocean gyres, weaker air-sea heat flux, paradoxically increased transport of warm subtropical waters poleward) contributes to the warm phase of AMV. Atmospheric blocking better describes the early 20thC warming and 1996-2010 warm period than does the NAO index. It has roots in the hemispheric circulation and jet stream dynamics. Subpolar Atlantic variability covaries with distant AMOC fields: both these connections may express the global influence of the subpolar North Atlantic ocean on the global climate system.

Do Southern Ocean Cloud Feedbacks Matter for 21st Century Warming?

NASA Astrophysics Data System (ADS)

Frey, W. R.; Maroon, E. A.; Pendergrass, A. G.; Kay, J. E.

2017-12-01

Cloud phase improvements in a state-of-the-art climate model produce a large 1.5 K increase in equilibrium climate sensitivity (ECS, the surface warming in response to instantaneously doubled CO2) via extratropical shortwave cloud feedbacks. Here we show that the same model improvements produce only a small surface warming increase in a realistic 21st century emissions scenario. The small 21st century warming increase is attributed to extratropical ocean heat uptake. Southern Ocean mean-state circulation takes up heat while a slowdown in North Atlantic circulation acts as a feedback to slow surface warming. Persistent heat uptake by extratropical oceans implies that extratropical cloud biases may not be as important to 21st century warming as biases in other regions. Observational constraints on cloud phase and shortwave radiation that produce a large ECS increase do not imply large changes in 21st century warming.

Ocean acidification ameliorates harmful effects of warming in primary consumer.

PubMed

Pedersen, Sindre Andre; Hanssen, Anja Elise

2018-01-01

Climate change-induced warming and ocean acidification are considered two imminent threats to marine biodiversity and current ecosystem structures. Here, we have for the first time examined an animal's response to a complete life cycle of exposure to co-occurring warming (+3°C) and ocean acidification (+1,600 μatm CO 2 ), using the key subarctic planktonic copepod, Calanus finmarchicus , as a model species. The animals were generally negatively affected by warming, which significantly reduced the females' energy status and reproductive parameters (respectively, 95% and 69%-87% vs. control). Unexpectedly, simultaneous acidification partially offset the negative effect of warming in an antagonistic manner, significantly improving reproductive parameters and hatching success (233%-340% improvement vs. single warming exposure). The results provide proof of concept that ocean acidification may partially offset negative effects caused by warming in some species. Possible explanations and ecological implications for the observed antagonistic effect are discussed.

77 FR 23209 - Endangered and Threatened Species; Proposed Delisting of Eastern DPS of Steller Sea Lions

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-18

... five potential sources of threat under this factor: 1. Global Climate Warming and Ocean Acidification... 5. Oil and Gas Development. Global climate warming and ocean acidification pose a potential threat... information suggests it is likely that global warming and ocean acidification may affect eastern North Pacific...

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

Methane hydrate-bearing seeps as a source of aged dissolved organic carbon to the oceans

USGS Publications Warehouse

Pohlman, John; Waite, William F.; Bauer, James E.; Osburn, Christopher L.; Chapman, N. Ross

2011-01-01

Marine sediments contain about 500–10,000 Gt of methane carbon1, 2, 3, primarily in gas hydrate. This reservoir is comparable in size to the amount of organic carbon in land biota, terrestrial soils, the atmosphere and sea water combined1, 4, but it releases relatively little methane to the ocean and atmosphere5. Sedimentary microbes convert most of the dissolved methane to carbon dioxide6, 7. Here we show that a significant additional product associated with microbial methane consumption is methane-derived dissolved organic carbon. We use Δ14C and δ13C measurements and isotopic mass-balance calculations to evaluate the contribution of methane-derived carbon to seawater dissolved organic carbon overlying gas hydrate-bearing seeps in the northeastern Pacific Ocean. We show that carbon derived from fossil methane accounts for up to 28% of the dissolved organic carbon. This methane-derived material is much older, and more depleted in 13C, than background dissolved organic carbon. We suggest that fossil methane-derived carbon may contribute significantly to the estimated 4,000–6,000 year age of dissolved organic carbon in the deep ocean8, and provide reduced organic matter and energy to deep-ocean microbial communities.

Ocean Heat Uptake Slows 21st Century Surface Warming Driven by Extratropical Cloud Feedbacks

NASA Astrophysics Data System (ADS)

Frey, W.; Maroon, E.; Pendergrass, A. G.; Kay, J. E.

2017-12-01

Equilibrium climate sensitivity (ECS), the warming in response to instantaneously doubled CO2, has long been used to compare climate models. In many models, ECS is well correlated with warming produced by transient forcing experiments. Modifications to cloud phase at high latitudes in a state-of-the-art climate model, the Community Earth System Model (CESM), produce a large increase in ECS (1.5 K) via extratropical cloud feedbacks. However, only a small surface warming increase occurs in a realistic 21st century simulation including a full-depth dynamic ocean and the "business as usual" RCP8.5 emissions scenario. In fact, the increase in surface warming is only barely above the internal variability-generated range in the CESM Large Ensemble. The small change in 21st century warming is attributed to subpolar ocean heat uptake in both hemispheres. In the Southern Ocean, the mean-state circulation takes up heat while in the North Atlantic a slowdown in circulation acts as a feedback to slow surface warming. These results show the importance of subpolar ocean heat uptake in controlling the pace of warming and demonstrate that ECS cannot be used to reliably infer transient warming when it is driven by extratropical feedbacks.

Seagrass ecophysiological performance under ocean warming and acidification.

PubMed

Repolho, Tiago; Duarte, Bernardo; Dionísio, Gisela; Paula, José Ricardo; Lopes, Ana R; Rosa, Inês C; Grilo, Tiago F; Caçador, Isabel; Calado, Ricardo; Rosa, Rui

2017-02-01

Seagrasses play an essential ecological role within coastal habitats and their worldwide population decline has been linked to different types of anthropogenic forces. We investigated, for the first time, the combined effects of future ocean warming and acidification on fundamental biological processes of Zostera noltii, including shoot density, leaf coloration, photophysiology (electron transport rate, ETR; maximum PSII quantum yield, F v /F m ) and photosynthetic pigments. Shoot density was severely affected under warming conditions, with a concomitant increase in the frequency of brownish colored leaves (seagrass die-off). Warming was responsible for a significant decrease in ETR and F v /F m (particularly under control pH conditions), while promoting the highest ETR variability (among experimental treatments). Warming also elicited a significant increase in pheophytin and carotenoid levels, alongside an increase in carotenoid/chlorophyll ratio and De-Epoxidation State (DES). Acidification significantly affected photosynthetic pigments content (antheraxanthin, β-carotene, violaxanthin and zeaxanthin), with a significant decrease being recorded under the warming scenario. No significant interaction between ocean acidification and warming was observed. Our findings suggest that future ocean warming will be a foremost determinant stressor influencing Z. noltii survival and physiological performance. Additionally, acidification conditions to occur in the future will be unable to counteract deleterious effects posed by ocean warming.

Seagrass ecophysiological performance under ocean warming and acidification

PubMed Central

Repolho, Tiago; Duarte, Bernardo; Dionísio, Gisela; Paula, José Ricardo; Lopes, Ana R.; Rosa, Inês C.; Grilo, Tiago F.; Caçador, Isabel; Calado, Ricardo; Rosa, Rui

2017-01-01

Seagrasses play an essential ecological role within coastal habitats and their worldwide population decline has been linked to different types of anthropogenic forces. We investigated, for the first time, the combined effects of future ocean warming and acidification on fundamental biological processes of Zostera noltii, including shoot density, leaf coloration, photophysiology (electron transport rate, ETR; maximum PSII quantum yield, Fv/Fm) and photosynthetic pigments. Shoot density was severely affected under warming conditions, with a concomitant increase in the frequency of brownish colored leaves (seagrass die-off). Warming was responsible for a significant decrease in ETR and Fv/Fm (particularly under control pH conditions), while promoting the highest ETR variability (among experimental treatments). Warming also elicited a significant increase in pheophytin and carotenoid levels, alongside an increase in carotenoid/chlorophyll ratio and De-Epoxidation State (DES). Acidification significantly affected photosynthetic pigments content (antheraxanthin, β-carotene, violaxanthin and zeaxanthin), with a significant decrease being recorded under the warming scenario. No significant interaction between ocean acidification and warming was observed. Our findings suggest that future ocean warming will be a foremost determinant stressor influencing Z. noltii survival and physiological performance. Additionally, acidification conditions to occur in the future will be unable to counteract deleterious effects posed by ocean warming. PMID:28145531

Understanding the El Niño-like Oceanic Response in the Tropical Pacific to Global Warming

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

Luo, Yiyong; Lu, Jian; Liu, Fukai

The enhanced central and eastern Pacific SST warming and the associated ocean processes under global warming are investigated using the ocean component of the Community Earth System Model (CESM), Parallel Ocean Program version 2 (POP2). The tropical SST warming pattern in the coupled CESM can be faithfully reproduced by the POP2 forced with surface fluxes computed using the aerodynamic bulk formula. By prescribing the wind stress and/or wind speed through the bulk formula, the effects of wind stress change and/or the wind-evaporation-SST (WES) feedback are isolated and their linearity is evaluated in this ocean-alone setting. Result shows that, although themore » weakening of the equatorial easterlies contributes positively to the El Niño-like SST warming, 80% of which can be simulated by the POP2 without considering the effects of wind change in both mechanical and thermodynamic fluxes. This result points to the importance of the air-sea thermal interaction and the relative feebleness of the ocean dynamical process in the El Niño-like equatorial Pacific SST response to global warming. On the other hand, the wind stress change is found to play a dominant role in the oceanic response in the tropical Pacific, accounting for most of the changes in the equatorial ocean current system and thermal structures, including the weakening of the surface westward currents, the enhancement of the near-surface stratification and the shoaling of the equatorial thermocline. Interestingly, greenhouse gas warming in the absence of wind stress change and WES feedback also contributes substantially to the changes at the subsurface equatorial Pacific. Further, this warming impact can be largely replicated by an idealized ocean experiment forced by a uniform surface heat flux, whereby, arguably, a purest form of oceanic dynamical thermostat is revealed.« less

Increased Ocean Heat Convergence Into the High Latitudes With CO 2 Doubling Enhances Polar-Amplified Warming: OCEAN HEAT AND POLAR WARMING

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

Singh, H. A.; Rasch, P. J.; Rose, B. E. J.

We isolate the role of the ocean in polar climate change by directly evaluating how changes in ocean dynamics with quasi-equilibrium CO2-doubling impact high-latitude climate. With CO2-doubling, the ocean heat flux convergence (OHFC) shifts poleward in winter in both hemispheres. Imposing this pattern of perturbed OHFC in a global climate model results in a poleward shift in ocean-to-atmosphere turbulent heat fluxes (both sensible and latent) and sea ice retreat; the high-latitudes warm while the midlatitudes cool, thereby amplifying polar warming. Furthermore, midlatitude cooling is propagated to the polar mid-troposphere on isentropic surfaces, augmenting the (positive) lapse rate feedback at highmore » latitudes. These results highlight the key role played by the partitioning of meridional energy transport changes between the atmosphere and ocean in high-latitude climate change.« less

The origins of the anomalous warming in the California coastal ocean and San Francisco Bay during 2014-2016

NASA Astrophysics Data System (ADS)

Chao, Yi; Farrara, John D.; Bjorkstedt, Eric; Chai, Fei; Chavez, Francisco; Rudnick, Daniel L.; Enright, Wendy; Fisher, Jennifer L.; Peterson, William T.; Welch, Gregory F.; Davis, Curtiss O.; Dugdale, Richard C.; Wilkerson, Frances P.; Zhang, Hongchun; Zhang, Yinglong; Ateljevich, Eli

2017-09-01

During 2014 exceptionally warm water temperatures developed across a wide area off the California coast and within San Francisco Bay (SFB) and persisted into 2016. Observations and numerical model output are used to document this warming and determine its origins. The coastal warming was mostly confined to the upper 100 m of the ocean and was manifested strongly in the two leading modes of upper ocean (0-100 m) temperature variability in the extratropical eastern Pacific. Observations suggest that the coastal warming in 2014 propagated into nearshore regions from the west while later indicating a warming influence that propagated from south to north into the region associated with the 2015-2016 El Niño event. An analysis of the upper ocean (0-100 m) heat budget in a Regional Ocean Modeling System (ROMS) simulation confirmed this scenario. The results from a set of sensitivity runs with the model in which the lateral boundary conditions varied supported the conclusions drawn from the heat budget analysis. Concerning the warming in the SFB, an examination of the observations and the heat budget in an unstructured-grid numerical model simulation suggested that the warming during the second half of 2014 and early 2016 originated in the adjacent California coastal ocean and propagated through the Golden Gate into the Bay. The finding that the coastal and Bay warming are due to the relatively slow propagation of signals from remote sources raises the possibility that such warming events may be predictable many months or even several seasons in advance.

Boosted nutritional quality of food by CO2 enrichment fails to offset energy demand of herbivores under ocean warming, causing energy depletion and mortality.

PubMed

Leung, Jonathan Y S; Nagelkerken, Ivan; Russell, Bayden D; Ferreira, Camilo M; Connell, Sean D

2018-05-20

The CO 2 -boosted trophic transfer from primary producers to herbivores has been increasingly discovered at natural CO 2 vents and in laboratory experiments. Despite the emerging knowledge of this boosting effect, we do not know the extent to which it may be enhanced or dampened by ocean warming. We investigated whether ocean acidification and warming enhance the nutritional quality (C:N ratio) and energy content of turf algae, which is speculated to drive higher feeding rate, greater energy budget and eventually faster growth of herbivores. This proposal was tested by observing the physiological (feeding rate, respiration rate and energy budget) and demographic responses (growth and survival) of a common grazing gastropod (Phasianella australis) to ocean acidification and warming in a 6-month mesocosm experiment. Whilst we observed the boosting effect of ocean acidification and warming in isolation on the energy budget of herbivores by either increasing feeding rate on the more nutritious algae or increasing energy gain per feeding effort, their growth and survival were reduced by the sublethal thermal stress under ocean warming, especially when both climate change stressors were combined. This reduced growth and survival occurred as a consequence of depleted energy reserves, suggesting that the boosting effect via trophic transfer might not sufficiently compensate for the increased energy demand imposed by ocean warming. In circumstances where ocean acidification and warming create an energy demand on herbivores that outweighs the energy enhancement of their food (i.e. primary producers), the performance of herbivores to control their blooming resources likely deteriorates and thus runaway primary production ensues. Copyright © 2018 Elsevier B.V. All rights reserved.

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.

Predicting interactions among fishing, ocean warming, and ocean acidification in a marine system with whole-ecosystem models.

PubMed

Griffith, Gary P; Fulton, Elizabeth A; Gorton, Rebecca; Richardson, Anthony J

2012-12-01

An important challenge for conservation is a quantitative understanding of how multiple human stressors will interact to mitigate or exacerbate global environmental change at a community or ecosystem level. We explored the interaction effects of fishing, ocean warming, and ocean acidification over time on 60 functional groups of species in the southeastern Australian marine ecosystem. We tracked changes in relative biomass within a coupled dynamic whole-ecosystem modeling framework that included the biophysical system, human effects, socioeconomics, and management evaluation. We estimated the individual, additive, and interactive effects on the ecosystem and for five community groups (top predators, fishes, benthic invertebrates, plankton, and primary producers). We calculated the size and direction of interaction effects with an additive null model and interpreted results as synergistic (amplified stress), additive (no additional stress), or antagonistic (reduced stress). Individually, only ocean acidification had a negative effect on total biomass. Fishing and ocean warming and ocean warming with ocean acidification had an additive effect on biomass. Adding fishing to ocean warming and ocean acidification significantly changed the direction and magnitude of the interaction effect to a synergistic response on biomass. The interaction effect depended on the response level examined (ecosystem vs. community). For communities, the size, direction, and type of interaction effect varied depending on the combination of stressors. Top predator and fish biomass had a synergistic response to the interaction of all three stressors, whereas biomass of benthic invertebrates responded antagonistically. With our approach, we were able to identify the regional effects of fishing on the size and direction of the interacting effects of ocean warming and ocean acidification. ©2012 Society for Conservation Biology.

Local atmospheric response to warm mesoscale ocean eddies in the Kuroshio-Oyashio Confluence region.

PubMed

Sugimoto, Shusaku; Aono, Kenji; Fukui, Shin

2017-09-19

In the extratropical regions, surface winds enhance upward heat release from the ocean to atmosphere, resulting in cold surface ocean: surface ocean temperature is negatively correlated with upward heat flux. However, in the western boundary currents and eddy-rich regions, the warmer surface waters compared to surrounding waters enhance upward heat release-a positive correlation between upward heat release and surface ocean temperature, implying that the ocean drives the atmosphere. The atmospheric response to warm mesoscale ocean eddies with a horizontal extent of a few hundred kilometers remains unclear because of a lack of observations. By conducting regional atmospheric model experiments, we show that, in the Kuroshio-Oyashio Confluence region, wintertime warm eddies heat the marine atmospheric boundary layer (MABL), and accelerate westerly winds in the near-surface atmosphere via the vertical mixing effect, leading to wind convergence around the eastern edge of eddies. The warm-eddy-induced convergence forms local ascending motion where convective precipitation is enhanced, providing diabatic heating to the atmosphere above MABL. Our results indicate that warm eddies affect not only near-surface atmosphere but also free atmosphere, and possibly synoptic atmospheric variability. A detailed understanding of warm eddy-atmosphere interaction is necessary to improve in weather and climate projections.

Coastal ocean acidification and increasing total alkalinity in the northwestern Mediterranean Sea

NASA Astrophysics Data System (ADS)

Kapsenberg, Lydia; Alliouane, Samir; Gazeau, Frédéric; Mousseau, Laure; Gattuso, Jean-Pierre

2017-05-01

Coastal time series of ocean carbonate chemistry are critical for understanding how global anthropogenic change manifests in near-shore ecosystems. Yet, they are few and have low temporal resolution. At the time series station Point B in the northwestern Mediterranean Sea, seawater was sampled weekly from 2007 through 2015, at 1 and 50 m, and analyzed for total dissolved inorganic carbon (CT) and total alkalinity (AT). Parameters of the carbonate system such as pH (pHT, total hydrogen ion scale) were calculated and a deconvolution analysis was performed to identify drivers of change. The rate of surface ocean acidification was -0.0028 ± 0.0003 units pHT yr-1. This rate is larger than previously identified open-ocean trends due to rapid warming that occurred over the study period (0.072 ± 0.022 °C yr-1). The total pHT change over the study period was of similar magnitude as the diel pHT variability at this site. The acidification trend can be attributed to atmospheric carbon dioxide (CO2) forcing (59 %, 2.08 ± 0.01 ppm CO2 yr-1) and warming (41 %). Similar trends were observed at 50 m but rates were generally slower. At 1 m depth, the increase in atmospheric CO2 accounted for approximately 40 % of the observed increase in CT (2.97 ± 0.20 µmol kg-1 yr-1). The remaining increase in CT may have been driven by the same unidentified process that caused an increase in AT (2.08 ± 0.19 µmol kg-1 yr-1). Based on the analysis of monthly trends, synchronous increases in CT and AT were fastest in the spring-summer transition. The driving process of the interannual increase in AT has a seasonal and shallow component, which may indicate riverine or groundwater influence. This study exemplifies the importance of understanding changes in coastal carbonate chemistry through the lens of biogeochemical cycling at the land-sea interface. This is the first coastal acidification time series providing multiyear data at high temporal resolution. The data confirm rapid warming in the Mediterranean Sea and demonstrate coastal acidification with a synchronous increase in total alkalinity.

Mechanisms controlling the dependence of surface warming on cumulative carbon emissions over the next century in a suite of Earth system models

NASA Astrophysics Data System (ADS)

Williams, Richard; Roussenov, Vassil; Goodwin, Philip; Resplandy, Laure; Bopp, Laurent

2017-04-01

Insight into how to avoid dangerous climate may be obtained from Earth system model projections, which reveal a near-linear dependence of global-mean surface warming on cumulative carbon emissions. This dependence of surface warming on carbon emissions is interpreted in terms of a product of three terms: the dependence of surface warming on radiative forcing, the fractional radiative forcing contribution from atmospheric CO2 and the dependence of radiative forcing from atmospheric CO2 on cumulative carbon emissions. Mechanistically each of these dependences varies, respectively, with ocean heat uptake, the CO2 and non-CO2 radiative forcing, and the ocean and terrestrial uptake of carbon. An ensemble of 9 Earth System models forced by up to 4 Representative Concentration Pathways are diagnosed. In all cases, the dependence of surface warming on carbon emissions evolves primarily due to competing effects of heat and carbon uptake over the upper ocean: there is a reduced effect of radiative forcing from CO2 due to ocean carbon uptake, which is partly compensated by enhanced surface warming due to a reduced effect of ocean heat uptake. There is a wide spread in the dependence of surface warming on carbon emissions, undermining the ability to identify the maximum permitted carbon emission to avoid dangerous climate. Our framework reveals how uncertainty in the future warming trend is high over the next few decades due to relatively high uncertainties in ocean heat uptake, non-CO2 radiative forcing and the undersaturation of carbon in the ocean.

Enhanced dissolved lipid production as a response to the sea surface warming

NASA Astrophysics Data System (ADS)

Novak, Tihana; Godrijan, Jelena; Pfannkuchen, Daniela Marić; Djakovac, Tamara; Mlakar, Marina; Baricevic, Ana; Tanković, Mirta Smodlaka; Gašparović, Blaženka

2018-04-01

The temperature increase in oceans reflects on marine ecosystem functioning and surely has consequences on the marine carbon cycle and carbon sequestration. In this study, we examined dissolved lipid, lipid classes and dissolved organic carbon (DOC) production in the northern Adriatic Sea, isolated diatom Chaetoceros pseudocurvisetus batch cultures grown in a wide temperature range (10-30 °C) and in contrasting nutrient regimes, phosphorus (P)-depleted and P-replete conditions. Additionally, lipids and DOC were analyzed in the northern Adriatic (NA) in two stations characterized with different P availability, occupied from February to August 2010 that covered a temperature range from 9.3 to 31.1 °C. To gain insight into factors governing lipid and lipid classes' production in the NA, apart from temperature (T), Chlorophyll a, phytoplankton community abundance and structure, nutrient concentrations were measured together with hydrographic parameters. We found enhanced accumulation of dissolved lipids, particulary glycolipids, with increasing T, especially during the highest in situ temperature. The effect of T on enhanced dissolved lipid release is much more pronounced under P-deplete conditions indicating that oligotrophic regions might be more vulnerable to T rise. Temperature between 25 and 30 °C is a threshold T range for C. pseudocurvisetus, at which a significant part of lipid production is directed toward the dissolved phase. Unlike monocultures, there are multiple factors influencing produced lipid composition, distribution and cycling in the NA that may counteract the T influence. The possible role of enhanced dissolved lipid concentration for carbon sequestration at elevated T is discussed. On the one hand, lipids are buoyant and do not sink, which enhances their retention at the surface layer. In addition, they are surface active, and therefore prone to adsorb on sinking particles, contributing to the C sequestration.

Dissolved Organic Nitrogen Inputs from Wastewater Treatment Plant Effluents Increase Responses of Planktonic Metabolic Rates to Warming.

PubMed

Vaquer-Sunyer, Raquel; Conley, Daniel J; Muthusamy, Saraladevi; Lindh, Markus V; Pinhassi, Jarone; Kritzberg, Emma S

2015-10-06

Increased anthropogenic pressures on coastal marine ecosystems in the last century are threatening their biodiversity and functioning. Global warming and increases in nutrient loadings are two major stressors affecting these systems. Global warming is expected to increase both atmospheric and water temperatures and increase precipitation and terrestrial runoff, further increasing organic matter and nutrient inputs to coastal areas. Dissolved organic nitrogen (DON) concentrations frequently exceed those of dissolved inorganic nitrogen in aquatic systems. Many components of the DON pool have been shown to supply nitrogen nutrition to phytoplankton and bacteria. Predictions of how global warming and eutrophication will affect metabolic rates and dissolved oxygen dynamics in the future are needed to elucidate their impacts on biodiversity and ecosystem functioning. Here, we experimentally determine the effects of simultaneous DON additions and warming on planktonic community metabolism in the Baltic Sea, the largest coastal area suffering from eutrophication-driven hypoxia. Both bacterioplankton community composition and metabolic rates changed in relation to temperature. DON additions from wastewater treatment plant effluents significantly increased the activation energies for community respiration and gross primary production. Activation energies for community respiration were higher than those for gross primary production. Results support the prediction that warming of the Baltic Sea will enhance planktonic respiration rates faster than it will for planktonic primary production. Higher increases in respiration rates than in production may lead to the depletion of the oxygen pool, further aggravating hypoxia in the Baltic Sea.

Medieval Warm Period and Little Ice Age Signatures in the Distribution of Modern Ocean Temperatures

NASA Astrophysics Data System (ADS)

Gebbie, G.; Huybers, P. J.

2017-12-01

It is well established both that global temperatures have varied overthe last millenium and that the interior ocean reflects surfaceproperties inherited over these timescales. Signatures of theMedieval Warm Period and Little Ice Age are thus to be expected in themodern ocean state, though the magnitude of these effects and whetherthey are detectable is unclear. Analysis of changes in temperatureacross those obtained in the 1870s as part of the theH.M.S. Challenger expedition, the 1990s World Ocean CirculationExperiment, and recent Argo observations shows a consistent pattern:the upper ocean and Atlantic have warmed, but the oldest waters inthe deep Pacific appear to have cooled. The implications of pressureeffects on the H.M.S. Challenger thermometers and uncertainties indepth of observations are non-negligible but do not appear tofundamentally alter this pattern. Inversion of the modern hydrographyusing ocean transport estimates derived from passive tracer andradiocarbon observations indicates that deep Pacific cooling could bea vestige of the Medieval Warm Period, and that warming elsewhere reflects thecombined effects of emergence from the Little Ice Age and modernanthropogenic warming. Implications for longterm variations in oceanheat uptake and separating natural and anthropogenic contributions to themodern energy imbalance are discussed.

Effects of warming, acidification, and reef-zone on the calcification of four Caribbean scleractinian corals of the Belize Barrier Reef System

NASA Astrophysics Data System (ADS)

Bove, C. B.; Ries, J. B.; Davies, S. W.; Westfield, I. T.; Castillo, K.

2016-02-01

Rising atmospheric carbon dioxide (pCO2) has caused ocean temperature to increase and ocean pH to decrease, raising concerns about the health of marine organisms. Previous studies have shown that corals are particularly vulnerable to these stressors, most likely due to their narrow thermal tolerance and use of carbonate ions in calcification, although response patterns vary across taxa. We conducted laboratory experiments for 95 days to investigate the independent and interactive effects of ocean warming (28, 31 °C) and acidification on the calcification rate and skeletal properties of four abundant and ubiquitously distributed Caribbean coral species (Pseudodiploria strigosa, Siderastrea siderea, Porites astreoides, Undaria tenuifolia) collected from nearshore and forereef environments of the Belize Barrier Reef. Aragonite saturation states of 3.9, 3.2, 2.2, and 0.7, constrained by total alkalinity measured via closed-cell potentiometric titration and dissolved inorganic carbon measured via coulometry, were attained by sparging natural seawater with air-CO2 mixtures formulated at 280, 400, 700, and 2800 ppmv pCO2, respectively. Temperature and pCO2 were fully crossed (N=3 tanks per treatment) and corals were gradually exposed to treatment conditions over a 30-day period, followed by an additional 30-day acclimation. Rates of linear skeletal extension were measured relative to a calcein spike emplaced in the coral skeletons at the start of the experiment, and net calcification rates were determined from coral buoyant weights obtained every 30 days. Initial results show that corals in all treatments continued to calcify on a net basis, however, the effect of warming on net calcification rates of P. asteroids and U. tenuifolia became more negative at lower saturation states. In addition, nearshore U. tenuifolia calcified faster than forereef conspecifics in all treatments.

Oxygen in the deep-sea: The challenge of maintaining uptake rates in a changing ocean

NASA Astrophysics Data System (ADS)

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

2011-12-01

Although focused on recently, ocean acidification is not the only effect of anthropogenic CO2 emissions on the ocean. Ocean warming will reduce dissolved oxygen concentrations and at the hypoxic limit for a given species this can pose challenges to marine life. The limit is traditionally reported simply as the static mass concentration property [O2]; here we treat it as a dynamic gas exchange problem for the animal analogous to gas exchange at the sea surface. The diffusive limit and its relationship to water velocity is critical for the earliest stages of marine life (eggs, embryos), but the effect is present for all animals at all stages of life. We calculate the external limiting O2 conditions for several representative metabolic rates and their relationship to flow of the bulk fluid under different environmental conditions. Ocean O2 concentrations decline by ≈ 14 μmol kg-1 for a 2 °C rise in temperature. At standard 1000 m depth conditions in the Pacific, flow over the surface would have to increase by ≈ 60% from 2.0 to 3.2 cm s-1 to compensate for this change. The functions derived allow new calculations of depth profiles of limiting O2 concentrations, as well as maximal diffusively sustainable metabolic oxygen consumption rates at various places around the world. Our treatment shows that there is a large variability in the global ocean in terms of facilitating aerobic life. This variability is greater than the variability of the oxygen concentration alone. It becomes clear that temperature and pressure dependencies of diffusion and partial pressure create a region typically around 1000 m depth where a maximal [O2] is needed to sustain a given metabolic rate. This zone of greatest physical constriction on the diffusive transport in the boundary layer is broadly consistent with the oxygen minimum zone, i.e., the zone of least oxygen concentration supply, resulting in a pronounced minimum of maximal diffusively sustainable metabolic oxygen consumption rates. This least-favorable zone for aerobic respiration is bound to expand with further ocean warming.

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.

Coastal warming and wind-driven upwelling: A global analysis.

PubMed

Varela, Rubén; Lima, Fernando P; Seabra, Rui; Meneghesso, Claudia; Gómez-Gesteira, Moncho

2018-10-15

Long-term sea surface temperature (SST) warming trends are far from being homogeneous, especially when coastal and ocean locations are compared. Using data from NOAA's AVHRR OISST, we have analyzed sea surface temperature trends over the period 1982-2015 at around 3500 worldwide coastal points and their oceanic counterparts with a spatial resolution of 0.25 arc-degrees. Significant warming was observed at most locations although with important differences between oceanic and coastal points. This is especially patent for upwelling regions, where 92% of the coastal locations showed lower warming trends than at neighboring ocean locations. This result strongly suggests that upwelling has the potential to buffer the effects of global warming nearshore, with wide oceanographic, climatic, and biogeographic implications. Copyright © 2018 Elsevier B.V. All rights reserved.

Microbial Community Response to Terrestrially Derived Dissolved Organic Matter in the Coastal Arctic.

PubMed

Sipler, Rachel E; Kellogg, Colleen T E; Connelly, Tara L; Roberts, Quinn N; Yager, Patricia L; Bronk, Deborah A

2017-01-01

Warming at nearly twice the global rate, higher than average air temperatures are the new 'normal' for Arctic ecosystems. This rise in temperature has triggered hydrological and geochemical changes that increasingly release carbon-rich water into the coastal ocean via increased riverine discharge, coastal erosion, and the thawing of the semi-permanent permafrost ubiquitous in the region. To determine the biogeochemical impacts of terrestrially derived dissolved organic matter (tDOM) on marine ecosystems we compared the nutrient stocks and bacterial communities present under ice-covered and ice-free conditions, assessed the lability of Arctic tDOM to coastal microbial communities from the Chukchi Sea, and identified bacterial taxa that respond to rapid increases in tDOM. Once thought to be predominantly refractory, we found that ∼7% of dissolved organic carbon and ∼38% of dissolved organic nitrogen from tDOM was bioavailable to receiving marine microbial communities on short 4 - 6 day time scales. The addition of tDOM shifted bacterial community structure toward more copiotrophic taxa and away from more oligotrophic taxa. Although no single order was found to respond universally (positively or negatively) to the tDOM addition, this study identified 20 indicator species as possible sentinels for increased tDOM. These data suggest the true ecological impact of tDOM will be widespread across many bacterial taxa and that shifts in coastal microbial community composition should be anticipated.

Atmospheric Blocking and Atlantic Multi-Decadal Ocean Variability

NASA Technical Reports Server (NTRS)

Haekkinen, Sirpa; Rhines, Peter B.; Worthlen, Denise L.

2011-01-01

Based on the 20th century atmospheric reanalysis, winters with more frequent blocking, in a band of blocked latitudes from Greenland to Western Europe, are found to persist over several decades and correspond to a warm North Atlantic Ocean, in-phase with Atlantic multi-decadal ocean variability. Atmospheric blocking over the northern North Atlantic, which involves isolation of large regions of air from the westerly circulation for 5 days or more, influences fundamentally the ocean circulation and upper ocean properties by impacting wind patterns. Winters with clusters of more frequent blocking between Greenland and western Europe correspond to a warmer, more saline subpolar ocean. The correspondence between blocked westerly winds and warm ocean holds in recent decadal episodes (especially, 1996-2010). It also describes much longer-timescale Atlantic multidecadal ocean variability (AMV), including the extreme, pre-greenhouse-gas, northern warming of the 1930s-1960s. The space-time structure of the wind forcing associated with a blocked regime leads to weaker ocean gyres and weaker heat-exchange, both of which contribute to the warm phase of AMV.

The positive Indian Ocean Dipole-like response in the tropical Indian Ocean to global warming

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

Luo, Yiyong; Lu, Jian; Liu, Fukai

Climate models project a positive Indian Ocean Dipole (pIOD)-like SST response in the tropical Indian Ocean to global warming. By employing the Community Earth System Model (CESM) and applying an overriding technique to its ocean component Parallel Ocean Program version 2 (POP2), this study investigates the similarity and difference of the formation mechanisms for the changes in the tropical Indian Ocean during the pIOD versus global warming. Results show that their formation processes and related seasonality are quite similar; in particular, the Bjerknes feedback is the leading mechanism in producing the anomalous cooling over the eastern tropics in both cases.more » Some differences are also found, including that the cooling effect of the vertical advection over the eastern tropical Indian Ocean is dominated by the anomalous vertical velocity during the pIOD while it is dominated by the anomalous upper-ocean stratification under global warming. Lastly, these findings above are further examined with an analysis of the mixed layer heat budget.« less

The positive Indian Ocean Dipole-like response in the tropical Indian Ocean to global warming

DOE PAGES

Luo, Yiyong; Lu, Jian; Liu, Fukai; ...

2016-02-04

Climate models project a positive Indian Ocean Dipole (pIOD)-like SST response in the tropical Indian Ocean to global warming. By employing the Community Earth System Model (CESM) and applying an overriding technique to its ocean component Parallel Ocean Program version 2 (POP2), this study investigates the similarity and difference of the formation mechanisms for the changes in the tropical Indian Ocean during the pIOD versus global warming. Results show that their formation processes and related seasonality are quite similar; in particular, the Bjerknes feedback is the leading mechanism in producing the anomalous cooling over the eastern tropics in both cases.more » Some differences are also found, including that the cooling effect of the vertical advection over the eastern tropical Indian Ocean is dominated by the anomalous vertical velocity during the pIOD while it is dominated by the anomalous upper-ocean stratification under global warming. Lastly, these findings above are further examined with an analysis of the mixed layer heat budget.« less

Dissolved organic sulfur in the ocean: Biogeochemistry of a petagram inventory

NASA Astrophysics Data System (ADS)

Ksionzek, Kerstin B.; Lechtenfeld, Oliver J.; McCallister, S. Leigh; Schmitt-Kopplin, Philippe; Geuer, Jana K.; Geibert, Walter; Koch, Boris P.

2016-10-01

Although sulfur is an essential element for marine primary production and critical for climate processes, little is known about the oceanic pool of nonvolatile dissolved organic sulfur (DOS). We present a basin-scale distribution of solid-phase extractable DOS in the East Atlantic Ocean and the Atlantic sector of the Southern Ocean. Although molar DOS versus dissolved organic nitrogen (DON) ratios of 0.11 ± 0.024 in Atlantic surface water resembled phytoplankton stoichiometry (sulfur/nitrogen ~ 0.08), increasing dissolved organic carbon (DOC) versus DOS ratios and decreasing methionine-S yield demonstrated selective DOS removal and active involvement in marine biogeochemical cycles. Based on stoichiometric estimates, the minimum global inventory of marine DOS is 6.7 petagrams of sulfur, exceeding all other marine organic sulfur reservoirs by an order of magnitude.

Achieving Negative CO2 Emissions by Protecting Ocean Chemistry

NASA Astrophysics Data System (ADS)

Cannara, A.

2016-12-01

Industrial Age CO2 added 1.8 trillion tons to the atmosphere. About ¼ has dissolved in seas. The rest still dissolves, bolstered by present emissions of >30 gigatons/year. Airborne & oceanic CO2 have induced sea warming & ocean acidification*. This paper suggests a way to induce a negative CO2-emissions environment for climate & oceans - preserve the planet`s dominant CO2-sequestration system ( 1 gigaton/year via calcifying sea life**) by promptly protecting ocean chemistry via expansion of clean power for both lime production & replacement of CO2-emitting sources. Provide natural alkali (CaO, MgO…) to oceans to maintain average pH above 8.0, as indicated by marine biologists. That alkali (lime) is available from past calcifying life's limestone deposits, so can be returned safely to seas once its CO2 is removed & permanently sequestered (Carbfix, BSCP, etc.***). Limestone is a dense source of CO2 - efficient processing per mole sequestered. Distribution of enough lime is possible via cargo-ship transits - 10,000 tons lime/transit, 1 million transits/year. New Panamax ships carry 120,000 tons. Just 10,000/transit allows gradual reduction of present & past CO2 emissions effects, if coupled with combustion-power reductions. CO2 separation from limestone, as in cement plants, consumes 400kWHrs of thermal energy per ton of output lime (or CO2). To combat yearly CO2 dissolution in seas, we must produce & distribute about 10gigatons of lime/year. Only nuclear power produces the clean energy (thousands of terawatt hours) to meet this need - 1000 dedicated 1GWe reactors, processing 12 cubic miles of limestone/year & sequestering CO2 into a similar mass of basalt. Basalt is common in the world. Researchers*** report it provides good, mineralized CO2 sequestration. The numbers above allow gradual CO2 reduction in air and seas, if we return to President Kennedy's energy path: http://tinyurl.com/6xgpkfa We're on an environmental precipice due to failure to eliminate combustion power by 2000, per JFK. Brewer says oceans are in "precarious balance". Robust action now gradually restores a safer environment through ocean protection. * "A short history of ocean acidification science in the 20th century", Brewer, MBARI, 2013. ** AAAS Science, Canfield & Kump, 1 Feb. 2013. *** AAAS Science, Mattcr et alia, 10 Jun 2016.

Dissolved oxygen in two Oregon estuaries: Importance of the ocean-estuary connection

EPA Science Inventory

We examined the role of the ocean –estuary connection in influencing periodic reductions in dissolved oxygen (DO) levels in Yaquina and Yachats estuaries, Oregon, USA. In the Yaquina Estuary, there is close coupling between the coastal ocean and the estuary. As a result, low DO ...

Dissolved oxygen in two Oregon estuaries: The importance of the ocean-estuary connection

EPA Science Inventory

We examined the role of the ocean –estuary connection in influencing periodic reductions in dissolved oxygen (DO) levels in Yaquina and Yachats estuaries, Oregon, USA. In the Yaquina Estuary, there is close coupling between the coastal ocean and the estuary. As a result, low DO ...

Ocean (de)oxygenation from the Last Glacial Maximum to the twenty-first century: insights from Earth System models.

PubMed

Bopp, L; Resplandy, L; Untersee, A; Le Mezo, P; Kageyama, M

2017-09-13

All Earth System models project a consistent decrease in the oxygen content of oceans for the coming decades because of ocean warming, reduced ventilation and increased stratification. But large uncertainties for these future projections of ocean deoxygenation remain for the subsurface tropical oceans where the major oxygen minimum zones are located. Here, we combine global warming projections, model-based estimates of natural short-term variability, as well as data and model estimates of the Last Glacial Maximum (LGM) ocean oxygenation to gain some insights into the major mechanisms of oxygenation changes across these different time scales. We show that the primary uncertainty on future ocean deoxygenation in the subsurface tropical oceans is in fact controlled by a robust compensation between decreasing oxygen saturation (O 2sat ) due to warming and decreasing apparent oxygen utilization (AOU) due to increased ventilation of the corresponding water masses. Modelled short-term natural variability in subsurface oxygen levels also reveals a compensation between O 2sat and AOU, controlled by the latter. Finally, using a model simulation of the LGM, reproducing data-based reconstructions of past ocean (de)oxygenation, we show that the deoxygenation trend of the subsurface ocean during deglaciation was controlled by a combination of warming-induced decreasing O 2sat and increasing AOU driven by a reduced ventilation of tropical subsurface waters.This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'. © 2017 The Author(s).

Ocean (de)oxygenation from the Last Glacial Maximum to the twenty-first century: insights from Earth System models

NASA Astrophysics Data System (ADS)

Bopp, L.; Resplandy, L.; Untersee, A.; Le Mezo, P.; Kageyama, M.

2017-08-01

All Earth System models project a consistent decrease in the oxygen content of oceans for the coming decades because of ocean warming, reduced ventilation and increased stratification. But large uncertainties for these future projections of ocean deoxygenation remain for the subsurface tropical oceans where the major oxygen minimum zones are located. Here, we combine global warming projections, model-based estimates of natural short-term variability, as well as data and model estimates of the Last Glacial Maximum (LGM) ocean oxygenation to gain some insights into the major mechanisms of oxygenation changes across these different time scales. We show that the primary uncertainty on future ocean deoxygenation in the subsurface tropical oceans is in fact controlled by a robust compensation between decreasing oxygen saturation (O2sat) due to warming and decreasing apparent oxygen utilization (AOU) due to increased ventilation of the corresponding water masses. Modelled short-term natural variability in subsurface oxygen levels also reveals a compensation between O2sat and AOU, controlled by the latter. Finally, using a model simulation of the LGM, reproducing data-based reconstructions of past ocean (de)oxygenation, we show that the deoxygenation trend of the subsurface ocean during deglaciation was controlled by a combination of warming-induced decreasing O2sat and increasing AOU driven by a reduced ventilation of tropical subsurface waters. This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'.

Characterisation of intact proteins in aquatic samples from the Florida Everglades

NASA Astrophysics Data System (ADS)

Jones, V.; Ruddell, C. J.; Wainwright, G.; Rees, H. H.; Jaffe, R.; Penkman, K. E. H.; Collins, C. J.; Wolff, G. A.

2003-04-01

Dissolved organic nitrogen (DON) is the largest reservoir of reduced nitrogen in the oceans. Limited knowledge of the molecular composition of DON hinders our understanding of its cycling. The need to comprehend the DON cycle is nowadays more imperative than ever, as there is evidence that concentrations of nitrate are decreasing, while concentrations of DON are increasing in the surface ocean, as an indirect effect of global warming and hence stratification of the water column (Karl et al., 2001). Proteins typically account for 5-10% of DON. Recently, it has been suggested that certain, bacterially-derived, proteins found in the ocean are not as labile as was originally thought (e.g. Tanoue et al., 1995) and may therefore form a crucial part of the long term DON cycle. Here, we have applied gel electrophoresis in combination with mass spectrometry and amino acid enantiomer (D/L) analysis, to characterise proteins from aquatic samples and consider their origin. Samples were collected in the Florida Everglades at locations selected to represent an array of ecosystems, ranging from marsh water to marine coastal environments. Application of gel electrophoresis in combination with mass spectrometry revealed that each sample had a complex and characteristic protein distribution. Some proteins were common to more than one site. The bacterial protein of 48 kDa, previously reported as ubiquitous in the open ocean (e.g. Tanoue et al., 1995), was only present at one sampling location strongly affected by offshore currents. Amino acid enantiomer (D/L) analysis revealed that the bacterial input to amino acid nitrogen was an order of magnitude smaller than that reported for open ocean samples (McCarthy et al., 1998), although a trend towards higher bacterial input was observed from freshwater to marine sampling locations. We suggest that this is due to the presence of additional sources of protein to the DON pool, such as the higher plant vegetation, in freshwater and coastal environments compared to the open ocean. References Karl, D., Bidigare, R.R., Letelier, R.M., 2001. Long-term changes in plankton community structure and productivity in the North Pacific Subtropical Gyre: The domain shift hypothesis. Deep-Sea Research II, 48: 1449-1470. McCarthy, M.D., Hedges, J.J. Benner, R., 1998. Major bacterial contribution to marine dissolved organic nitrogen. Science, 281: 231-234. Tanoue E., Sumie, N., Kamo, M., Tsurita, A, 1995. Bacterial membranes: Possible sources of major dissolved protein in seawater. Geochimica and Cosmochimica Acta, 59: 2643-2648

Cadmium cycling in the water column of the Kuroshio-Oyashio Extension region: Insights from dissolved and particulate isotopic composition

NASA Astrophysics Data System (ADS)

Yang, Shun-Chung; Zhang, Jing; Sohrin, Yoshiki; Ho, Tung-Yuan

2018-07-01

We measured dissolved and particulate Cd isotopic composition in the water column of a meridional transect across the Kuroshio-Oyashio Extension region in a Japanese GEOTRACES cruise to investigate the relative influence of physical and biogeochemical processes on Cd cycling in the Northwestern Pacific Ocean. Located at 30-50°N along 165°E, the transect across the extension region possesses dramatic hydrographic contrast. Cold surface water and a relatively narrow and shallow thermocline characterizes the Oyashio Extension region in contrast to a relatively warm and highly stratified surface water and thermocline in the Kuroshio Extension region. The contrasting hydrographic distinction at the study site provides us with an ideal platform to investigate the spatial variations of Cd isotope fractionation systems in the ocean. Particulate samples demonstrated biologically preferential uptake of light Cd isotopes, and the fractionation effect varied dramatically in the surface water of the two regions, with relatively large fractionation factors in the Oyashio region. Based on the relationship of dissolved Cd concentrations and isotopic composition, we found that a closed system fractionation model can reasonably explain the relationship in the Kuroshio region. However, using dissolved Cd isotopic data, either a closed system or steady-state open system fractionation model may explain the relationship in the surface water of the Oyashio region. Particulate δ114/110Cd data further supports that the surface water of the Oyashio region matches a steady-state open system model more closely. Contrary to the surface water, the distribution of potential density exhibits comparable patterns with Cd elemental and isotopic composition in the thermocline and deep water in the two extension regions, showing that physical processes are the dominant forcing controlling Cd cycling in the deep waters. The results demonstrate that Cd isotope fractionation can match either a closed or open system Rayleigh fractionation model, depending on the relative contribution of physical and biogeochemical processes on its cycling.

Incorporating Density Properties of MgSO4 Brines Into Icy World Ocean Simulations

NASA Astrophysics Data System (ADS)

Goodman, J. C.; Vance, S.

2011-12-01

The structure and flow of the subsurface oceans in icy worlds depends on the sources of buoyancy within these oceans. Buoyancy is determined by the equation of state, in which density is a nonlinear function of temperature, salinity, and pressure. Equations of state for terrestrial seawater (with Na and Cl as the principal dissolved species) are well-developed, but icy world oceans may contain a different balance of species, including Na, Mg, SO4, and NH4 (Kargel et al, 2000). Recent work by Vance and Brown (2011, pers. comm.) has mapped out the density and thermodynamic properties of MgSO4 brines under icy world conditions. We have developed code to incorporate this equation of state data for MgSO4 brines into two different ocean simulation models. First, we investigate a single-column convection model, which is able to find the equilibrium structure and heat transport of an icy world ocean. We explore the heat transport through the ocean subject to a variety of assumptions about ocean salinity and seafloor heat and salt flux. We resolve the paradox posed by Vance and Brown (2004): warm salty MgSO4 brine emitted by a seafloor hydrothermal system may be positively buoyant at the seafloor, but become negatively buoyant (sinking) at lower pressure. How does heat escape the ocean, if it cannot be transported by convection? Second, we add MgSO4 dynamics to a full 3-D time-dependent general circulation model (the MIT GCM), which is able to simulate both the global-scale circulation of the world's ocean and investigate the highly turbulent dynamics of buoyant hydrothermal systems. We ask, "Are buoyancy-driven flows in a MgSO4 brine ocean significantly different than similarly-driven flows in terrestrial seawater?"

The Indonesian Throughflow (ITF) and its impacts on the Indian Ocean during the global warming slowdown period

NASA Astrophysics Data System (ADS)

Makarim, S.; Liu, Z.; Yu, W.; Yan, X.; Sprintall, J.

2016-12-01

The global warming slowdown indicated by a slower warming rate at the surface layer accompanied by stronger heat transport into the deeper layers has been explored in the Indian Ocean. Although the mechanisms of the global warming slowdown are still under warm debate, some clues have been recognized that decadal La Nina like-pattern induced decadal cooling in the Pacific Ocean and generated an increase of the Indonesian Throughflow (ITF) transport in 2004-2010. However, how the ITF spreading to the interior of the Indian Ocean and the impact of ITF changes on the Indian Ocean, in particular its water mass transformation and current system are still unknown. To this end, we analyzed thermohaline structure and current system at different depths in the Indian Ocean both during and just before the global warming slowdown period using the ORAS4 and ARGO dataset. Here, we found the new edge of ITF at off Sumatra presumably as northward deflection of ITF Lombok Strait, and The Monsoon Onset Monitoring and Social Ecology Impact (MOMSEI) and Java Upwelling Variation Observation (JUVO) dataset confirmed this evident. An isopycnal mixing method initially proposed by Du et al. (2013) is adopted to quantify the spreading of ITF water in the Indian Ocean, and therefore the impacts of ITF changes on the variation of the Agulhas Current, Leuween Current, Bay of Bengal Water. This study also prevailed the fresher salinity in the Indian Ocean during the slowdown warming period were not only contributed by stronger transport of the ITF, but also by freshening Arabian Sea and infiltrating Antartic Intermediate Water (AAIW).

Mean hydrography on the continental shelf from 26 repeat glider deployments along Southeastern Australia

NASA Astrophysics Data System (ADS)

Schaeffer, Amandine; Roughan, Moninya; Austin, Tim; Everett, Jason D.; Griffin, David; Hollings, Ben; King, Edward; Mantovanelli, Alessandra; Milburn, Stuart; Pasquer, Benedicte; Pattiaratchi, Charitha; Robertson, Robin; Stanley, Dennis; Suthers, Iain; White, Dana

2016-08-01

Since 2008, 26 glider missions have been undertaken along the continental shelf of southeastern Australia. Typically these missions have spanned the continental shelf on the inshore edge of the East Australian Current from 29.5-33.5°S. This comprehensive dataset of over 33,600 CTD profiles from the surface to within 10 m of the bottom in water depths ranging 25-200 m provides new and unprecedented high resolution observations of the properties of the continental shelf waters adjacent to a western boundary current, straddling the region where it separates from the coast. The region is both physically and biologically significant, and is also in a hotspot of ocean warming. We present gridded mean fields for temperature, salinity and density, but also dissolved oxygen and chlorophyll-a fluorescence indicative of phytoplankton biomass. This data will be invaluable for understanding shelf stratification, circulation, biophysical and bio-geochemical interactions, as well as for the validation of high-resolution ocean models or serving as teaching material.

Mean hydrography on the continental shelf from 26 repeat glider deployments along Southeastern Australia.

PubMed

Schaeffer, Amandine; Roughan, Moninya; Austin, Tim; Everett, Jason D; Griffin, David; Hollings, Ben; King, Edward; Mantovanelli, Alessandra; Milburn, Stuart; Pasquer, Benedicte; Pattiaratchi, Charitha; Robertson, Robin; Stanley, Dennis; Suthers, Iain; White, Dana

2016-08-30

Since 2008, 26 glider missions have been undertaken along the continental shelf of southeastern Australia. Typically these missions have spanned the continental shelf on the inshore edge of the East Australian Current from 29.5-33.5°S. This comprehensive dataset of over 33,600 CTD profiles from the surface to within 10 m of the bottom in water depths ranging 25-200 m provides new and unprecedented high resolution observations of the properties of the continental shelf waters adjacent to a western boundary current, straddling the region where it separates from the coast. The region is both physically and biologically significant, and is also in a hotspot of ocean warming. We present gridded mean fields for temperature, salinity and density, but also dissolved oxygen and chlorophyll-a fluorescence indicative of phytoplankton biomass. This data will be invaluable for understanding shelf stratification, circulation, biophysical and bio-geochemical interactions, as well as for the validation of high-resolution ocean models or serving as teaching material.

Distinctive ocean interior changes during the recent warming slowdown

PubMed Central

Cheng, Lijing; Zheng, Fei; Zhu, Jiang

2015-01-01

The earth system experiences continuous heat input, but a “climate hiatus” of upper ocean waters has been observed in this century. This leads to a question: where is the extra heat going? Using four in situ observation datasets, we explore the ocean subsurface temperature changes from 2004 to 2013. The observations all show that the ocean has continued to gain heat in this century, which is indicative of anthropogenic global warming. However, a distinctive pattern of change in the interior ocean is observed. The sea surface (1–100 m) temperature has decreased in this century, accompanied by warming in the 101–300 m layer. This pattern is due to the changes in the frequency of El Niño and La Niña events (ENSO characteristics), according to both observations and CMIP5 model simulations. In addition, we show for the first time that the ocean subsurface within 301–700 m experienced a net cooling, indicative of another instance of variability in the natural ocean. Furthermore, the ocean layer of 701–1500 m has experienced significant warming. PMID:26394551

Distinctive ocean interior changes during the recent warming slowdown.

PubMed

Cheng, Lijing; Zheng, Fei; Zhu, Jiang

2015-09-23

The earth system experiences continuous heat input, but a "climate hiatus" of upper ocean waters has been observed in this century. This leads to a question: where is the extra heat going? Using four in situ observation datasets, we explore the ocean subsurface temperature changes from 2004 to 2013. The observations all show that the ocean has continued to gain heat in this century, which is indicative of anthropogenic global warming. However, a distinctive pattern of change in the interior ocean is observed. The sea surface (1-100 m) temperature has decreased in this century, accompanied by warming in the 101-300 m layer. This pattern is due to the changes in the frequency of El Niño and La Niña events (ENSO characteristics), according to both observations and CMIP5 model simulations. In addition, we show for the first time that the ocean subsurface within 301-700 m experienced a net cooling, indicative of another instance of variability in the natural ocean. Furthermore, the ocean layer of 701-1500 m has experienced significant warming.

Stochastic Modeling and Global Warming Trend Extraction For Ocean Acoustic Travel Times.

DTIC Science & Technology

1995-01-06

consideration and that these models can not currently be relied upon by themselves to predict global warming . Experimental data is most certainly needed, not...only to measure global warming itself, but to help improve the ocean model themselves. (AN)

Decreased abundance of crustose coralline algae due to ocean acidification

USGS Publications Warehouse

Kuffner, Ilsa B.; Andersson, Andreas J; Jokiel, Paul L.; Rodgers, Ku'ulei S.; Mackenzie, Fred T.

2008-01-01

Owing to anthropogenic emissions, atmospheric concentrations of carbon dioxide could almost double between 2006 and 2100 according to business-as-usual carbon dioxide emission scenarios1. Because the ocean absorbs carbon dioxide from the atmosphere2, 3, 4, increasing atmospheric carbon dioxide concentrations will lead to increasing dissolved inorganic carbon and carbon dioxide in surface ocean waters, and hence acidification and lower carbonate saturation states2, 5. As a consequence, it has been suggested that marine calcifying organisms, for example corals, coralline algae, molluscs and foraminifera, will have difficulties producing their skeletons and shells at current rates6, 7, with potentially severe implications for marine ecosystems, including coral reefs6, 8, 9, 10, 11. Here we report a seven-week experiment exploring the effects of ocean acidification on crustose coralline algae, a cosmopolitan group of calcifying algae that is ecologically important in most shallow-water habitats12, 13, 14. Six outdoor mesocosms were continuously supplied with sea water from the adjacent reef and manipulated to simulate conditions of either ambient or elevated seawater carbon dioxide concentrations. The recruitment rate and growth of crustose coralline algae were severely inhibited in the elevated carbon dioxide mesocosms. Our findings suggest that ocean acidification due to human activities could cause significant change to benthic community structure in shallow-warm-water carbonate ecosystems.

Dissolved oxygen in two Oregon estuaries: The importance of the ocean-estuary connection - May 16, 2011

EPA Science Inventory

We examined the role of the ocean –estuary connection in influencing periodic reductions in dissolved oxygen (DO) levels in Yaquina and Yachats estuaries, Oregon, USA. In the Yaquina Estuary, there is close coupling between the coastal ocean and the estuary. As a result, low DO ...

Utilizing Colored Dissolved Organic Matter to Derive Dissolved Black Carbon Export by Arctic Rivers

NASA Astrophysics Data System (ADS)

Stubbins, Aron; Spencer, Robert; Mann, Paul; Holmes, R.; McClelland, James; Niggemann, Jutta; Dittmar, Thorsten

2015-10-01

Wildfires have produced black carbon (BC) since land plants emerged. Condensed aromatic compounds, a form of BC, have accumulated to become a major component of the soil carbon pool. Condensed aromatics leach from soils into rivers, where they are termed dissolved black carbon (DBC). The transport of DBC by rivers to the sea is a major term in the global carbon and BC cycles. To estimate Arctic river DBC export, 25 samples collected from the six largest Arctic rivers (Kolyma, Lena, Mackenzie, Ob’, Yenisey and Yukon) were analyzed for dissolved organic carbon (DOC), colored dissolved organic matter (CDOM), and DBC. A simple, linear regression between DOC and DBC indicated that DBC accounted for 8.9 ± 0.3% DOC exported by Arctic rivers. To improve upon this estimate, an optical proxy for DBC was developed based upon the linear correlation between DBC concentrations and CDOM light absorption coefficients at 254 nm (a254). Relatively easy to measure a254 values were determined for 410 Arctic river samples between 2004 and 2010. Each of these a254 values was converted to a DBC concentration based upon the linear correlation, providing an extended record of DBC concentration. The extended DBC record was coupled with daily discharge data from the six rivers to estimate riverine DBC loads using the LOADEST modeling program. The six rivers studied cover 53% of the pan-Arctic watershed and exported 1.5 ± 0.1 million tons of DBC per year. Scaling up to the full area of the pan-Arctic watershed, we estimate that Arctic rivers carry 2.8 ± 0.3 million tons of DBC from land to the Arctic Ocean each year. This equates to ~8% of Arctic river DOC export, slightly less than indicated by the simpler DBC vs DOC correlation-based estimate. Riverine discharge is predicted to increase in a warmer Arctic. DBC export was positively correlated with river runoff, suggesting that the export of soil BC to the Arctic Ocean is likely to increase as the Arctic warms.

Change in ocean subsurface environment to suppress tropical cyclone intensification under global warming.

PubMed

Huang, Ping; Lin, I-I; Chou, Chia; Huang, Rong-Hui

2015-05-18

Tropical cyclones (TCs) are hazardous natural disasters. Because TC intensification is significantly controlled by atmosphere and ocean environments, changes in these environments may cause changes in TC intensity. Changes in surface and subsurface ocean conditions can both influence a TC's intensification. Regarding global warming, minimal exploration of the subsurface ocean has been undertaken. Here we investigate future subsurface ocean environment changes projected by 22 state-of-the-art climate models and suggest a suppressive effect of subsurface oceans on the intensification of future TCs. Under global warming, the subsurface vertical temperature profile can be sharpened in important TC regions, which may contribute to a stronger ocean coupling (cooling) effect during the intensification of future TCs. Regarding a TC, future subsurface ocean environments may be more suppressive than the existing subsurface ocean environments. This suppressive effect is not spatially uniform and may be weak in certain local areas.

Change in ocean subsurface environment to suppress tropical cyclone intensification under global warming

PubMed Central

Huang, Ping; Lin, I. -I; Chou, Chia; Huang, Rong-Hui

2015-01-01

Tropical cyclones (TCs) are hazardous natural disasters. Because TC intensification is significantly controlled by atmosphere and ocean environments, changes in these environments may cause changes in TC intensity. Changes in surface and subsurface ocean conditions can both influence a TC's intensification. Regarding global warming, minimal exploration of the subsurface ocean has been undertaken. Here we investigate future subsurface ocean environment changes projected by 22 state-of-the-art climate models and suggest a suppressive effect of subsurface oceans on the intensification of future TCs. Under global warming, the subsurface vertical temperature profile can be sharpened in important TC regions, which may contribute to a stronger ocean coupling (cooling) effect during the intensification of future TCs. Regarding a TC, future subsurface ocean environments may be more suppressive than the existing subsurface ocean environments. This suppressive effect is not spatially uniform and may be weak in certain local areas. PMID:25982028

Sensitive monitoring of iodine species in sea water using capillary electrophoresis: vertical profiles of dissolved iodine in the Pacific Ocean.

PubMed

Huang, Zhuo; Ito, Kazuaki; Morita, Isamu; Yokota, Kuriko; Fukushi, Keiichi; Timerbaev, Andrei R; Watanabe, Shuichi; Hirokawa, Takeshi

2005-08-01

Using a novel high-sensitivity capillary electrophoretic method, vertical distributions of iodate, iodide, total inorganic iodine, dissolved organic iodine and total iodine in the North Pacific Ocean (0-5500 m) were determined without any sample pre-treatment other than UV irradiation before total iodine analysis. An extensive set of data demonstrated that the iodine behaviour in the ocean water collected during a cruise in the North Pacific Ocean in February-March 2003 was not conservative but correlated with variations in concentrations of dissolved oxygen and nutrient elements such as silicon, nitrogen and phosphorus. This suggests that the vertical distribution of iodine is associated with biological activities. The dissolved organic iodine was found in the euphotic zone in accord with observations elsewhere in the oceans. The vertical profile of dissolved organic iodine also appears to be related to biogeochemical activity. The concentrations of all measured iodine species vary noticeably above 1000 m but only minor latitudinal changes occur below 1000 m and slight vertical alterations can be observed below 2400 m. These findings are thought to reflect the stratification of nutrients and iodine species with different biological activities in the water column.

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.

Warming and surface ocean acidification over the last deglaciation: implications for foraminiferal assemblages

NASA Astrophysics Data System (ADS)

Dyez, K. A.; Hoenisch, B.; deMenocal, P. B.

2017-12-01

Although plankton drift with ocean currents, their presence and relative abundance varies across latitudes and environmental seawater conditions (e.g. temperature, pH, salinity). While earlier studies have focused on temperature as the primary factor for determining the regional species composition of planktic foraminiferal communities, evidence has recently been presented that foraminiferal shell thickness varies with ocean pH, and it remains unclear whether ongoing ocean acidification will cause ecological shifts within this plankton group. The transition from the last glacial maximum (LGM; 19,000-23,000 years B.P.) to the late Holocene (0-5,000 years B.P.) was characterized by both warming and acidification of the surface ocean, and thus provides an opportunity to study ecosystem shifts in response to these environmental changes. Here we provide new δ11B, Mg/Ca, and δ18O measurements from a suite of global sediment cores spanning this time range. We use these geochemical data to reconstruct ocean temperature, pH and salinity and pair the new data with previously published analyses of planktic foraminifera assemblages to study the respective effects of ocean warming and acidification on the foraminiferal habitat. At most open-ocean sample locations, our proxies indicate warming and acidification similar to previously published estimates, but in some marginal seas and coastal locations pH changes little between over the glacial termination. At face value, these observations suggest that warming is generally more important for ecosystem changes than acidification, at least over the slow rates of warming and ocean acidification in this time period. While geochemical data collection is being completed, we aim to include these data in an ecological model of foraminiferal habitat preferences.

Impact of ocean acidification and warming on the productivity of a rock pool community.

PubMed

Legrand, Erwann; Riera, Pascal; Bohner, Olivier; Coudret, Jérôme; Schlicklin, Ferdinand; Derrien, Marie; Martin, Sophie

2018-05-01

This study examined experimentally the combined effect of ocean acidification and warming on the productivity of rock pool multi-specific assemblages, composed of coralline algae, fleshy algae, and grazers. Natural rock pool communities experience high environmental fluctuations. This may confer physiological advantage to rock pool communities when facing predicted acidification and warming. The effect of ocean acidification and warming have been assessed at both individual and assemblage level to examine the importance of species interactions in the response of assemblages. We hypothesized that rock pool assemblages have physiological advantage when facing predicted ocean acidification and warming. Species exhibited species-specific responses to increased temperature and pCO 2 . Increased temperature and pCO 2 have no effect on assemblage photosynthesis, which was mostly influenced by fleshy algal primary production. The response of coralline algae to ocean acidification and warming depended on the season, which evidenced the importance of physiological adaptations to their environment in their response to climate change. We suggest that rock pool assemblages are relatively robust to changes in temperature and pCO 2 , in terms of primary production. Copyright © 2018 Elsevier Ltd. All rights reserved.

Alkyl nitrate (C1-C3) depth profiles in the tropical Pacific Ocean

NASA Astrophysics Data System (ADS)

Dahl, E. E.; Yvon-Lewis, S. A.; Saltzman, E. S.

2007-01-01

This paper reports the first depth profile measurements of methyl, ethyl, isopropyl and n-propyl nitrates in the tropical Pacific Ocean. Depth profile measurements were made at 22 stations during the Project Halocarbon Air Sea Exchange cruise, in warm pool, equatorial, subequatorial, and gyre waters. The highest concentrations, up to several hundred pM of methyl nitrate, were observed in the central Pacific within 8 degrees of the equator. In general, alkyl nitrate levels were highest in the surface mixed layer, and decreased with depth below the mixed layer. The spatial distribution of the alkyl nitrates suggests that there is a strong source associated with biologically productive ocean regions, that is characterized by high ratios of methyl:ethyl nitrate. However, the data do not allow discrimination between direct biological emissions and photochemistry as production mechanisms. Alkyl nitrates were consistently detectable at several hundred meters depth. On the basis of the estimated chemical loss rate of these compounds, we conclude that deep water alkyl nitrates must be produced in situ. Possible sources include free radical processes initiated by radioactive decay or cosmic rays, enzymatically mediated reactions involving bacteria, or unidentified chemical mechanisms involving dissolved organic matter.

Predicting Chromophoric Dissolved Organic Matter Distributions in Coastal Waters

DTIC Science & Technology

2006-01-01

Predicting Chromophoric Dissolved Organic Matter Distributions in Coastal Waters Robert F. Chen Environmental , Earth and Ocean Sciences...G. Bernard Gardner Environmental , Coastal and Ocean Sciences University of Massachusetts Boston 100 Morrissey Boulevard Boston, MA 02125-3393...phone: (617)287-7451 fax: (617)287-7474 email: bernie.gardner@umb.edu Yong Tian Environmental , Coastal and Ocean Sciences University of

Predicting Chromophoric Dissolved Organic Matter Distributions in Coastal Waters

DTIC Science & Technology

2007-09-30

Predicting Chromophoric Dissolved Organic Matter Distributions in Coastal Waters Robert F. Chen Environmental , Earth and Ocean Sciences...G. Bernard Gardner Environmental , Coastal and Ocean Sciences University of Massachusetts Boston 100 Morrissey Boulevard Boston, MA 02125-3393...phone: (617)287-7451 fax: (617)287-7474 email: bernie.gardner@umb.edu Yong Tian Environmental , Coastal and Ocean Sciences University of

Predicting Chromophoric Dissolved Organic Matter Distributions in Coastal Waters

DTIC Science & Technology

2008-09-30

Predicting Chromophoric Dissolved Organic Matter Distributions in Coastal Waters Robert F. Chen Environmental , Earth and Ocean...umb.edu G. Bernard Gardner Environmental , Coastal and Ocean Sciences University of Massachusetts Boston 100 Morrissey Boulevard Boston, MA...02125-3393 phone: (617) 287-7451 fax: (617) 287-7474 email: bernie.gardner@umb.edu Yong Tian Environmental , Coastal and Ocean Sciences

Fluvial response to abrupt global warming at the Palaeocene/Eocene boundary.

PubMed

Foreman, Brady Z; Heller, Paul L; Clementz, Mark T

2012-11-01

Climate strongly affects the production of sediment from mountain catchments as well as its transport and deposition within adjacent sedimentary basins. However, identifying climatic influences on basin stratigraphy is complicated by nonlinearities, feedback loops, lag times, buffering and convergence among processes within the sediment routeing system. The Palaeocene/Eocene thermal maximum (PETM) arguably represents the most abrupt and dramatic instance of global warming in the Cenozoic era and has been proposed to be a geologic analogue for anthropogenic climate change. Here we evaluate the fluvial response in western Colorado to the PETM. Concomitant with the carbon isotope excursion marking the PETM we document a basin-wide shift to thick, multistoried, sheets of sandstone characterized by variable channel dimensions, dominance of upper flow regime sedimentary structures, and prevalent crevasse splay deposits. This progradation of coarse-grained lithofacies matches model predictions for rapid increases in sediment flux and discharge, instigated by regional vegetation overturn and enhanced monsoon precipitation. Yet the change in fluvial deposition persisted long after the approximately 200,000-year-long PETM with its increased carbon dioxide levels in the atmosphere, emphasizing the strong role the protracted transmission of catchment responses to distant depositional systems has in constructing large-scale basin stratigraphy. Our results, combined with evidence for increased dissolved loads and terrestrial clay export to world oceans, indicate that the transient hyper-greenhouse climate of the PETM may represent a major geomorphic 'system-clearing event', involving a global mobilization of dissolved and solid sediment loads on Earth's surface.

Ocean acidification but not warming alters sex determination in the Sydney rock oyster, Saccostrea glomerata.

PubMed

Parker, Laura M; O'Connor, Wayne A; Byrne, Maria; Dove, Michael; Coleman, Ross A; Pörtner, Hans-O; Scanes, Elliot; Virtue, Patti; Gibbs, Mitchell; Ross, Pauline M

2018-02-14

Whether sex determination of marine organisms can be altered by ocean acidification and warming during this century remains a significant, unanswered question. Here, we show that exposure of the protandric hermaphrodite oyster, Saccostrea glomerata to ocean acidification, but not warming, alters sex determination resulting in changes in sex ratios. After just one reproductive cycle there were 16% more females than males. The rate of gametogenesis, gonad area, fecundity, shell length, extracellular pH and survival decreased in response to ocean acidification. Warming as a sole stressor slightly increased the rate of gametogenesis, gonad area and fecundity, but this increase was masked by the impact of ocean acidification at a level predicted for this century. Alterations to sex determination, sex ratios and reproductive capacity will have flow on effects to reduce larval supply and population size of oysters and potentially other marine organisms. © 2018 The Author(s).

Effects of Multiple Stressors on Red Abalone (Haliotis rufescens) Fertilization Success

NASA Astrophysics Data System (ADS)

Boch, C. A.; Aalto, E.; De Leo, G.; Litvin, S.; Lovera, C.; Micheli, F.; Woodson, C. B.; Monismith, S. G.; Barry, J. P.

2016-02-01

Acidification, hypoxia, and ocean warming are escalating threats in the world's coastal waters, with potentially severe consequences for marine life and ocean-based economies. In particular, eastern boundary current ecosystems, including the California Current Large Marine Ecosystem (CCLME), are experiencing large-scale declines in pH and dissolved oxygen (DO)—with the latter linked to changes in thermal stratification and shoaling of the oxygen minimum zone. To examine the consequences of ocean acidification and other climate-related changes in oceanographic conditions on nearshore marine populations within the CCLME, we are assessing the potential effects of current and future upwelling-type conditions on the population dynamics of the red abalone (Haliotis rufescens), with a focus on sensitive early life history phases (e.g., fertilization, larval development, and juvenile growth and survival) expected to be important determinants of population dynamics. Here, we present the first experimental results on the impacts of combined exposures of low pH and low DO on abalone fertilization success. Our results show that abalone fertilization success is significantly reduced when the gametes are exposed to a decrease in seawater pH from 8.0 to 7.2. Furthermore, low pH in combination with hypoxic exposure—e.g., a decrease in dissolved oxygen from 6 mg/L DO to 1 mg/L DO—does not further decrease fertilization rates, suggesting a lack of synergistic or additive effects of these multiple stressors on the reduction of fertilization success. Although the focus of this study is to characterize the effects of multiple stressors on the early life history of abalone, the implications of these results are expected to be relevant for a variety of marine taxa with similar reproductive modes.

National Security Implications of Climate-related Risks and a Changing Climate

DTIC Science & Technology

2015-07-23

ocean acidification , and increased ocean warming pose threats to fish stocks, coral, mangroves, recreation and tourism, and the control of disease...vulnerable locations. USSOUTHCOM similarly highlights the threat that sea 23 July 2015 8 level rise and ocean acidification and warming...aids to GCCs. In addition, the National Oceanic and Atmospheric Administration (NOAA) provides long-term global climate projections, weather

Oceans Melting Greenland (OMG): 2017 Observations and the First Look at Yearly Ocean/Ice Changes

NASA Astrophysics Data System (ADS)

Willis, J. K.; Rignot, E. J.; Fenty, I. G.; Khazendar, A.; Moller, D.; Tinto, K. J.; Morison, J.; Schodlok, M.; Thompson, A. F.; Fukumori, I.; Holland, D.; Forsberg, R.; Jakobsson, M.; Dinardo, S. J.

2017-12-01

Oceans Melting Greenland (OMG) is an airborne NASA Mission to investigate the role of the oceans in ice loss around the margins of the Greenland Ice Sheet. A five-year campaign, OMG will directly measure ocean warming and glacier retreat around all of Greenland. By relating these two, we will explore one of the most pressing open questions about how climate change drives sea level rise: How quickly are the warming oceans melting the Greenland Ice Sheet from the edges? This year, OMG collected its second set of both elevation maps of marine terminating glaciers and ocean temperature and salinity profiles around all of Greenland. This give us our first look at year-to-year changes in both ice volume at the margins, as well as the volume and extent of warm, salty Atlantic water present on the continental shelf. In addition, we will compare recent data in east Greenland waters with historical ocean observations that suggest a long-term warming trend there. Finally, we will briefly review the multi-beam sonar and airborne gravity campaigns—both of which were completed last year—and the dramatic improvement they had on bathymetry maps over the continental shelf around Greenland.

Opposing authigenic controls on the isotopic signature of dissolved iron in hydrothermal plumes

NASA Astrophysics Data System (ADS)

Lough, A. J. M.; Klar, J. K.; Homoky, W. B.; Comer-Warner, S. A.; Milton, J. A.; Connelly, D. P.; James, R. H.; Mills, R. A.

2017-04-01

Iron is a scarce but essential micronutrient in the oceans that limits primary productivity in many regions of the surface ocean. The mechanisms and rates of Fe supply to the ocean interior are still poorly understood and quantified. Iron isotope ratios of different Fe pools can potentially be used to trace sources and sinks of the global Fe biogeochemical cycle if these boundary fluxes have distinct signatures. Seafloor hydrothermal vents emit metal rich fluids from mid-ocean ridges into the deep ocean. Iron isotope ratios have the potential to be used to trace the input of hydrothermal dissolved iron to the oceans if the local controls on the fractionation of Fe isotopes during plume dispersal in the deep ocean are understood. In this study we assess the behaviour of Fe isotopes in a Southern Ocean hydrothermal plume using a sampling program of Total Dissolvable Fe (TDFe), and dissolved Fe (dFe). We demonstrate that δ56Fe values of dFe (δ56dFe) within the hydrothermal plume change dramatically during early plume dispersal, ranging from -2.39 ± 0.05‰ to -0.13 ± 0.06‰ (2 SD). The isotopic composition of TDFe (δ56TDFe) was consistently heavier than dFe values, ranging from -0.31 ± 0.03‰ to 0.78 ± 0.05‰, consistent with Fe oxyhydroxide precipitation as the plume samples age. The dFe present in the hydrothermal plume includes stabilised dFe species with potential to be transported to the deep ocean. We estimate that stable dFe exported from the plume will have a δ56Fe of -0.28 ± 0.17‰. Further, we show that the proportion of authigenic iron-sulfide and iron-oxyhydroxide minerals precipitating in the buoyant plume exert opposing controls on the resultant isotope composition of dissolved Fe passed into the neutrally buoyant plume. We show that such controls yield variable dissolved Fe isotope signatures under the authigenic conditions reported from modern vent sites elsewhere, and so ought to be considered during iron isotope reconstructions of past hydrothermalism from ocean sediment records.

Amplified Arctic warming by phytoplankton under greenhouse warming.

PubMed

Park, Jong-Yeon; Kug, Jong-Seong; Bader, Jürgen; Rolph, Rebecca; Kwon, Minho

2015-05-12

Phytoplankton have attracted increasing attention in climate science due to their impacts on climate systems. A new generation of climate models can now provide estimates of future climate change, considering the biological feedbacks through the development of the coupled physical-ecosystem model. Here we present the geophysical impact of phytoplankton, which is often overlooked in future climate projections. A suite of future warming experiments using a fully coupled ocean-atmosphere model that interacts with a marine ecosystem model reveals that the future phytoplankton change influenced by greenhouse warming can amplify Arctic surface warming considerably. The warming-induced sea ice melting and the corresponding increase in shortwave radiation penetrating into the ocean both result in a longer phytoplankton growing season in the Arctic. In turn, the increase in Arctic phytoplankton warms the ocean surface layer through direct biological heating, triggering additional positive feedbacks in the Arctic, and consequently intensifying the Arctic warming further. Our results establish the presence of marine phytoplankton as an important potential driver of the future Arctic climate changes.

Indian Ocean corals reveal crucial role of World War II bias for twentieth century warming estimates.

PubMed

Pfeiffer, M; Zinke, J; Dullo, W-C; Garbe-Schönberg, D; Latif, M; Weber, M E

2017-10-31

The western Indian Ocean has been warming faster than any other tropical ocean during the 20 th century, and is the largest contributor to the global mean sea surface temperature (SST) rise. However, the temporal pattern of Indian Ocean warming is poorly constrained and depends on the historical SST product. As all SST products are derived from the International Comprehensive Ocean-Atmosphere dataset (ICOADS), it is challenging to evaluate which product is superior. Here, we present a new, independent SST reconstruction from a set of Porites coral geochemical records from the western Indian Ocean. Our coral reconstruction shows that the World War II bias in the historical sea surface temperature record is the main reason for the differences between the SST products, and affects western Indian Ocean and global mean temperature trends. The 20 th century Indian Ocean warming pattern portrayed by the corals is consistent with the SST product from the Hadley Centre (HadSST3), and suggests that the latter should be used in climate studies that include Indian Ocean SSTs. Our data shows that multi-core coral temperature reconstructions help to evaluate the SST products. Proxy records can provide estimates of 20 th century SST that are truly independent from the ICOADS data base.

Microbial Community Response to Terrestrially Derived Dissolved Organic Matter in the Coastal Arctic

PubMed Central

Sipler, Rachel E.; Kellogg, Colleen T. E.; Connelly, Tara L.; Roberts, Quinn N.; Yager, Patricia L.; Bronk, Deborah A.

2017-01-01

Warming at nearly twice the global rate, higher than average air temperatures are the new ‘normal’ for Arctic ecosystems. This rise in temperature has triggered hydrological and geochemical changes that increasingly release carbon-rich water into the coastal ocean via increased riverine discharge, coastal erosion, and the thawing of the semi-permanent permafrost ubiquitous in the region. To determine the biogeochemical impacts of terrestrially derived dissolved organic matter (tDOM) on marine ecosystems we compared the nutrient stocks and bacterial communities present under ice-covered and ice-free conditions, assessed the lability of Arctic tDOM to coastal microbial communities from the Chukchi Sea, and identified bacterial taxa that respond to rapid increases in tDOM. Once thought to be predominantly refractory, we found that ∼7% of dissolved organic carbon and ∼38% of dissolved organic nitrogen from tDOM was bioavailable to receiving marine microbial communities on short 4 – 6 day time scales. The addition of tDOM shifted bacterial community structure toward more copiotrophic taxa and away from more oligotrophic taxa. Although no single order was found to respond universally (positively or negatively) to the tDOM addition, this study identified 20 indicator species as possible sentinels for increased tDOM. These data suggest the true ecological impact of tDOM will be widespread across many bacterial taxa and that shifts in coastal microbial community composition should be anticipated. PMID:28649233

Crustacean zooplankton release copious amounts of dissolved organic matter as taurine in the ocean.

PubMed

Clifford, Elisabeth L; Hansell, Dennis A; Varela, Marta M; Nieto-Cid, Mar; Herndl, Gerhard J; Sintes, Eva

2017-11-01

Taurine (Tau), an amino acid-like compound, is present in almost all marine metazoans including crustacean zooplankton. It plays an important physiological role in these organisms and is released into the ambient water throughout their life cycle. However, limited information is available on the release rates by marine organisms, the concentrations and turnover of Tau in the ocean. We determined dissolved free Tau concentrations throughout the water column and its release by abundant crustacean mesozooplankton at two open ocean sites (Gulf of Alaska and North Atlantic). At both locations, the concentrations of dissolved free Tau were in the low nM range (up to 15.7 nM) in epipelagic waters, declining sharply in the mesopelagic to about 0.2 nM and remaining fairly stable throughout the bathypelagic waters. Pacific amphipod-copepod assemblages exhibited lower dissolved free Tau release rates per unit biomass (0.8 ± 0.4 μmol g -1 C-biomass h -1 ) than Atlantic copepods (ranging between 1.3 ± 0.4 μmol g -1 C-biomass h -1 and 9.5 ± 2.1 μmol g -1 C-biomass h -1 ), in agreement with the well-documented inverse relationship between biomass-normalized excretion rates and body size. Our results indicate that crustacean zooplankton might contribute significantly to the dissolved organic matter flux in marine ecosystems via dissolved free Tau release. Based on the release rates and assuming steady state dissolved free Tau concentrations, turnover times of dissolved free Tau range from 0.05 d to 2.3 d in the upper water column and are therefore similar to those of dissolved free amino acids. This rapid turnover indicates that dissolved free Tau is efficiently consumed in oceanic waters, most likely by heterotrophic bacteria.

Characterization of water quality and suspended sediment during cold-season flows, warm-season flows, and stormflows in the Fountain and Monument Creek watersheds, Colorado, 2007–2015

USGS Publications Warehouse

Miller, Lisa D.; Stogner, Sr., Robert W.

2017-09-01

From 2007 through 2015, the U.S. Geological Survey, in cooperation with Colorado Springs City Engineering, conducted a study in the Fountain and Monument Creek watersheds, Colorado, to characterize surface-water quality and suspended-sediment conditions for three different streamflow regimes with an emphasis on characterizing water quality during storm runoff. Data collected during this study were used to evaluate the effects of stormflows and wastewater-treatment effluent discharge on Fountain and Monument Creeks in the Colorado Springs, Colorado, area. Water-quality samples were collected at 2 sites on Upper Fountain Creek, 2 sites on Monument Creek, 3 sites on Lower Fountain Creek, and 13 tributary sites during 3 flow regimes: cold-season flow (November–April), warm-season flow (May–October), and stormflow from 2007 through 2015. During 2015, additional samples were collected and analyzed for Escherichia coli (E. coli) during dry weather conditions at 41 sites, located in E. coli impaired stream reaches, to help identify source areas and scope of the impairment.Concentrations of E. coli, total arsenic, and dissolved copper, selenium, and zinc in surface-water samples were compared to Colorado in-stream standards. Stormflow concentrations of E. coli frequently exceeded the recreational use standard of 126 colonies per 100 milliliters at main-stem and tributary sites by more than an order of magnitude. Even though median E. coli concentrations in warm-season flow samples were lower than median concentrations in storm-flow samples, the water quality standard for E. coli was still exceeded at most main-stem sites and many tributary sites during warm-season flows. Six samples (three warm-season flow and three stormflow samples) collected from Upper Fountain Creek, upstream from the confluence of Monument Creek, and two stormflow samples collected from Lower Fountain Creek, downstream from the confluence with Monument Creek, exceeded the acute water-quality standard for total arsenic of 50 micrograms per liter. All concentrations of dissolved copper, selenium, and zinc measured in samples were below the water-quality standard.Concentrations of dissolved nitrate plus nitrite generally increased from upstream to downstream during all flow periods. The largest downstream increase in dissolved nitrate plus nitrite concentration was measured between sites 07103970 and 07104905 on Monument Creek. All but one tributary that drain into Monument Creek between the two sites had higher median nitrate plus nitrite concentrations than the nearest upstream site on Monument Creek, site 07103970 (MoCr_Woodmen). Increases in the concentration of dissolved nitrate plus nitrite were also evident below wastewater treatment plants located on Fountain Creek.Most stormflow concentrations of dissolved trace elements were smaller than concentrations from cold-season flow or warm-season samples. However, median concentrations of total arsenic, lead, manganese, nickel, and zinc generally were much larger during periods of stormflow than during cold-season flow or warm-season fl. Median concentrations of total arsenic, total copper, total lead, dissolved and total manganese, total nickel, dissolved and total selenium, and dissolved and total zinc concentrations increased from 1.5 to 28.5 times from site 07103700 (FoCr_Manitou) to 07103707 (FoCr_8th) during cold-season and warm-season flows, indicating a large source of trace elements between these two sites. Both of these sites are located on Fountain Creek, upstream from the confluence with Monument Creek.Median suspended-sediment concentrations and median suspended-sediment loads increased in the downstream direction during all streamflow regimes between Monument Creek sites 07103970 (MoCr_Woodmen) and 07104905 (MoCr_Bijou); however, statistically significant increase (p-value less than 0.05) were only present during warm-season flow and stormflow. Significant increases in median suspended sediment concentrations were measured during cold-season flow and warm-season flow between Upper Fountain Creek site 07103707 (FoCr_8th) and Lower Fountain Creek site 07105500 (FoCr_Nevada) because of inflows from Monument Creek with higher suspended-sediment concentrations. Median suspended-sediment concentrations between sites 07104905 (MoCr_Bijou) and 07105500 (FoCr_Nevada) increased significantly during warm-season flow but showed no significant differences during cold-season flow and stormflow. Significant decreases in median suspended-sediment concentrations were measured between sites 07105500 (FoCr_Nevada) and 07105530 (FoCr_Janitell) during all flow regimes.Suspended-sediment concentrations, discharges, and yields associated with stormflow were significantly larger than those associated with warm-season flow. Although large spatial variations in suspended-sediment yields occurred during warm-season flows, the suspended-sediment yield associated with stormflow were as much as 1,000 times larger than the suspended-sediment yields that occurred during warm-season flow. 

Effects of short-term warming and nitrogen addition on the quantity and quality of dissolved organic matter in a subtropical Cunninghamia lanceolata plantation.

PubMed

Yuan, Xiaochun; Si, Youtao; Lin, Weisheng; Yang, Jingqing; Wang, Zheng; Zhang, Qiufang; Qian, Wei; Chen, Yuehmin; Yang, Yusheng

2018-01-01

Increasing temperature and nitrogen (N) deposition are two large-scale changes projected to occur over the coming decades. The effects of these changes on dissolved organic matter (DOM) are largely unknown. This study aimed to assess the effects of warming and N addition on the quantity and quality of DOM from a subtropical Cunninghamia lanceolata plantation. Between 2014 and 2016, soil solutions were collected from 0-15, 15-30, and 30-60 cm depths by using a negative pressure sampling method. The quantity and quality of DOM were measured under six different treatments. The spectra showed that the DOM of the forest soil solution mainly consisted of aromatic protein-like components, microbial degradation products, and negligible amounts of humic-like substances. Warming, N addition, and warming + N addition significantly inhibited the concentration of dissolved organic carbon (DOC) in the surface (0-15 cm) soil solution. Our results suggested that warming reduced the amount of DOM originating from microbes. The decrease in protein and carboxylic acid contents was mostly attributed to the reduction of DOC following N addition. The warming + N addition treatment showed an interactive effect rather than an additive effect. Thus, short-term warming and warming + N addition decreased the quantity of DOM and facilitated the migration of nutrients to deeper soils. Further, N addition increased the complexity of the DOM structure. Hence, the loss of soil nutrients and the rational application of N need to be considered in order to prevent the accumulation of N compounds in soil.

Effects of short-term warming and nitrogen addition on the quantity and quality of dissolved organic matter in a subtropical Cunninghamia lanceolata plantation

PubMed Central

Yuan, Xiaochun; Si, Youtao; Lin, Weisheng; Yang, Jingqing; Wang, Zheng; Zhang, Qiufang; Qian, Wei; Yang, Yusheng

2018-01-01

Increasing temperature and nitrogen (N) deposition are two large-scale changes projected to occur over the coming decades. The effects of these changes on dissolved organic matter (DOM) are largely unknown. This study aimed to assess the effects of warming and N addition on the quantity and quality of DOM from a subtropical Cunninghamia lanceolata plantation. Between 2014 and 2016, soil solutions were collected from 0–15, 15–30, and 30–60 cm depths by using a negative pressure sampling method. The quantity and quality of DOM were measured under six different treatments. The spectra showed that the DOM of the forest soil solution mainly consisted of aromatic protein-like components, microbial degradation products, and negligible amounts of humic-like substances. Warming, N addition, and warming + N addition significantly inhibited the concentration of dissolved organic carbon (DOC) in the surface (0–15 cm) soil solution. Our results suggested that warming reduced the amount of DOM originating from microbes. The decrease in protein and carboxylic acid contents was mostly attributed to the reduction of DOC following N addition. The warming + N addition treatment showed an interactive effect rather than an additive effect. Thus, short-term warming and warming + N addition decreased the quantity of DOM and facilitated the migration of nutrients to deeper soils. Further, N addition increased the complexity of the DOM structure. Hence, the loss of soil nutrients and the rational application of N need to be considered in order to prevent the accumulation of N compounds in soil. PMID:29360853

Interhemispheric SST gradient trends in the Indian Ocean prior to and during the recent global warming hiatus

NASA Astrophysics Data System (ADS)

Dong, L.; McPhaden, M. J.

2016-12-01

Sea surface temperatures (SSTs) have been rising for decades in the Indian Ocean in response to greenhouse gas forcing. However, in this study we show that during the recent hiatus in global warming, a striking interhemispheric gradient in Indian Ocean SST trends developed around 2000, with relatively weak or little warming to the north of 10°S and accelerated warming to the south of 10oS. We present evidence from a wide variety of data sources that this interhemispheric gradient in SST trends is forced primarily by an increase of Indonesian Throughflow (ITF) transport from the Pacific into the Indian Ocean induced by stronger Pacific trade winds. This increased transport led to a depression of the thermocline that facilitated SST warming presumably through a reduction in the vertical turbulent transport of heat in the southern Indian Ocean. Surface wind changes in the Indian Ocean linked to the enhanced Walker circulation also may have contributed to thermocline depth variations and associated SST changes, with downwelling favorable wind stress curls between 10oS and 20oS and upwelling favorable wind stress curls between the equator and 10oS. In addition, the anomalous southwesterly wind stresses off the coast of Somalia favored intensified coastal upwelling and off-shore advection of upwelled water, which would have led to reduced warming of the northern Indian Ocean. Though highly uncertain, lateral heat advection associated with the ITF and surface heat fluxes may also have played a role in forming the interhemispheric SST gradient change.

Estimating the Cross-Shelf Export of Riverine Materials: Part 2. Estimates of Global Freshwater and Nutrient Export

NASA Astrophysics Data System (ADS)

Izett, Jonathan G.; Fennel, Katja

2018-02-01

Rivers deliver large amounts of fresh water, nutrients, and other terrestrially derived materials to the coastal ocean. Where inputs accumulate on the shelf, harmful effects such as hypoxia and eutrophication can result. In contrast, where export to the open ocean is efficient riverine inputs contribute to global biogeochemical budgets. Assessing the fate of riverine inputs is difficult on a global scale. Global ocean models are generally too coarse to resolve the relatively small scale features of river plumes. High-resolution regional models have been developed for individual river plume systems, but it is impractical to apply this approach globally to all rivers. Recently, generalized parameterizations have been proposed to estimate the export of riverine fresh water to the open ocean (Izett & Fennel, 2018, https://doi.org/10.1002/2017GB005667; Sharples et al., 2017, https://doi.org/10.1002/2016GB005483). Here the relationships of Izett and Fennel, https://doi.org/10.1002/2017GB005667 are used to derive global estimates of open-ocean export of fresh water and dissolved inorganic silicate, dissolved organic carbon, and dissolved organic and inorganic phosphorus and nitrogen. We estimate that only 15-53% of riverine fresh water reaches the open ocean directly in river plumes; nutrient export is even less efficient because of processing on continental shelves. Due to geographic differences in riverine nutrient delivery, dissolved silicate is the most efficiently exported to the open ocean (7-56.7%), while dissolved inorganic nitrogen is the least efficiently exported (2.8-44.3%). These results are consistent with previous estimates and provide a simple way to parameterize export to the open ocean in global models.

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.

Drivers of Arctic Ocean warming in CMIP5 models

NASA Astrophysics Data System (ADS)

Burgard, Clara; Notz, Dirk

2017-05-01

We investigate changes in the Arctic Ocean energy budget simulated by 26 general circulation models from the Coupled Model Intercomparison Project Phase 5 framework. Our goal is to understand whether the Arctic Ocean warming between 1961 and 2099 is primarily driven by changes in the net atmospheric surface flux or by changes in the meridional oceanic heat flux. We find that the simulated Arctic Ocean warming is driven by positive anomalies in the net atmospheric surface flux in 11 models, by positive anomalies in the meridional oceanic heat flux in 11 models, and by positive anomalies in both energy fluxes in four models. The different behaviors are mainly characterized by the different changes in meridional oceanic heat flux that lead to different changes in the turbulent heat loss to the atmosphere. The multimodel ensemble mean is hence not representative of a consensus across the models in Arctic climate projections.

Impact of Icebergs on Net Primary Productivity in the Southern Ocean

NASA Astrophysics Data System (ADS)

Wu, Shuang-Ye; Hou, Shugui

2017-04-01

Productivity in the Southern Ocean (SO) is iron-limited, and supply of iron dissolved from aeolian dust is believed to be the main source from outside the marine environment. However, recent studies show that icebergs could provide comparable amount of bioavailable iron to the SO as aeolian dust. In addition, small scale areal studies suggest increased concentrations of chlorophyll, krill, and seabirds surrounding icebergs. Based on previous research, this study aims to examine whether iceberg occurrence has a significant impact on marine productivity at the scale of the SO, using remote sensing data of iceberg occurrences and ocean net primary productivity (NPP) covering the period 2002-2014. The impacts of both large and small icebergs are examined in four major ecological zones of the SO: the continental shelf zone (CSZ), the seasonal ice zone (SIZ), the permanent open ocean zone (POOZ) and the polar front zone (PFZ). We found that both large and small icebergs have an observable positive impact on NPP, but their impacts vary in different zones. Small icebergs on average increase NPP in most iron deficient zones: by 21% for the SIZ, 16% for the POOZ, and 12% for the PFZ, but have relatively small effect in the CSZ where iron is supplied from melt water and sediment input from the continent. Large icebergs on average increase the NPP by about 10%. Their impacts are stronger at higher latitudes, where they are more concentrated. From 1992-2014, there is a significant increasing trend for both small and large icebergs. The increase was most rapid in the early 2000s, and has levelled off since then. As the climate continues to warm, the Antarctic Ice Sheet is expected to experience increased mass loss as a whole, which could lead to more icebergs in the region. Based on our study, this could result in higher level of NPP in the SO as a whole, providing a negative feedback for global warming.

Designing connected marine reserves in the face of global warming.

PubMed

Álvarez-Romero, Jorge G; Munguía-Vega, Adrián; Beger, Maria; Del Mar Mancha-Cisneros, Maria; Suárez-Castillo, Alvin N; Gurney, Georgina G; Pressey, Robert L; Gerber, Leah R; Morzaria-Luna, Hem Nalini; Reyes-Bonilla, Héctor; Adams, Vanessa M; Kolb, Melanie; Graham, Erin M; VanDerWal, Jeremy; Castillo-López, Alejandro; Hinojosa-Arango, Gustavo; Petatán-Ramírez, David; Moreno-Baez, Marcia; Godínez-Reyes, Carlos R; Torre, Jorge

2018-02-01

Marine reserves are widely used to protect species important for conservation and fisheries and to help maintain ecological processes that sustain their populations, including recruitment and dispersal. Achieving these goals requires well-connected networks of marine reserves that maximize larval connectivity, thus allowing exchanges between populations and recolonization after local disturbances. However, global warming can disrupt connectivity by shortening potential dispersal pathways through changes in larval physiology. These changes can compromise the performance of marine reserve networks, thus requiring adjusting their design to account for ocean warming. To date, empirical approaches to marine prioritization have not considered larval connectivity as affected by global warming. Here, we develop a framework for designing marine reserve networks that integrates graph theory and changes in larval connectivity due to potential reductions in planktonic larval duration (PLD) associated with ocean warming, given current socioeconomic constraints. Using the Gulf of California as case study, we assess the benefits and costs of adjusting networks to account for connectivity, with and without ocean warming. We compare reserve networks designed to achieve representation of species and ecosystems with networks designed to also maximize connectivity under current and future ocean-warming scenarios. Our results indicate that current larval connectivity could be reduced significantly under ocean warming because of shortened PLDs. Given the potential changes in connectivity, we show that our graph-theoretical approach based on centrality (eigenvector and distance-weighted fragmentation) of habitat patches can help design better-connected marine reserve networks for the future with equivalent costs. We found that maintaining dispersal connectivity incidentally through representation-only reserve design is unlikely, particularly in regions with strong asymmetric patterns of dispersal connectivity. Our results support previous studies suggesting that, given potential reductions in PLD due to ocean warming, future marine reserve networks would require more and/or larger reserves in closer proximity to maintain larval connectivity. © 2017 John Wiley & Sons Ltd.

The global distribution and dynamics of chromophoric dissolved organic matter.

PubMed

Nelson, Norman B; Siegel, David A

2013-01-01

Chromophoric dissolved organic matter (CDOM) is a ubiquitous component of the open ocean dissolved matter pool, and is important owing to its influence on the optical properties of the water column, its role in photochemistry and photobiology, and its utility as a tracer of deep ocean biogeochemical processes and circulation. In this review, we discuss the global distribution and dynamics of CDOM in the ocean, concentrating on developments in the past 10 years and restricting our discussion to open ocean and deep ocean (below the main thermocline) environments. CDOM has been demonstrated to exert primary control on ocean color by its absorption of light energy, which matches or exceeds that of phytoplankton pigments in most cases. This has important implications for assessing the ocean biosphere via ocean color-based remote sensing and the evaluation of ocean photochemical and photobiological processes. The general distribution of CDOM in the global ocean is controlled by a balance between production (primarily microbial remineralization of organic matter) and photolysis, with vertical ventilation circulation playing an important role in transporting CDOM to and from intermediate water masses. Significant decadal-scale fluctuations in the abundance of global surface ocean CDOM have been observed using remote sensing, indicating a potentially important role for CDOM in ocean-climate connections through its impact on photochemistry and photobiology.

Oceanic an climatic consequences of a sudden large-scale West Antarctic Ice Sheet collapse

NASA Astrophysics Data System (ADS)

Scarff, Katie; Green, Mattias; Schmittner, Andreas

2015-04-01

Atmospheric warming is progressing to the point where the West Antarctic Ice Sheet (WAIS) will experience an elevated rate of discharge. The current discharge rate of WAIS is around 0.005Sv, but this rate will most likely accelerate over this century. The input of freshwater, in the form of ice, may have a profound effect on oceanic circulation systems, including potentially reducing the formation of deep water in the Southern Ocean and thus triggering or enhancing the bipolar seesaw. Using UVic - an intermediate complexity ocean-climate model - we investigate how various hosing rates from the WAIS will impact of the present and future ocean circulation and climate. These scenarios range from observed hosing rates (~0.005Sv) being applied for 100 years, to a total collapse of the WAIS over the next 100 years (the equivalent to a0.7Sv hosing). We show that even the present day observed rates can have a significant impact on the ocean and atmospheric temperatures, and that the bipolar seesaw may indeed be enhanced by the Southern Ocean hosing. Consequently, there is a speed-up of the Meridional Overturning Circulation (MOC) early on during the hosing, which leads to a warming over the North Atlantic, and a subsequent reduction in the MOC on centennial scales. The larger hosing cases show more dramatic effects with near-complete shutdowns of the MOC during the hosing. Furthermore, global warming scenarios based on the IPCC "business as usual" scenario show that the atmospheric warming will change the response of the ocean to Southern Ocean hosing and that the warming will dominate the perturbation. The potential feedback between changes in the ocean stratification in the scenarios and tidally driven abyssal mixing via tidal conversion is also explored.

Association between mean and interannual equatorial Indian Ocean subsurface temperature bias in a coupled model

NASA Astrophysics Data System (ADS)

Srinivas, G.; Chowdary, Jasti S.; Gnanaseelan, C.; Prasad, K. V. S. R.; Karmakar, Ananya; Parekh, Anant

2018-03-01

In the present study the association between mean and interannual subsurface temperature bias over the equatorial Indian Ocean (EIO) is investigated during boreal summer (June through September; JJAS) in the National Centers for Environmental Prediction (NCEP) Climate Forecast System (CFSv2) hindcast. Anomalously high subsurface warm bias (greater than 3 °C) over the eastern EIO (EEIO) region is noted in CFSv2 during summer, which is higher compared to other parts of the tropical Indian Ocean. Prominent eastward current bias in the upper 100 m over the EIO region induced by anomalous westerly winds is primarily responsible for subsurface temperature bias. The eastward currents transport warm water to the EEIO and is pushed down to subsurface due to downwelling. Thus biases in both horizontal and vertical currents over the EIO region support subsurface warm bias. The evolution of systematic subsurface warm bias in the model shows strong interannual variability. These maximum subsurface warming episodes over the EEIO are mainly associated with La Niña like forcing. Strong convergence of low level winds over the EEIO and Maritime continent enhanced the westerly wind bias over the EIO during maximum warming years. This low level convergence of wind is induced by the bias in the gradient in the mean sea level pressure with positive bias over western EIO and negative bias over EEIO and parts of western Pacific. Consequently, changes in the atmospheric circulation associated with La Niña like conditions affected the ocean dynamics by modulating the current bias thereby enhancing the subsurface warm bias over the EEIO. It is identified that EEIO subsurface warming is stronger when La Niña co-occurred with negative Indian Ocean Dipole events as compared to La Niña only years in the model. Ocean general circulation model (OGCM) experiments forced with CFSv2 winds clearly support our hypothesis that ocean dynamics influenced by westerly winds bias is primarily responsible for the strong subsurface warm bias over the EEIO. This study advocates the importance of understanding the ability of the models in representing the large scale air-sea interactions over the tropics and their impact on ocean biases for better monsoon forecast.

Accelerated warming of the Southern Ocean and its impacts on the hydrological cycle and sea ice.

PubMed

Liu, Jiping; Curry, Judith A

2010-08-24

The observed sea surface temperature in the Southern Ocean shows a substantial warming trend for the second half of the 20th century. Associated with the warming, there has been an enhanced atmospheric hydrological cycle in the Southern Ocean that results in an increase of the Antarctic sea ice for the past three decades through the reduced upward ocean heat transport and increased snowfall. The simulated sea surface temperature variability from two global coupled climate models for the second half of the 20th century is dominated by natural internal variability associated with the Antarctic Oscillation, suggesting that the models' internal variability is too strong, leading to a response to anthropogenic forcing that is too weak. With increased loading of greenhouse gases in the atmosphere through the 21st century, the models show an accelerated warming in the Southern Ocean, and indicate that anthropogenic forcing exceeds natural internal variability. The increased heating from below (ocean) and above (atmosphere) and increased liquid precipitation associated with the enhanced hydrological cycle results in a projected decline of the Antarctic sea ice.

Increased Ocean Heat Convergence Into the High Latitudes With CO2 Doubling Enhances Polar-Amplified Warming

NASA Astrophysics Data System (ADS)

Singh, H. A.; Rasch, P. J.; Rose, B. E. J.

2017-10-01

We isolate the role of the ocean in polar climate change by directly evaluating how changes in ocean dynamics with quasi-equilibrium CO2 doubling impact high-latitude climate. With CO2 doubling, the ocean heat flux convergence (OHFC) shifts poleward in winter in both hemispheres. Imposing this pattern of perturbed OHFC in a global climate model results in a poleward shift in ocean-to-atmosphere turbulent heat fluxes (both sensible and latent) and sea ice retreat; the high latitudes warm, while the midlatitudes cool, thereby amplifying polar warming. Furthermore, midlatitude cooling is propagated to the polar midtroposphere on isentropic surfaces, augmenting the (positive) lapse rate feedback at high latitudes. These results highlight the key role played by the partitioning of meridional energy transport changes between the atmosphere and ocean in high-latitude climate change.

Effect of Global Warming and Increased Freshwater Flux on Northern Hemispheric Cooling

NASA Astrophysics Data System (ADS)

Girihagama, L. N.; Nof, D.

2016-02-01

We wish to answer the, fairly complicated, question of whether global warming and an increased freshwater flux can cause Northern Hemispheric warming or cooling. Starting from the assumption that the ocean is the primary source of variability in the Northern hemispheric ocean-atmosphere coupled system, we employed a simple non-linear one-dimensional coupled ocean-atmosphere model. The simplicity of the model allows us to analytically predict the evolution of many dynamical variables of interest such as, the strength of the Atlantic Meridional overturning circulation (AMOC), temperatures of the ocean and atmosphere, mass transports, salinity, and ocean-atmosphere heat fluxes. The model results show that a reduced AMOC transport due to an increased freshwater flux causes cooling in both the atmosphere and ocean in the North Atlantic (NA) deep-water formation region. Cooling in both the ocean and atmosphere can cause reduction of the ocean-atmosphere temperature difference, which in turn reduces heat fluxes in both the ocean and atmosphere. For present day climate parameters, the calculated critical freshwater flux needed to arrest AMOC is 0.08 Sv. For a constant atmospheric zonal flow, there is minimal reduction in the AMOC strength, as well as minimal warming of the ocean and atmosphere. This model provides a conceptual framework for a dynamically sound response of the ocean and atmosphere to AMOC variability as a function of increased freshwater flux. The results are qualitatively consistent with numerous realistic coupled numerical models of varying complexity.

Variability of dissolved oxygen over the last millennium and the 21st century in CESM

NASA Astrophysics Data System (ADS)

Hameau, Angélique; Joos, Fortunat; Mignot, Juliette; Keller, Kathrin

2017-04-01

The earth system models simulate a depletion of the oxygen content in the ocean under global warming conditions (Cocco et al. 2012, Frölicher et al. 2009). The response to external forcing and mechanism underlying this evolution are not completely understood. Physical and biogeochemical processes are involved and tangled up to each other leading to a decrease of the global mean concentration of O2 in the ocean with the increase of the ocean temperature. This result is supported by experimental and observational studies in Atlantic and Pacific oceans (Stramma et al. 2008, Brandt et al. 2010). Here, we study the evolution of dissolved oxygen in a climate simulation of the Community Earth System Model (CESM) covering the last millennium and the 21st century. This long period allows us to identify the natural variability of the climate in this system, and therefore analyse the time of emergence (ToE) of the anthropogenic signal under the RCP8.5 scenario. Based on Keller et al. 2014, the time of emergence is defined as the point in time when the trend signal reaches twice the standard deviation of the signal during the preindustrial period (1000 years). The ToE of oxygen and of temperature present an offset. We show that the anthropogenic emissions are seen in a first hand by the oxygen and only then by the temperature. We also look at the OMZ response. The oxygen minimum zones result from a combination of weak ventilation and sustained respiration by the microorgamisms. With a global decrease of the oceanic oxygen content, the OMZ may therefore expand impacting the environment of marine species. But this statement is questioned by Deutsch et al 2014, who relates the variations of Pacific OMZ to the variations of the tropical Walker circulation. The CESM climate model predicts an expansion of the oxygen low zones and the emergence of new ones over the last century. Magnitude and timescales of these responses will be discussed and compared to natural variability.

Antarctic warming driven by internal Southern Ocean deep convection oscillations

NASA Astrophysics Data System (ADS)

Martin, Torge; Pedro, Joel B.; Steig, Eric J.; Jochum, Markus; Park, Wonsun; Rasmussen, Sune O.

2016-04-01

Simulations with the free-running, complex coupled Kiel Climate Model (KCM) show that heat release associated with recurring Southern Ocean deep convection can drive centennial-scale Antarctic temperature variations of 0.5-2.0 °C. We propose a mechanism connecting the intrinsic ocean variability with Antarctic warming that involves the following three steps: Preconditioning: heat supplied by the lower branch of the Atlantic Meridional Overturning Circulation (AMOC) accumulates at depth in the Southern Ocean, trapped by the Weddell Gyre circulation; Convection onset: wind and/or sea-ice changes tip the preconditioned, thermally unstable system into the convective state; Antarctic warming: fast sea-ice-albedo feedbacks (on annual to decadal timescales) and slower Southern Ocean frontal and sea-surface temperature adjustments to the convective heat release (on multi-decadal to centennial timescales), drive an increase in atmospheric heat and moisture transport towards Antarctica resulting in warming over the continent. Further, we discuss the potential role of this mechanism to explain climate variability observed in Antarctic ice-core records.

Large-Scale Ocean Circulation-Cloud Interactions Reduce the Pace of Transient Climate Change

NASA Technical Reports Server (NTRS)

Trossman, D. S.; Palter, J. B.; Merlis, T. M.; Huang, Y.; Xia, Y.

2016-01-01

Changes to the large scale oceanic circulation are thought to slow the pace of transient climate change due, in part, to their influence on radiative feedbacks. Here we evaluate the interactions between CO2-forced perturbations to the large-scale ocean circulation and the radiative cloud feedback in a climate model. Both the change of the ocean circulation and the radiative cloud feedback strongly influence the magnitude and spatial pattern of surface and ocean warming. Changes in the ocean circulation reduce the amount of transient global warming caused by the radiative cloud feedback by helping to maintain low cloud coverage in the face of global warming. The radiative cloud feedback is key in affecting atmospheric meridional heat transport changes and is the dominant radiative feedback mechanism that responds to ocean circulation change. Uncertainty in the simulated ocean circulation changes due to CO2 forcing may contribute a large share of the spread in the radiative cloud feedback among climate models.

Mangroves, a major source of dissolved organic carbon to the oceans

NASA Astrophysics Data System (ADS)

Dittmar, Thorsten; Hertkorn, Norbert; Kattner, Gerhard; Lara, RubéN. J.

2006-03-01

Organic matter, which is dissolved in low concentrations in the vast waters of the oceans, contains a total amount of carbon similar to atmospheric carbon dioxide. To understand global biogeochemical cycles, it is crucial to quantify the sources of marine dissolved organic carbon (DOC). We investigated the impact of mangroves, the dominant intertidal vegetation of the tropics, on marine DOC inventories. Stable carbon isotopes and proton nuclear magnetic resonance spectroscopy showed that mangroves are the main source of terrigenous DOC in the open ocean off northern Brazil. Sunlight efficiently destroyed aromatic molecules during transport offshore, removing about one third of mangrove-derived DOC. The remainder was refractory and may thus be distributed over the oceans. On a global scale, we estimate that mangroves account for >10% of the terrestrially derived, refractory DOC transported to the ocean, while they cover only <0.1% of the continents' surface.

Temperature, but not pH, compromises sea urchin fertilization and early development under near-future climate change scenarios.

PubMed

Byrne, Maria; Ho, Melanie; Selvakumaraswamy, Paulina; Nguyen, Hong D; Dworjanyn, Symon A; Davis, Andy R

2009-05-22

Global warming is causing ocean warming and acidification. The distribution of Heliocidaris erythrogramma coincides with the eastern Australia climate change hot spot, where disproportionate warming makes marine biota particularly vulnerable to climate change. In keeping with near-future climate change scenarios, we determined the interactive effects of warming and acidification on fertilization and development of this echinoid. Experimental treatments (20-26 degrees C, pH 7.6-8.2) were tested in all combinations for the 'business-as-usual' scenario, with 20 degrees C/pH 8.2 being ambient. Percentage of fertilization was high (>89%) across all treatments. There was no difference in percentage of normal development in any pH treatment. In elevated temperature conditions, +4 degrees C reduced cleavage by 40 per cent and +6 degrees C by a further 20 per cent. Normal gastrulation fell below 4 per cent at +6 degrees C. At 26 degrees C, development was impaired. As the first study of interactive effects of temperature and pH on sea urchin development, we confirm the thermotolerance and pH resilience of fertilization and embryogenesis within predicted climate change scenarios, with negative effects at upper limits of ocean warming. Our findings place single stressor studies in context and emphasize the need for experiments that address ocean warming and acidification concurrently. Although ocean acidification research has focused on impaired calcification, embryos may not reach the skeletogenic stage in a warm ocean.

Nitrous oxide production in the eastern tropical South Pacific oxygen minimum zone

NASA Astrophysics Data System (ADS)

Ji, Qixing; Altabet, Mark; Arevalo-Martinez, Damian; Bange, Hermann; Ma, Xiao; Marandino, Christa; Sun, Mingshuang; Grundle, Damian

2017-04-01

Nitrous oxide (N2O) is an important climate active trace gas that contributes to both atmospheric warming and ozone destruction, and the ocean is an important source of N2O to the atmosphere. Dissolved oxygen concentrations play an important role in regulating N2O production in the ocean, such that under low oxygen conditions major shifts in the predominant production pathways (i.e. nitrification vs. denitrification) can occur and the magnitude of production may increase substantially. To this end, major oceanic oxygen minimum zones (OMZs) are responsible for a disproportionately high amount of marine N2O production. During the October 2015 ASTRA-OMZ cruise to the eastern tropical South Pacific (ETSP), one of the three major oceanic OMZs, we measured a suite of N2O parameters which included N2O concentrations, N2O production, and natural abundance N2O isotope (i.e. del 15N and del 18O) and isotopomer (i.e. 15N site-preference) signatures. Based on the results from these measurements, our presentation will demonstrate how N2O production and the different production pathways change along the oxygen concentration gradients from the oxygenated surface waters through the oxygen minimum layer. Our data could better constrain the importance of the ETSP-OMZ as source of marine N2O. Results from this work will provide insights into how N2O cycling responds to ocean deoxygenation as a result of climate change.

Decadal prediction skill using a high-resolution climate model

NASA Astrophysics Data System (ADS)

Monerie, Paul-Arthur; Coquart, Laure; Maisonnave, Éric; Moine, Marie-Pierre; Terray, Laurent; Valcke, Sophie

2017-11-01

The ability of a high-resolution coupled atmosphere-ocean general circulation model (with a horizontal resolution of a quarter of a degree in the ocean and of about 0.5° in the atmosphere) to predict the annual means of temperature, precipitation, sea-ice volume and extent is assessed based on initialized hindcasts over the 1993-2009 period. Significant skill in predicting sea surface temperatures is obtained, especially over the North Atlantic, the tropical Atlantic and the Indian Ocean. The Sea Ice Extent and volume are also reasonably predicted in winter (March) and summer (September). The model skill is mainly due to the external forcing associated with well-mixed greenhouse gases. A decrease in the global warming rate associated with a negative phase of the Pacific Decadal Oscillation is simulated by the model over a suite of 10-year periods when initialized from starting dates between 1999 and 2003. The model ability to predict regional change is investigated by focusing on the mid-90's Atlantic Ocean subpolar gyre warming. The model simulates the North Atlantic warming associated with a meridional heat transport increase, a strengthening of the North Atlantic current and a deepening of the mixed layer over the Labrador Sea. The atmosphere plays a role in the warming through a modulation of the North Atlantic Oscillation: a negative sea level pressure anomaly, located south of the subpolar gyre is associated with a wind speed decrease over the subpolar gyre. This leads to a reduced oceanic heat-loss and favors a northward displacement of anomalously warm and salty subtropical water that both concur to the subpolar gyre warming. We finally conclude that the subpolar gyre warming is mainly triggered by ocean dynamics with a possible contribution of atmospheric circulation favoring its persistence.

Slow acidification of the winter mixed layer in the subarctic western North Pacific

NASA Astrophysics Data System (ADS)

Wakita, Masahide; Nagano, Akira; Fujiki, Tetsuichi; Watanabe, Shuichi

2017-08-01

We used carbon dioxide (CO2) system data collected during 1999-2015 to investigate ocean acidification at time series sites in the western subarctic region of the North Pacific Ocean. The annual mean pH at station K2 decreased at a rate of 0.0025 ± 0.0010 year-1 mostly in response to oceanic uptake of anthropogenic CO2. The Revelle factor increased rapidly (0.046 ± 0.022 year-1), an indication that the buffering capacity of this region of the ocean has declined faster than at other time series sites. In the western subarctic region, the pH during the winter decline at a slower rate of 0.0008 ± 0.0004 year-1. This was attributed to a reduced rate of increase of dissolved inorganic carbon (DIC) and an increase of total alkalinity (TA). The reduction of DIC increase was caused by the decline of surface water density associated with the pycnocline depression and the reduction of vertical diffusion flux from the upper pycnocline. These physical changes were probably caused by northward shrinkage of the western subarctic gyre and global warming. Meanwhile, the contribution of the density decline to the TA increase is canceled out by that of the reduced vertical diffusive flux. We speculated that the winter TA increase is caused mainly by the accumulation of TA due to the weakened calcification by organisms during the winter.

Circumpolar dynamics of a marine top-predator track ocean warming rates.

PubMed

Descamps, Sébastien; Anker-Nilssen, Tycho; Barrett, Robert T; Irons, David B; Merkel, Flemming; Robertson, Gregory J; Yoccoz, Nigel G; Mallory, Mark L; Montevecchi, William A; Boertmann, David; Artukhin, Yuri; Christensen-Dalsgaard, Signe; Erikstad, Kjell-Einar; Gilchrist, H Grant; Labansen, Aili L; Lorentsen, Svein-Håkon; Mosbech, Anders; Olsen, Bergur; Petersen, Aevar; Rail, Jean-Francois; Renner, Heather M; Strøm, Hallvard; Systad, Geir H; Wilhelm, Sabina I; Zelenskaya, Larisa

2017-09-01

Global warming is a nonlinear process, and temperature may increase in a stepwise manner. Periods of abrupt warming can trigger persistent changes in the state of ecosystems, also called regime shifts. The responses of organisms to abrupt warming and associated regime shifts can be unlike responses to periods of slow or moderate change. Understanding of nonlinearity in the biological responses to climate warming is needed to assess the consequences of ongoing climate change. Here, we demonstrate that the population dynamics of a long-lived, wide-ranging marine predator are associated with changes in the rate of ocean warming. Data from 556 colonies of black-legged kittiwakes Rissa tridactyla distributed throughout its breeding range revealed that an abrupt warming of sea-surface temperature in the 1990s coincided with steep kittiwake population decline. Periods of moderate warming in sea temperatures did not seem to affect kittiwake dynamics. The rapid warming observed in the 1990s may have driven large-scale, circumpolar marine ecosystem shifts that strongly affected kittiwakes through bottom-up effects. Our study sheds light on the nonlinear response of a circumpolar seabird to large-scale changes in oceanographic conditions and indicates that marine top predators may be more sensitive to the rate of ocean warming rather than to warming itself. © 2017 John Wiley & Sons Ltd.

The biological carbon pump in the ocean: Reviewing model representations and its feedbacks on climate perturbations.

NASA Astrophysics Data System (ADS)

Hülse, Dominik; Arndt, Sandra; Ridgwell, Andy; Wilson, Jamie

2016-04-01

The ocean-sediment system, as the biggest carbon reservoir in the Earth's carbon cycle, plays a crucial role in regulating atmospheric carbon dioxide concentrations and climate. Therefore, it is essential to constrain the importance of marine carbon cycle feedbacks on global warming and ocean acidification. Arguably, the most important single component of the ocean's carbon cycle is the so-called "biological carbon pump". It transports carbon that is fixed in the light-flooded surface layer of the ocean to the deep ocean and the surface sediment, where it is degraded/dissolved or finally buried in the deep sediments. Over the past decade, progress has been made in understanding different factors that control the efficiency of the biological carbon pump and their feedbacks on the global carbon cycle and climate (i.e. ballasting = ocean acidification feedback; temperature dependant organic matter degradation = global warming feedback; organic matter sulphurisation = anoxia/euxinia feedback). Nevertheless, many uncertainties concerning the interplay of these processes and/or their relative significance remain. In addition, current Earth System Models tend to employ empirical and static parameterisations of the biological pump. As these parametric representations are derived from a limited set of present-day observations, their ability to represent carbon cycle feedbacks under changing climate conditions is limited. The aim of my research is to combine past carbon cycling information with a spatially resolved global biogeochemical model to constrain the functioning of the biological pump and to base its mathematical representation on a more mechanistic approach. Here, I will discuss important aspects that control the efficiency of the ocean's biological carbon pump, review how these processes of first order importance are mathematically represented in existing Earth system Models of Intermediate Complexity (EMIC) and distinguish different approaches to approximate biogeochemical processes in the sediments. The performance of the respective mathematical representations in constraining the importance of carbon pump feedbacks on marine biogeochemical dynamics is then compared and evaluated under different extreme climate scenarios (e.g. OAE2, Eocene) using the Earth system model 'GENIE' and proxy records. The compiled mathematical descriptions and the model results underline the lack of a complete and mechanistic framework to represent the short-term carbon cycle in most EMICs which seriously limits the ability of these models to constrain the response of the ocean's carbon cycle to past and in particular future climate change. In conclusion, this presentation will critically evaluate the approaches currently used in marine biogeochemical modelling and outline key research directions concerning model development in the future.

Impact of ocean warming and ocean acidification on larval development and calcification in the sea urchin Tripneustes gratilla.

PubMed

Sheppard Brennand, Hannah; Soars, Natalie; Dworjanyn, Symon A; Davis, Andrew R; Byrne, Maria

2010-06-29

As the oceans simultaneously warm, acidify and increase in P(CO2), prospects for marine biota are of concern. Calcifying species may find it difficult to produce their skeleton because ocean acidification decreases calcium carbonate saturation and accompanying hypercapnia suppresses metabolism. However, this may be buffered by enhanced growth and metabolism due to warming. We examined the interactive effects of near-future ocean warming and increased acidification/P(CO2) on larval development in the tropical sea urchin Tripneustes gratilla. Larvae were reared in multifactorial experiments in flow-through conditions in all combinations of three temperature and three pH/P(CO2) treatments. Experiments were placed in the setting of projected near future conditions for SE Australia, a global change hot spot. Increased acidity/P(CO2) and decreased carbonate mineral saturation significantly reduced larval growth resulting in decreased skeletal length. Increased temperature (+3 degrees C) stimulated growth, producing significantly bigger larvae across all pH/P(CO2) treatments up to a thermal threshold (+6 degrees C). Increased acidity (-0.3-0.5 pH units) and hypercapnia significantly reduced larval calcification. A +3 degrees C warming diminished the negative effects of acidification and hypercapnia on larval growth. This study of the effects of ocean warming and CO(2) driven acidification on development and calcification of marine invertebrate larvae reared in experimental conditions from the outset of development (fertilization) shows the positive and negative effects of these stressors. In simultaneous exposure to stressors the dwarfing effects of acidification were dominant. Reduction in size of sea urchin larvae in a high P(CO2) ocean would likely impair their performance with negative consequent effects for benthic adult populations.

Impact of Ocean Warming and Ocean Acidification on Larval Development and Calcification in the Sea Urchin Tripneustes gratilla

PubMed Central

Sheppard Brennand, Hannah; Soars, Natalie; Dworjanyn, Symon A.; Davis, Andrew R.; Byrne, Maria

2010-01-01

Background As the oceans simultaneously warm, acidify and increase in P CO2, prospects for marine biota are of concern. Calcifying species may find it difficult to produce their skeleton because ocean acidification decreases calcium carbonate saturation and accompanying hypercapnia suppresses metabolism. However, this may be buffered by enhanced growth and metabolism due to warming. Methodology/Principal Findings We examined the interactive effects of near-future ocean warming and increased acidification/P CO2 on larval development in the tropical sea urchin Tripneustes gratilla. Larvae were reared in multifactorial experiments in flow-through conditions in all combinations of three temperature and three pH/P CO2 treatments. Experiments were placed in the setting of projected near future conditions for SE Australia, a global change hot spot. Increased acidity/P CO2 and decreased carbonate mineral saturation significantly reduced larval growth resulting in decreased skeletal length. Increased temperature (+3°C) stimulated growth, producing significantly bigger larvae across all pH/P CO2 treatments up to a thermal threshold (+6°C). Increased acidity (-0.3-0.5 pH units) and hypercapnia significantly reduced larval calcification. A +3°C warming diminished the negative effects of acidification and hypercapnia on larval growth. Conclusions and Significance This study of the effects of ocean warming and CO2 driven acidification on development and calcification of marine invertebrate larvae reared in experimental conditions from the outset of development (fertilization) shows the positive and negative effects of these stressors. In simultaneous exposure to stressors the dwarfing effects of acidification were dominant. Reduction in size of sea urchin larvae in a high P CO2 ocean would likely impair their performance with negative consequent effects for benthic adult populations. PMID:20613879

Atmospheric Blocking and Atlantic Multi-Decadal Ocean Variability

NASA Technical Reports Server (NTRS)

Hakkinen, Sirpa; Rhines, Peter B.; Worthen, Denise L.

2011-01-01

Atmospheric blocking over the northern North Atlantic involves isolation of large regions of air from the westerly circulation for 5-14 days or more. From a recent 20th century atmospheric reanalysis (1,2) winters with more frequent blocking persist over several decades and correspond to a warm North Atlantic Ocean, in-phase with Atlantic multi-decadal ocean variability (AMV). Ocean circulation is forced by wind-stress curl and related air/sea heat exchange, and we find that their space-time structure is associated with dominant blocking patterns: weaker ocean gyres and weaker heat exchange contribute to the warm phase of AMV. Increased blocking activity extending from Greenland to British Isles is evident when winter blocking days of the cold years (1900-1929) are subtracted from those of the warm years (1939-1968).

Variability of Coastal and Ocean Water Temperature in the Upper 700 m along the Western Iberian Peninsula from 1975 to 2006

PubMed Central

Santos, Fran; Gómez-Gesteira, Moncho; deCastro, Maite; Álvarez, Inés

2012-01-01

Temperature is observed to have different trends at coastal and ocean locations along the western Iberian Peninsula from 1975 to 2006, which corresponds to the last warming period in the area under study. The analysis was carried out by means of the Simple Ocean Data Assimilation (SODA). Reanalysis data are available at monthly scale with a horizontal resolution of 0.5°×0.5° and a vertical resolution of 40 levels, which allows obtaining information beneath the sea surface. Only the first 21 vertical levels (from 5.0 m to 729.35 m) were considered here, since the most important changes in heat content observed for the world ocean during the last decades, correspond to the upper 700 m. Warming was observed to be considerably higher at ocean locations than at coastal ones. Ocean warming ranged from values on the order of 0.3°C dec−1 near surface to less than 0.1°C dec−1 at 500 m, while coastal warming showed values close to 0.2°C dec−1 near surface, decreasing rapidly below 0.1°C dec−1 for depths on the order of 50 m. The heat content anomaly for the upper 700 m, showed a sharp increase from coast (0.46 Wm−2) to ocean (1.59 Wm−2). The difference between coastal and ocean values was related to the presence of coastal upwelling, which partially inhibits the warming from surface of near shore water. PMID:23226533

Iron persistence in a distal hydrothermal plume supported by dissolved-particulate exchange

NASA Astrophysics Data System (ADS)

Fitzsimmons, Jessica N.; John, Seth G.; Marsay, Christopher M.; Hoffman, Colleen L.; Nicholas, Sarah L.; Toner, Brandy M.; German, Christopher R.; Sherrell, Robert M.

2017-02-01

Hydrothermally sourced dissolved metals have been recorded in all ocean basins. In the oceans' largest known hydrothermal plume, extending westwards across the Pacific from the Southern East Pacific Rise, dissolved iron and manganese were shown by the GEOTRACES program to be transported halfway across the Pacific. Here, we report that particulate iron and manganese in the same plume also exceed background concentrations, even 4,000 km from the vent source. Both dissolved and particulate iron deepen by more than 350 m relative to 3He--a non-reactive tracer of hydrothermal input--crossing isopycnals. Manganese shows no similar descent. Individual plume particle analyses indicate that particulate iron occurs within low-density organic matrices, consistent with its slow sinking rate of 5-10 m yr-1. Chemical speciation and isotopic composition analyses reveal that particulate iron consists of Fe(III) oxyhydroxides, whereas dissolved iron consists of nanoparticulate Fe(III) oxyhydroxides and an organically complexed iron phase. The descent of plume-dissolved iron is best explained by reversible exchange onto slowly sinking particles, probably mediated by organic compounds binding iron. We suggest that in ocean regimes with high particulate iron loadings, dissolved iron fluxes may depend on the balance between stabilization in the dissolved phase and the reversibility of exchange onto sinking particles.

Enceladus Hydrothermal Activity

NASA Image and Video Library

2017-04-13

This graphic illustrates how scientists on NASA's Cassini mission think water interacts with rock at the bottom of the ocean of Saturn's icy moon Enceladus, producing hydrogen gas (H2). The Cassini spacecraft detected the hydrogen in the plume of gas and icy material spraying from Enceladus during its deepest and last dive through the plume on Oct. 28, 2015. Cassini also sampled the plume's composition during previous flybys, earlier in the mission. From these observations scientists have determined that nearly 98 percent of the gas in the plume is water vapor, about 1 percent is hydrogen, and the rest is a mixture of other molecules including carbon dioxide, methane and ammonia. The graphic shows water from the ocean circulating through the seafloor, where it is heated and interacts chemically with the rock. This warm water, laden with minerals and dissolved gases (including hydrogen and possibly methane) then pours into the ocean creating chimney-like vents. The hydrogen measurements were made using Cassini's Ion and Neutral Mass Spectrometer, or INMS, instrument, which sniffs gases to determine their composition. The finding is an independent line of evidence that hydrothermal activity is taking place in the Enceladus ocean. Previous results from Cassini's Cosmic Dust Analyzer instrument, published in March 2015, suggested hot water is interacting with rock beneath the ocean; the new findings support that conclusion and indicate that the rock is reduced in its geochemistry. With the discovery of hydrogen gas, scientists can now conclude that there is a source of chemical free energy in Enceladus' ocean. https://photojournal.jpl.nasa.gov/catalog/PIA21442

Highlighting patterns of fungal diversity and composition shaped by ocean currents using the East China Sea as a model.

PubMed

Li, Wei; Wang, Mengmeng; Pan, Haoqin; Burgaud, Gaëtan; Liang, Shengkang; Guo, Jiajia; Luo, Tian; Li, Zhaoxia; Zhang, Shoumei; Cai, Lei

2018-01-01

How ocean currents shape fungal transport, dispersal and more broadly fungal biogeography remains poorly understood. The East China Sea (ECS) is a complex and dynamic habitat with different water masses blending microbial communities. The internal transcribed spacer 2 region of fungal rDNA was analysed in water and sediment samples directly collected from the coastal (CWM), Kuroshio (KSWM), Taiwan warm (TWM) and the shelf mixed water mass (MWM), coupled with hydrographic properties measurements, to determine how ocean currents impact the fungal community composition. Almost 9k fungal operational taxonomic units (OTUs) spanning six phyla, 25 known classes, 102 orders and 694 genera were obtained. The typical terrestrial and freshwater fungal genus, Byssochlamys, was dominant in the CWM, while increasing abundance of a specific OTU affiliated with Aspergillus was revealed from coastal to open ocean water masses (TWM and KSWM). Compared with water samples, sediment harboured an increased diversity with distinct fungal communities. The proximity of the Yangtze and Qiantang estuaries homogenizes the surface water and sediment communities. A significant influence of ocean currents on community structure was found, which is believed to reduce proportionally the variation explained by environmental parameters at the scale of the total water masses. Dissolved oxygen and depth were identified as the major parameters structuring the fungal community. Our results indicate that passive fungal dispersal driven by ocean currents and river run-off, in conjunction with the distinct hydrographic conditions of individual water masses, shapes the fungal community composition and distribution pattern in the ECS. © 2017 John Wiley & Sons Ltd.

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.

The transient response of ice-shelf melting to ocean change

NASA Astrophysics Data System (ADS)

Holland, P.

2017-12-01

Idealised modelling studies show that the melting of ice shelves varies as a quadratic function of ocean temperature. This means that warm-water ice shelves have higher melt rates and are also more sensitive to ocean warming. However, this result is the equilibrium response, derived from a set of ice—ocean simulations subjected to a fixed ocean forcing and run until steady. This study considers instead the transient response of melting, using unsteady simulations subjected to forcing conditions that are oscillated in time with a range of periods. The results show that when the ocean forcing is varied slowly, the melt rates follow the equililbrium response. However, for rapid ocean change melting deviates from the equilibrium response in interesting ways. The residence time of water in the sub-ice cavity offers a critical timescale. When the forcing varies slowly (period of oscillation >> residence time), the cavity is fully-flushed with forcing anomalies at all stages of the cycle and melting follows the equilibrium response. When the forcing varies rapidly (period ≤ residence time), multiple cold and warm anomalies coexist in the cavity, cancelling each other in the spatial mean and thus inducing a relatively steady melt rate. This implies that all ice shelves have a maximum frequency of ocean variability that can be manifested in melting. The results also show that ice shelves forced by warm water have high melt rates, high equilibrium sensitivity, and short residence times, hence a short timescale over which the equilibrium sensitivity is manifest. The most rapid melting adjustment is induced by warm anomalies that are also saline. Thus, ice shelves in the Amundsen and Bellingshausen seas, Antarctica, are highly sensitive to ocean change.

Numerical Simulation of Salinity and Dissolved Oxygen at Perdido Bay and Adjacent Coastal Ocean

EPA Science Inventory

Environmental Fluid Dynamic Code (EFDC), a numerical estuarine and coastal ocean circulation hydrodynamic model, was used to simulate the distribution of the salinity, temperature, nutrients and dissolved oxygen (DO) in Perdido Bay and adjacent Gulf of Mexico. External forcing fa...

Warm tropical ocean surface and global anoxia during the mid-Cretaceous period.

PubMed

Wilson, P A; Norris, R D

2001-07-26

The middle of the Cretaceous period (about 120 to 80 Myr ago) was a time of unusually warm polar temperatures, repeated reef-drowning in the tropics and a series of oceanic anoxic events (OAEs) that promoted both the widespread deposition of organic-carbon-rich marine sediments and high biological turnover. The cause of the warm temperatures is unproven but widely attributed to high levels of atmospheric greenhouse gases such as carbon dioxide. In contrast, there is no consensus on the climatic causes and effects of the OAEs, with both high biological productivity and ocean 'stagnation' being invoked as the cause of ocean anoxia. Here we show, using stable isotope records from multiple species of well-preserved foraminifera, that the thermal structure of surface waters in the western tropical Atlantic Ocean underwent pronounced variability about 100 Myr ago, with maximum sea surface temperatures 3-5 degrees C warmer than today. This variability culminated in a collapse of upper-ocean stratification during OAE-1d (the 'Breistroffer' event), a globally significant period of organic-carbon burial that we show to have fundamental, stratigraphically valuable, geochemical similarities to the main OAEs of the Mesozoic era. Our records are consistent with greenhouse forcing being responsible for the warm temperatures, but are inconsistent both with explanations for OAEs based on ocean stagnation, and with the traditional view (reviewed in ref. 12) that past warm periods were more stable than today's climate.

River fluxes to the sea from the oceanʼs 10Be/9Be ratio

NASA Astrophysics Data System (ADS)

von Blanckenburg, Friedhelm; Bouchez, Julien

2014-02-01

The ratio of the meteoric cosmogenic radionuclide 10Be to the stable isotope 9Be is proposed here to be a flux proxy of terrigenous input into the oceans. The ocean's dissolved 10Be/9Be is set by (1) the flux of meteoric 10Be produced in the atmosphere; (2) the denudational flux of the rivers discharging into a given ocean basin; (3) the fraction of 9Be that is released from primary minerals during weathering (meaning the 9Be transported by rivers in either the dissolved form or adsorbed onto sedimentary particles and incorporated into secondary oxides); and (4) the fraction of riverine 10Be and 9Be actually released into seawater. Using published 10Be/9Be data of rivers for which independent denudation rate estimates exist we first find that the global average fraction of 9Be released during weathering into river waters and their particulate load is 20% and does not depend on denudation rate. We then evaluate this quantitative proxy for terrigenous inputs by using published dissolved seawater Be isotope data and a compilation of global river loads. We find that the measured global average oceanic dissolved 10Be/9Be ratio of about 0.9×10-7 is satisfied by the mass balance if only about 6% of the dissolved and adsorbed riverine Be is eventually released to the open ocean after escaping the coastal zone. When we establish this mass balance for individual ocean basins good agreement results between 10Be/9Be ratios predicted from known river basin denudation rates and measured ocean 10Be/9Be ratios. Only in the South Atlantic and the South Pacific the 10Be/9Be ratio is dominated by advected Be and in these basins the ratio is a proxy for ocean circulation. As the seawater 10Be/9Be ratio is faithfully recorded in marine chemical precipitates the 10Be/9Be ratio extracted from authigenic sediments can now serve to estimate relative changes in terrigenous input into the oceans back through time on a global and on an ocean basin scale.

Importance of ocean salinity for climate and habitability

PubMed Central

Cullum, Jodie; Stevens, David P.; Joshi, Manoj M.

2016-01-01

Modeling studies of terrestrial extrasolar planetary climates are now including the effects of ocean circulation due to a recognition of the importance of oceans for climate; indeed, the peak equator-pole ocean heat transport on Earth peaks at almost half that of the atmosphere. However, such studies have made the assumption that fundamental oceanic properties, such as salinity, temperature, and depth, are similar to Earth. This assumption results in Earth-like circulations: a meridional overturning with warm water moving poleward at the surface, being cooled, sinking at high latitudes, and traveling equatorward at depth. Here it is shown that an exoplanetary ocean with a different salinity can circulate in the opposite direction: an equatorward flow of polar water at the surface, sinking in the tropics, and filling the deep ocean with warm water. This alternative flow regime results in a dramatic warming in the polar regions, demonstrated here using both a conceptual model and an ocean general circulation model. These results highlight the importance of ocean salinity for exoplanetary climate and consequent habitability and the need for its consideration in future studies. PMID:27044090

Importance of ocean salinity for climate and habitability.

PubMed

Cullum, Jodie; Stevens, David P; Joshi, Manoj M

2016-04-19

Modeling studies of terrestrial extrasolar planetary climates are now including the effects of ocean circulation due to a recognition of the importance of oceans for climate; indeed, the peak equator-pole ocean heat transport on Earth peaks at almost half that of the atmosphere. However, such studies have made the assumption that fundamental oceanic properties, such as salinity, temperature, and depth, are similar to Earth. This assumption results in Earth-like circulations: a meridional overturning with warm water moving poleward at the surface, being cooled, sinking at high latitudes, and traveling equatorward at depth. Here it is shown that an exoplanetary ocean with a different salinity can circulate in the opposite direction: an equatorward flow of polar water at the surface, sinking in the tropics, and filling the deep ocean with warm water. This alternative flow regime results in a dramatic warming in the polar regions, demonstrated here using both a conceptual model and an ocean general circulation model. These results highlight the importance of ocean salinity for exoplanetary climate and consequent habitability and the need for its consideration in future studies.

Climate. Varying planetary heat sink led to global-warming slowdown and acceleration.

PubMed

Chen, Xianyao; Tung, Ka-Kit

2014-08-22

A vacillating global heat sink at intermediate ocean depths is associated with different climate regimes of surface warming under anthropogenic forcing: The latter part of the 20th century saw rapid global warming as more heat stayed near the surface. In the 21st century, surface warming slowed as more heat moved into deeper oceans. In situ and reanalyzed data are used to trace the pathways of ocean heat uptake. In addition to the shallow La Niña-like patterns in the Pacific that were the previous focus, we found that the slowdown is mainly caused by heat transported to deeper layers in the Atlantic and the Southern oceans, initiated by a recurrent salinity anomaly in the subpolar North Atlantic. Cooling periods associated with the latter deeper heat-sequestration mechanism historically lasted 20 to 35 years. Copyright © 2014, American Association for the Advancement of Science.

Utilizing chromophoric dissolved organic matter measurements to derive export and reactivity of dissolved organic carbon exported to the Arctic Ocean: A case study of the Yukon River, Alaska

USGS Publications Warehouse

Spencer, R.G.M.; Aiken, G.R.; Butler, K.D.; Dornblaser, M.M.; Striegl, Robert G.; Hernes, P.J.

2009-01-01

The quality and quantity of dissolved organic matter (DOM) exported by Arctic rivers is known to vary with hydrology and this exported material plays a fundamental role in the biogeochemical cycling of carbon at high latitudes. We highlight the potential of optical measurements to examine DOM quality across the hydrograph in Arctic rivers. Furthermore, we establish chromophoric DOM (CDOM) relationships to dissolved organic carbon (DOC) and lignin phenols in the Yukon River and model DOC and lignin loads from CDOM measurements, the former in excellent agreement with long-term DOC monitoring data. Intensive sampling across the historically under-sampled spring flush period highlights the importance of this time for total export of DOC and particularly lignin. Calculated riverine DOC loads to the Arctic Ocean show an increase from previous estimates, especially when new higher discharge data are incorporated. Increased DOC loads indicate decreased residence times for terrigenous DOM in the Arctic Ocean with important implications for the reactivity and export of this material to the Atlantic Ocean. Citation: Spencer, R. G. M., G. R. Aiken, K. D. Butler, M. M. Dornblaser, R. G. Striegl, and P. J. Hernes (2009), Utilizing chromophoric dissolved organic matter measurements to derive export and reactivity of dissolved organic carbon exported to the Arctic Ocean: A case study of the Yukon River, Alaska, Geophys. Res. Lett., 36, L06401, doi:10.1029/ 2008GL036831. Copyright 2009 by the American Geophysical Union.

Uncertainty in Indian Ocean Dipole response to global warming: the role of internal variability

NASA Astrophysics Data System (ADS)

Hui, Chang; Zheng, Xiao-Tong

2018-01-01

The Indian Ocean Dipole (IOD) is one of the leading modes of interannual sea surface temperature (SST) variability in the tropical Indian Ocean (TIO). The response of IOD to global warming is quite uncertain in climate model projections. In this study, the uncertainty in IOD change under global warming, especially that resulting from internal variability, is investigated based on the community earth system model large ensemble (CESM-LE). For the IOD amplitude change, the inter-member uncertainty in CESM-LE is about 50% of the intermodel uncertainty in the phase 5 of the coupled model intercomparison project (CMIP5) multimodel ensemble, indicating the important role of internal variability in IOD future projection. In CESM-LE, both the ensemble mean and spread in mean SST warming show a zonal positive IOD-like (pIOD-like) pattern in the TIO. This pIOD-like mean warming regulates ocean-atmospheric feedbacks of the interannual IOD mode, and weakens the skewness of the interannual variability. However, as the changes in oceanic and atmospheric feedbacks counteract each other, the inter-member variability in IOD amplitude change is not correlated with that of the mean state change. Instead, the ensemble spread in IOD amplitude change is correlated with that in ENSO amplitude change in CESM-LE, reflecting the close inter-basin relationship between the tropical Pacific and Indian Ocean in this model.

Mean hydrography on the continental shelf from 26 repeat glider deployments along Southeastern Australia

PubMed Central

Schaeffer, Amandine; Roughan, Moninya; Austin, Tim; Everett, Jason D.; Griffin, David; Hollings, Ben; King, Edward; Mantovanelli, Alessandra; Milburn, Stuart; Pasquer, Benedicte; Pattiaratchi, Charitha; Robertson, Robin; Stanley, Dennis; Suthers, Iain; White, Dana

2016-01-01

Since 2008, 26 glider missions have been undertaken along the continental shelf of southeastern Australia. Typically these missions have spanned the continental shelf on the inshore edge of the East Australian Current from 29.5–33.5°S. This comprehensive dataset of over 33,600 CTD profiles from the surface to within 10 m of the bottom in water depths ranging 25–200 m provides new and unprecedented high resolution observations of the properties of the continental shelf waters adjacent to a western boundary current, straddling the region where it separates from the coast. The region is both physically and biologically significant, and is also in a hotspot of ocean warming. We present gridded mean fields for temperature, salinity and density, but also dissolved oxygen and chlorophyll-a fluorescence indicative of phytoplankton biomass. This data will be invaluable for understanding shelf stratification, circulation, biophysical and bio-geochemical interactions, as well as for the validation of high-resolution ocean models or serving as teaching material. PMID:27575831

How much riverine nutrients do shelf seas allow into the open ocean?

NASA Astrophysics Data System (ADS)

Sharples, J.; Fennel, K.; Jickells, T. D.

2016-02-01

Globally rivers deliver 35 Tg of dissolved N and 2 Tg of dissolved P into the coastal zone each year. Investigating the effects of this nutrient supply on the open ocean generally takes one of two approaches: either all or none of the nutrients are assumed to enter the open ocean. Here we use some general assumptions on the behaviour of river plumes on the shelf to arrive at an estimate of the proportions of dissolved N and P that are processed on the shelf, and thus the amount of riverine nutrient that enters the open ocean. Using the Global NEWS database of 6000 rivers we assume that discharges to the shelf are initially constrained within coastal buoyancy currents of width 2 internal Rossby radii. This width is compared to the local shelf width for each river. For plume widths greater than the shelf width riverine nutrients are assumed to be transported over the shelf edge within the plume. For plume widths less than the shelf width we assume that exchange with the open ocean is controlled by physical processes at the shelf break. For each river an estimate of the residence time of riverine water is made, based on the transport or exchange rate and the shelf volume. Empirical relationships between residence time and the proportion of supplied N and P that is retained on the shelf are then used to estimate the amount of dissolved N and P that escapes to the open ocean. The results suggest that 25% of dissolved N and 20% of dissolved P are processed in shelf seas, with the rest exported to the open ocean. There is a latitudinal pattern, with tropical rivers delivering more nutrients to the open ocean. This is partially a result of the high discharges of some tropical rivers, but a key issue is our assumption of the internal Rossby radius governing plume width. A range of values for transport rates within plumes and exchange rates across the shelf break are used to assess the sensitivity of these results, which appear to be robust.

Ocean acidification exerts negative effects during warming conditions in a developing Antarctic fish

PubMed Central

Flynn, Erin E; Bjelde, Brittany E; Miller, Nathan A

2015-01-01

Abstract Anthropogenic CO2 is rapidly causing oceans to become warmer and more acidic, challenging marine ectotherms to respond to simultaneous changes in their environment. While recent work has highlighted that marine fishes, particularly during early development, can be vulnerable to ocean acidification, we lack an understanding of how life-history strategies, ecosystems and concurrent ocean warming interplay with interspecific susceptibility. To address the effects of multiple ocean changes on cold-adapted, slowly developing fishes, we investigated the interactive effects of elevated partial pressure of carbon dioxide (pCO2) and temperature on the embryonic physiology of an Antarctic dragonfish (Gymnodraco acuticeps), with protracted embryogenesis (∼10 months). Using an integrative, experimental approach, our research examined the impacts of near-future warming [−1 (ambient) and 2°C (+3°C)] and ocean acidification [420 (ambient), 650 (moderate) and 1000 μatm pCO2 (high)] on survival, development and metabolic processes over the course of 3 weeks in early development. In the presence of increased pCO2 alone, embryonic mortality did not increase, with greatest overall survival at the highest pCO2. Furthermore, embryos were significantly more likely to be at a later developmental stage at high pCO2 by 3 weeks relative to ambient pCO2. However, in combined warming and ocean acidification scenarios, dragonfish embryos experienced a dose-dependent, synergistic decrease in survival and developed more slowly. We also found significant interactions between temperature, pCO2 and time in aerobic enzyme activity (citrate synthase). Increased temperature alone increased whole-organism metabolic rate (O2 consumption) and developmental rate and slightly decreased osmolality at the cost of increased mortality. Our findings suggest that developing dragonfish are more sensitive to ocean warming and may experience negative physiological effects of ocean acidification only in the presence of an increased temperature. In addition to reduced hatching success, alterations in development and metabolism due to ocean warming and acidification could have negative ecological consequences owing to changes in phenology (i.e. early hatching) in the highly seasonal Antarctic ecosystem. PMID:27293718

Ocean acidification exerts negative effects during warming conditions in a developing Antarctic fish.

PubMed

Flynn, Erin E; Bjelde, Brittany E; Miller, Nathan A; Todgham, Anne E

2015-01-01

Anthropogenic CO2 is rapidly causing oceans to become warmer and more acidic, challenging marine ectotherms to respond to simultaneous changes in their environment. While recent work has highlighted that marine fishes, particularly during early development, can be vulnerable to ocean acidification, we lack an understanding of how life-history strategies, ecosystems and concurrent ocean warming interplay with interspecific susceptibility. To address the effects of multiple ocean changes on cold-adapted, slowly developing fishes, we investigated the interactive effects of elevated partial pressure of carbon dioxide (pCO2) and temperature on the embryonic physiology of an Antarctic dragonfish (Gymnodraco acuticeps), with protracted embryogenesis (∼10 months). Using an integrative, experimental approach, our research examined the impacts of near-future warming [-1 (ambient) and 2°C (+3°C)] and ocean acidification [420 (ambient), 650 (moderate) and 1000 μatm pCO2 (high)] on survival, development and metabolic processes over the course of 3 weeks in early development. In the presence of increased pCO2 alone, embryonic mortality did not increase, with greatest overall survival at the highest pCO2. Furthermore, embryos were significantly more likely to be at a later developmental stage at high pCO2 by 3 weeks relative to ambient pCO2. However, in combined warming and ocean acidification scenarios, dragonfish embryos experienced a dose-dependent, synergistic decrease in survival and developed more slowly. We also found significant interactions between temperature, pCO2 and time in aerobic enzyme activity (citrate synthase). Increased temperature alone increased whole-organism metabolic rate (O2 consumption) and developmental rate and slightly decreased osmolality at the cost of increased mortality. Our findings suggest that developing dragonfish are more sensitive to ocean warming and may experience negative physiological effects of ocean acidification only in the presence of an increased temperature. In addition to reduced hatching success, alterations in development and metabolism due to ocean warming and acidification could have negative ecological consequences owing to changes in phenology (i.e. early hatching) in the highly seasonal Antarctic ecosystem.

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

How Do I Manage Side Effects?

MedlinePlus

... Gargle with one teaspoon of table salt or baking soda dissolved in one cup of warm water ... sick Keep your mouth very clean (gargle with baking soda and warm water) Avoid flowers and plants ( ...

How robust is the atmospheric circulation response to Arctic sea-ice loss in isolation?

NASA Astrophysics Data System (ADS)

Kushner, P. J.; Hay, S. E.; Blackport, R.; McCusker, K. E.; Oudar, T.

2017-12-01

It is now apparent that active dynamical coupling between the ocean and atmosphere determines a good deal of how Arctic sea-ice loss changes the large-scale atmospheric circulation. In coupled ocean-atmosphere models, Arctic sea-ice loss indirectly induces a 'mini' global warming and circulation changes that extend into the tropics and the Southern Hemisphere. Ocean-atmosphere coupling also amplifies by about 50% Arctic free-tropospheric warming arising from sea-ice loss (Deser et al. 2015, 2016). The mechanisms at work and how to separate the response to sea-ice loss from the rest of the global warming process remain poorly understood. Different studies have used distinctive numerical approaches and coupled ocean-atmosphere models to address this problem. We put these studies on comparable footing using pattern scaling (Blackport and Kushner 2017) to separately estimate the part of the circulation response that scales with sea-ice loss in the absence of low-latitude warming from the part that scales with low-latitude warming in the absence of sea-ice loss. We consider well-sampled simulations from three different coupled ocean-atmosphere models (CESM1, CanESM2, CNRM-CM5), in which greenhouse warming and sea-ice loss are driven in different ways (sea ice albedo reduction/transient RCP8.5 forcing for CESM1, nudged sea ice/CO2 doubling for CanESM2, heat-flux forcing/constant RCP8.5-derived forcing for CNRM-CM5). Across these different simulations, surprisingly robust influences of Arctic sea-ice loss on atmospheric circulation can be diagnosed using pattern scaling. For boreal winter, the isolated sea-ice loss effect acts to increase warming in the North American Sub-Arctic, decrease warming of the Eurasian continent, enhance precipitation over the west coast of North America, and strengthen the Aleutian Low and the Siberian High. We will also discuss how Arctic free tropospheric warming might be enhanced via midlatitude ocean surface warming induced by sea-ice loss. Less robust is the part of the response that scales with low-latitude warming, which, depending on the model, can reinforce or cancel the response to sea-ice loss. The extent to which a "tug of war" exists between tropical and high-latitude influences on the general circulation might thus be model dependent.

Aerobic Marine Habitat Loss During the Late Permian Extinction

NASA Astrophysics Data System (ADS)

Penn, J. L.; Deutsch, C.; Payne, J.; Sperling, E. A.

2016-12-01

Rapid climate change at the end of the Permian is thought to have triggered the most severe mass extinction in Earth's history, but the precise mechanism of biodiversity loss is unknown. Geological evidence points to lethally hot equatorial temperatures and an expansion of anoxic ocean waters as likely culprits. However, previous climate model simulations of the warm Early Triassic exhibit weak tropical warming, and anoxic conditions require a massive and unconstrained increase in the ocean nutrient reservoir. Reconciling model predictions with the geologic record remains a key challenge to identifying the kill-mechanism, which must also take into account the role of animal physiology. Here we apply a recently developed index for the metabolic scope of marine animals to the first global climate simulations of the Permian-Triassic transition to quantify the effects of ocean warming and oxygen (O2) depletion on aerobic habitat availability. Forcing with extreme CO2 concentrations warms the surface ocean by over 10oC, consistent with paleoproxies for upper ocean temperature change. Warming depletes global O2, with greatest losses occuring in tropical deep waters as a result of their reduced ventilation. Together warming and deoxygenation would have constricted the occurrence of marine habitat by 80% globally, by decreasing the metabolic index of the Permian ocean. These changes are most pronounced in the tropics where the fossil record suggests recovery was severely inhibited. Fossil deposits also record changes in animal body size across the extinction. We find that adaptation via body size reductions can compensate for increasing hypoxia at high latitudes, and even prevent extinction there, but cannot maintain the habitability of the tropics.

Hydrological processes and permafrost regulate magnitude, source and chemical characteristics of dissolved organic carbon export in a peatland catchment of northeastern China

NASA Astrophysics Data System (ADS)

Guo, Yuedong; Song, Changchun; Tan, Wenwen; Wang, Xianwei; Lu, Yongzheng

2018-02-01

Permafrost thawing in peatlands has the potential to alter the catchment export of dissolved organic carbon (DOC), thus influencing the carbon balance and cycling in linked aquatic and ocean ecosystems. Peatlands along the southern margins of the Eurasian permafrost are relatively underexplored despite the considerable risks associated with permafrost degradation due to climate warming. This study examined dynamics of DOC export from a permafrost peatland catchment located in northeastern China during the 2012 to 2014 growing seasons. The estimated annual DOC loads varied greatly between 3211 and 19 022 kg yr-1, with a mean DOC yield of 4.7 g m-2 yr-1. Although the estimated DOC yield was in the lower range compared with other permafrost regions, it was still significant for the net carbon balance in the studied catchment. There were strong linkages between daily discharge and DOC concentrations in both wet and dry years, suggesting a transport-limited process of DOC delivery from the catchment. Discharge explained the majority of both seasonal and interannual variations of DOC concentrations, which made annual discharge a good indicator of total DOC load from the catchment. As indicated by three fluorescence indices, DOC source and chemical characteristics tracked the shift of flow paths during runoff processes closely. Interactions between the flow path and DOC chemical characteristics were greatly influenced by the seasonal thawing of the soil active layer. The deepening of the active layer due to climate warming likely increases the proportion of microbial-originated DOC in baseflow discharge.

21 CFR 347.52 - Labeling of astringent drug products.

Code of Federal Regulations, 2011 CFR

2011-04-01

... states “[bullet] dissolve 1 to 3 packets in [insert volume] of cool or warm water [bullet] stir until... [bullet] stir until fully dissolved; do not strain or filter. The resulting mixture contains [insert...

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.

From global to regional and back again: common climate stressors of marine ecosystems relevant for adaptation across five ocean warming hotspots.

PubMed

Popova, Ekaterina; Yool, Andrew; Byfield, Valborg; Cochrane, Kevern; Coward, Andrew C; Salim, Shyam S; Gasalla, Maria A; Henson, Stephanie A; Hobday, Alistair J; Pecl, Gretta T; Sauer, Warwick H; Roberts, Michael J

2016-06-01

Ocean warming 'hotspots' are regions characterized by above-average temperature increases over recent years, for which there are significant consequences for both living marine resources and the societies that depend on them. As such, they represent early warning systems for understanding the impacts of marine climate change, and test-beds for developing adaptation options for coping with those impacts. Here, we examine five hotspots off the coasts of eastern Australia, South Africa, Madagascar, India and Brazil. These particular hotspots have underpinned a large international partnership that is working towards improving community adaptation by characterizing, assessing and projecting the likely future of coastal-marine food resources through the provision and sharing of knowledge. To inform this effort, we employ a high-resolution global ocean model forced by Representative Concentration Pathway 8.5 and simulated to year 2099. In addition to the sea surface temperature, we analyse projected stratification, nutrient supply, primary production, anthropogenic CO2 -driven ocean acidification, deoxygenation and ocean circulation. Our simulation finds that the temperature-defined hotspots studied here will continue to experience warming but, with the exception of eastern Australia, may not remain the fastest warming ocean areas over the next century as the strongest warming is projected to occur in the subpolar and polar areas of the Northern Hemisphere. Additionally, we find that recent rapid change in SST is not necessarily an indicator that these areas are also hotspots of the other climatic stressors examined. However, a consistent facet of the hotspots studied here is that they are all strongly influenced by ocean circulation, which has already shown changes in the recent past and is projected to undergo further strong change into the future. In addition to the fast warming, change in local ocean circulation represents a distinct feature of present and future climate change impacting marine ecosystems in these areas. © 2016 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

Climate, ocean circulation, and sea level changes under stabilization and overshoot pathways to 1.5 K warming

NASA Astrophysics Data System (ADS)

Palter, Jaime B.; Frölicher, Thomas L.; Paynter, David; John, Jasmin G.

2018-06-01

The Paris Agreement has initiated a scientific debate on the role that carbon removal - or net negative emissions - might play in achieving less than 1.5 K of global mean surface warming by 2100. Here, we probe the sensitivity of a comprehensive Earth system model (GFDL-ESM2M) to three different atmospheric CO2 concentration pathways, two of which arrive at 1.5 K of warming in 2100 by very different pathways. We run five ensemble members of each of these simulations: (1) a standard Representative Concentration Pathway (RCP4.5) scenario, which produces 2 K of surface warming by 2100 in our model; (2) a stabilization pathway in which atmospheric CO2 concentration never exceeds 440 ppm and the global mean temperature rise is approximately 1.5 K by 2100; and (3) an overshoot pathway that passes through 2 K of warming at mid-century, before ramping down atmospheric CO2 concentrations, as if using carbon removal, to end at 1.5 K of warming at 2100. Although the global mean surface temperature change in response to the overshoot pathway is similar to the stabilization pathway in 2100, this similarity belies several important differences in other climate metrics, such as warming over land masses, the strength of the Atlantic Meridional Overturning Circulation (AMOC), ocean acidification, sea ice coverage, and the global mean sea level change and its regional expressions. In 2100, the overshoot ensemble shows a greater global steric sea level rise and weaker AMOC mass transport than in the stabilization scenario, with both of these metrics close to the ensemble mean of RCP4.5. There is strong ocean surface cooling in the North Atlantic Ocean and Southern Ocean in response to overshoot forcing due to perturbations in the ocean circulation. Thus, overshoot forcing in this model reduces the rate of sea ice loss in the Labrador, Nordic, Ross, and Weddell seas relative to the stabilized pathway, suggesting a negative radiative feedback in response to the early rapid warming. Finally, the ocean perturbation in response to warming leads to strong pathway dependence of sea level rise in northern North American cities, with overshoot forcing producing up to 10 cm of additional sea level rise by 2100 relative to stabilization forcing.

Bathymetric controls on Pliocene North Atlantic and Arctic sea surface temperature and deepwater production

USGS Publications Warehouse

Robinson, M.M.; Valdes, P.J.; Haywood, A.M.; Dowsett, H.J.; Hill, D.J.; Jones, S.M.

2011-01-01

The mid-Pliocene warm period (MPWP; ~. 3.3 to 3.0. Ma) is the most recent interval in Earth's history in which global temperatures reached and remained at levels similar to those projected for the near future. The distribution of global warmth, however, was different than today in that the high latitudes warmed more than the tropics. Multiple temperature proxies indicate significant sea surface warming in the North Atlantic and Arctic Oceans during the MPWP, but predictions from a fully coupled ocean-atmosphere model (HadCM3) have so far been unable to fully predict the large scale of sea surface warming in the high latitudes. If climate proxies accurately represent Pliocene conditions, and if no weakness exists in the physics of the model, then model boundary conditions may be in error. Here we alter a single boundary condition (bathymetry) to examine if Pliocene high latitude warming was aided by an increase in poleward heat transport due to changes in the subsidence of North Atlantic Ocean ridges. We find an increase in both Arctic sea surface temperature and deepwater production in model experiments that incorporate a deepened Greenland-Scotland Ridge. These results offer both a mechanism for the warming in the North Atlantic and Arctic Oceans indicated by numerous proxies and an explanation for the apparent disparity between proxy data and model simulations of Pliocene northern North Atlantic and Arctic Ocean conditions. Determining the causes of Pliocene warmth remains critical to fully understanding comparisons of the Pliocene warm period to possible future climate change scenarios. ?? 2011.

Sustained Observations of Air-Sea Fluxes and Air-Sea Interaction at the Stratus Ocean Reference Station

NASA Astrophysics Data System (ADS)

Weller, Robert

2014-05-01

Since October 2000, a well-instrumented surface mooring has been maintained some 1,500 km west of the coast of northern Chile, roughly in the location of the climatological maximum in marine stratus clouds. Statistically significant increases in wind stress and decreases in annual net air-sea heat flux and in latent heat flux have been observed. If the increased oceanic heat loss continues, the region will within the next decade change from one of net annual heat gain by the ocean to one of neat annual heat loss. Already, annual evaporation of about 1.5 m of sea water a year acts to make the warm, salty surface layer more dense. Of interest is examining whether or not increased oceanic heat loss has the potential to change the structure of the upper ocean and potentially remove the shallow warm, salty mixed layer that now buffers the atmosphere from the interior ocean. Insights into how that warm, shallow layer is formed and maintained come from looking at oceanic response to the atmosphere at diurnal tie scales. Restratification each spring and summer is found to depend upon the occurrence of events in which the trade winds decay, allowing diurnal warming in the near-surface ocean to occur, and when the winds return resulting in a net upward step in sea surface temperature. This process is proving hard to accurately model.

Tropical Atlantic climate response to different freshwater input in high latitudes with an ocean-only general circulation model

NASA Astrophysics Data System (ADS)

Men, Guang; Wan, Xiuquan; Liu, Zedong

2016-10-01

Tropical Atlantic climate change is relevant to the variation of Atlantic meridional overturning circulation (AMOC) through different physical processes. Previous coupled climate model simulation suggested a dipole-like SST structure cooling over the North Atlantic and warming over the South Tropical Atlantic in response to the slowdown of the AMOC. Using an ocean-only global ocean model here, an attempt was made to separate the total influence of various AMOC change scenarios into an oceanic-induced component and an atmospheric-induced component. In contrast with previous freshwater-hosing experiments with coupled climate models, the ocean-only modeling presented here shows a surface warming in the whole tropical Atlantic region and the oceanic-induced processes may play an important role in the SST change in the equatorial south Atlantic. Our result shows that the warming is partly governed by oceanic process through the mechanism of oceanic gateway change, which operates in the regime where freshwater forcing is strong, exceeding 0.3 Sv. Strong AMOC change is required for the gateway mechanism to work in our model because only when the AMOC is sufficiently weak, the North Brazil Undercurrent can flow equatorward, carrying warm and salty north Atlantic subtropical gyre water into the equatorial zone. This threshold is likely to be model-dependent. An improved understanding of these issues may have help with abrupt climate change prediction later.

Eocene Temperature Evolution of the Tropical Atlantic Ocean

NASA Astrophysics Data System (ADS)

Cramwinckel, M.; Kocken, I.; Agnini, C.; Huber, M.; van der Ploeg, R.; Frieling, J.; Bijl, P.; Peterse, F.; Roehl, U.; Bohaty, S. M.; Schouten, S.; Sluijs, A.

2016-12-01

The transition from the early Eocene ( 50 Ma) hothouse towards the Oligocene ( 33 Ma) icehouse was interrupted by the Middle Eocene Climatic Optimum (MECO) ( 40 Ma), a 500,000-year long episode of deep sea and Southern Ocean warming. It remains unclear whether this transient warming event was global, and whether it was caused by changes in atmospheric greenhouse gas concentrations or confined to high latitudes resulting from ocean circulation change. Here we show, based on biomarker paleothermometry applied at Ocean Drilling Program Site 959, offshore Ghana, that sea surface temperatures in the eastern equatorial Atlantic Ocean declined by 7°C over the middle-late Eocene, in agreement with temperature trends documented in the southern high latitudes. In the equatorial Atlantic, this long-term trend was punctuated by 2.5°C warming during the MECO. At the zenith of MECO warmth, changes in dinoflagellate cyst assemblages and laminated sediments at Site 959 point to open ocean hyperstratification and seafloor deoxygenation, respectively. Remarkably, the data reveal that the magnitude of temperature change in the tropics was approximately half that in the Southern Ocean. This suggests that the generally ice free Eocene yielded limited but significant polar amplification of climate change. Crucially, general circulation model (GCM) simulations reveal that the recorded tropical and deep ocean temperature trends are best explained by greenhouse gas forcing, controlling both middle-late Eocene cooling and the superimposed MECO warming.

Multistressor impacts of warming and acidification of the ocean on marine invertebrates' life histories.

PubMed

Byrne, Maria; Przeslawski, Rachel

2013-10-01

Benthic marine invertebrates live in a multistressor world where stressor levels are, and will continue to be, exacerbated by global warming and increased atmospheric carbon dioxide. These changes are causing the oceans to warm, decrease in pH, become hypercapnic, and to become less saturated in carbonate minerals. These stressors have strong impacts on biological processes, but little is known about their combined effects on the development of marine invertebrates. Increasing temperature has a stimulatory effect on development, whereas hypercapnia can depress developmental processes. The pH, pCO2, and CaCO3 of seawater change simultaneously with temperature, challenging our ability to predict future outcomes for marine biota. The need to consider both warming and acidification is reflected in the recent increase in cross-factorial studies of the effects of these stressors on development of marine invertebrates. The outcomes and trends in these studies are synthesized here. Based on this compilation, significant additive or antagonistic effects of warming and acidification of the ocean are common (16 of 20 species studied), and synergistic negative effects also are reported. Fertilization can be robust to near-future warming and acidification, depending on the male-female mating pair. Although larvae and juveniles of some species tolerate near-future levels of warming and acidification (+2°C/pH 7.8), projected far-future conditions (ca. ≥4°C/ ≤pH 7.6) are widely deleterious, with a reduction in the size and survival of larvae. It appears that larvae that calcify are sensitive both to warming and acidification, whereas those that do not calcify are more sensitive to warming. Different sensitivities of life-history stages and species have implications for persistence and community function in a changing ocean. Some species are more resilient than others and may be potential "winners" in the climate-change stakes. As the ocean will change more gradually over coming decades than in "future shock" perturbation investigations, it is likely that some species, particularly those with short generation times, may be able to tolerate near-future oceanic change through acclimatization and/or adaption.

The role stratification on Indian ocean mixing under global warming

NASA Astrophysics Data System (ADS)

Praveen, V.; Valsala, V.; Ravindran, A. M.

2017-12-01

The impact of changes in Indian ocean stratification on mixing under global warming is examined. Previous studies on global warming and associated weakening of winds reported to increase the stratification of the world ocean leading to a reduction in mixing, increased acidity, reduced oxygen and there by a reduction in productivity. However this processes is not uniform and are also modulated by changes in wind pattern of the future. Our study evaluate the role of stratification and surface fluxes on mixing focusing northern Indian ocean. A dynamical downscaling study using Regional ocean Modelling system (ROMS) forced with stratification and surface fluxes from selected CMIP5 models are presented. Results from an extensive set of historical and Representative Concentration Pathways 8.5 (rcp8.5) scenario simulations are used to quantify the distinctive role of stratification on mixing.

River fluxes to the sea from the ocean's 10Be/9Be ratio

NASA Astrophysics Data System (ADS)

von Blanckenburg, F.; Bouchez, J.

2013-12-01

The ratio of the meteoric cosmogenic radionuclide 10Be to the stable isotope 9Be is proposed here to be a flux proxy of terrigenous input into the oceans. The ocean's dissolved 10Be/9Be is set by (1) the flux of meteoric 10Be produced in the atmosphere; (2) the denudational flux of the rivers discharging into a given ocean basin; (3) the fraction of 9Be that is released from primary minerals during weathering (meaning the 9Be transported by rivers in either the dissolved form or adsorbed onto sedimentary particles and incorporated into secondary oxides); and (4) the fraction of riverine 10Be and 9Be actually released into seawater. Using published 10Be/9Be data of rivers for which independent denudation rate estimates exist we first find that the global average fraction of 9Be released during weathering into river waters and their particulate load is 20% and does not depend on denudation rate. We then evaluate this quantitative denudation rate proxy by using published dissolved seawater Be isotope data and a compilation of global river loads (15Gt/yr). We find that the measured global average oceanic dissolved 10Be/9Be ratio of about 0.9E-7 is satisfied by the mass balance if only 6.5% of the dissolved and reactive riverine Be is eventually released to the open ocean by boundary exchange. Except for the South Atlantic and the South Pacific, in which the 10Be/9Be ratio is dominated by Be advected through ocean circulation, good agreement results between 10Be/9Be ratios predicted by denudation rates and measured ocean 10Be/9Be ratios when we establish this mass balance for individual ocean basins. As the seawater 10Be/9Be ratio is faithfully recorded in marine chemical precipitates the 10Be/9Be ratio extracted from authigenic sediments can now serve to estimate relative changes in terrigenous input into the oceans back through time on a global and on a basin scale.

The phenology of Arctic Ocean surface warming.

PubMed

Steele, Michael; Dickinson, Suzanne

2016-09-01

In this work, we explore the seasonal relationships (i.e., the phenology) between sea ice retreat, sea surface temperature (SST), and atmospheric heat fluxes in the Pacific Sector of the Arctic Ocean, using satellite and reanalysis data. We find that where ice retreats early in most years, maximum summertime SSTs are usually warmer, relative to areas with later retreat. For any particular year, we find that anomalously early ice retreat generally leads to anomalously warm SSTs. However, this relationship is weak in the Chukchi Sea, where ocean advection plays a large role. It is also weak where retreat in a particular year happens earlier than usual, but still relatively late in the season, primarily because atmospheric heat fluxes are weak at that time. This result helps to explain the very different ocean warming responses found in two recent years with extreme ice retreat, 2007 and 2012. We also find that the timing of ice retreat impacts the date of maximum SST, owing to a change in the ocean surface buoyancy and momentum forcing that occurs in early August that we term the Late Summer Transition (LST). After the LST, enhanced mixing of the upper ocean leads to cooling of the ocean surface even while atmospheric heat fluxes are still weakly downward. Our results indicate that in the near-term, earlier ice retreat is likely to cause enhanced ocean surface warming in much of the Arctic Ocean, although not where ice retreat still occurs late in the season.

River Export of Dissolved and Particulate Organic Carbon from Permafrost and Peat Deposits across the Siberian Arctic

NASA Astrophysics Data System (ADS)

Wild, B.; Andersson, A.; Bröder, L.; Vonk, J.; Hugelius, G.; McClelland, J. W.; Raymond, P. A.; Gustafsson, O.

2017-12-01

Permafrost and peat deposits of northern high latitudes store more than 1300 Pg of organic carbon. This carbon has been preserved for thousands of years by cold and moist conditions, but is now increasingly mobilized as temperatures rise. While part will be degraded to CO2 and CH4 and amplify global warming, part will be exported by rivers to the Arctic Ocean where it can be degraded or re-buried by sedimentation. We here use the four large Siberian rivers Ob, Yenisey, Lena, and Kolyma as natural integrators of carbon mobilization in their catchments. We apply isotope based source apportionments and Markov Chain Monte Carlo Simulations to quantify contributions of organic carbon from permafrost and peat deposits to organic carbon exported by these rivers. More specifically, we compare the 14C signatures of dissolved and particulate organic carbon (DOC, POC) sampled close to the river mouths with those of five potential carbon sources; (1) recent aquatic and (2) terrestrial primary production, (3) the active layer of permafrost soils, (4) deep Holocene deposits (including thermokarst and peat deposits) and (5) Ice Complex Deposits. 14C signatures of these endmembers were constrained based on extensive literature review. We estimate that the four rivers together exported 2.4-4.5 Tg organic carbon from permafrost and peat deposits per year. While total organic carbon export was dominated by DOC (90%), the export of organic carbon from permafrost and peat deposits was more equally distributed between DOC (56%) and POC (44%). Recent models predict that ca. 200 Pg carbon will be lost as CO2 or CH4 by 2100 (RCP8.5) from the circumarctic permafrost area, of which roughly a quarter is drained by the Ob, Yenisey, Lena, and Kolyma rivers. Our comparatively low estimates of river carbon export thus suggest limited transfer of organic carbon from permafrost and peat deposits to high latitude rivers, or its rapid degradation within rivers. Our findings highlight the importance of both DOC and POC, and its degradation, for the fate of carbon mobilized from high latitude deposits under global warming, and indicate a low potential for its stabilization in the Arctic Ocean.

Ocean acidification and global warming impair shark hunting behaviour and growth.

PubMed

Pistevos, Jennifer C A; Nagelkerken, Ivan; Rossi, Tullio; Olmos, Maxime; Connell, Sean D

2015-11-12

Alterations in predation pressure can have large effects on trophically-structured systems. Modification of predator behaviour via ocean warming has been assessed by laboratory experimentation and metabolic theory. However, the influence of ocean acidification with ocean warming remains largely unexplored for mesopredators, including experimental assessments that incorporate key components of the assemblages in which animals naturally live. We employ a combination of long-term laboratory and mesocosm experiments containing natural prey and habitat to assess how warming and acidification affect the development, growth, and hunting behaviour in sharks. Although embryonic development was faster due to temperature, elevated temperature and CO2 had detrimental effects on sharks by not only increasing energetic demands, but also by decreasing metabolic efficiency and reducing their ability to locate food through olfaction. The combination of these effects led to considerable reductions in growth rates of sharks held in natural mesocosms with elevated CO2, either alone or in combination with higher temperature. Our results suggest a more complex reality for predators, where ocean acidification reduces their ability to effectively hunt and exert strong top-down control over food webs.

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.

Ocean acidification and global warming impair shark hunting behaviour and growth

PubMed Central

Pistevos, Jennifer C. A.; Nagelkerken, Ivan; Rossi, Tullio; Olmos, Maxime; Connell, Sean D.

2015-01-01

Alterations in predation pressure can have large effects on trophically-structured systems. Modification of predator behaviour via ocean warming has been assessed by laboratory experimentation and metabolic theory. However, the influence of ocean acidification with ocean warming remains largely unexplored for mesopredators, including experimental assessments that incorporate key components of the assemblages in which animals naturally live. We employ a combination of long-term laboratory and mesocosm experiments containing natural prey and habitat to assess how warming and acidification affect the development, growth, and hunting behaviour in sharks. Although embryonic development was faster due to temperature, elevated temperature and CO2 had detrimental effects on sharks by not only increasing energetic demands, but also by decreasing metabolic efficiency and reducing their ability to locate food through olfaction. The combination of these effects led to considerable reductions in growth rates of sharks held in natural mesocosms with elevated CO2, either alone or in combination with higher temperature. Our results suggest a more complex reality for predators, where ocean acidification reduces their ability to effectively hunt and exert strong top-down control over food webs. PMID:26559327

Attribution of the 2015 record high sea surface temperatures over the central equatorial Pacific and tropical Indian Ocean

NASA Astrophysics Data System (ADS)

Park, In-Hong; Min, Seung-Ki; Yeh, Sang-Wook; Weller, Evan; Kim, Seon Tae

2017-04-01

This study assessed the anthropogenic contribution to the 2015 record-breaking high sea surface temperatures (SSTs) observed in the central equatorial Pacific and tropical Indian Ocean. Considering a close link between extreme warm events in these regions, we conducted a joint attribution analysis using a fraction of attributable risk approach. Probability of occurrence of such extreme anomalies and long-term trends for the two oceanic regions were compared between CMIP5 multi-model simulations with and without anthropogenic forcing. Results show that the excessive warming in both regions is well beyond the range of natural variability and robustly attributable to human activities due to greenhouse gas increase. We further explored associated mechanisms including the Bjerknes feedback and background anthropogenic warming. It is concluded that background warming was the main contribution to the 2015 extreme SST event over the central equatorial Pacific Ocean on a developing El Niño condition, which in turn induced the extreme SST event over the tropical Indian Ocean through the atmospheric bridge effect.

Dissolved lead in the deep Southeast Pacific Ocean: results of the 2013 US GEOTRACES cruise

NASA Astrophysics Data System (ADS)

Boyle, E. A.; Lee, J. M.; Zhang, J.; Echegoyen, Y.

2014-12-01

Lead (Pb) in the modern ocean is dominated by anthropogenic Pb, which has been evidenced by highly elevated seawater Pb concentrations and Pb stable isotope ratios (204Pb, 206Pb, 207Pb, and 208Pb) altered from pre-anthropogenic values. A number of studies have shown the human impact on oceanic Pb in many parts of the world ocean, but little Pb data has been available for the Southeast Pacific Ocean. In this presentation, we will show the dissolved Pb (<0.2µm) results from the US GEOTRACES cruise in October - December 2013, which sailed from Manta, Ecuador, to Tahiti along around 12 degrees south. Dissolved Pb concentrations from all 36 surface stations and deep (>1000m) Pb profiles from 18 stations will be presented, and the results will be also compared to our unpublished data from the BiG RAPA cruise in 2010, whose cruise track from Arica, Peru, to Easter Island is slightly south of the US GEOTRACES cruise. The BiG RAPA data showed that dissolved Pb concentrations of the southeast Pacific Ocean are relatively low, varying in the range of 8-20 pmol/kg at the surface with a slight maximum (14-22 pmol/kg) at around 400m depth, and 2-10 pmol/kg in deep waters below 1000m depth. The Pb concentrations were found to be higher at a marginal station off Peru, reaching 45 pmol/kg at the surface and 65 pmol/kg in the subsurface maximum at 150m depth, and varying between 17 and 23 pmol/kg in deep waters. Our dataset, along with the results from the BiG RAPA cruise, will provide the first overview on the dissolved Pb distribution of the southeast Pacific Ocean, which will further our understanding on the human impact on the global ocean.

Nd isotopic composition and REE pattern in the surface waters of the eastern Indian Ocean and its adjacent seas

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

Amakawa, Hiroshi; Alibo, D.S.; Nozaki, Yoshiyuki

2000-05-01

The Nd isotopic composition and dissolved rare earth elements (REEs) have been measured in the surface waters along the 1996/97 R.V. Hakuho-Maru Expedition route from Tokyo to the Southern Ocean, southwest of Australia, through the Philippine and Indonesian Archipelago, the eastern Indian Ocean, the Bay of Bengal and the South China Sea. The radiogenic {epsilon}{sub Nd} values of {minus}1.3 and {minus}1.4 were found in the Sulu Sea and near the Lombok Strait, indicating the strong influence of surrounding volcanic islands, whereas non-radiogenic {epsilon}{sub Nd} values of less than {minus}10 were found in the Southern Ocean and the Bay of Bengalmore » suggesting Nd of continental origin. The dissolved Nd concentrations also showed a wide range of variation from 2.8 to 19.6 pmol/kg and the trivalent REE patterns exhibited characteristic features that can be grouped into each different oceanic province. The geographical distribution of dissolved Nd is different from that of atmospherically derived {sup 210}Pb, but generally resembles that of coastally derived {sup 228}Ra. This strongly suggests that fluvial and coastal input predominates over eolian input for dissolved Nd in the surface ocean. However, the riverine dissolved Nd flux appears to be relatively minor, and remobilization of Nd from coastal and shelf sediments may play an important role in the total Nd input to the ocean. By modeling the distributions of the isotopic composition and concentration of Nd together with the activity ratio of {sup 228}Ra/{sup 226}Ra in the southeastern Indian Ocean, the authors estimate a mean residence time of Nd in the surface mixed layer to be 1.5--2.6 years. The short mean residence time is comparable with, or slightly longer than that of {sup 210}Pb suggesting similar chemical reactivity.« less

Hurricane Matthew (2016) and its Storm Surge Inundation under Global Warming Scenarios: Application of an Interactively Coupled Atmosphere-Ocean Model

NASA Astrophysics Data System (ADS)

Jisan, M. A.; Bao, S.; Pietrafesa, L.; Pullen, J.

2017-12-01

An interactively coupled atmosphere-ocean model was used to investigate the impacts of future ocean warming, both at the surface and the layers below, on the track and intensity of a hurricane and its associated storm surge and inundation. The category-5 hurricane Matthew (2016), which made landfall on the South Carolina coast of the United States, was used for the case study. Future ocean temperature changes and sea level rise (SLR) were estimated based on the projection of Inter-Governmental Panel on Climate Change (IPCC)'s Representative Concentration Pathway scenarios RCP 2.6 and RCP 8.5. After being validated with the present-day observational data, the model was applied to simulate the changes in track, intensity, storm surge and inundation that Hurricane Matthew would cause under future climate change scenarios. It was found that a significant increase in hurricane intensity, storm surge water level, and inundation area for Hurricane Matthew under future ocean warming and SLR scenarios. For example, under the RCP 8.5 scenario, the maximum wind speed would increase by 17 knots (14.2%), the minimum sea level pressure would decrease by 26 hPa (2.85%), and the inundated area would increase by 401 km2 (123%). By including the effect of SLR for the middle-21st-century scenario, the inundated area will further increase by up to 49.6%. The increase in the hurricane intensity and the inundated area was also found for the RCP 2.6 scenario. The response of sea surface temperature was analyzed to investigate the change in intensity. A comparison was made between the impacts when only the sea surface warming is considered versus when both the sea surface and the underneath layers are considered. These results showed that even without the effect of SLR, the storm surge level and the inundated area would be higher due to the increased hurricane intensity under the influence of the future warmer ocean temperature. The coupled effect of ocean warming and SLR would cause the hurricane-induced storm surge and inundation to be amplified. The relative importance of the ocean warming versus the SLR was evaluated. Keywords: Hurricane Matthew, Global Warming, Coupled Atmosphere-Ocean Model, Air-Sea interactions, Storm Surge, Inundation

Combined Effects of Ocean Warming and Acidification on Copepod Abundance, Body Size and Fatty Acid Content.

PubMed

Garzke, Jessica; Hansen, Thomas; Ismar, Stefanie M H; Sommer, Ulrich

2016-01-01

Concerns about increasing atmospheric CO2 concentrations and global warming have initiated studies on the consequences of multiple-stressor interactions on marine organisms and ecosystems. We present a fully-crossed factorial mesocosm study and assess how warming and acidification affect the abundance, body size, and fatty acid composition of copepods as a measure of nutritional quality. The experimental set-up allowed us to determine whether the effects of warming and acidification act additively, synergistically, or antagonistically on the abundance, body size, and fatty acid content of copepods, a major group of lower level consumers in marine food webs. Copepodite (developmental stages 1-5) and nauplii abundance were antagonistically affected by warming and acidification. Higher temperature decreased copepodite and nauplii abundance, while acidification partially compensated for the temperature effect. The abundance of adult copepods was negatively affected by warming. The prosome length of copepods was significantly reduced by warming, and the interaction of warming and CO2 antagonistically affected prosome length. Fatty acid composition was also significantly affected by warming. The content of saturated fatty acids increased, and the ratios of the polyunsaturated essential fatty acids docosahexaenoic- (DHA) and arachidonic acid (ARA) to total fatty acid content increased with higher temperatures. Additionally, here was a significant additive interaction effect of both parameters on arachidonic acid. Our results indicate that in a future ocean scenario, acidification might partially counteract some observed effects of increased temperature on zooplankton, while adding to others. These may be results of a fertilizing effect on phytoplankton as a copepod food source. In summary, copepod populations will be more strongly affected by warming rather than by acidifying oceans, but ocean acidification effects can modify some temperature impacts.

Combined Effects of Ocean Warming and Acidification on Copepod Abundance, Body Size and Fatty Acid Content

PubMed Central

Hansen, Thomas; Ismar, Stefanie M. H.; Sommer, Ulrich

2016-01-01

Concerns about increasing atmospheric CO2 concentrations and global warming have initiated studies on the consequences of multiple-stressor interactions on marine organisms and ecosystems. We present a fully-crossed factorial mesocosm study and assess how warming and acidification affect the abundance, body size, and fatty acid composition of copepods as a measure of nutritional quality. The experimental set-up allowed us to determine whether the effects of warming and acidification act additively, synergistically, or antagonistically on the abundance, body size, and fatty acid content of copepods, a major group of lower level consumers in marine food webs. Copepodite (developmental stages 1–5) and nauplii abundance were antagonistically affected by warming and acidification. Higher temperature decreased copepodite and nauplii abundance, while acidification partially compensated for the temperature effect. The abundance of adult copepods was negatively affected by warming. The prosome length of copepods was significantly reduced by warming, and the interaction of warming and CO2 antagonistically affected prosome length. Fatty acid composition was also significantly affected by warming. The content of saturated fatty acids increased, and the ratios of the polyunsaturated essential fatty acids docosahexaenoic- (DHA) and arachidonic acid (ARA) to total fatty acid content increased with higher temperatures. Additionally, here was a significant additive interaction effect of both parameters on arachidonic acid. Our results indicate that in a future ocean scenario, acidification might partially counteract some observed effects of increased temperature on zooplankton, while adding to others. These may be results of a fertilizing effect on phytoplankton as a copepod food source. In summary, copepod populations will be more strongly affected by warming rather than by acidifying oceans, but ocean acidification effects can modify some temperature impacts. PMID:27224476

Role of CO2-forced Antarctic shelf freshening on local shelf warming in an eddying global climate model

NASA Astrophysics Data System (ADS)

Goddard, P.; Dufour, C.; Yin, J.; Griffies, S. M.; Winton, M.

2017-12-01

Ocean warming near the Antarctic ice shelves has critical implications for future ice sheet mass loss and global sea level rise. A global climate model (GFDL CM2.6) with an eddying ocean is used to quantify and better understand the mechanisms contributing to ocean warming on the Antarctic continental shelf in an idealized 2xCO2 experiment. The results indicate that the simulated shelf region warming varies in magnitude at different locations. Relatively large warm anomalies occur both in the upper 100 m and at depth, which are controlled by different mechanisms. Here, we focus on the deep shelf warming and its relationship to shelf freshening. Under CO2-forcing, enhanced runoff from Antarctica, more regional precipitation, and reduction of sea ice contribute to the shelf freshening. The freshening increases the lateral density gradient of the Antarctic Slope Front, which can limit along-isopycnal onshore transport of heat from the Circumpolar Deep Water across the shelf break. Thus, the magnitude and location of the freshening anomalies govern the magnitude and location of onshore heat transport and deep warm anomalies. Additionally, the freshening increases vertical stratification on the shelf. The enhanced stratification reduces vertical mixing of heat associated with diffusion and gravitational instabilities, further contributing to the build-up of temperature anomalies at depth. Freshening is a crucial driver of the magnitude and location of the warming; however, other drivers influence the warming such as CO2-forced weakening of the easterly wind stress and associated shoaling of isotherms. Understanding the relative role of freshening in the inhomogeneous ocean warming of the Antarctic continental shelf would lead to better projections of future ice sheet mass loss, especially near the most vulnerable calving fronts.

Pteropods on the edge: Cumulative effects of ocean acidification, warming, and deoxygenation

NASA Astrophysics Data System (ADS)

Bednaršek, Nina; Harvey, Chris J.; Kaplan, Isaac C.; Feely, Richard A.; Možina, Jasna

2016-06-01

We review the state of knowledge of the individual and community responses of euthecosome (shelled) pteropods in the context of global environmental change. In particular, we focus on their responses to ocean acidification, in combination with ocean warming and ocean deoxygenation, as inferred from a growing body of empirical literature, and their relatively nascent place in ecosystem-scale models. Our objectives are: (1) to summarize the threats that these stressors pose to pteropod populations; (2) to demonstrate that pteropods are strong candidate indicators for cumulative effects of OA, warming, and deoxygenation in marine ecosystems; and (3) to provide insight on incorporating pteropods into population and ecosystem models, which will help inform ecosystem-based management of marine resources under future environmental regimes.

Warming of the Global Ocean: Spatial Structure and Water-Mass Trends

NASA Technical Reports Server (NTRS)

Hakkinen, Sirpa; Rhines, Peter B.; Worthen, Denise L.

2016-01-01

This study investigates the multidecadal warming and interannual-to-decadal heat content changes in the upper ocean (0-700 m), focusing on vertical and horizontal patterns of variability. These results support a nearly monotonic warming over much of the World Ocean, with a shift toward Southern Hemisphere warming during the well-observed past decade. This is based on objectively analyzed gridded observational datasets and on a modeled state estimate. Besides the surface warming, a warming climate also has a subsurface effect manifesting as a strong deepening of the midthermocline isopycnals, which can be diagnosed directly from hydrographic data. This deepening appears to be a result of heat entering via subduction and spreading laterally from the high-latitude ventilation regions of subtropical mode waters. The basin-average multidecadal warming mainly expands the subtropical mode water volume, with weak changes in the temperature-salinity (u-S) relationship (known as ''spice'' variability). However, the spice contribution to the heat content can be locally large, for example in Southern Hemisphere. Multidecadal isopycnal sinking has been strongest over the southern basins and weaker elsewhere with the exception of the Gulf Stream/North Atlantic Current/subtropical recirculation gyre. At interannual to decadal time scales, wind-driven sinking and shoaling of density surfaces still dominate ocean heat content changes, while the contribution from temperature changes along density surfaces tends to decrease as time scales shorten.

Connecting Ocean Heat Transport Changes from the Midlatitudes to the Arctic Ocean

NASA Astrophysics Data System (ADS)

Hezel, P.; Nummelin, A.; Li, C.

2017-12-01

Under greenhouse warming, climate models simulate a weakening of the Atlantic Meridional Overturning Circulation and the associated ocean heat transport at midlatitudes but an increase in the ocean heat transport to the Arctic Ocean. These opposing trends lead to what could appear to be a discrepancy in the reported ocean contribution to Arctic amplification. This study clarifies how ocean heat transport affects Arctic climate under strong greenhouse warming using a set of the 21st century simulations performed within the Coupled Model Intercomparison Project. The results suggest that a future reduction in subpolar ocean heat loss enhances ocean heat transport to the Arctic Ocean, driving an increase in Arctic Ocean heat content and contributing to the intermodel spread in Arctic amplification. The results caution against extrapolating the forced oceanic signal from the midlatitudes to the Arctic.

Dissolved oxygen in two Oregon estuaries: Importance of the ocean-estuary connection - March 2011

EPA Science Inventory

We examined the role of the ocean–estuary connection in influencing periodic reductions in dissolved oxygen (DO) levels in Yaquina and Yachats estuaries, Oregon, USA. In the Yaquina Estuary, there is close coupling between the coastal ocean and the estuary. As a result, low DO w...

Potential cobalt limitation of vitamin B12 synthesis in the North Atlantic Ocean

NASA Astrophysics Data System (ADS)

Panzeca, C.; Beck, A. J.; Leblanc, K.; Taylor, G. T.; Hutchins, D. A.; SañUdo-Wilhelmy, S. A.

2008-06-01

While recent studies have confirmed the ecological importance of vitamin B12, it is unclear whether the production of this vitamin could be limited by dissolved Co, a trace metal required for B12 biosynthesis, but found at only subnanomolar concentrations in the open ocean. Herein, we demonstrate that the spatial distribution of dissolved B12 (range: 0.13-5 pmol L-1) in the North Atlantic Ocean follows the abundance of total dissolved Co (range: 15-81 pmol L-1). Similar patterns were observed for bacterial productivity (range: 20-103 pmol 3H leucine L-1 hr-1) and algal biomass (range: 0.4-3.9 μg L-1). In contrast, vitamin B1 concentrations (range: 0.7-30 pM) were decoupled from both Co and B12 concentrations. Cobalt amendment experiments carried out in low-dissolved Co waters (˜20 pmol L-1) enhanced B12 production two-fold over unamended controls. This study provides evidence that B12 synthesis could be limited by the availability of Co in some regions of the world ocean.

Modeling the air-sea feedback system of Madeira Island

NASA Astrophysics Data System (ADS)

Pullen, Julie; Caldeira, Rui; Doyle, James D.; May, Paul; Tomé, Ricardo

2017-07-01

A realistic nested data-assimilating two-way coupled ocean/atmosphere modeling study (highest resolution 2 km) of Madeira Island was conducted for June 2011, when conditions were favorable for atmospheric vortex shedding. The simulation's island lee region exhibited relatively cloud-free conditions, promoting warmer ocean temperatures (˜2°C higher than adjacent waters). The model reasonably reproduced measured fields at 14 meteorological stations, and matched the dimensions and magnitude of the warm sea surface temperature (SST) wake imaged by satellite. The warm SSTs in the wake are shown to imprint onto the atmospheric boundary layer (ABL) over several diurnal cycles by modulating the ABL depth up to ˜200-500 m. The erosion and dissipation of the warm ocean wake overnight was aided by atmospheric drainage flow and offshore advection of cold air (ΔT = 2°C) that produced strong upward heat fluxes (˜50 W/m2 sensible and ˜250 W/m2 latent) on an episodic basis. Nevertheless, the warm wake was never entirely eroded at night due to the cumulative effect of the diurnal cycle. The spatial pattern of the diurnal warming varied day-to-day in location and extent. Significant mutual interaction of the oceanic and atmospheric boundary layers was diagnosed via fluxes and temperature cross sections and reinforced by sensitivity runs. The simulation produces for the first time the interactive nature of the ocean and atmosphere boundary layers in the warm wake region of an island with complex terrain.

Temperature, productivity and sediment characteristics as drivers of seasonal and spatial variations of dissolved methane in the near-shore coastal areas (Belgian coastal zone, North Sea)

NASA Astrophysics Data System (ADS)

Borges, Alberto V.; Speeckaert, Gaëlle; Champenois, Willy; Scranton, Mary I.; Gypens, Nathalie

2017-04-01

The open ocean is a modest source of CH4 to the atmosphere compared to other natural and anthropogenic CH4 emissions. Coastal regions are more intense sources of CH4 to the atmosphere than open oceanic waters, in particular estuarine zones. The CH4 emission to the atmosphere from coastal areas is sustained by riverine inputs and methanogenesis in the sediments due to high organic matter (OM) deposition. Additionally, natural gas seeps are sources of CH4 to bottom waters leading to high dissolved CH4 concentrations in bottom waters (from tenths of nmol L-1 up to several µmol L-1). We report a data set of dissolved CH4 concentrations obtained at nine fixed stations in the Belgian coastal zone (Southern North Sea), during one yearly cycle, with a bi-monthly frequency in spring, and a monthly frequency during the rest of the year. This is a coastal area with multiple possible sources of CH4 such as from rivers and gassy sediments, and where intense phytoplankton blooms are dominated by the high dimethylsulfoniopropionate (DMSP) producing micro-algae Phaeocystis globosa, leading to DMSP and dimethylsulfide (DMS) concentrations. Furthermore, the BCZ is a site of important OM sedimentation and accumulation unlike the rest of the North Sea. Spatial variations of dissolved CH4 concentrations were very marked with a minimum yearly average of 9 nmol L-1 in one of the most off-shore stations and maximum yearly average of 139 nmol L-1 at one of the most near-shore stations. The spatial variations of dissolved CH4 concentrations were related to the organic matter (OM) content of sediments, although the highest concentrations seemed to also be related to inputs of CH4 from gassy sediments associated to submerged peat. In the near-shore stations with fine sand or muddy sediments with a high OM content, the seasonal cycle of dissolved CH4 concentration closely followed the seasonal cycle of water temperature, suggesting the control of methanogenesis by temperature in these OM replete sediments. In the off-shore stations with permeable sediments with a low OM content, the seasonal cycle of dissolved CH4 concentration showed a yearly peak following the chlorophyll-a spring peak. This suggests that in these OM poor sediments, methanogenesis depended on the delivery to the sediments of freshly produced OM. In both types of sediments, the seasonal cycle of dissolved CH4 concentrations was unrelated the seasonal cycles of DMS, and DMSP, despite the fact that these quantities were very high during the spring Phaeocystis globosa bloom. This suggests that in this shallow coastal environment CH4 production is overwhelmingly related to benthic processes and unrelated to DMS(P) transformations in the water column as recently suggested in several open ocean regions. The annual average CH4 emission was 41 mmol m-2 yr-1 in the most near-shore stations ( 4 km from the coast) and 10 mmol m-2 yr-1 in the most off-shore stations ( 23 km from the coast), 410-100 times higher than the average value in the open ocean (0.1 mmol m-2 yr-1). The strong control of CH4 concentrations by sediment OM content and by temperature suggests that marine coastal CH4 emissions, in particular shallow coastal areas, should respond in future to eutrophication and warming of climate. This is confirmed by the comparison of CH4 concentrations at five stations obtained in March in years 1990 and 2016, showing a decreasing trend consistent with alleviation of eutrophication in the area.

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).

Black Carbon in Estuarine (Coastal) High-molecular-weight Dissolved Organic Matter

NASA Technical Reports Server (NTRS)

Mannino, Antonio; Harvey, H. Rodger

2003-01-01

Dissolved organic matter (DOM) in the ocean constitutes one of the largest pools of organic carbon in the biosphere, yet much of its composition is uncharacterized. Observations of black carbon (BC) particles (by-products of fossil fuel combustion and biomass burning) in the atmosphere, ice, rivers, soils and marine sediments suggest that this material is ubiquitous, yet the contribution of BC to the ocean s DOM pool remains unknown. Analysis of high-molecular-weight DOM isolated from surface waters of two estuaries in the northwest Atlantic Ocean finds that BC is a significant component of DOM, suggesting that river-estuary systems are important exporters of BC to the ocean through DOM. We show that BC comprises 4-7% of the dissolved organic carbon (DOC) at coastal ocean sites, which supports the hypothesis that the DOC pool is the intermediate reservoir in which BC ages prior to sedimentary deposition. Flux calculations suggest that BC could be as important as vascular plant-derived lignin in terms of carbon inputs to the ocean. Production of BC sequesters fossil fuel- and biomass-derived carbon into a refractory carbon pool. Hence, BC may represent a significant sink for carbon to the ocean.

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.

Sources of global warming of the upper ocean on decadal period scales

USGS Publications Warehouse

White, Warren B.; Dettinger, M.D.; Cayan, D.R.

2003-01-01

Recent studies find global climate variability in the upper ocean and lower atmosphere during the twentieth century dominated by quasi-biennial, interannual, quasi-decadal and interdecadal signals. The quasi-decadal signal in upper ocean temperature undergoes global warming/cooling of ???0.1??C, similar to that occuring with the interannual signal (i.e., El Nin??o-Southern Oscillation), both signals dominated by global warming/cooling in the tropics. From the National Centers for Environmental Prediction troposphere reanalysis and Scripps Institution of Oceanography upper ocean temperature reanalysis we examine the quasi-decadal global tropical diabetic heat storage (DHS) budget from 1975 to 2000. We find the anomalous DHS warming tendency of 0.3-0.9 W m-2 driven principally by a downward global tropical latent-plus-sensible heat flux anomaly into the ocean, overwhelming the tendency by weaker upward shortwave-minus-longwave heat flux anomaly to drive an anomalous DHS cooling tendency. During the peak quasi-decadal warming the estimated dissipation of DHS anomaly of 0.2-0.5 W m-2 into the deep ocean and a similar loss to the overlying atmosphere through air-sea heat flux anomaly are balanced by a decrease in the net poleward Ekman heat advection out of the tropics of 0.4-0.7 W m-2. This scenario is nearly the opposite of that accounting for global tropical warming during the El Nin??o. These diagnostics confirm that even though the global quasi-decadal signal is phase-locked to the 11-year signal in the Sun's surface radiative forcing of ???0.1 W m-2, the anomalous global tropical DHS tendency cannot be driven by it directly.

Transport and Degradation of Dissolved Organic Matter and Associated Freshwater Pathways in the Laptev Sea (Siberian Arctic)

NASA Astrophysics Data System (ADS)

Hoelemann, J. A.; Janout, M. A.; Koch, B.; Bauch, D.; Novikhin, A.; Heim, B.; Eulenburg, A.; Kassens, H.; Timokhov, L.

2016-02-01

The Siberian shelves are seasonally ice-covered and characterized by large freshwater runoff rates from some of the largest rivers on earth. These rivers also provide a considerable amount of dissolved organic carbon (DOC) to the Arctic Ocean. With an annual load of about 6 Tg DOC a-1 the Lena River contributes nearly 20 percent of the annual DOC discharge to the Arctic Ocean. We present a comprehensive dataset collected during multiple Laptev Sea expeditions carried out in spring, summer and fall (2010-15) in order to explore the processes controlling the dispersal and degradation of DOM during the river water's passage across the shelf. Our investigations are focused on CDOM (Colored Dissolved Organic Matter), which resembles the DOC concentration, interacts with solar radiation and forms a major fraction of the organic matter pool. Our results show an inverse correlation between salinity and CDOM, which emphasizes its terrigenous source. Further, the spectral slope of CDOM absorption indicates that photochemical bleaching is the main process that reduces the CDOM absorption ( 20%) in freshwater along its transport across the shelf. The distribution of the Lena river water is primarily controlled by winds in summer. During summers with easterly or southerly winds, the plume remains on the central and northern Laptev shelf, and is available for export into the Arctic Basin. The CDOM-rich river water increases the absorption of solar radiation and enhances warming of a shallow surface layer. This emphasizes the importance of CDOM for sea surface temperatures and lateral ice melt on the shelf and adjacent basin. DOC concentrations in freshwater vary seasonally and become larger with increasing discharge. Our data indicate that the CDOM concentrations are highest during the freshet when landfast ice is still present. Subsequent mixing with local sea ice meltwater lowers CDOM to values that are characteristic for the Lena freshwater during the rest of the year.

Transport and degradation of dissolved organic matter and associated freshwater pathways in the Laptev Sea (Siberian Arctic)

NASA Astrophysics Data System (ADS)

Hoelemann, Jens; Janout, Markus; Koch, Boris; Bauch, Dorothea; Hellmann, Sebastian; Eulenburg, Antje; Heim, Birgit; Kassens, Heidemarie; Timokhov, leonid

2016-04-01

The Siberian shelves are seasonally ice-covered and characterized by large freshwater runoff rates from some of the largest rivers on earth. These rivers also provide a considerable amount of dissolved organic carbon (DOC) to the Arctic Ocean. With an annual load of about 6 Tg DOC a-1 the Lena River contributes nearly 20 percent of the annual DOC discharge to the Arctic Ocean. We present a comprehensive dataset collected during multiple Laptev Sea expeditions carried out in spring, summer and fall (2010-15) in order to explore the processes controlling the dispersal and degradation of DOM during the river water's passage across the shelf. Our investigations are focused on CDOM (Colored Dissolved Organic Matter), which resembles the DOC concentration, interacts with solar radiation and forms a major fraction of the organic matter pool. Our results show an inverse correlation between salinity and CDOM, which emphasizes its terrigenous source. Further, the spectral slope of CDOM absorption indicates that photochemical bleaching is the main process that reduces the CDOM absorption (~ 20%) in freshwater along its transport across the shelf. The distribution of the Lena river water is primarily controlled by winds in summer. During summers with easterly or southerly winds, the plume remains on the central and northern Laptev shelf, and is available for export into the Arctic Basin. The CDOM-rich river water increases the absorption of solar radiation and enhances warming of a shallow surface layer. This emphasizes the importance of CDOM for sea surface temperatures and lateral ice melt on the shelf and adjacent basin. DOC concentrations in freshwater vary seasonally and become larger with increasing discharge. Our data indicate that the CDOM concentrations are highest during the freshet when landfast ice is still present. Subsequent mixing with local sea ice meltwater lowers CDOM to values that are characteristic for the Lena freshwater during the rest of the year.

Pan-arctic trends in terrestrial dissolved organic matter from optical measurements

NASA Astrophysics Data System (ADS)

Mann, Paul; Spencer, Robert; Hernes, Peter; Six, Johan; Aiken, George; Tank, Suzanne; McClelland, James; Butler, Kenna; Dyda, Rachael; Holmes, Robert

2016-03-01

Climate change is causing extensive warming across arctic regions resulting in permafrost degradation, alterations to regional hydrology, and shifting amounts and composition of dissolved organic matter (DOM) transported by streams and rivers. Here, we characterize the DOM composition and optical properties of the six largest arctic rivers draining into the Arctic Ocean to examine the ability of optical measurements to provide meaningful insights into terrigenous carbon export patterns and biogeochemical cycling. The chemical composition of aquatic DOM varied with season, spring months were typified by highest lignin phenol and dissolved organic carbon (DOC) concentrations with greater hydrophobic acid content, and lower proportions of hydrophilic compounds, relative to summer and winter months. Chromophoric DOM (CDOM) spectral slope (S275-295) tracked seasonal shifts in DOM composition across river basins. Fluorescence and parallel factor analysis identified seven components across the six Arctic rivers. The ratios of 'terrestrial humic-like' versus 'marine humic-like' fluorescent components co-varied with lignin monomer ratios over summer and winter months, suggesting fluorescence may provide information on the age and degradation state of riverine DOM. CDOM absorbance (a350) proved a sensitive proxy for lignin phenol concentrations across all six river basins and over the hydrograph, enabling for the first time the development of a single pan-arctic relationship between a350 and terrigenous DOC (R2 = 0.93). Combining this lignin proxy with high-resolution monitoring of a350, pan-arctic estimates of annual lignin flux were calculated to range from 156 to 185 Gg, resulting in shorter and more constrained estimates of terrigenous DOM residence times in the Arctic Ocean (spanning 7 months to 2½ years). Furthermore, multiple linear regression models incorporating both absorbance and fluorescence variables proved capable of explaining much of the variability in lignin composition across rivers and seasons. Our findings suggest that synoptic, high-resolution optical measurements can provide improved understanding of northern high-latitude organic matter cycling and flux, and prove an important technique for capturing future climate-driven changes.

The relative importance of oceanic nutrient inputs for Bass Harbor Marsh Estuary at Acadia National Park, Maine

USGS Publications Warehouse

Huntington, Thomas G.; Culbertson, Charles W.; Fuller, Christopher; Glibert, Patricia; Sturtevant, Luke

2014-01-01

The U.S. Geological Survey and Acadia National Park (ANP) collaborated on a study of nutrient inputs into Bass Harbor Marsh Estuary on Mount Desert Island, Maine, to better understand ongoing eutrophication, oceanic nutrient inputs, and potential management solutions. This report includes the estimation of loads of nitrate, ammonia, total dissolved nitrogen, and total dissolved phosphorus to the estuary derived from runoff within the watershed and oceanic inputs during summers 2011 and 2012. Nutrient outputs from the estuary were also monitored, and nutrient inputs in direct precipitation to the estuary were calculated. Specific conductance, water temperature, and turbidity were monitored at the estuary outlet. This report presents a first-order analysis of the potential effects of projected sea-level rise on the inundated area and estuary volume. Historical aerial photographs were used to investigate the possibility of widening of the estuary channel over time. The scope of this report also includes analysis of sediment cores collected from the estuary and fringing marsh surfaces to assess the sediment mass accumulation rate. Median concentrations of nitrate, ammonium, and total dissolved phosphorus on the flood tide were approximately 25 percent higher than on the ebb tide during the 2011 and 2012 summer seasons. Higher concentrations on the flood tide suggest net assimilation of these nutrients in biota within the estuary. The dissolved organic nitrogen fraction dominated the dissolved nitrogen fraction in all tributaries. The median concentration of dissolved organic nitrogen was about twice as high on the on the ebb tide than the flood tide, indicating net export of dissolved organic nitrogen from the estuary. The weekly total oceanic inputs of nitrate, ammonium, and total dissolved phosphorus to the estuary were usually much larger than inputs from runoff or direct precipitation. The estuary was a net sink for nitrate and ammonium in most weeks during both years. Oceanic inputs of nitrate and ammonium were an important source of inorganic nitrogen to the estuary in both years. In both years, the total seasonal inputs of ammonium to the estuary in flood tides were much larger than the inputs from watershed runoff or direct precipitation. In 2011, the total seasonal input of nitrate from flood tides to the estuary was more than twice as large the inputs from watershed runoff and precipitation, but in 2012, the inputs from flood tides were only marginally larger than the inputs from watershed runoff and precipitation. Turbidity was measured intermittently in 2012, and the pattern that emerged from the measurements indicated that the estuary was a source of particulate matter to the ocean rather than the ocean being a source to the estuary. From the nutrient budgets determined for the estuary it is evident that oceanic sources of nitrate and ammonium are an important part of the supply of nutrients that are contributing to the growth of macroalgae in the estuary. The relative importance of these oceanic nutrients compared with sources within the watershed typically increases as the summer progresses and runoff decreases. It is likely that rising sea levels, estimated by the National Oceanic and Atmospheric Administration to be 11 centimeters from 1950 through 2006 in nearby Bar Harbor, have resulted in an increase in oceanic inputs (tidal volume and nutrients derived from oceanic sources).

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

Archer, D.

A two-dimensional model of a passive continental margin was adapted to the simulation of the methane cycle on Siberian continental shelf and slope, attempting to account for the impacts of glacial/interglacial cycles in sea level, alternately exposing the continental shelf to freezing conditions with deep permafrost formation during glacial times, and immersion in the ocean in interglacial times. The model is used to gauge the impact of the glacial cycles, and potential anthropogenic warming in the deep future, on the atmospheric methane emission flux, and the sensitivities of that flux to processes such as permafrost formation and terrestrial organic carbonmore » (Yedoma) deposition. Hydrological forcing drives a freshening and ventilation of pore waters in areas exposed to the atmosphere, which is not quickly reversed by invasion of seawater upon submergence, since there is no analogous saltwater pump. This hydrological pump changes the salinity enough to affect the stability of permafrost and methane hydrates on the shelf. Permafrost formation inhibits bubble transport through the sediment column, by construction in the model. The impact of permafrost on the methane budget is to replace the bubble flux by offshore groundwater flow containing dissolved methane, rather than accumulating methane for catastrophic release when the permafrost seal fails during warming. By far the largest impact of the glacial/interglacial cycles on the atmospheric methane flux is attenuation by dissolution of bubbles in the ocean when sea level is high. Methane emissions are highest during the regression (soil freezing) part of the cycle, rather than during transgression (thawing). The model-predicted methane flux to the atmosphere in response to a warming climate is small, relative to the global methane production rate, because of the ongoing flooding of the continental shelf. A slight increase due to warming could be completely counteracted by sea level rise on geologic time scales, decreasing the efficiency of bubble transit through the water column. The methane cycle on the shelf responds to climate change on a long time constant of thousands of years, because hydrate is excluded thermodynamically from the permafrost zone by water limitation, leaving the hydrate stability zone at least 300 m below the sediment surface.« less

Ice Melt, Sea Level Rise and Superstorms: Evidence from Paleoclimate Data, Climate Modeling, and Modern Observations that 2C Global Warming Could Be Dangerous

NASA Technical Reports Server (NTRS)

Hansen, J.; Sato, Makiko; Hearty, Paul; Ruedy, Reto; Kelley, Maxwell; Masson-Delmotte, Valerie; Russell, Gary; Tselioudis, George; Cao, Junji; Rignot, Eric;

Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous

NASA Astrophysics Data System (ADS)

Hansen, James; Sato, Makiko; Hearty, Paul; Ruedy, Reto; Kelley, Maxwell; Masson-Delmotte, Valerie; Russell, Gary; Tselioudis, George; Cao, Junji; Rignot, Eric; Velicogna, Isabella; Tormey, Blair; Donovan, Bailey; Kandiano, Evgeniya; von Schuckmann, Karina; Kharecha, Pushker; Legrande, Allegra N.; Bauer, Michael; Lo, Kwok-Wai

2016-03-01

We use numerical climate simulations, paleoclimate data, and modern observations to study the effect of growing ice melt from Antarctica and Greenland. Meltwater tends to stabilize the ocean column, inducing amplifying feedbacks that increase subsurface ocean warming and ice shelf melting. Cold meltwater and induced dynamical effects cause ocean surface cooling in the Southern Ocean and North Atlantic, thus increasing Earth's energy imbalance and heat flux into most of the global ocean's surface. Southern Ocean surface cooling, while lower latitudes are warming, increases precipitation on the Southern Ocean, increasing ocean stratification, slowing deepwater formation, and increasing ice sheet mass loss. These feedbacks make ice sheets in contact with the ocean vulnerable to accelerating disintegration. We hypothesize that ice mass loss from the most vulnerable ice, sufficient to raise sea level several meters, is better approximated as exponential than by a more linear response. Doubling times of 10, 20 or 40 years yield multi-meter sea level rise in about 50, 100 or 200 years. Recent ice melt doubling times are near the lower end of the 10-40-year range, but the record is too short to confirm the nature of the response. The feedbacks, including subsurface ocean warming, help explain paleoclimate data and point to a dominant Southern Ocean role in controlling atmospheric CO2, which in turn exercised tight control on global temperature and sea level. The millennial (500-2000-year) timescale of deep-ocean ventilation affects the timescale for natural CO2 change and thus the timescale for paleo-global climate, ice sheet, and sea level changes, but this paleo-millennial timescale should not be misinterpreted as the timescale for ice sheet response to a rapid, large, human-made climate forcing. These climate feedbacks aid interpretation of events late in the prior interglacial, when sea level rose to +6-9 m with evidence of extreme storms while Earth was less than 1 °C warmer than today. Ice melt cooling of the North Atlantic and Southern oceans increases atmospheric temperature gradients, eddy kinetic energy and baroclinicity, thus driving more powerful storms. The modeling, paleoclimate evidence, and ongoing observations together imply that 2 °C global warming above the preindustrial level could be dangerous. Continued high fossil fuel emissions this century are predicted to yield (1) cooling of the Southern Ocean, especially in the Western Hemisphere; (2) slowing of the Southern Ocean overturning circulation, warming of the ice shelves, and growing ice sheet mass loss; (3) slowdown and eventual shutdown of the Atlantic overturning circulation with cooling of the North Atlantic region; (4) increasingly powerful storms; and (5) nonlinearly growing sea level rise, reaching several meters over a timescale of 50-150 years. These predictions, especially the cooling in the Southern Ocean and North Atlantic with markedly reduced warming or even cooling in Europe, differ fundamentally from existing climate change assessments. We discuss observations and modeling studies needed to refute or clarify these assertions.

Carbon monoxide photoproduction: implications for photoreactivity of Arctic permafrost-derived soil dissolved organic matter.

PubMed

Hong, Jun; Xie, Huixiang; Guo, Laodong; Song, Guisheng

2014-08-19

Apparent quantum yields of carbon monoxide (CO) photoproduction (AQY(CO)) for permafrost-derived soil dissolved organic matter (SDOM) from the Yukon River Basin and Alaska coast were determined to examine the dependences of AQY(CO) on temperature, ionic strength, pH, and SDOM concentration. SDOM from different locations and soil depths all exhibited similar AQY(CO) spectra irrespective of soil age. AQY(CO) increased by 68% for a 20 °C warming, decreased by 25% from ionic strength 0 to 0.7 mol L(-1), and dropped by 25-38% from pH 4 to 8. These effects combined together could reduce AQY(CO) by up to 72% when SDOM transits from terrestrial environemnts to open-ocean conditions during summer in the Arctic. A Michaelis-Menten kinetics characterized the influence of SDOM dilution on AQY(CO) with a very low substrate half-saturation concentration. Generalized global-scale relationships between AQY(CO) and salinity and absorbance demostrate that the CO-based photoreactivity of ancient permaforst SDOM is comparable to that of modern riverine DOM and that the effects of the physicochemical variables revealed here alone could account for the seaward decline of AQY(CO) observed in diverse estuarine and coastal water bodies.

Iron and sulfur in the pre-biologic ocean

NASA Technical Reports Server (NTRS)

Walker, J. C.; Brimblecombe, P.

1985-01-01

Tentative geochemical cycles for the pre-biologic Earth are developed by comparing the relative fluxes of oxygen, dissolved iron, and sulfide to the atmosphere and ocean. The flux of iron is found to exceed both the oxygen and the sulfide fluxes. Because of the insolubility of iron oxides and sulfides the implication is that dissolved iron was fairly abundant and that oxygen and sulfide were rare in the atmosphere and ocean. Sulfate, produced by the oxidation of volcanogenic sulfur gases, was the most abundant sulfur species in the ocean, but its concentration was low by modern standards because of the absence of the river-borne flux of dissolved sulfate produced by oxidative weathering of the continents. These findings are consistent with the geologic record of the isotopic composition of sedimentary sulfates and sulfides. Except in restricted environments, the sulfur metabolism of the earliest organisms probably involved oxidized sulfur species not sulfide.

Volcanoes and climate: Krakatoa's signature persists in the ocean.

PubMed

Gleckler, P J; Wigley, T M L; Santer, B D; Gregory, J M; Achutarao, K; Taylor, K E

2006-02-09

We have analysed a suite of 12 state-of-the-art climate models and show that ocean warming and sea-level rise in the twentieth century were substantially reduced by the colossal eruption in 1883 of the volcano Krakatoa in the Sunda strait, Indonesia. Volcanically induced cooling of the ocean surface penetrated into deeper layers, where it persisted for decades after the event. This remarkable effect on oceanic thermal structure is longer lasting than has previously been suspected and is sufficient to offset a large fraction of ocean warming and sea-level rise caused by anthropogenic influences.

Is Europa's Subsurface Water Ocean Warm?

NASA Technical Reports Server (NTRS)

Melosh, H. J.; Ekholm, A. G.; Showman, A. P.; Lorenz, R. D.

2002-01-01

Europa's subsurface water ocean may be warm: that is, at the temperature of water's maximum density. This provides a natural explanation of chaos melt-through events and leads to a correct estimate of the age of its surface. Additional information is contained in the original extended abstract.

Lead isotope exchange between dissolved and fluvial particulate matter: a laboratory study from the Johor River estuary

NASA Astrophysics Data System (ADS)

Chen, Mengli; Boyle, Edward A.; Lee, Jong-Mi; Nurhati, Intan; Zurbrick, Cheryl; Switzer, Adam D.; Carrasco, Gonzalo

2016-11-01

Atmospheric aerosols are the dominant source of Pb to the modern marine environment, and as a result, in most regions of the ocean the Pb isotopic composition of dissolved Pb in the surface ocean (and in corals) matches that of the regional aerosols. In the Singapore Strait, however, there is a large offset between seawater dissolved and coral Pb isotopes and that of the regional aerosols. We propose that this difference results from isotope exchange between dissolved Pb supplied by anthropogenic aerosol deposition and adsorbed natural crustal Pb on weathered particles delivered to the ocean by coastal rivers. To investigate this issue, Pb isotope exchange was assessed through a closed-system exchange experiment using estuarine waters collected at the Johor River mouth (which discharges to the Singapore Strait). During the experiment, a known amount of dissolved Pb with the isotopic composition of NBS-981 (206Pb/207Pb = 1.093) was spiked into the unfiltered Johor water (dissolved and particulate 206Pb/207Pb = 1.199) and the changing isotopic composition of the dissolved Pb was monitored. The mixing ratio of the estuarine and spike Pb should have produced a dissolved 206Pb/207Pb isotopic composition of 1.161, but within a week, the 206Pb/207Pb in the water increased to 1.190 and continued to increase to 1.197 during the next two months without significant changes of the dissolved Pb concentration. The kinetics of isotope exchange was assessed using a simple Kd model, which assumes multiple sub-reservoirs within the particulate matter with different exchange rate constants. The Kd model reproduced 56% of the observed Pb isotope variance. Both the closed-system experiment and field measurements imply that isotope exchange can be an important mechanism for controlling Pb and Pb isotopes in coastal waters. A similar process may occur for other trace elements. This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

Increased ventilation of Antarctic deep water during the warm mid-Pliocene.

PubMed

Zhang, Zhongshi; Nisancioglu, Kerim H; Ninnemann, Ulysses S

2013-01-01

The mid-Pliocene warm period is a recent warm geological period that shares similarities with predictions of future climate. It is generally held the mid-Pliocene Atlantic Meridional Overturning Circulation must have been stronger, to explain a weak Atlantic meridional δ(13)C gradient and large northern high-latitude warming. However, climate models do not simulate such stronger Atlantic Meridional Overturning Circulation, when forced with mid-Pliocene boundary conditions. Proxy reconstructions allow for an alternative scenario that the weak δ(13)C gradient can be explained by increased ventilation and reduced stratification in the Southern Ocean. Here this alternative scenario is supported by simulations with the Norwegian Earth System Model (NorESM-L), which simulate an intensified and slightly poleward shifted wind field off Antarctica, giving enhanced ventilation and reduced stratification in the Southern Ocean. Our findings challenge the prevailing theory and show how increased Southern Ocean ventilation can reconcile existing model-data discrepancies about Atlantic Meridional Overturning Circulation while explaining fundamental ocean features.

Increased ventilation of Antarctic deep water during the warm mid-Pliocene

PubMed Central

Zhang, Zhongshi; Nisancioglu, Kerim H.; Ninnemann, Ulysses S.

2013-01-01

The mid-Pliocene warm period is a recent warm geological period that shares similarities with predictions of future climate. It is generally held the mid-Pliocene Atlantic Meridional Overturning Circulation must have been stronger, to explain a weak Atlantic meridional δ13C gradient and large northern high-latitude warming. However, climate models do not simulate such stronger Atlantic Meridional Overturning Circulation, when forced with mid-Pliocene boundary conditions. Proxy reconstructions allow for an alternative scenario that the weak δ13C gradient can be explained by increased ventilation and reduced stratification in the Southern Ocean. Here this alternative scenario is supported by simulations with the Norwegian Earth System Model (NorESM-L), which simulate an intensified and slightly poleward shifted wind field off Antarctica, giving enhanced ventilation and reduced stratification in the Southern Ocean. Our findings challenge the prevailing theory and show how increased Southern Ocean ventilation can reconcile existing model-data discrepancies about Atlantic Meridional Overturning Circulation while explaining fundamental ocean features. PMID:23422667

Global warming hiatus contributed to the increased occurrence of intense tropical cyclones in the coastal regions along East Asia.

PubMed

Zhao, Jiuwei; Zhan, Ruifen; Wang, Yuqing

2018-04-16

The recent global warming hiatus (GWH) was characterized by a La Niña-like cooling in the tropical Eastern Pacific accompanied with the Indian Ocean and the tropical Atlantic Ocean warming. Here we show that the recent GWH contributed significantly to the increased occurrence of intense tropical cyclones in the coastal regions along East Asia since 1998. The GWH associated sea surface temperature anomalies triggered a pair of anomalous cyclonic and anticyclonic circulations and equatorial easterly anomalies over the Northwest Pacific, which favored TC genesis and intensification over the western Northwest Pacific but suppressed TC genesis and intensification over the southeastern Northwest Pacific due to increased vertical wind shear and anticyclonic circulation anomalies. Results from atmospheric general circulation model experiments demonstrate that the Pacific La Niña-like cooling dominated the Indian Ocean and the tropical Atlantic Ocean warming in contributing to the observed GWH-related anomalous atmospheric circulation over the Northwest Pacific.

Ocean Warming, More than Acidification, Reduces Shell Strength in a Commercial Shellfish Species during Food Limitation

PubMed Central

Mackenzie, Clara L.; Ormondroyd, Graham A.; Curling, Simon F.; Ball, Richard J.; Whiteley, Nia M.; Malham, Shelagh K.

2014-01-01

Ocean surface pH levels are predicted to fall by 0.3–0.4 pH units by the end of the century and are likely to coincide with an increase in sea surface temperature of 2–4°C. The combined effect of ocean acidification and warming on the functional properties of bivalve shells is largely unknown and of growing concern as the shell provides protection from mechanical and environmental challenges. We examined the effects of near-future pH (ambient pH –0.4 pH units) and warming (ambient temperature +4°C) on the shells of the commercially important bivalve, Mytilus edulis when fed for a limited period (4–6 h day−1). After six months exposure, warming, but not acidification, significantly reduced shell strength determined as reductions in the maximum load endured by the shells. However, acidification resulted in a reduction in shell flex before failure. Reductions in shell strength with warming could not be explained by alterations in morphology, or shell composition but were accompanied by reductions in shell surface area, and by a fall in whole-body condition index. It appears that warming has an indirect effect on shell strength by re-allocating energy from shell formation to support temperature-related increases in maintenance costs, especially as food supply was limited and the mussels were probably relying on internal energy reserves. The maintenance of shell strength despite seawater acidification suggests that biomineralisation processes are unaffected by the associated changes in CaCO3 saturation levels. We conclude that under near-future climate change conditions, ocean warming will pose a greater risk to shell integrity in M. edulis than ocean acidification when food availability is limited. PMID:24489785

Ocean warming, more than acidification, reduces shell strength in a commercial shellfish species during food limitation.

PubMed

Mackenzie, Clara L; Ormondroyd, Graham A; Curling, Simon F; Ball, Richard J; Whiteley, Nia M; Malham, Shelagh K

2014-01-01

Ocean surface pH levels are predicted to fall by 0.3-0.4 pH units by the end of the century and are likely to coincide with an increase in sea surface temperature of 2-4 °C. The combined effect of ocean acidification and warming on the functional properties of bivalve shells is largely unknown and of growing concern as the shell provides protection from mechanical and environmental challenges. We examined the effects of near-future pH (ambient pH -0.4 pH units) and warming (ambient temperature +4 °C) on the shells of the commercially important bivalve, Mytilus edulis when fed for a limited period (4-6 h day(-1)). After six months exposure, warming, but not acidification, significantly reduced shell strength determined as reductions in the maximum load endured by the shells. However, acidification resulted in a reduction in shell flex before failure. Reductions in shell strength with warming could not be explained by alterations in morphology, or shell composition but were accompanied by reductions in shell surface area, and by a fall in whole-body condition index. It appears that warming has an indirect effect on shell strength by re-allocating energy from shell formation to support temperature-related increases in maintenance costs, especially as food supply was limited and the mussels were probably relying on internal energy reserves. The maintenance of shell strength despite seawater acidification suggests that biomineralisation processes are unaffected by the associated changes in CaCO3 saturation levels. We conclude that under near-future climate change conditions, ocean warming will pose a greater risk to shell integrity in M. edulis than ocean acidification when food availability is limited.

Assessment of oceanic productivity with the triple-isotope composition of dissolved oxygen.

PubMed

Luz, B; Barkan, E

2000-06-16

Plant production in the sea is a primary mechanism of global oxygen formation and carbon fixation. For this reason, and also because the ocean is a major sink for fossil fuel carbon dioxide, much attention has been given to estimating marine primary production. Here, we describe an approach for estimating production of photosynthetic oxygen, based on the isotopic composition of dissolved oxygen of seawater. This method allows the estimation of integrated oceanic productivity on a time scale of weeks.

Atlantic Induced Pan-tropical Climate Variability in the Upper-ocean and Atmosphere

NASA Astrophysics Data System (ADS)

Li, X.; Xie, S. P.; Gille, S. T.; Yoo, C.

2016-02-01

During the last three decades, tropical sea surface temperature (SST) exhibited dipole-like trends, with warming over the tropical Atlantic and Indo-Western Pacific but cooling over the Eastern Pacific. The Eastern Pacific cooling has recently been identified as a driver of the global warming hiatus. Previous studies revealed atmospheric bridges between the tropical Pacific, Atlantic, and Indian Ocean, which could potentially contribute to this zonally asymmetric SST pattern. However, the mechanisms and the interactions between these teleconnections remain unclear. To investigate these questions, we performed a `pacemaker' simulation by restoring the tropical Atlantic SST changes in a state-of-the-art climate model - the CESM1. Results show that the Atlantic plays a key role in initiating the tropical-wide teleconnections, and the Atlantic-induced anomalies contribute 55%-75% of the total tropical SST and circulation changes during the satellite era. A hierarchy of oceanic and atmospheric models are then used to investigate the physical mechanisms of these teleconnections: the Atlantic warming enhances atmospheric deep convection, drives easterly wind anomalies over the Indo-Western Pacific through the Kelvin wave, and westerly anomalies over the eastern Pacific as Rossby waves, in line with Gill's solution (Fig1a). These wind changes induce an Indo-Western Pacific warming via the wind-evaporation-SST effect, and this warming intensifies the La Niña-type response in the upper Pacific Ocean by enhancing the easterly trade winds and through the Bjerknes ocean-dynamical processes (Fig1b). The teleconnection finally develops into a tropical-wide SST dipole pattern with an enhanced trade wind and Walker circulation, similar as the observed changes during the satellite era. This mechanism reveals that the tropical ocean basins are more tightly connected than previously thought, and the Atlantic plays a key role in the tropical climate pattern formation and further the global warming hiatus. The tropical Atlantic warming is likely due to radiative forcing and Atlantic meridional overturning circulation (AMOC). Our study suggests that the AMOC may force the decadal variability of the tropical ocean and atmosphere, and thus contributes to the decadal predictability of the global climate.

A simple model of the effect of ocean ventilation on ocean heat uptake

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

Nadiga, Balasubramanya T.; Urban, Nathan Mark

Presentation includes slides on Earth System Models vs. Simple Climate Models; A Popular SCM: Energy Balance Model of Anomalies; On calibrating against one ESM experiment, the SCM correctly captures that ESM's surface warming response with other forcings; Multi-Model Analysis: Multiple ESMs, Single SCM; Posterior Distributions of ECS; However In Excess of 90% of TOA Energy Imbalance is Sequestered in the World Oceans; Heat Storage in the Two Layer Model; Heat Storage in the Two Layer Model; Including TOA Rad. Imbalance and Ocean Heat in Calibration Improves Repr., but Significant Errors Persist; Improved Vertical Resolution Does Not Fix Problem; A Seriesmore » of Expts. Confirms That Anomaly-Diffusing Models Cannot Properly Represent Ocean Heat Uptake; Physics of the Thermocline; Outcropping Isopycnals and Horizontally-Averaged Layers; Local interactions between outcropping isopycnals leads to non-local interactions between horizontally-averaged layers; Both Surface Warming and Ocean Heat are Well Represented With Just 4 Layers; A Series of Expts. Confirms That When Non-Local Interactions are Allowed, the SCMs Can Represent Both Surface Warming and Ocean Heat Uptake; and Summary and Conclusions.« less

Biogeochemical Trends and Their Ecosystem Impacts in Atlantic Canada

NASA Astrophysics Data System (ADS)

Fennel, Katja; Rutherford, Krysten; Kuhn, Angela; Zhang, Wenxia; Brennan, Katie; Zhang, Rui

2017-04-01

The representation of coastal oceans in global biogeochemical models is a challenge, yet the ecosystems in these regions are most vulnerable to the combined stressors of ocean warming, deoxygenation, acidification, eutrophication and fishing. Coastal regions also have large air-sea fluxes of CO2, making them an important but poorly quantified component of the global carbon cycle, and are the most relevant for human activities. Regional model applications that are nested within large-scale or global models are necessary for detailed studies of coastal regions. We present results from such a regional biogeochemical model for the northwestern North Atlantic shelves and adjacent deep ocean of Atlantic Canada. The model is an implementation of the Regional Ocean Modeling System (ROMS) and includes an NPZD-type nitrogen cycle model with explicit representation of dissolved oxygen and inorganic carbon. The region is at the confluence of the Gulf Stream and Labrador Current making it highly dynamic, a challenge for analysis and prediction, and prone to large changes. Historically a rich fishing ground, coastal ecosystems in Atlantic Canada have undergone dramatic changes including the collapse of several economically important fish stocks and the listing of many species as threatened or endangered. Furthermore it is unclear whether the region is a net source or sink of atmospheric CO2 with estimates of the size and direction of the net air-sea CO2 flux remaining controversial. We will discuss simulated patterns of primary production, inorganic carbon fluxes and oxygen trends in the context of circulation features and shelf residence times for the present ocean state and present future projections.

High particulate iron(II) content in glacially sourced dusts enhances productivity of a model diatom

PubMed Central

Shoenfelt, Elizabeth M.; Sun, Jing; Winckler, Gisela; Kaplan, Michael R.; Borunda, Alejandra L.; Farrell, Kayla R.; Moreno, Patricio I.; Gaiero, Diego M.; Recasens, Cristina; Sambrotto, Raymond N.; Bostick, Benjamin C.

2017-01-01

Little is known about the bioavailability of iron (Fe) in natural dusts and the impact of dust mineralogy on Fe utilization by photosynthetic organisms. Variation in the supply of bioavailable Fe to the ocean has the potential to influence the global carbon cycle by modulating primary production in the Southern Ocean. Much of the dust deposited across the Southern Ocean is sourced from South America, particularly Patagonia, where the waxing and waning of past and present glaciers generate fresh glaciogenic material that contrasts with aged and chemically weathered nonglaciogenic sediments. We show that these two potential sources of modern-day dust are mineralogically distinct, where glaciogenic dust sources contain mostly Fe(II)-rich primary silicate minerals, and nearby nonglaciogenic dust sources contain mostly Fe(III)-rich oxyhydroxide and Fe(III) silicate weathering products. In laboratory culture experiments, Phaeodactylum tricornutum, a well-studied coastal model diatom, grows more rapidly, and with higher photosynthetic efficiency, with input of glaciogenic particulates compared to that of nonglaciogenic particulates due to these differences in Fe mineralogy. Monod nutrient accessibility models fit to our data suggest that particulate Fe(II) content, rather than abiotic solubility, controls the Fe bioavailability in our Fe fertilization experiments. Thus, it is possible for this diatom to access particulate Fe in dusts by another mechanism besides uptake of unchelated Fe (Fe′) dissolved from particles into the bulk solution. If this capability is widespread in the Southern Ocean, then dusts deposited to the Southern Ocean in cold glacial periods are likely more bioavailable than those deposited in warm interglacial periods. PMID:28691098

Climate change and the oceans--what does the future hold?

PubMed

Bijma, Jelle; Pörtner, Hans-O; Yesson, Chris; Rogers, Alex D

2013-09-30

The ocean has been shielding the earth from the worst effects of rapid climate change by absorbing excess carbon dioxide from the atmosphere. This absorption of CO2 is driving the ocean along the pH gradient towards more acidic conditions. At the same time ocean warming is having pronounced impacts on the composition, structure and functions of marine ecosystems. Warming, freshening (in some areas) and associated stratification are driving a trend in ocean deoxygenation, which is being enhanced in parts of the coastal zone by upwelling of hypoxic deep water. The combined impact of warming, acidification and deoxygenation are already having a dramatic effect on the flora and fauna of the oceans with significant changes in distribution of populations, and decline of sensitive species. In many cases, the impacts of warming, acidification and deoxygenation are increased by the effects of other human impacts, such as pollution, eutrophication and overfishing. The interactive effects of this deadly trio mirrors similar events in the Earth's past, which were often coupled with extinctions of major species' groups. Here we review the observed impacts and, using past episodes in the Earth's history, set out what the future may hold if carbon emissions and climate change are not significantly reduced with more or less immediate effect. Copyright © 2013. Published by Elsevier Ltd.

Understanding Decreases in Land Relative Humidity with Global Warming: Conceptual Model and GCM Simulations

NASA Astrophysics Data System (ADS)

Byrne, Michael P.; O'Gorman, Paul A.

2016-12-01

Climate models simulate a strong land-ocean contrast in the response of near-surface relative humidity to global warming: relative humidity tends to increase slightly over oceans but decrease substantially over land. Surface energy balance arguments have been used to understand the response over ocean but are difficult to apply over more complex land surfaces. Here, a conceptual box model is introduced, involving moisture transport between the land and ocean boundary layers and evapotranspiration, to investigate the decreases in land relative humidity as the climate warms. The box model is applied to idealized and full-complexity (CMIP5) general circulation model simulations, and it is found to capture many of the features of the simulated changes in land relative humidity. The box model suggests there is a strong link between fractional changes in specific humidity over land and ocean, and the greater warming over land than ocean then implies a decrease in land relative humidity. Evapotranspiration is of secondary importance for the increase in specific humidity over land, but it matters more for the decrease in relative humidity. Further analysis shows there is a strong feedback between changes in surface-air temperature and relative humidity, and this can amplify the influence on relative humidity of factors such as stomatal conductance and soil moisture.

The Question of Future Droughts in a CO2-Warmed World

NASA Technical Reports Server (NTRS)

Rind, David

1999-01-01

Increased droughts are to be expected in a warmer world, and so are increased floods. A warmer atmosphere can hold more moisture, and evaporate more water from the surface. Thus, when it is not raining, available soil water should be reduced. When it is raining, it could very well rain harder. Most researchers agree then that a warmer world will have greater hydrologic extremes. In addition, there is a basic imbalance that develops as climate warms, between the loss of moisture from the soil by evaporation and replenishment via precipitation. The land has a smaller heat capacity than the ocean, so it should warm faster. Evaporation from the land proceeds at the rate of its warming, while precipitation derives primarily from evaporation at the ocean surface. As the latter is increasing more slowly, in a warmer world, precipitation will not increase as rapidly as evaporation due to the fact that the oceans warm more slowly than the land surface (evaporation over the ocean is slower than over the land). Hence, more droughts are anticipated in a warmer world, but the specific location of such droughts is somewhat uncertain. To address the question of where droughts are likely to occur, one first needs to have a reasonable sense of what the future magnitude of warming will be, and what the latitudinal distribution of warming will be. For example, the greater the warming at high latitudes relative to low latitudes, the more likely there will be increased drought over the U.S. in summer. In contrast, substantial tropical warming could give us El Nino-like precipitation, with intensified flooding along the southern tier of the U.S. All of these conditions are likely to intensify as the global temperature rises.

Sources of global warming in upper ocean temperature during El Niño

USGS Publications Warehouse

White, Warren B.; Cayan, Daniel R.; Dettinger, Mike; Auad, Guillermo

2001-01-01

Global average sea surface temperature (SST) from 40°S to 60°N fluctuates ±0.3°C on interannual period scales, with global warming (cooling) during El Niño (La Niña). About 90% of the global warming during El Niño occurs in the tropical global ocean from 20°S to 20°N, half because of large SST anomalies in the tropical Pacific associated with El Niño and the other half because of warm SST anomalies occurring over ∼80% of the tropical global ocean. From examination of National Centers for Environmental Prediction [Kalnay et al., 1996] and Comprehensive Ocean-Atmosphere Data Set [Woodruff et al., 1993] reanalyses, tropical global warming during El Niño is associated with higher troposphere moisture content and cloud cover, with reduced trade wind intensity occurring during the onset phase of El Niño. During this onset phase the tropical global average diabatic heat storage tendency in the layer above the main pycnocline is 1–3 W m−2above normal. Its principal source is a reduction in the poleward Ekman heat flux out of the tropical ocean of 2–5 W m−2. Subsequently, peak tropical global warming during El Niño is dissipated by an increase in the flux of latent heat to the troposphere of 2–5 W m−2, with reduced shortwave and longwave radiative fluxes in response to increased cloud cover tending to cancel each other. In the extratropical global ocean the reduction in poleward Ekman heat flux out of the tropics during the onset of El Niño tends to be balanced by reduction in the flux of latent heat to the troposphere. Thus global warming and cooling during Earth's internal mode of interannual climate variability arise from fluctuations in the global hydrological balance, not the global radiation balance. Since it occurs in the absence of extraterrestrial and anthropogenic forcing, global warming on decadal, interdecadal, and centennial period scales may also occur in association with Earth's internal modes of climate variability on those scales.

The global warming hiatus: Slowdown or redistribution?

NASA Astrophysics Data System (ADS)

Yan, Xiao-Hai; Boyer, Tim; Trenberth, Kevin; Karl, Thomas R.; Xie, Shang-Ping; Nieves, Veronica; Tung, Ka-Kit; Roemmich, Dean

2016-11-01

Global mean surface temperatures (GMST) exhibited a smaller rate of warming during 1998-2013, compared to the warming in the latter half of the 20th Century. Although, not a "true" hiatus in the strict definition of the word, this has been termed the "global warming hiatus" by IPCC (2013). There have been other periods that have also been defined as the "hiatus" depending on the analysis. There are a number of uncertainties and knowledge gaps regarding the "hiatus." This report reviews these issues and also posits insights from a collective set of diverse information that helps us understand what we do and do not know. One salient insight is that the GMST phenomenon is a surface characteristic that does not represent a slowdown in warming of the climate system but rather is an energy redistribution within the oceans. Improved understanding of the ocean distribution and redistribution of heat will help better monitor Earth's energy budget and its consequences. A review of recent scientific publications on the "hiatus" shows the difficulty and complexities in pinpointing the oceanic sink of the "missing heat" from the atmosphere and the upper layer of the oceans, which defines the "hiatus." Advances in "hiatus" research and outlooks (recommendations) are given in this report.

Patterns and Trends of Primary Production, Inorganic Carbon and Oxygen and Their Ecosystem Impacts in a Regional Biogeochemical Ocean Model for Atlantic Canada

NASA Astrophysics Data System (ADS)

Fennel, K.; Rutherford, K. E.; Kuhn, A. M.; Zhang, W.; Brennan, C. E.; Zhang, R.

2016-12-01

Representing coastal oceans in global biogeochemical models is a challenge, yet the ecosystems in these regions are most vulnerable to the combined stressors of ocean warming, deoxygenation, acidification, eutrophication and fishing. Coastal regions also have large air-sea fluxes of CO2, making them an important but poorly quantified component of the global carbon cycle, and are the most relevant for human activities. Regional model applications that are nested within large-scale or global models are necessary for detailed studies of coastal regions. We present results from such a regional biogeochemical model for the northwestern North Atlantic shelves and adjacent deep ocean of Atlantic Canada. The model is an implementation of the Regional Ocean Modeling System (ROMS) and includes an NPZD-type nitrogen cycle model with explicit representation of dissolved oxygen and inorganic carbon. The region is at the confluence of the Gulf Stream and Labrador Current making it highly dynamic, a challenge for analysis and prediction, and prone to large changes. Historically a rich fishing ground, coastal ecosystems in Atlantic Canada have undergone dramatic changes including the collapse of several economically important fish stocks and the listing of many species as threatened or endangered. Furthermore it is unclear whether the region is a net source or sink of atmospheric CO2 with estimates of the size and direction of the net air-sea CO2 flux remaining controversial. We will discuss simulated patterns of primary production, inorganic carbon fluxes and oxygen trends in the context of circulation features and shelf residence times for the present ocean state and present future projections.

OCoc- from Ocean Colour to Organic Carbon

NASA Astrophysics Data System (ADS)

Heim, B.; Overduin, P. P.; Schirrmeister, L.; Lantuit, H.; Doerffer, R.

2009-12-01

Enhanced permafrost warming and increased arctic river discharges have heightened concern about the input of terrigenous matter into Arctic coastal waters. The ‘OCoc-from Ocean Colour to Organic Carbon’ project (IPY-project 1176), funded by the German Research Foundation (DFG), is an Ocean Colour study joined with the Arctic Coastal Dynamics ACD network and Arctic Circum-polar Coastal Observatory Network ACCO-Net (IPY-project 90). OCoc uses Ocean Colour satellite data for synoptical monitoring of organic matter fluxes from fluvial and coastal sources. Initial results from German-Russian expeditions at the southeastern Laptev Sea Coast (Arctic Siberia, Russia) in August 2008 and August 2009 are presented. Large parts of this coastal zone are characterized by highly erosive organic-rich material. Ocean Colour MERIS Reduced Resolution (RR)-LIB data of the have been processed towards optical aquatic parameters using Beam-Visat4.2 and the MERIS case2 regional processor for coastal application (C2R). Calculated aquatic parameters are absorption and backscattering coefficients, apparent optical properties such as the first attenuation depth (‘Z90’) and calculated concentrations of chlorophyll, total suspended matter and coloured dissolved organic matter absorption from the water leaving reflectances. Initial comparisons with expedition data (Secchi depths, cDOM) show that the MERIS-C2R optical parameters ’total absorption’ and the first attenuation depth, ’Z90’, seem adequately to represent true conditions. High attenuation values in the spectral blue wavelength range may serve as tracer for the organic-rich terrigenous input. The synoptic information of Ocean Colour products will provide valuable spatial and dynamical information on the Organic Carbon and sediment fluxes from the Siberian permafrost coast.

Modeling the Influence of Different Processes on Iron Solubilization in Mineral Aerosols: From the Gobi Desert to the North Pacific Ocean

NASA Astrophysics Data System (ADS)

Meskhidze, N.; Chameides, W. L.; Chen, G.

2002-12-01

Atmospheric transport is the only known means to deliver dissolved iron from the continents to remote oceanic areas. Dissolved iron is one of the necessary nutrients for photosynthesis of microscopic, single-celled marine organisms (phytoplankton) that grow abundantly in oceans around the world. Alteration of dissolved iron fluxes may substantially affect ocean ecosystem productivity and even exert a global-scale influence on climate by affecting the rate at which atmospheric CO2 is fixed by oceanic biota. On continents, iron mainly exists in forms of highly insoluble minerals (iron-oxides and iron-aluminosilicates) and the processes that can solubilize iron in mineral aerosols during their long-range transport remain poorly understood. In this work we attempt to elucidate the key processes that control the solubilization of iron in mineral aerosols using a simple Lagrangian box model to simulate the transport and chemical alteration of iron-containing mineral aerosols as they are transported from the east coast of China to the remote western North Pacific Ocean. Model parameters and initial conditions are set using a combination of soil and aerosol data from the Gobi Desert, as well as from measurements made during specific PEM-West B flights that encountered dust storm plumes over the Pacific Ocean that had originated in China. Our preliminary results indicate that the amount of acidic pollutants in the air along the dust transport pathways can have a significant effect on the amount of iron that is solubilized in advecting mineral aerosols. This suggests that there may be a link between the flux of the dissolved iron to the remote North Pacific Ocean and the rate at which pollutants such as sulfur dioxide, nitrogen oxides, and ammonia are emitted in East Asia.

Impact of Ocean Warming on Tropical Cyclone Size and Its Destructiveness.

PubMed

Sun, Yuan; Zhong, Zhong; Li, Tim; Yi, Lan; Hu, Yijia; Wan, Hongchao; Chen, Haishan; Liao, Qianfeng; Ma, Chen; Li, Qihua

2017-08-15

The response of tropical cyclone (TC) destructive potential to global warming is an open issue. A number of previous studies have ignored the effect of TC size change in the context of global warming, which resulted in a significant underestimation of the TC destructive potential. The lack of reliable and consistent historical data on TC size limits the confident estimation of the linkage between the observed trend in TC size and that in sea surface temperature (SST) under the background of global climate warming. A regional atmospheric model is used in the present study to investigate the response of TC size and TC destructive potential to increases in SST. The results show that a large-scale ocean warming can lead to not only TC intensification but also TC expansion. The TC size increase in response to the ocean warming is possibly attributed to the increase in atmospheric convective instability in the TC outer region below the middle troposphere, which facilitates the local development of grid-scale ascending motion, low-level convergence and the acceleration of tangential winds. The numerical results indicate that TCs will become stronger, larger, and unexpectedly more destructive under global warming.

Mitochondrial acclimation capacities to ocean warming and acidification are limited in the antarctic Nototheniid Fish, Notothenia rossii and Lepidonotothen squamifrons.

PubMed

Strobel, Anneli; Graeve, Martin; Poertner, Hans O; Mark, Felix C

2013-01-01

Antarctic notothenioid fish are characterized by their evolutionary adaptation to the cold, thermostable Southern Ocean, which is associated with unique physiological adaptations to withstand the cold and reduce energetic requirements but also entails limited compensation capacities to environmental change. This study compares the capacities of mitochondrial acclimation to ocean warming and acidification between the Antarctic nototheniid Notothenia rossii and the sub-Antarctic Lepidonotothen squamifrons, which share a similar ecology, but different habitat temperatures. After acclimation of L. squamifrons to 9°C and N. rossii to 7°C (normocapnic/hypercapnic, 0.2 kPa CO2/2000 ppm CO2) for 4-6 weeks, we compared the capacities of their mitochondrial respiratory complexes I (CI) and II (CII), their P/O ratios (phosphorylation efficiency), proton leak capacities and mitochondrial membrane fatty acid compositions. Our results reveal reduced CII respiration rates in warm-acclimated L. squamifrons and cold hypercapnia-acclimated N. rossii. Generally, L. squamifrons displayed a greater ability to increase CI contribution during acute warming and after warm-acclimation than N. rossii. Membrane unsaturation was not altered by warm or hypercapnia-acclimation in both species, but membrane fatty acids of warm-acclimated L. squamifrons were less saturated than in warm normocapnia-/hypercapnia-acclimated N. rossii. Proton leak capacities were not affected by warm or hypercapnia-acclimation of N. rossii. We conclude that an acclimatory response of mitochondrial capacities may include higher thermal plasticity of CI supported by enhanced utilization of anaplerotic substrates (via oxidative decarboxylation reactions) feeding into the citrate cycle. L. squamifrons possesses higher relative CI plasticities than N. rossii, which may facilitate the usage of energy efficient NADH-related substrates under conditions of elevated energy demand, possibly induced by ocean warming and acidification. The observed adjustments of electron transport system complexes with a higher flux through CI under warming and acidification suggest a metabolic acclimation potential of the sub-Antarctic L. squamifrons, but only limited acclimation capacities for N. rossii.

A Smoking Gun for Methane Hydrate Release During the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Frieling, J.; Peterse, F.; Lunt, D. J.; Bohaty, S. M.; S Sinninghe Damsté, J.; Reichart, G. J.; Sluijs, A.

2016-12-01

The Paleocene-Eocene Thermal Maximum (PETM; 56 Ma) was a period of rapid 4-5ºC global warming and a global negative carbon isotope excursion (CIE) of 3-4.5‰, signaling the input of at least 1500 Gt of δ13C-depleted carbon into the ocean-atmosphere system. Methane from submarine hydrates has long been proposed as a carbon source, but direct and indirect evidence is lacking. We generated a new high-resolution TEX86 and δ13C record from Ocean Drilling Program Site 959 in the eastern tropical Atlantic and find that initial warming preceded the PETM CIE by 10 kyr. Moreover, time-shifted cross-correlations on these new and published temperature-δ13C data imply that substantial (2-3 °C) warming lead 13C-depleted carbon injection by an average of 2-3 kyr globally. Finally, a data compilation shows that global burial fluxes of biogenic Ba approximately doubled across all depths of the ocean studied, which on PETM time scales can only be explained by significant Ba addition to the oceans. Submarine hydrates are Ba-rich and require warming to dissociate. The simplest explanation for the temperature lead and Ba addition to the ocean is that methane hydrate dissociated as a response to initial warming and acted as a positive carbon cycle feedback during the PETM.

The reef-building coral Siderastrea siderea exhibits parabolic responses to ocean acidification and warming.

PubMed

Castillo, Karl D; Ries, Justin B; Bruno, John F; Westfield, Isaac T

2014-12-22

Anthropogenic increases in atmospheric CO2 over this century are predicted to cause global average surface ocean pH to decline by 0.1-0.3 pH units and sea surface temperature to increase by 1-4°C. We conducted controlled laboratory experiments to investigate the impacts of CO2-induced ocean acidification (pCO2 = 324, 477, 604, 2553 µatm) and warming (25, 28, 32°C) on the calcification rate of the zooxanthellate scleractinian coral Siderastrea siderea, a widespread, abundant and keystone reef-builder in the Caribbean Sea. We show that both acidification and warming cause a parabolic response in the calcification rate within this coral species. Moderate increases in pCO2 and warming, relative to near-present-day values, enhanced coral calcification, with calcification rates declining under the highest pCO2 and thermal conditions. Equivalent responses to acidification and warming were exhibited by colonies across reef zones and the parabolic nature of the corals' response to these stressors was evident across all three of the experiment's 30-day observational intervals. Furthermore, the warming projected by the Intergovernmental Panel on Climate Change for the end of the twenty-first century caused a fivefold decrease in the rate of coral calcification, while the acidification projected for the same interval had no statistically significant impact on the calcification rate-suggesting that ocean warming poses a more immediate threat than acidification for this important coral species.

The reef-building coral Siderastrea siderea exhibits parabolic responses to ocean acidification and warming

PubMed Central

Castillo, Karl D.; Ries, Justin B.; Bruno, John F.; Westfield, Isaac T.

2014-01-01

Anthropogenic increases in atmospheric CO2 over this century are predicted to cause global average surface ocean pH to decline by 0.1–0.3 pH units and sea surface temperature to increase by 1–4°C. We conducted controlled laboratory experiments to investigate the impacts of CO2-induced ocean acidification (pCO2 = 324, 477, 604, 2553 µatm) and warming (25, 28, 32°C) on the calcification rate of the zooxanthellate scleractinian coral Siderastrea siderea, a widespread, abundant and keystone reef-builder in the Caribbean Sea. We show that both acidification and warming cause a parabolic response in the calcification rate within this coral species. Moderate increases in pCO2 and warming, relative to near-present-day values, enhanced coral calcification, with calcification rates declining under the highest pCO2 and thermal conditions. Equivalent responses to acidification and warming were exhibited by colonies across reef zones and the parabolic nature of the corals' response to these stressors was evident across all three of the experiment's 30-day observational intervals. Furthermore, the warming projected by the Intergovernmental Panel on Climate Change for the end of the twenty-first century caused a fivefold decrease in the rate of coral calcification, while the acidification projected for the same interval had no statistically significant impact on the calcification rate—suggesting that ocean warming poses a more immediate threat than acidification for this important coral species. PMID:25377455

Deglacial upwelling, productivity and CO2 outgassing in the North Pacific Ocean

NASA Astrophysics Data System (ADS)

Gray, William R.; Rae, James W. B.; Wills, Robert C. J.; Shevenell, Amelia E.; Taylor, Ben; Burke, Andrea; Foster, Gavin L.; Lear, Caroline H.

2018-05-01

The interplay between ocean circulation and biological productivity affects atmospheric CO2 levels and marine oxygen concentrations. During the warming of the last deglaciation, the North Pacific experienced a peak in productivity and widespread hypoxia, with changes in circulation, iron supply and light limitation all proposed as potential drivers. Here we use the boron-isotope composition of planktic foraminifera from a sediment core in the western North Pacific to reconstruct pH and dissolved CO2 concentrations from 24,000 to 8,000 years ago. We find that the productivity peak during the Bølling-Allerød warm interval, 14,700 to 12,900 years ago, was associated with a decrease in near-surface pH and an increase in pCO2, and must therefore have been driven by increased supply of nutrient- and CO2-rich waters. In a climate model ensemble (PMIP3), the presence of large ice sheets over North America results in high rates of wind-driven upwelling within the subpolar North Pacific. We suggest that this process, combined with collapse of North Pacific Intermediate Water formation at the onset of the Bølling-Allerød, led to high rates of upwelling of water rich in nutrients and CO2, and supported the peak in productivity. The respiration of this organic matter, along with poor ventilation, probably caused the regional hypoxia. We suggest that CO2 outgassing from the North Pacific helped to maintain high atmospheric CO2 concentrations during the Bølling-Allerød and contributed to the deglacial CO2 rise.

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.

Seahorses under a changing ocean: the impact of warming and acidification on the behaviour and physiology of a poor-swimming bony-armoured fish.

PubMed

Faleiro, Filipa; Baptista, Miguel; Santos, Catarina; Aurélio, Maria L; Pimentel, Marta; Pegado, Maria Rita; Paula, José Ricardo; Calado, Ricardo; Repolho, Tiago; Rosa, Rui

2015-01-01

Seahorses are currently facing great challenges in the wild, including habitat degradation and overexploitation, and how they will endure additional stress from rapid climate change has yet to be determined. Unlike most fishes, the poor swimming skills of seahorses, along with the ecological and biological constraints of their unique lifestyle, place great weight on their physiological ability to cope with climate changes. In the present study, we evaluate the effects of ocean warming (+4°C) and acidification (ΔpH = -0.5 units) on the physiological and behavioural ecology of adult temperate seahorses, Hippocampus guttulatus. Adult seahorses were found to be relatively well prepared to face future changes in ocean temperature, but not the combined effect of warming and acidification. Seahorse metabolism increased normally with warming, and behavioural and feeding responses were not significantly affected. However, during hypercapnia the seahorses exhibited signs of lethargy (i.e. reduced activity levels) combined with a reduction of feeding and ventilation rates. Nonetheless, metabolic rates were not significantly affected. Future ocean changes, particularly ocean acidification, may further threaten seahorse conservation, turning these charismatic fishes into important flagship species for global climate change issues.

Ocean warming increases threat of invasive species in a marine fouling community.

PubMed

Sorte, Cascade J B; Williams, Susan L; Zerebecki, Robyn A

2010-08-01

We addressed the potential for climate change to facilitate invasions and precipitate shifts in community composition by testing effects of ocean warming on species in a marine fouling community in Bodega Harbor, Bodega Bay, California, USA. First, we determined that introduced species tolerated significantly higher temperatures than natives, suggesting that climate change will have a disproportionately negative impact on native species. Second, we assessed the temperature dependence of survival and growth by exposing juveniles to an ambient control temperature and increased temperatures predicted by ocean warming scenarios (+3 degrees C and +4.5 degrees C) in laboratory mesocosms. We found that responses differed between species, species origins, and demographic processes. Based on the temperature tolerance, survival, and growth results, we predict that, as ocean temperatures increase, native species will decrease in abundance, whereas introduced species are likely to increase in this system. Facilitation of invasions by climate change may already be underway; locally, invasive dominance has increased concurrent with ocean warming over the past approximately 40 years. We suggest that the effects of climate change on communities can occur via both direct impacts on the diversity and abundance of native species and indirect effects due to increased dominance of introduced species.

Recent Decrease in Typhoon Destructive Potential and Global Warming Implications

NASA Astrophysics Data System (ADS)

Lin, I. I.

2016-02-01

Despite the severe impact of individual tropical cyclones like Sandy (2012) and Haiyan (2013), global TC activities as a whole have actually dropped considerably since the early 1990's. Especially over the most active and hazardous TC basin on earth, the Western North Pacific (WNP) typhoon Main Development Region (MDR), an evident decrease in TC activity has been observed, as characterised by the drop in the annual Power Dissipation Index (Emanuel 2005). Paradoxically, this decrease occurred despite evident ocean warming, with upper ocean heat content increased by 12% over the western North Pacific MDR (Pun et al. 2013; Lin et al. 2014). This study explores the interesting interplay between atmosphere and ocean on the WNP typhoons. Though ocean may become more favourable (warming) to fuel individual typhoon event through temporal relaxation in the atmosphere condition (e.g. Haiyan in 2013), the overall `worsened' atmospheric condition (e.g. increase in vertical wind shear) can `over-powers' the `better' ocean to suppress the overall WNP typhoon activities. This stronger negative contribution from reduced typhoon frequency over the increased intensity is also present under the global warming scenario, based on analysis of the simulated typhoon data from high-resolution modelling.

Recent Decrease in Typhoon Destructive Potential and Global Warming Implications

NASA Astrophysics Data System (ADS)

Lin, I. I.

2015-12-01

Despite the severe impact of individual tropical cyclones like Sandy (2012) and Haiyan (2013), global TC activities as a whole have actually dropped considerably since the early 1990's. Especially over the most active and hazardous TC basin on earth, the Western North Pacific (WNP) typhoon Main Development Region (MDR), an evident decrease in TC activity has been observed, as characterised by the drop in the annual Power Dissipation Index (Emanuel 2005). Paradoxically, this decrease occurred despite evident ocean warming, with upper ocean heat content increased by ~ 12% over the western North Pacific MDR (Pun et al. 2013; Lin et al. 2014). This study explores the interesting interplay between atmosphere and ocean on the WNP typhoons. Though ocean may become more favourable (warming) to fuel individual typhoon event through temporal relaxation in the atmosphere condition (e.g. Haiyan in 2013), the overall 'worsened' atmospheric condition (e.g. increase in vertical wind shear) can 'over-powers' the 'better' ocean to suppress the overall WNP typhoon activities. This stronger negative contribution from reduced typhoon frequency over the increased intensity is also present under the global warming scenario, based on analysis of the simulated typhoon data from high-resolution modelling.

Consumers mediate the effects of experimental ocean acidification and warming on primary producers.

PubMed

Alsterberg, Christian; Eklöf, Johan S; Gamfeldt, Lars; Havenhand, Jonathan N; Sundbäck, Kristina

2013-05-21

It is well known that ocean acidification can have profound impacts on marine organisms. However, we know little about the direct and indirect effects of ocean acidification and also how these effects interact with other features of environmental change such as warming and declining consumer pressure. In this study, we tested whether the presence of consumers (invertebrate mesograzers) influenced the interactive effects of ocean acidification and warming on benthic microalgae in a seagrass community mesocosm experiment. Net effects of acidification and warming on benthic microalgal biomass and production, as assessed by analysis of variance, were relatively weak regardless of grazer presence. However, partitioning these net effects into direct and indirect effects using structural equation modeling revealed several strong relationships. In the absence of grazers, benthic microalgae were negatively and indirectly affected by sediment-associated microalgal grazers and macroalgal shading, but directly and positively affected by acidification and warming. Combining indirect and direct effects yielded no or weak net effects. In the presence of grazers, almost all direct and indirect climate effects were nonsignificant. Our analyses highlight that (i) indirect effects of climate change may be at least as strong as direct effects, (ii) grazers are crucial in mediating these effects, and (iii) effects of ocean acidification may be apparent only through indirect effects and in combination with other variables (e.g., warming). These findings highlight the importance of experimental designs and statistical analyses that allow us to separate and quantify the direct and indirect effects of multiple climate variables on natural communities.

Feedback attribution of the land-sea warming contrast in a global warming simulation of the NCAR CCSM4

DOE PAGES

Sejas, Sergio A.; Albert, Oriene S.; Cai, Ming; ...

2014-12-02

One of the salient features in both observations and climate simulations is a stronger land warming than sea. This paper provides a quantitative understanding of the main processes that contribute to the land-sea warming asymmetry in a global warming simulation of the NCAR CCSM4. The CO 2 forcing alone warms the surface nearly the same for both land and sea, suggesting that feedbacks are responsible for the warming contrast. Our analysis on one hand confirms that the principal contributor to the above-unity land-to-sea warming ratio is the evaporation feedback; on the other hand the results indicate that the sensible heatmore » flux feedback has the largest land-sea warming difference that favors a greater ocean than land warming. Furthermore, the results uniquely highlight the importance of other feedbacks in establishing the above-unity land-to-sea warming ratio. Particularly, the SW cloud feedback and the ocean heat storage in the transient response are key contributors to the greater warming over land than sea.« less

Feedback attribution of the land-sea warming contrast in a global warming simulation of the NCAR CCSM4

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

Sejas, Sergio A.; Albert, Oriene S.; Cai, Ming

One of the salient features in both observations and climate simulations is a stronger land warming than sea. This paper provides a quantitative understanding of the main processes that contribute to the land-sea warming asymmetry in a global warming simulation of the NCAR CCSM4. The CO 2 forcing alone warms the surface nearly the same for both land and sea, suggesting that feedbacks are responsible for the warming contrast. Our analysis on one hand confirms that the principal contributor to the above-unity land-to-sea warming ratio is the evaporation feedback; on the other hand the results indicate that the sensible heatmore » flux feedback has the largest land-sea warming difference that favors a greater ocean than land warming. Furthermore, the results uniquely highlight the importance of other feedbacks in establishing the above-unity land-to-sea warming ratio. Particularly, the SW cloud feedback and the ocean heat storage in the transient response are key contributors to the greater warming over land than sea.« less

Dissolved carbon biogeochemistry and export in mangrove-dominated rivers of the Florida Everglades

NASA Astrophysics Data System (ADS)

Ho, David T.; Ferrón, Sara; Engel, Victor C.; Anderson, William T.; Swart, Peter K.; Price, René M.; Barbero, Leticia

2017-05-01

The Shark and Harney rivers, located on the southwest coast of Florida, USA, originate in the freshwater, karstic marshes of the Everglades and flow through the largest contiguous mangrove forest in North America. In November 2010 and 2011, dissolved carbon source-sink dynamics was examined in these rivers during SF6 tracer release experiments. Approximately 80 % of the total dissolved carbon flux out of the Shark and Harney rivers during these experiments was in the form of inorganic carbon, either via air-water CO2 exchange or longitudinal flux of dissolved inorganic carbon (DIC) to the coastal ocean. Between 42 and 48 % of the total mangrove-derived DIC flux into the rivers was emitted to the atmosphere, with the remaining being discharged to the coastal ocean. Dissolved organic carbon (DOC) represented ca. 10 % of the total mangrove-derived dissolved carbon flux from the forests to the rivers. The sum of mangrove-derived DIC and DOC export from the forest to these rivers was estimated to be at least 18.9 to 24.5 mmol m-2 d-1, a rate lower than other independent estimates from Shark River and from other mangrove forests. Results from these experiments also suggest that in Shark and Harney rivers, mangrove contribution to the estuarine flux of dissolved carbon to the ocean is less than 10 %.

Magnitude and pattern of Arctic warming governed by the seasonality of radiative forcing.

PubMed

Bintanja, R; Krikken, F

2016-12-02

Observed and projected climate warming is strongest in the Arctic regions, peaking in autumn/winter. Attempts to explain this feature have focused primarily on identifying the associated climate feedbacks, particularly the ice-albedo and lapse-rate feedbacks. Here we use a state-of-the-art global climate model in idealized seasonal forcing simulations to show that Arctic warming (especially in winter) and sea ice decline are particularly sensitive to radiative forcing in spring, during which the energy is effectively 'absorbed' by the ocean (through sea ice melt and ocean warming, amplified by the ice-albedo feedback) and consequently released to the lower atmosphere in autumn and winter, mainly along the sea ice periphery. In contrast, winter radiative forcing causes a more uniform response centered over the Arctic Ocean. This finding suggests that intermodel differences in simulated Arctic (winter) warming can to a considerable degree be attributed to model uncertainties in Arctic radiative fluxes, which peak in summer.

Intraseasonal sea surface warming in the western Indian Ocean by oceanic equatorial Rossby waves

DTIC Science & Technology

2017-05-09

using observational and reanalysis products , respectively. In the heat budget, horizontal advection is the leading contributor to warming, in part due to...warming and cooling in these studies . SST is observed to maximize just ahead of MJO convection. After convection begins, SST rapidly cools and reaches a...minimum ~5 days later. However, several studies have observed a certain class of MJO events that deviate from the previously observed relationship of

Widespread gas hydrate instability on the upper U.S. Beaufort margin

NASA Astrophysics Data System (ADS)

Phrampus, Benjamin J.; Hornbach, Matthew J.; Ruppel, Carolyn D.; Hart, Patrick E.

2014-12-01

The most climate-sensitive methane hydrate deposits occur on upper continental slopes at depths close to the minimum pressure and maximum temperature for gas hydrate stability. At these water depths, small perturbations in intermediate ocean water temperatures can lead to gas hydrate dissociation. The Arctic Ocean has experienced more dramatic warming than lower latitudes, but observational data have not been used to study the interplay between upper slope gas hydrates and warming ocean waters. Here we use (a) legacy seismic data that constrain upper slope gas hydrate distributions on the U.S. Beaufort Sea margin, (b) Alaskan North Slope borehole data and offshore thermal gradients determined from gas hydrate stability zone thickness to infer regional heat flow, and (c) 1088 direct measurements to characterize multidecadal intermediate ocean warming in the U.S. Beaufort Sea. Combining these data with a three-dimensional thermal model shows that the observed gas hydrate stability zone is too deep by 100 to 250 m. The disparity can be partially attributed to several processes, but the most important is the reequilibration (thinning) of gas hydrates in response to significant (~0.5°C at 2σ certainty) warming of intermediate ocean temperatures over 39 years in a depth range that brackets the upper slope extent of the gas hydrate stability zone. Even in the absence of additional ocean warming, 0.44 to 2.2 Gt of methane could be released from reequilibrating gas hydrates into the sediments underlying an area of ~5-7.5 × 103 km2 on the U.S. Beaufort Sea upper slope during the next century.

A Wave Glider for Studies of Biofouling and Ocean Productivity

DTIC Science & Technology

2017-11-07

sensors for conductivity, water and air temperature , dissolved oxygen , chlorophyll-a fluorescence, wind speed and direction, barometric pressure, and...endurance, reduce fuel consumption , and reduce carbon emissions. During deployments, vessels encounter a range of planktonic assemblages and ocean...with an acoustic Doppler current profiler, an optical camera system, and standard sensors for conductivity, water and air temperature , dissolved

Indian Ocean warming during 1958-2004 simulated by a climate system model and its mechanism

NASA Astrophysics Data System (ADS)

Dong, Lu; Zhou, Tianjun; Wu, Bo

2014-01-01

The mechanism responsible for Indian Ocean Sea surface temperature (SST) basin-wide warming trend during 1958-2004 is studied based on both observational data analysis and numerical experiments with a climate system model FGOALS-gl. To quantitatively estimate the relative contributions of external forcing (anthropogenic and natural forcing) and internal variability, three sets of numerical experiments are conducted, viz. an all forcing run forced by both anthropogenic forcing (greenhouse gases and sulfate aerosols) and natural forcing (solar constant and volcanic aerosols), a natural forcing run driven by only natural forcing, and a pre-industrial control run. The model results are compared to the observations. The results show that the observed warming trend during 1958-2004 (0.5 K (47-year)-1) is largely attributed to the external forcing (more than 90 % of the total trend), while the residual is attributed to the internal variability. Model results indicate that the anthropogenic forcing accounts for approximately 98.8 % contribution of the external forcing trend. Heat budget analysis shows that the surface latent heat flux due to atmosphere and surface longwave radiation, which are mainly associated with anthropogenic forcing, are in favor of the basin-wide warming trend. The basin-wide warming is not spatially uniform, but with an equatorial IOD-like pattern in climate model. The atmospheric processes, oceanic processes and climatological latent heat flux together form an equatorial IOD-like warming pattern, and the oceanic process is the most important in forming the zonal dipole pattern. Both the anthropogenic forcing and natural forcing result in easterly wind anomalies over the equator, which reduce the wind speed, thereby lead to less evaporation and warmer SST in the equatorial western basin. Based on Bjerknes feedback, the easterly wind anomalies uplift the thermocline, which is unfavorable to SST warming in the eastern basin, and contribute to SST warming via deeper thermocline in the western basin. The easterly anomalies also drive westward anomalous equatorial currents, against the eastward climatology currents, which is in favor of the SST warming in the western basin via anomalous warm advection. Therefore, both the atmospheric and oceanic processes are in favor of the IOD-like warming pattern formation over the equator.

The influence of meridional ice transport on Europa's ocean stratification and heat content

NASA Astrophysics Data System (ADS)

Zhu, Peiyun; Manucharyan, Georgy E.; Thompson, Andrew F.; Goodman, Jason C.; Vance, Steven D.

2017-06-01

Jupiter's moon Europa likely hosts a saltwater ocean beneath its icy surface. Geothermal heating and rotating convection in the ocean may drive a global overturning circulation that redistributes heat vertically and meridionally, preferentially warming the ice shell at the equator. Here we assess the previously unconstrained influence of ocean-ice coupling on Europa's ocean stratification and heat transport. We demonstrate that a relatively fresh layer can form at the ice-ocean interface due to a meridional ice transport forced by the differential ice shell heating between the equator and the poles. We provide analytical and numerical solutions for the layer's characteristics, highlighting their sensitivity to critical ocean parameters. For a weakly turbulent and highly saline ocean, a strong buoyancy gradient at the base of the freshwater layer can suppress vertical tracer exchange with the deeper ocean. As a result, the freshwater layer permits relatively warm deep ocean temperatures.

The influence of meridional ice transport on Europa's ocean stratification and heat content

NASA Astrophysics Data System (ADS)

Zhu, P.; Manucharyan, G.; Thompson, A. F.; Goodman, J. C.; Vance, S.

2017-12-01

Jupiter's moon Europa likely hosts a saltwater ocean beneath its icy surface. Geothermal heating and rotating convection in the ocean may drive a global overturning circulation that redistributes heat vertically and meridionally, preferentially warming the ice shell at the equator. Here we assess thepreviously unconstrained influence of ocean-ice coupling on Europa's ocean stratification and heat transport. We demonstrate that a relatively fresh layer can form at the ice-ocean interface due to a meridional ice transport forced by the differential ice shell heating between the equator and the poles. We provide analytical and numerical solutions for the layer's characteristics, highlighting their sensitivity to critical ocean parameters. For a weakly turbulent and highly saline ocean, a strong buoyancy gradient at the base of the freshwater layer can suppress vertical tracer exchange with the deeper ocean. As a result, the freshwater layer permits relatively warm deep ocean temperatures.

Northwestern Pacific typhoon intensity controlled by changes in ocean temperatures.

PubMed

Mei, Wei; Xie, Shang-Ping; Primeau, François; McWilliams, James C; Pasquero, Claudia

2015-05-01

Dominant climatic factors controlling the lifetime peak intensity of typhoons are determined from six decades of Pacific typhoon data. We find that upper ocean temperatures in the low-latitude northwestern Pacific (LLNWP) and sea surface temperatures in the central equatorial Pacific control the seasonal average lifetime peak intensity by setting the rate and duration of typhoon intensification, respectively. An anomalously strong LLNWP upper ocean warming has favored increased intensification rates and led to unprecedentedly high average typhoon intensity during the recent global warming hiatus period, despite a reduction in intensification duration tied to the central equatorial Pacific surface cooling. Continued LLNWP upper ocean warming as predicted under a moderate [that is, Representative Concentration Pathway (RCP) 4.5] climate change scenario is expected to further increase the average typhoon intensity by an additional 14% by 2100.

An integrated perspective on the Permian-Triassic "Great Dying"

NASA Astrophysics Data System (ADS)

Algeo, T. J.

2017-12-01

The 252-Ma end-Permian mass extinction (EPME), marked by the loss of 90% of marine invertebrate species, was the largest biocrisis in Earth history. Intensive study of this "Great Dying" has led to major insights and a broad consensus regarding many aspects of this event. The ultimate trigger is regarded as eruption of the Siberian Traps Large Igneous Province (STLIP), which released large quantities of greenhouse gases (CO2 and CH4) and sulfate aerosols, triggering a catastrophic global warming of 10°C and acidification of both land surfaces and the surface ocean. On land, a massive die-off of vegetation led to a transient episode of rapid soil erosion and a longer-term increase in weathering rates linked to elevated temperatures. In the ocean, widespread anoxia developed concurrently with the EPME, triggered by ocean-surface warming that reduced dissolved oxygen solubility in seawater and that intensified vertical stratification. Expanded anoxia led to massive burial of organic matter and reduced sulfur, although the evidence for this is indirect (C, U and S isotopes); few organic-rich deposits of Early Triassic age have been found, suggesting that organic sedimentation occurred mainly on continental slopes or in the deep ocean. Other aspects of the end-Permian crisis remain under debate. For example, there is no consensus regarding changes in marine productivity levels in the aftermath of the EPME, which would have been stimulated by enhanced subaerial weathering but depressed by reduced overturning circulation-the evidence to date may favor localized positive and negative changes in productivity. Also under scrutiny is evidence for volcanic eruptions and environmental perturbations during the 100 kyr prior to the EPME, which are likely to have occurred but remain poorly dated and quantified. The greatest uncertainty, however, may surround the nature of the proximate kill mechanism(s) during the EPME. Many hypotheses have been advanced including mechanisms based on redox, temperature, and pH changes. Determining which environmental factors were most harmful to end-Permian life is inherently difficult as the taphocoenotic clues are challenging to interpret. Indeed, many organisms may not have succumbed to a single environmental factor but to the combined effects of multiple concurrent changes.

Impact of icebergs on net primary productivity in the Southern Ocean

NASA Astrophysics Data System (ADS)

Wu, Shuang-Ye; Hou, Shugui

2017-03-01

Productivity in the Southern Ocean (SO) is iron-limited, and supply of iron dissolved from aeolian dust is believed to be the main source from outside the marine environment. However, recent studies show that icebergs could provide a comparable amount of bioavailable iron to the SO as aeolian dust. In addition, small-scale areal studies suggest increased concentrations of chlorophyll, krill, and seabirds surrounding icebergs. Based on previous research, this study aims to examine whether iceberg occurrence has a significant impact on marine productivity at the scale of the SO, using remote sensing data of iceberg occurrences and ocean net primary productivity (NPP) covering the period 2002-2014. The impacts of both large and small icebergs are examined in four major ecological zones of the SO: the continental shelf zone (CSZ), the seasonal ice zone (SIZ), the permanent open ocean zone (POOZ), and the polar front zone (PFZ). We found that the presence of icebergs is associated with elevated levels of NPP, but the differences vary in different zones. Grid cells with small icebergs on average have higher NPP than other cells in most iron-deficient zones: 21 % higher for the SIZ, 16 % for the POOZ, and 12 % for the PFZ. The difference is relatively small in the CSZ where iron is supplied from meltwater and sediment input from the continent. In addition, NPP of grid cells adjacent to large icebergs on average is 10 % higher than that of control cells in the vicinity. The difference is larger at higher latitudes, where most large icebergs are concentrated. From 1992 to 2014, there is a significant increasing trend for both small and large icebergs. The increase was most rapid in the early 2000s and has leveled off since then. As the climate continues to warm, the Antarctic Ice Sheet is expected to experience increased mass loss as a whole, which could lead to more icebergs in the region. Based on our study, this could result in a higher level of NPP in the SO as a whole, providing a possible negative feedback for global warming in near future.

Ocean-Glaciers Interactions in the Southern Svalbard Fjord, Hornsund.

NASA Astrophysics Data System (ADS)

Walczowski, W.; Beszczynska-Moeller, A.; Prominska, A.; Kruss, A.

2017-12-01

The Arctic fjords constitute a link between the ocean and land, therefore there are highly vulnerable to warming and are expected to exhibit the earliest environmental changes resulting from anthropogenic impacts on climate. In the Arctic, the inshore boundary of a fjord system is usually dominated by tidewater glaciers while its offshore boundary is strongly influenced by warm oceanic waters. Improved understanding of the fjord-ocean exchange and processes within Arctic fjords is of a highest importance because their response to atmospheric, oceanic and glacial variability provides a key to understand the past and to forecast the future of the high latitude glaciers and Arctic climate. The results of field measurements in the Hornsund fjord (southern Svalbard), collected under the Polish-Norwegian projects GLAERE and AWAKE-2, will be presented. Interannual variability of warm Atlantic water entering the fjord, seasonal changes of ocean properties in the glacier bays and the structure of the water column in the vicinity of the glacier termination will be addressed. Direct contact of warm oceanic water with a glacier's wall causes submarine melting, undercutting and glacier calving. Turbulent plumes of subglacial meltwater constitute an important mechanism of heat transfer and also influence a glacier retreat. However our understanding of these processes is limited due to problems with obtaining in situ data close to the glacier wall. Therefore special attention will be paid to observations of the underwater parts of Hornsund glaciers and new measurements of water column fine structure and mixing in the turbulent meltwater plumes.

Connecting tropical climate change with Southern Ocean heat uptake

NASA Astrophysics Data System (ADS)

Hwang, Yen-Ting; Xie, Shang-Ping; Deser, Clara; Kang, Sarah M.

2017-09-01

Under increasing greenhouse gas forcing, climate models project tropical warming that is greater in the Northern than the Southern Hemisphere, accompanied by a reduction in the northeast trade winds and a strengthening of the southeast trades. While the ocean-atmosphere coupling indicates a positive feedback, what triggers the coupled asymmetry and favors greater warming in the northern tropics remains unclear. Far away from the tropics, the Southern Ocean (SO) has been identified as the major region of ocean heat uptake. Beyond its local effect on the magnitude of sea surface warming, we show by idealized modeling experiments in a coupled slab ocean configuration that enhanced SO heat uptake has a profound global impact. This SO-to-tropics connection is consistent with southward atmospheric energy transport across the equator. Enhanced SO heat uptake results in a zonally asymmetric La-Nina-like pattern of sea surface temperature change that not only affects tropical precipitation but also has influences on the Asian and North American monsoons.

Modeling geologically abrupt climate changes in the Miocene

NASA Astrophysics Data System (ADS)

Haupt, B. J.; Seidov, D.

2010-12-01

The gradual cooling of the Cenozoic, including the Miocene epoch, was punctuated by many geologically abrupt warming and cooling episodes - strong deviations from the cooling trend with time span of ten to hundred thousands of years. Our working hypothesis is that some of those warming episodes at least partially might have been caused by dynamics of the emerging Antarctic Ice Sheet, which, in turn, might have caused strong changes of sea surface salinity in the Miocene Southern Ocean. Feasibility of this hypothesis is explored in a series of coupled ocean-atmosphere computer experiments. The results suggest that relatively small and geologically short-lived changes in freshwater balance in the Southern Ocean could have significantly contributed to at least two prominent warming episodes in the Miocene. Importantly, the experiments also suggest that the Southern Ocean was more sensitive to the salinity changes in the Miocene than today, which can attributed to the opening of the Central American Isthmus as a major difference between the Miocene and the present-day ocean-sea geometry.

Trichodesmium blooms and warm-core ocean surface features in the Arabian Sea and the Bay of Bengal.

PubMed

Jyothibabu, R; Karnan, C; Jagadeesan, L; Arunpandi, N; Pandiarajan, R S; Muraleedharan, K R; Balachandran, K K

2017-08-15

Trichodesmium is a bloom-forming, diazotrophic, non-heterocystous cyanobacteria widely distributed in the warmer oceans, and their bloom is considered a 'biological indication' of stratification and nitrogen limitation in the ocean surface layer. In the first part of this paper, based on the retrospective analyses of the ocean surface mesoscale features associated with 59 Trichodesmium bloom incidences recorded in the past, 32 from the Arabian Sea and the Bay of Bengal, and 27 from the rest of the world, we have showed that warm-core features have an inducing effect on bloom formation. In the second part, we have considered the environmental preferences of Trichodesmium bloom based on laboratory and field studies across the globe, and proposed a view about how warm-core features could provide an inducing pre-requisite condition for the bloom formation in the Arabian Sea and the Bay of Bengal. Proposed that the subsurface waters of warm-core features maintain more likely chances for the conducive nutrient and light conditions required for the triggering of the blooms. Copyright © 2017 Elsevier Ltd. All rights reserved.

A synthesis of light absorption properties of the Arctic Ocean: application to semianalytical estimates of dissolved organic carbon concentrations from space

NASA Astrophysics Data System (ADS)

Matsuoka, A.; Babin, M.; Doxaran, D.; Hooker, S. B.; Mitchell, B. G.; Bélanger, S.; Bricaud, A.

2014-06-01

In addition to scattering coefficients, the light absorption coefficients of particulate and dissolved materials are the main factors determining the light propagation of the visible part of the spectrum and are, thus, important for developing ocean color algorithms. While these absorption properties have recently been documented by a few studies for the Arctic Ocean (e.g., Matsuoka et al., 2007, 2011; Ben Mustapha et al., 2012), the data sets used in the literature were sparse and individually insufficient to draw a general view of the basin-wide spatial and temporal variations in absorption. To achieve such a task, we built a large absorption database of the Arctic Ocean by pooling the majority of published data sets and merging new data sets. Our results show that the total nonwater absorption coefficients measured in the eastern Arctic Ocean (EAO; Siberian side) are significantly higher than in the western Arctic Ocean (WAO; North American side). This higher absorption is explained by higher concentration of colored dissolved organic matter (CDOM) in watersheds on the Siberian side, which contains a large amount of dissolved organic carbon (DOC) compared to waters off North America. In contrast, the relationship between the phytoplankton absorption (aϕ(λ)) and chlorophyll a (chl a) concentration in the EAO was not significantly different from that in the WAO. Because our semianalytical CDOM absorption algorithm is based on chl a-specific aϕ(λ) values (Matsuoka et al., 2013), this result indirectly suggests that CDOM absorption can be appropriately derived not only for the WAO but also for the EAO using ocean color data. Based on statistics, derived CDOM absorption values were reasonable compared to in situ measurements. By combining this algorithm with empirical DOC versus CDOM relationships, a semianalytical algorithm for estimating DOC concentrations for river-influenced coastal waters of the Arctic Ocean is presented and applied to satellite ocean color data.

Shift in tuna catches due to ocean warming.

PubMed

Monllor-Hurtado, Alberto; Pennino, Maria Grazia; Sanchez-Lizaso, José Luis

2017-01-01

Ocean warming is already affecting global fisheries with an increasing dominance of catches of warmer water species at higher latitudes and lower catches of tropical and subtropical species in the tropics. Tuna distributions are highly conditioned by sea temperature, for this reason and their worldwide distribution, their populations may be a good indicator of the effect of climate change on global fisheries. This study shows the shift of tuna catches in subtropical latitudes on a global scale. From 1965 to 2011, the percentage of tropical tuna in longliner catches exhibited a significantly increasing trend in a study area that included subtropical regions of the Atlantic and western Pacific Oceans and partially the Indian Ocean. This may indicate a movement of tropical tuna populations toward the poles in response to ocean warming. Such an increase in the proportion of tropical tuna in the catches does not seem to be due to a shift of the target species, since the trends in Atlantic and Indian Oceans of tropical tuna catches are decreasing. Our results indicate that as populations shift towards higher latitudes the catches of these tropical species did not increase. Thus, at least in the Atlantic and Indian Oceans, tropical tuna catches have reduced in tropical areas.

Temperature and CO2 additively regulate physiology, morphology and genomic responses of larval sea urchins, Strongylocentrotus purpuratus

PubMed Central

Padilla-Gamiño, Jacqueline L.; Kelly, Morgan W.; Evans, Tyler G.; Hofmann, Gretchen E.

2013-01-01

Ocean warming and ocean acidification, both consequences of anthropogenic production of CO2, will combine to influence the physiological performance of many species in the marine environment. In this study, we used an integrative approach to forecast the impact of future ocean conditions on larval purple sea urchins (Strongylocentrotus purpuratus) from the northeast Pacific Ocean. In laboratory experiments that simulated ocean warming and ocean acidification, we examined larval development, skeletal growth, metabolism and patterns of gene expression using an orthogonal comparison of two temperature (13°C and 18°C) and pCO2 (400 and 1100 μatm) conditions. Simultaneous exposure to increased temperature and pCO2 significantly reduced larval metabolism and triggered a widespread downregulation of histone encoding genes. pCO2 but not temperature impaired skeletal growth and reduced the expression of a major spicule matrix protein, suggesting that skeletal growth will not be further inhibited by ocean warming. Importantly, shifts in skeletal growth were not associated with developmental delay. Collectively, our results indicate that global change variables will have additive effects that exceed thresholds for optimized physiological performance in this keystone marine species. PMID:23536595

Recent decrease in typhoon destructive potential and global warming implications.

PubMed

Lin, I-I; Chan, Johnny C L

2015-05-20

Typhoons (tropical cyclones) severely impact the half-billion population of the Asian Pacific. Intriguingly, during the recent decade, typhoon destructive potential (Power Dissipation Index, PDI) has decreased considerably (by ∼ 35%). This decrease, paradoxically, has occurred despite the increase in typhoon intensity and ocean warming. Using the method proposed by Emanuel (in 2007), we show that the stronger negative contributions from typhoon frequency and duration, decrease to cancel the positive contribution from the increasing intensity, controlling the PDI. Examining the typhoons' environmental conditions, we find that although the ocean condition became more favourable (warming) in the recent decade, the atmospheric condition 'worsened' at the same time. The 'worsened' atmospheric condition appears to effectively overpower the 'better' ocean conditions to suppress PDI. This stronger negative contribution from reduced typhoon frequency over the increased intensity is also present under the global warming scenario, based on analysis of the simulated typhoon data from high-resolution modelling.

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.

Developmental and physiological challenges of octopus (Octopus vulgaris) early life stages under ocean warming.

PubMed

Repolho, Tiago; Baptista, Miguel; Pimentel, Marta S; Dionísio, Gisela; Trübenbach, Katja; Lopes, Vanessa M; Lopes, Ana Rita; Calado, Ricardo; Diniz, Mário; Rosa, Rui

2014-01-01

The ability to understand and predict the effects of ocean warming (under realistic scenarios) on marine biota is of paramount importance, especially at the most vulnerable early life stages. Here we investigated the impact of predicted environmental warming (+3 °C) on the development, metabolism, heat shock response and antioxidant defense mechanisms of the early stages of the common octopus, Octopus vulgaris. As expected, warming shortened embryonic developmental time by 13 days, from 38 days at 18 °C to 25 days at 21 °C. Concomitantly, survival decreased significantly (~29.9 %). Size at hatching varied inversely with temperature, and the percentage of smaller premature paralarvae increased drastically, from 0 % at 18 °C to 17.8 % at 21 °C. The metabolic costs of the transition from an encapsulated embryo to a free planktonic form increased significantly with warming, and HSP70 concentrations and glutathione S-transferase activity levels were significantly magnified from late embryonic to paralarval stages. Yet, despite the presence of effective antioxidant defense mechanisms, ocean warming led to an augmentation of malondialdehyde levels (an indicative of enhanced ROS action), a process considered to be one of the most frequent cellular injury mechanisms. Thus, the present study provides clues about how the magnitude and rate of ocean warming will challenge the buffering capacities of octopus embryos and hatchlings' physiology. The prediction and understanding of the biochemical and physiological responses to warmer temperatures (under realistic scenarios) is crucial for the management of highly commercial and ecologically important species, such as O. vulgaris.

Controls of Methane Dynamics and Emissions in an Arctic Warming Experiment

NASA Astrophysics Data System (ADS)

Nielsen, C. S.; Elberling, B.; Michelsen, A.; Strobel, B. W.; Wulff, K.; Banyasz, I.

2015-12-01

Climatic changes have resulted in increasing air temperatures across the Arctic. This may increase anaerobic decomposition of soil organic matter to methane (CH4) in wetlands and increase plant growth and thereby production of substrate. Little is known about how seasonal variations in dissolved CH4 in soil water, substrate availability, and the effect of warming affect arctic wetland dynamics of CH4 production and emission. In 2013 we established two experiments in a fen at Disko Island, W Greenland; one with year round warming by open-top chambers and removal of shrubs, and one with removal of the aerenchymatous sedge Carex aquatilis ssp. stans. Throughout the growing season 2014 we measured how the treatments affected CH4 emissions, dissolved CH4 in the soil water, and substrate availability. Ecosystem CH4 emissions peaked at August 5th 2014 (7.5 μmol m-2 h-1) without coinciding with time of highest concentrations of dissolved CH4 or acetate indicating a decoupling between production and emission of CH4. The peak in dissolved CH4 concentration, at ten cm depth (1368 ppm, September 18th 2014), followed the peak in concentration of acetate in the same depth (0.30 ppm, August 30th 2014) highlighting the importance of this substance as a substrate for methanogenesis. C. aquatilis ssp. stans accounted for 60% and 77% of the ecosystem CH4 emissions in areas of the fen with water table above and below soil surface showing the importance of the presence of this species to serve as a pipe for CH4 emission which is bypassing the upper soil zone and potential methane oxidation. Throughout the season, warming increased the air temperature at soil surface by on average 0.89°C and occasionally warming and shrub removal increased soil temperature in 2 and 5 cm depth, but there was no effect of the treatments on the CH4 emissions indicating that this wetland is quite resilient towards future climate change.

Comment on “Dissolved organic sulfur in the ocean: Biogeochemistry of a petagram inventory”

NASA Astrophysics Data System (ADS)

Dittmar, Thorsten; Stubbins, Aron; Ito, Takamitsu; Jones, Daniel C.

2017-05-01

Ksionzek et al. (Reports, 28 October 2016, p. 456) provide important data describing the distribution of dissolved organic sulfur (DOS) in the Atlantic Ocean. Here, we show that mixing between water masses is sufficient to explain the observed distribution of DOS, concluding that the turnover time of refractory DOS that Ksionzek et al. present cannot be deduced from their data.

SAR11 Bacteria: The Most Abundant Plankton in the Oceans.

PubMed

Giovannoni, Stephen J

2017-01-03

SAR11 is a group of small, carbon-oxidizing bacteria that reach a global estimated population size of 2.4×10 28 cells-approximately 25% of all plankton. They are found throughout the oceans but reach their largest numbers in stratified, oligotrophic gyres, which are an expanding habitat in the warming oceans. SAR11 likely had a Precambrian origin and, over geological time, evolved into the niche of harvesting labile, low-molecular-weight dissolved organic matter (DOM). SAR11 cells are minimal in size and complexity, a phenomenon known as streamlining that is thought to benefit them by lowering the material costs of replication and maximizing transport functions that are essential to competition at ultralow nutrient concentrations. One of the surprises in SAR11 metabolism is their ability to both oxidize and produce a variety of volatile organic compounds that can diffuse into the atmosphere. SAR11 cells divide slowly and lack many forms of regulation commonly used by bacterial cells to adjust to changing environmental conditions. As a result of genome reduction, they require an unusual range of nutrients, which leads to complex biochemical interactions with other plankton. The study of SAR11 is providing insight into the biogeochemistry of labile DOM and is affecting microbiology beyond marine science by providing a model for understanding the evolution and function of streamlined cells.

THE ROLE OF NITROGEN IN CHROMOPHORIC AND FLUORESCENT DISSOLVED ORGANIC MATTER FORMATION

EPA Science Inventory

Microbial and photochemical processes affect chromophoric dissolved organic matter (CDOM) dynamics in the ocean. Some evidence suggests that dissolved nitrogen plays a role in CDOM formation, although this has received little systematic attention in marine ecosystems. Coastal sea...

Distinct iron isotopic signatures and supply from marine sediment dissolution.

PubMed

Homoky, William B; John, Seth G; Conway, Tim M; Mills, Rachel A

2013-01-01

Oceanic iron inputs must be traced and quantified to learn how they affect primary productivity and climate. Chemical reduction of iron in continental margin sediments provides a substantial dissolved flux to the oceans, which is isotopically lighter than the crust, and so may be distinguished in seawater from other sources, such as wind-blown dust. However, heavy iron isotopes measured in seawater have recently led to the proposition of another source of dissolved iron from 'non-reductive' dissolution of continental margins. Here we present the first pore water iron isotope data from a passive-tectonic and semi-arid ocean margin (South Africa), which reveals a smaller and isotopically heavier flux of dissolved iron to seawater than active-tectonic and dysoxic continental margins. These data provide in situ evidence of non-reductive iron dissolution from a continental margin, and further show that geological and hydro-climatic factors may affect the amount and isotopic composition of iron entering the ocean.

Distinct iron isotopic signatures and supply from marine sediment dissolution

PubMed Central

Homoky, William B.; John, Seth G.; Conway, Tim M.; Mills, Rachel A.

2013-01-01

Oceanic iron inputs must be traced and quantified to learn how they affect primary productivity and climate. Chemical reduction of iron in continental margin sediments provides a substantial dissolved flux to the oceans, which is isotopically lighter than the crust, and so may be distinguished in seawater from other sources, such as wind-blown dust. However, heavy iron isotopes measured in seawater have recently led to the proposition of another source of dissolved iron from ‘non-reductive’ dissolution of continental margins. Here we present the first pore water iron isotope data from a passive-tectonic and semi-arid ocean margin (South Africa), which reveals a smaller and isotopically heavier flux of dissolved iron to seawater than active-tectonic and dysoxic continental margins. These data provide in situ evidence of non-reductive iron dissolution from a continental margin, and further show that geological and hydro-climatic factors may affect the amount and isotopic composition of iron entering the ocean. PMID:23868399

Deoxygenation alters bacterial diversity and community composition in the ocean's largest oxygen minimum zone.

PubMed

Beman, J Michael; Carolan, Molly T

2013-01-01

Oceanic oxygen minimum zones (OMZs) have a central role in biogeochemical cycles and are expanding as a consequence of climate change, yet how deoxygenation will affect the microbial communities that control these cycles is unclear. Here we sample across dissolved oxygen gradients in the oceans' largest OMZ and show that bacterial richness displays a unimodal pattern with decreasing dissolved oxygen, reaching maximum values on the edge of the OMZ and decreasing within it. Rare groups on the OMZ margin are abundant at lower dissolved oxygen concentrations, including sulphur-cycling Chromatiales, for which 16S rRNA was amplified from extracted RNA. Microbial species distribution models accurately replicate community patterns based on multivariate environmental data, demonstrate likely changes in distributions and diversity in the eastern tropical North Pacific Ocean, and highlight the sensitivity of key bacterial groups to deoxygenation. Through these mechanisms, OMZ expansion may alter microbial composition, competition, diversity and function, all of which have implications for biogeochemical cycling in OMZs.

The Impact of Ocean Data Assimilation on Seasonal-to-Interannual Forecasts: A Case Study of the 2006 El Nino Event

NASA Technical Reports Server (NTRS)

Yang, Shu-Chih; Rienecker, Michele; Keppenne, Christian

2010-01-01

This study investigates the impact of four different ocean analyses on coupled forecasts of the 2006 El Nino event. Forecasts initialized in June 2006 using ocean analyses from an assimilation that uses flow-dependent background error covariances are compared with those using static error covariances that are not flow dependent. The flow-dependent error covariances reflect the error structures related to the background ENSO instability and are generated by the coupled breeding method. The ocean analyses used in this study result from the assimilation of temperature and salinity, with the salinity data available from Argo floats. Of the analyses, the one using information from the coupled bred vectors (BV) replicates the observed equatorial long wave propagation best and exhibits more warming features leading to the 2006 El Nino event. The forecasts initialized from the BV-based analysis agree best with the observations in terms of the growth of the warm anomaly through two warming phases. This better performance is related to the impact of the salinity analysis on the state evolution in the equatorial thermocline. The early warming is traced back to salinity differences in the upper ocean of the equatorial central Pacific, while the second warming, corresponding to the mature phase, is associated with the effect of the salinity assimilation on the depth of the thermocline in the western equatorial Pacific. The series of forecast experiments conducted here show that the structure of the salinity in the initial conditions is important to the forecasts of the extension of the warm pool and the evolution of the 2006 El Ni o event.

Decadal trends in Red Sea maximum surface temperature.

PubMed

Chaidez, V; Dreano, D; Agusti, S; Duarte, C M; Hoteit, I

2017-08-15

Ocean warming is a major consequence of climate change, with the surface of the ocean having warmed by 0.11 °C decade -1 over the last 50 years and is estimated to continue to warm by an additional 0.6 - 2.0 °C before the end of the century 1 . However, there is considerable variability in the rates experienced by different ocean regions, so understanding regional trends is important to inform on possible stresses for marine organisms, particularly in warm seas where organisms may be already operating in the high end of their thermal tolerance. Although the Red Sea is one of the warmest ecosystems on earth, its historical warming trends and thermal evolution remain largely understudied. We characterized the Red Sea's thermal regimes at the basin scale, with a focus on the spatial distribution and changes over time of sea surface temperature maxima, using remotely sensed sea surface temperature data from 1982 - 2015. The overall rate of warming for the Red Sea is 0.17 ± 0.07 °C decade -1 , while the northern Red Sea is warming between 0.40 and 0.45 °C decade -1 , all exceeding the global rate. Our findings show that the Red Sea is fast warming, which may in the future challenge its organisms and communities.

Tropical Pacific Climate, Carbon, and Ocean Biogeochemical Response to the Central American Seaway in a GFDL Earth System Model

NASA Astrophysics Data System (ADS)

Sentman, L. T.; Dunne, J. P.; Stouffer, R. J.; Krasting, J. P.; Wittenberg, A. T.; Toggweiler, J. R.; Broccoli, A. J.

2017-12-01

To explore the tropical Pacific climate, carbon, and ocean biogeochemical response to the shoaling and closure of the Central American Seaway during the Pliocene (5.3-2.6 Ma), we performed a suite of sensitivity experiments using the Geophysical Fluid Dynamics Laboratory Earth System Model, GFDL-ESM2G, varying only the seaway widths and sill depths. These novel ESM simulations include near-final closure of the seaway with a very narrow, 1º grid cell wide opening. Net mass transport through the seaway into the Caribbean is 20.5-23.1 Sv with a deep seaway, but only 14.1 Sv for the wide/shallow seaway because of the inter-basin bi-directional horizontal mass transport. Seaway transport originates from the Antarctic Circumpolar Current in the Pacific and rejoins it in the South Atlantic, reducing the Indonesian Throughflow and transporting heat and salt southward into the South Atlantic, in contrast to present-day and previous seaway simulations. Tropical Pacific mean climate and interannual variability is sensitive to the seaway shoaling, with the largest response to the wider/deeper seaway. In the tropical Pacific, the top 300-m warms 0.4-0.8°C, the equatorial east-west sea surface temperature gradient increases, the north-south sea surface temperature asymmetry at 110°W decreases, thermocline deepens 5-11 m, and the east-west thermocline gradient increases. In the Niño-3 region, ENSO amplitude increases, skewed toward more cold (La Niña) events, El Niño and La Niña develops earlier ( 3 months), the annual cycle weakens and the semi-annual and interannual cycles strengthen from increased symmetry of the north-south sea surface temperature gradient, and atmospheric global teleconnections strengthen with the seaway. The increase in global ocean overturning with the seaway results in a younger average ocean ideal age, reduced dissolved inorganic carbon inventory and marine net primary productivity, and altered inter-basin patterns of surface sediment carbonate sedimentation and preservation in the Caribbean and eastern equatorial Pacific, consistent with paleoclimate proxy data. The air-sea CO2 flux into the ocean decreases with the narrow seaway, thereby increasing atmospheric pCO2 concentrations by at least 236 ppm compared with present-day, with implications for warming during the Pliocene.

Sea urchin development in a global change hotspot, potential for southerly migration of thermotolerant propagules

NASA Astrophysics Data System (ADS)

Byrne, M.; Selvakumaraswamy, P.; Ho, M. A.; Woolsey, E.; Nguyen, H. D.

2011-03-01

The distribution of the sea urchin Heliocidaris erythrogramma coincides with the southeast Australia global change hot spot where marine ecosystems are warming significantly due to changes in ocean circulation. To address questions on future vulnerabilities, the thermotolerance of the planktonic life phase of H. erythrogramma was investigated in the climate and regionally relevant setting of projected near-future (2100) ocean warming. Experimental treatments ranged from 18 to 26 °C, with 26 °C representing +3-4 °C above recent ambient sea-surface temperatures. Developmental success across all stages (gastrula, 24 h; larva, 72 h; juvenile, 120 h) decreased with increasing temperature. Development was tolerant to a +1-2 °C increase above ambient, but significant deleterious effects were evident at +3-4 °C. However, larvae that developed through the early bottleneck of normal development at 26 °C metamorphosed successfully. The inverse relationship between temperature and planktonic larval duration (PLD) was seen in a 25% decrease in the PLD of H. erythrogramma at 24 and 26 oC. Ocean warming may be advantageous to a subset of larvae through early settlement and reduction of the vulnerable planktonic period. This positive effect of temperature may help buffer the negative effects of ocean warming. In parallel studies with progeny derived from northern (Coffs Harbour) and southern (Sydney) H. erythrogramma, northern embryos had significantly higher thermotolerance. This provides the possibility that H. erythrogramma populations might keep up with a warming world through poleward migration of thermotolerant propagules, facilitated by the strong southward flow of the East Australian Current. It is uncertain whether H. erythrogramma populations at the northern range of this species, with no source of immigrants, will have the capacity to persist in a warm ocean. Due to its extensive latitudinal distribution, its potential developmental thermotolerance and independence of its lecithotrophic larvae from exogenous food and the need to make a functional skeleton, H. erythrogramma may be particularly robust to ocean change.

Quality of water, Quillayute River basin, Washington

USGS Publications Warehouse

Fretwell, M.O.

1984-01-01

Groundwater in Quillayute River basin is generally of the calcium bicarbonate type, although water from some wells is affected by seawater intrusion and is predominantly of the sodium chloride type. The water is generally of excellent quality for most uses. River-water quality was generally excellent, as evaluated against Washington State water-use and water-quality criteria. Fecal coliform concentrations in all major tributaries met State water-quality criteria; water temperatures occasionally exceeded criteria maximum during periods of warm weather and low streamflow. Nutrient concentrations were generally low to very low. The four largest lakes in the basin were temperature-stratified in summer and one had an algal bloom. The Quillayute estuary had salt-wedge mixing characteristics; pollutants entering the salt wedge tended to spread to the toe of the wedge. Upwelling ocean water was the major cause of the low dissolved-oxygen concentrations observed in the estuary; ammonia concentrations in the estuary, however, were increased by the upwelling ocean waters. As in the rivers, total-coliform bacteria concentrations in the estuary were greater than fecal-coliform concentrations, indicating that many of the bacteria were of nonfecal origin and probably originated from soils. (USGS)

Sedimentary particulate iron: the missing micronutrients ?

NASA Astrophysics Data System (ADS)

Beghoura, Houda; Gorgues, Thomas; Aumont, Olivier; Planquette, Hélène

2017-04-01

Iron is known to regulate the marine primary production and to impact the structure of ecosystems. Indeed, iron is the limiting nutrient for the phytoplankton growth over about 30% of the global ocean. However, the nature of the external sources of iron to the ocean and their quantification remain uncertain. Among these external sources, the sediment sources have been recently shown to be underestimated. Besides, since the operationally defined dissolved iron (which is the sum of truly dissolved and colloidal iron) was traditionally assumed to be the only form available to phytoplankton and bacteria, most studies have focused on the supply of dissolved iron to the ocean, the role of the particulate fraction of iron being largely ignored. This traditional view has been recently challenged, noticeably, by observational evidences. Indeed, in situ observations have shown that large amounts of particulate iron are being resuspended from continental margins to the open ocean thanks to fine grained particles' transport over long distances. A fraction of this particulate iron may dissolve and thereby fuel the phytoplankton growth. The magnitude of the sedimentary sources of particulate iron and the releasing processes affecting this iron phase are not yet well constrained or quantified. As a consequence, the role of sedimentary particulate iron in the biogeochemical cycles is still unclear despite its potentially major widespread importance. Here, we propose a modeling exercise to assess the first order impacts of this newly considered particulate sedimentary iron on global ocean biogeochemistry. We designed global experiments with a coupled dynamical-biogeochemical model (NEMO-PISCES). First, a control simulation that includes only a sediment source of iron in the dissolved phase has been run. Then, this control simulation is being compared with simulations, in which we include a sediment source of iron in both phases (dissolved as well as particulate). Those latter simulations have been performed using a range of particulate iron dissolution rates (from published studies and laboratory experiment results) that will permit to test the sensitivity of the biogeochemical response.

Marine nekton off Oregon and the 1997 98 El Nino

NASA Astrophysics Data System (ADS)

Pearcy, W. G.

2002-09-01

Several species of migratory, warm-water, oceanic fishes invaded Oregon waters during the summer of 1997. Also, the jumbo squid ( Dosidicus gigas), common in the eastern tropical Pacific, was reported for the first time in 1997 and was caught in large numbers. The occurrence of these oceanic nekton was associated with inshore advection of anomalously warm water. During 1998, after arrival of the main El Niño signal, some warm-water coastal fishes appeared off Oregon. However, unlike observations off California, fewer species of warm-water coastal fishes were noted during the 1997-98 El Niño than during the 1982-83 El Niño.

Decadal-scale variation in diet forecasts persistently poor breeding under ocean warming in a tropical seabird

PubMed Central

Tompkins, Emily M.; Townsend, Howard M.

2017-01-01

Climate change effects on population dynamics of natural populations are well documented at higher latitudes, where relatively rapid warming illuminates cause-effect relationships, but not in the tropics and especially the marine tropics, where warming has been slow. Here we forecast the indirect effect of ocean warming on a top predator, Nazca boobies in the equatorial Galápagos Islands, where rising water temperature is expected to exceed the upper thermal tolerance of a key prey item in the future, severely reducing its availability within the boobies’ foraging envelope. From 1983 to 1997 boobies ate mostly sardines, a densely aggregated, highly nutritious food. From 1997 until the present, flying fish, a lower quality food, replaced sardines. Breeding success under the poor diet fell dramatically, causing the population growth rate to fall below 1, indicating a shrinking population. Population growth may not recover: rapid future warming is predicted around Galápagos, usually exceeding the upper lethal temperature and maximum spawning temperature of sardines within 100 years, displacing them permanently from the boobies’ island-constrained foraging range. This provides rare evidence of the effect of ocean warming on a tropical marine vertebrate. PMID:28832597

Decadal-scale variation in diet forecasts persistently poor breeding under ocean warming in a tropical seabird.

PubMed

Tompkins, Emily M; Townsend, Howard M; Anderson, David J

2017-01-01

Climate change effects on population dynamics of natural populations are well documented at higher latitudes, where relatively rapid warming illuminates cause-effect relationships, but not in the tropics and especially the marine tropics, where warming has been slow. Here we forecast the indirect effect of ocean warming on a top predator, Nazca boobies in the equatorial Galápagos Islands, where rising water temperature is expected to exceed the upper thermal tolerance of a key prey item in the future, severely reducing its availability within the boobies' foraging envelope. From 1983 to 1997 boobies ate mostly sardines, a densely aggregated, highly nutritious food. From 1997 until the present, flying fish, a lower quality food, replaced sardines. Breeding success under the poor diet fell dramatically, causing the population growth rate to fall below 1, indicating a shrinking population. Population growth may not recover: rapid future warming is predicted around Galápagos, usually exceeding the upper lethal temperature and maximum spawning temperature of sardines within 100 years, displacing them permanently from the boobies' island-constrained foraging range. This provides rare evidence of the effect of ocean warming on a tropical marine vertebrate.

Along - Strike Analysis of Contemporary Ocean Temperature Change on the Cascadia Margin and Implications to Upper Slope Hydrate Instability

NASA Astrophysics Data System (ADS)

Phrampus, B.; Harris, R. N.; Trehu, A. M.; Embley, R. W.; Merle, S. G.

2017-12-01

Gas hydrates are found globally on continental margins and due to the large amount of sequestered carbon in hydrate reservoirs, whether these deposits are dynamic or stable has significant implications for slope stability, ocean/atmosphere carbon budget, and deep-water energy exploration. Recent studies indicate that upper slope hydrate degradation may be relatively widespread on passive margins due to recent ocean temperature warming between 0.012 and 0.033 °C/yr (e.g. Svalbard, North Alaska, and US Atlantic margin). However, the potential and breadth of warming induced hydrate instability remains contentious based on multiple observations including: 1) seep locations not consistent with locations of hydrate dissociation, 2) a lack of hydrate in regions of warming, and 3) evidence for long-lived seepage in regions associated with contemporary warming-induced hydrate dissociation. At the Cascadia margin, a recent study suggests that contemporary warming of intermediate water intersects the hydrate stability zone leading to hydrate dissociation that feeds upper slope seeps. Here, we provide a systematic analysis of along-strike variations in hydrate distribution along the Cascadia margin combined with a multivariable regression of ocean temperatures to characterize the potential of upper slope hydrate instability. Preliminary seep locations reveal upper slope seeps and observed regions of hydrate are correlated spatially between 42.5 and 48.0 °N, outside this region there is a dearth of identified upper slope hydrate and seeps. Between 44.5 and 48.0 °N a contemporary warming trend is as large as 0.006 °C/yr and is collocated with upper slope hydrate and gas seepage. This warming rate is relatively small, 2-5x smaller than warming trends identified in the Arctic where temperature induced hydrate instability remains uncertain. Additionally, we identify a region between 42.5 and 44.5 °N with collocated upper slope seepage and hydrate but no evidence of ocean warming, suggesting upper slope seepage is not driven by temperature induced hydrate instability, but maybe driven by tectonic uplift. These results highlight the absence of temperature driven seepage and slope instability on the Cascadia margin and deemphasize the impact of lower latitude warming on global hydrate dynamics and carbon budget.

Lead isotope exchange between dissolved and fluvial particulate matter: a laboratory study from the Johor River estuary

PubMed Central

Chen, Mengli; Lee, Jong-Mi; Nurhati, Intan; Zurbrick, Cheryl; Switzer, Adam D.; Carrasco, Gonzalo

2016-01-01

Atmospheric aerosols are the dominant source of Pb to the modern marine environment, and as a result, in most regions of the ocean the Pb isotopic composition of dissolved Pb in the surface ocean (and in corals) matches that of the regional aerosols. In the Singapore Strait, however, there is a large offset between seawater dissolved and coral Pb isotopes and that of the regional aerosols. We propose that this difference results from isotope exchange between dissolved Pb supplied by anthropogenic aerosol deposition and adsorbed natural crustal Pb on weathered particles delivered to the ocean by coastal rivers. To investigate this issue, Pb isotope exchange was assessed through a closed-system exchange experiment using estuarine waters collected at the Johor River mouth (which discharges to the Singapore Strait). During the experiment, a known amount of dissolved Pb with the isotopic composition of NBS-981 (206Pb/207Pb = 1.093) was spiked into the unfiltered Johor water (dissolved and particulate 206Pb/207Pb = 1.199) and the changing isotopic composition of the dissolved Pb was monitored. The mixing ratio of the estuarine and spike Pb should have produced a dissolved 206Pb/207Pb isotopic composition of 1.161, but within a week, the 206Pb/207Pb in the water increased to 1.190 and continued to increase to 1.197 during the next two months without significant changes of the dissolved Pb concentration. The kinetics of isotope exchange was assessed using a simple Kd model, which assumes multiple sub-reservoirs within the particulate matter with different exchange rate constants. The Kd model reproduced 56% of the observed Pb isotope variance. Both the closed-system experiment and field measurements imply that isotope exchange can be an important mechanism for controlling Pb and Pb isotopes in coastal waters. A similar process may occur for other trace elements. This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’. PMID:29035266

Indian Ocean warming modulates Pacific climate change.

PubMed

Luo, Jing-Jia; Sasaki, Wataru; Masumoto, Yukio

2012-11-13

It has been widely believed that the tropical Pacific trade winds weakened in the last century and would further decrease under a warmer climate in the 21st century. Recent high-quality observations, however, suggest that the tropical Pacific winds have actually strengthened in the past two decades. Precise causes of the recent Pacific climate shift are uncertain. Here we explore how the enhanced tropical Indian Ocean warming in recent decades favors stronger trade winds in the western Pacific via the atmosphere and hence is likely to have contributed to the La Niña-like state (with enhanced east-west Walker circulation) through the Pacific ocean-atmosphere interactions. Further analysis, based on 163 climate model simulations with centennial historical and projected external radiative forcing, suggests that the Indian Ocean warming relative to the Pacific's could play an important role in modulating the Pacific climate changes in the 20th and 21st centuries.

Seahorses under a changing ocean: the impact of warming and acidification on the behaviour and physiology of a poor-swimming bony-armoured fish

PubMed Central

Baptista, Miguel; Santos, Catarina; Aurélio, Maria L; Pimentel, Marta; Pegado, Maria Rita; Paula, José Ricardo; Calado, Ricardo; Repolho, Tiago; Rosa, Rui

2015-01-01

Abstract Seahorses are currently facing great challenges in the wild, including habitat degradation and overexploitation, and how they will endure additional stress from rapid climate change has yet to be determined. Unlike most fishes, the poor swimming skills of seahorses, along with the ecological and biological constraints of their unique lifestyle, place great weight on their physiological ability to cope with climate changes. In the present study, we evaluate the effects of ocean warming (+4°C) and acidification (ΔpH = −0.5 units) on the physiological and behavioural ecology of adult temperate seahorses, Hippocampus guttulatus. Adult seahorses were found to be relatively well prepared to face future changes in ocean temperature, but not the combined effect of warming and acidification. Seahorse metabolism increased normally with warming, and behavioural and feeding responses were not significantly affected. However, during hypercapnia the seahorses exhibited signs of lethargy (i.e. reduced activity levels) combined with a reduction of feeding and ventilation rates. Nonetheless, metabolic rates were not significantly affected. Future ocean changes, particularly ocean acidification, may further threaten seahorse conservation, turning these charismatic fishes into important flagship species for global climate change issues. PMID:27293694

Dissolved Oxygen Sensor in Animal-Borne Instruments: An Innovation for Monitoring the Health of Oceans and Investigating the Functioning of Marine Ecosystems

PubMed Central

Bailleul, Frederic; Vacquie-Garcia, Jade; Guinet, Christophe

2015-01-01

The current decline in dissolved oxygen concentration within the oceans is a sensitive indicator of the effect of climate change on marine environment. However the impact of its declining on marine life and ecosystems’ health is still quite unclear because of the difficulty in obtaining in situ data, especially in remote areas, like the Southern Ocean (SO). Southern elephant seals (Mirounga leonina) proved to be a relevant alternative to the traditional oceanographic platforms to measure physical and biogeochemical structure of oceanic regions rarely observed. In this study, we use a new stage of development in biologging technology to draw a picture of dissolved oxygen concentration in the SO. We present the first results obtained from a dissolved oxygen sensor added to Argos CTD-SRDL tags and deployed on 5 female elephant seals at Kerguelen. From October 2010 and October 2011, 742 oxygen profiles associated with temperature and salinity measurements were recorded. Whether a part of the data must be considered cautiously, especially because of offsets and temporal drifts of the sensors, the range of values recorded was consistent with a concomitant survey conducted from a research vessel (Keops-2 project). Once again, elephant seals reinforced the relationship between marine ecology and oceanography, delivering essential information about the water masses properties and the biological status of the Southern Ocean. But more than the presentation of a new stage of development in animal-borne instrumentation, this pilot study opens a new field of investigation in marine ecology and could be enlarged in a near future to other key marine predators, especially large fish species like swordfish, tuna or sharks, for which dissolved oxygen is expected to play a crucial role in distribution and behaviour. PMID:26200780

Dissolved Oxygen Sensor in Animal-Borne Instruments: An Innovation for Monitoring the Health of Oceans and Investigating the Functioning of Marine Ecosystems.

PubMed

Bailleul, Frederic; Vacquie-Garcia, Jade; Guinet, Christophe

2015-01-01

The current decline in dissolved oxygen concentration within the oceans is a sensitive indicator of the effect of climate change on marine environment. However the impact of its declining on marine life and ecosystems' health is still quite unclear because of the difficulty in obtaining in situ data, especially in remote areas, like the Southern Ocean (SO). Southern elephant seals (Mirounga leonina) proved to be a relevant alternative to the traditional oceanographic platforms to measure physical and biogeochemical structure of oceanic regions rarely observed. In this study, we use a new stage of development in biologging technology to draw a picture of dissolved oxygen concentration in the SO. We present the first results obtained from a dissolved oxygen sensor added to Argos CTD-SRDL tags and deployed on 5 female elephant seals at Kerguelen. From October 2010 and October 2011, 742 oxygen profiles associated with temperature and salinity measurements were recorded. Whether a part of the data must be considered cautiously, especially because of offsets and temporal drifts of the sensors, the range of values recorded was consistent with a concomitant survey conducted from a research vessel (Keops-2 project). Once again, elephant seals reinforced the relationship between marine ecology and oceanography, delivering essential information about the water masses properties and the biological status of the Southern Ocean. But more than the presentation of a new stage of development in animal-borne instrumentation, this pilot study opens a new field of investigation in marine ecology and could be enlarged in a near future to other key marine predators, especially large fish species like swordfish, tuna or sharks, for which dissolved oxygen is expected to play a crucial role in distribution and behaviour.

A westward extension of the warm pool leads to a westward extension of the Walker circulation, drying eastern Africa

USGS Publications Warehouse

Funk, Christopher C.; Williams, A. Park

2011-01-01

Observations and simulations link anthropogenic greenhouse and aerosol emissions with rapidly increasing Indian Ocean sea surface temperatures (SSTs). Over the past 60 years, the Indian Ocean warmed two to three times faster than the central tropical Pacific, extending the tropical warm pool to the west by ~40° longitude (>4,000 km). This propensity toward rapid warming in the Indian Ocean has been the dominant mode of interannual variability among SSTs throughout the tropical Indian and Pacific Oceans (55°E–140°W) since at least 1948, explaining more variance than anomalies associated with the El Niño-Southern Oscillation (ENSO). In the atmosphere, the primary mode of variability has been a corresponding trend toward greatly increased convection and precipitation over the tropical Indian Ocean. The temperature and rainfall increases in this region have produced a westward extension of the western, ascending branch of the atmospheric Walker circulation. Diabatic heating due to increased mid-tropospheric water vapor condensation elicits a westward atmospheric response that sends an easterly flow of dry air aloft toward eastern Africa. In recent decades (1980–2009), this response has suppressed convection over tropical eastern Africa, decreasing precipitation during the ‘long-rains’ season of March–June. This trend toward drought contrasts with projections of increased rainfall in eastern Africa and more ‘El Niño-like’ conditions globally by the Intergovernmental Panel on Climate Change. Increased Indian Ocean SSTs appear likely to continue to strongly modulate the Warm Pool circulation, reducing precipitation in eastern Africa, regardless of whether the projected trend in ENSO is realized. These results have important food security implications, informing agricultural development, environmental conservation, and water resource planning.

A westward extension of the warm pool leads to a westward extension of the Walker circulation, drying eastern Africa

USGS Publications Warehouse

Williams, A. Park; Funk, Christopher C.

2011-01-01

Observations and simulations link anthropogenic greenhouse and aerosol emissions with rapidly increasing Indian Ocean sea surface temperatures (SSTs). Over the past 60 years, the Indian Ocean warmed two to three times faster than the central tropical Pacific, extending the tropical warm pool to the west by ~40° longitude (>4,000 km). This propensity toward rapid warming in the Indian Ocean has been the dominant mode of interannual variability among SSTs throughout the tropical Indian and Pacific Oceans (55°E–140°W) since at least 1948, explaining more variance than anomalies associated with the El Niño-Southern Oscillation (ENSO). In the atmosphere, the primary mode of variability has been a corresponding trend toward greatly increased convection and precipitation over the tropical Indian Ocean. The temperature and rainfall increases in this region have produced a westward extension of the western, ascending branch of the atmospheric Walker circulation. Diabatic heating due to increased mid-tropospheric water vapor condensation elicits a westward atmospheric response that sends an easterly flow of dry air aloft toward eastern Africa. In recent decades (1980–2009), this response has suppressed convection over tropical eastern Africa, decreasing precipitation during the ‘long-rains’ season of March–June. This trend toward drought contrasts with projections of increased rainfall in eastern Africa and more ‘El Niño-like’ conditions globally by the Intergovernmental Panel on Climate Change. Increased Indian Ocean SSTs appear likely to continue to strongly modulate the Warm Pool circulation, reducing precipitation in eastern Africa, regardless of whether the projected trend in ENSO is realized. These results have important food security implications, informing agricultural development, environmental conservation, and water resource planning.

Global Sea Surface Temperature and Ecosystem Change Across the Mid-Miocene Climatic Optimum

NASA Astrophysics Data System (ADS)

Veenstra, T. J. T.; Bakker, V. B.; Sangiorgi, F.; Peterse, F.; Schouten, S.; Sluijs, A.

2016-12-01

Even though the term Mid-Miocene Climatic Optimum (MMCO; ca. 17 to 14 Ma) has been widely used in the literature since the early 1990's, almost no early-middle Miocene sea surface temperature (SST) proxy records have been published that support climate warming across its onset. Benthic (and diagenetically altered planktic) foram δ18O records show a decrease, suggesting (deep) ocean warming and/or Antarctic ice sheet melting. However, reliable absolute SST proxy records are absent from the tropics and very scarce in temperate and polar regions. This leaves the question if the warmth of the MMCO was truly global and how its onset relates to the widely recorded positive (Monterey) carbon isotope excursion and volcanism. Finally, it remains uncertain how marine ecosystems responded to this hypothesized warming. We present organic biomarker SST proxy records (Uk'37 and TEX86) spanning the MMCO for several locations in the Atlantic and Pacific Ocean along a pole-to-pole transect, including Ocean Drilling Program Site 959 in the eastern Tropical Atlantic, ODP Site 643 in the Norwegian Sea, ODP Site 1007 on the Great Bahama Bank and Integrated Ocean Drilling Program Site U1352 off New Zealand. Additionally, we use marine palynology (mostly dinoflagellate cysts) to assess ecosystem change at these locations. The resulting spatial reconstruction of SST change shows that Middle Miocene warming was global. Nevertheless, the records also show distinct regional variability, including relatively large warming in the Norwegian Sea and a damped signal in the southern hemisphere, suggesting pronounced changes in ocean circulation. The onset of the MMCO was marked by prominent changes in ecological and depositional setting at the studied sites, likely also related to ocean circulation changes.

Eocene climate and Arctic paleobathymetry: A tectonic sensitivity study using GISS ModelE-R

NASA Astrophysics Data System (ADS)

Roberts, C. D.; Legrande, A. N.; Tripati, A. K.

2009-12-01

The early Paleogene (65-45 million years ago, Ma) was a ‘greenhouse’ interval with global temperatures warmer than any other time in the last 65 Ma. This period was characterized by high levels of CO2, warm high-latitudes, warm surface-and-deep oceans, and an intensified hydrological cycle. Sediments from the Arctic suggest that the Eocene surface Arctic Ocean was warm, brackish, and episodically enabled the freshwater fern Azolla to bloom. The precise mechanisms responsible for the development of these conditions remain uncertain. We present equilibrium climate conditions derived from a fully-coupled, water-isotope enabled, general circulation model (GISS ModelE-R) configured for the early Eocene. We also present model-data comparison plots for key climatic variables (SST and δ18O) and analyses of the leading modes of variability in the tropical Pacific and North Atlantic regions. Our tectonic sensitivity study indicates that Northern Hemisphere climate would have been very sensitive to the degree of oceanic exchange through the seaways connecting the Arctic to the Atlantic and Tethys. By restricting these seaways, we simulate freshening of the surface Arctic Ocean to ~6 psu and warming of sea-surface temperatures by 2°C in the North Atlantic and 5-10°C in the Labrador Sea. Our results may help explain the occurrence of low-salinity tolerant taxa in the Arctic Ocean during the Eocene and provide a mechanism for enhanced warmth in the north western Atlantic. We also suggest that the formation of a volcanic land-bridge between Greenland and Europe could have caused increased ocean convection and warming of intermediate waters in the Atlantic. If true, this result is consistent with the theory that bathymetry changes may have caused thermal destabilisation of methane clathrates in the Atlantic.

Widespread gas hydrate instability on the upper U.S. Beaufort margin

USGS Publications Warehouse

Phrampus, Benjamin J.; Hornbach, Matthew J.; Ruppel, Carolyn D.; Hart, Patrick E.

2014-01-01

The most climate-sensitive methane hydrate deposits occur on upper continental slopes at depths close to the minimum pressure and maximum temperature for gas hydrate stability. At these water depths, small perturbations in intermediate ocean water temperatures can lead to gas hydrate dissociation. The Arctic Ocean has experienced more dramatic warming than lower latitudes, but observational data have not been used to study the interplay between upper slope gas hydrates and warming ocean waters. Here we use (a) legacy seismic data that constrain upper slope gas hydrate distributions on the U.S. Beaufort Sea margin, (b) Alaskan North Slope borehole data and offshore thermal gradients determined from gas hydrate stability zone thickness to infer regional heat flow, and (c) 1088 direct measurements to characterize multidecadal intermediate ocean warming in the U.S. Beaufort Sea. Combining these data with a three-dimensional thermal model shows that the observed gas hydrate stability zone is too deep by 100 to 250 m. The disparity can be partially attributed to several processes, but the most important is the reequilibration (thinning) of gas hydrates in response to significant (~0.5°C at 2σ certainty) warming of intermediate ocean temperatures over 39 years in a depth range that brackets the upper slope extent of the gas hydrate stability zone. Even in the absence of additional ocean warming, 0.44 to 2.2 Gt of methane could be released from reequilibrating gas hydrates into the sediments underlying an area of ~5–7.5 × 103 km2 on the U.S. Beaufort Sea upper slope during the next century.

Amplified Arctic warming by phytoplankton under greenhouse warming

PubMed Central

Park, Jong-Yeon; Kug, Jong-Seong; Bader, Jürgen; Rolph, Rebecca; Kwon, Minho

2015-01-01

Phytoplankton have attracted increasing attention in climate science due to their impacts on climate systems. A new generation of climate models can now provide estimates of future climate change, considering the biological feedbacks through the development of the coupled physical–ecosystem model. Here we present the geophysical impact of phytoplankton, which is often overlooked in future climate projections. A suite of future warming experiments using a fully coupled ocean−atmosphere model that interacts with a marine ecosystem model reveals that the future phytoplankton change influenced by greenhouse warming can amplify Arctic surface warming considerably. The warming-induced sea ice melting and the corresponding increase in shortwave radiation penetrating into the ocean both result in a longer phytoplankton growing season in the Arctic. In turn, the increase in Arctic phytoplankton warms the ocean surface layer through direct biological heating, triggering additional positive feedbacks in the Arctic, and consequently intensifying the Arctic warming further. Our results establish the presence of marine phytoplankton as an important potential driver of the future Arctic climate changes. PMID:25902494

Sclerosponges: a key to understanding the influence of global warming on ocean thermocline and mixed layer variability..an example from the Caribbean

NASA Astrophysics Data System (ADS)

Winter, A.; Sherman, C.; Appeldoorn, R.; Swart, P. K.; Hamann, Y.; Eisenhauer, A.

2009-12-01

We present preliminary oxygen isotope and XRF core-scanner data taken from U/Th dated sclerosponges from a depth transect (0-100m) off southwest Puerto Rico. Combining information from trace elements and oxygen isotopes can give data about temperature and salinity of the water column as a function of depth and time. The sclerosponges were obtained from different depths off the southwest shore of Puerto Rico by a five-member team members consisting of faculty, staff and graduate students of the University of Puerto Rico’s NOAA Coral Reef Ecosystems Studies. They use the latest mixed-gas/rebreather technology capable of reaching depths to 100m. The rate of heat storage in the ocean is one of the most important numbers that is needed to understand the importance of anthropogenic influence on decadal climate change. A number of studies have detected that a warming signal has penetrated into the world's ocean and there is little doubt that there is a human-induced signal in this environment. Nevertheless, the rate and extend of the signal is poorly understood. Most of the observational data used to determine the extent of ocean warming comes from the surface of the oceans and even this dataset has limitations because of possible temperature biases associated with differing instrumentation. Data below the ocean surface is much sparser. The fact that little data exists from ocean depth imposes severe limitation on the assessment of the long-term temperature variability. One way to improve our understanding of ocean warming is to use paleo-archives which can document the temperature record of the oceans beyond that which is available from instruments. Sclerosponges are widely spread throughout the world ocean to a depth of 200m. Because sclerosponges do not depend on photosynthesis they can live in deep water. Ceraptorella nicholsoni is present in tropical reef caves and at the deeper slopes of the Caribbean and Bahamas. It grows very slowly at rates of 0.1-0.4 mm/y. Their lateral and vertical coverage is important because they can give information about the expansion of the mixed layer and vertical movement of the thermocline as a result of warming in differing ocean basins.

Hazards of decreasing marine oxygen: the near-term and millennial-scale benefits of meeting the Paris climate targets

NASA Astrophysics Data System (ADS)

Battaglia, Gianna; Joos, Fortunat

2018-06-01

Ocean deoxygenation is recognized as key ecosystem stressor of the future ocean and associated climate-related ocean risks are relevant for current policy decisions. In particular, benefits of reaching the ambitious 1.5 °C warming target mentioned by the Paris Agreement compared to higher temperature targets are of high interest. Here, we model oceanic oxygen, warming and their compound hazard in terms of metabolic conditions on multi-millennial timescales for a range of equilibrium temperature targets. Scenarios where radiative forcing is stabilized by 2300 are used in ensemble simulations with the Bern3D Earth System Model of Intermediate Complexity. Transiently, the global mean ocean oxygen concentration decreases by a few percent under low forcing and by 40 % under high forcing. Deoxygenation peaks about a thousand years after stabilization of radiative forcing and new steady-state conditions are established after AD 8000 in our model. Hypoxic waters expand over the next millennium and recovery is slow and remains incomplete under high forcing. Largest transient decreases in oxygen are projected for the deep sea. Distinct and near-linear relationships between the equilibrium temperature response and marine O2 loss emerge. These point to the effectiveness of the Paris climate target in reducing marine hazards and risks. Mitigation measures are projected to reduce peak decreases in oceanic oxygen inventory by 4.4 % °C-1 of avoided equilibrium warming. In the upper ocean, the decline of a metabolic index, quantified by the ratio of O2 supply to an organism's O2 demand, is reduced by 6.2 % °C-1 of avoided equilibrium warming. Definitions of peak hypoxia demonstrate strong sensitivity to additional warming. Volumes of water with less than 50 mmol O2 m-3, for instance, increase between 36 % and 76 % °C-1 of equilibrium temperature response. Our results show that millennial-scale responses should be considered in assessments of ocean deoxygenation and associated climate-related ocean risks. Peak hazards occur long after stabilization of radiative forcing and new steady-state conditions establish after AD 8000.

A model of the methane cycle, permafrost, and hydrology of the Siberian continental margin

NASA Astrophysics Data System (ADS)

Archer, D.

2015-05-01

A two-dimensional model of a sediment column, with Darcy fluid flow, biological and thermal methane production, and permafrost and methane hydrate formation, is subjected to glacial-interglacial cycles in sea level, alternately exposing the continental shelf to the cold atmosphere during glacial times and immersing it in the ocean in interglacial times. The glacial cycles are followed by a "long-tail" 100 kyr warming due to fossil fuel combustion. The salinity of the sediment column in the interior of the shelf can be decreased by hydrological forcing to depths well below sea level when the sediment is exposed to the atmosphere. There is no analogous advective seawater-injecting mechanism upon resubmergence, only slower diffusive mechanisms. This hydrological ratchet is consistent with the existence of freshwater beneath the sea floor on continental shelves around the world, left over from the last glacial period. The salt content of the sediment column affects the relative proportions of the solid and fluid H2O-containing phases, but in the permafrost zone the salinity in the pore fluid brine is a function of temperature only, controlled by equilibrium with ice. Ice can tolerate a higher salinity in the pore fluid than methane hydrate can at low pressure and temperature, excluding methane hydrate from thermodynamic stability in the permafrost zone. The implication is that any methane hydrate existing today will be insulated from anthropogenic climate change by hundreds of meters of sediment, resulting in a response time of thousands of years. The strongest impact of the glacial-interglacial cycles on the atmospheric methane flux is due to bubbles dissolving in the ocean when sea level is high. When sea level is low and the sediment surface is exposed to the atmosphere, the atmospheric flux is sensitive to whether permafrost inhibits bubble migration in the model. If it does, the atmospheric flux is highest during the glaciating, sea level regression (soil-freezing) part of the cycle rather than during deglacial transgression (warming and thawing). The atmospheric flux response to a warming climate is small, relative to the rest of the methane sources to the atmosphere in the global budget, because of the ongoing flooding of the continental shelf. The increased methane flux due to ocean warming could be completely counteracted by a sea level rise of tens of meters on millennial timescales due to the loss of ice sheets, decreasing the efficiency of bubble transit through the water column. The model results give no indication of a mechanism by which methane emissions from the Siberian continental shelf could have a significant impact on the near-term evolution of Earth's climate, but on millennial timescales the release of carbon from hydrate and permafrost could contribute significantly to the fossil fuel carbon burden in the atmosphere-ocean-terrestrial carbon cycle.

Competing influences of greenhouse warming and aerosols on Asian summer monsoon circulation and rainfall

NASA Astrophysics Data System (ADS)

Lau, William Ka-Ming; Kim, Kyu-Myong

2017-05-01

In this paper, we have compared and contrasted competing influences of greenhouse gases (GHG) warming and aerosol forcing on Asian summer monsoon circulation and rainfall based on CMIP5 historical simulations. Under GHG-only forcing, the land warms much faster than the ocean, magnifying the pre-industrial climatological land-ocean thermal contrast and hemispheric asymmetry, i.e., warmer northern than southern hemisphere. A steady increasing warm-ocean-warmer-land (WOWL) trend has been in effect since the 1950's substantially increasing moisture transport from adjacent oceans, and enhancing rainfall over the Asian monsoon regions. However, under GHG warming, increased atmospheric stability due to strong reduction in mid-tropospheric and near surface relative humidity coupled to an expanding subsidence areas, associated with the Deep Tropical Squeeze (DTS, Lau and Kim, 2015b) strongly suppress monsoon convection and rainfall over subtropical and extratropical land, leading to a weakening of the Asian monsoon meridional circulation. Increased anthropogenic aerosol emission strongly masks WOWL, by over 60% over the northern hemisphere, negating to a large extent the rainfall increase due to GHG warming, and leading to a further weakening of the monsoon circulation, through increasing atmospheric stability, most likely associated with aerosol solar dimming and semi-direct effects. Overall, we find that GHG exerts stronger positive rainfall sensitivity, but less negative circulation sensitivity in SASM compared to EASM. In contrast, aerosols exert stronger negative impacts on rainfall, but less negative impacts on circulation in EASM compared to SASM.

Human perturbation increases the fluxes of dissolved molybdenum from land to ocean - The case of the Jiulong River in China.

PubMed

Wang, Deli; Lu, Shuimiao; Chen, Nengwang; Dai, Minhan; Guéguen, Céline

2018-03-15

Rivers contribute a substantial amount of trace metals including molybdenum (Mo) into the oceans. The driving forces controlling the riverine fluxes of dissolved metals still remain not fully understood. Our study then investigated the spatial variations of dissolved metals including molybdenum in a typically human perturbed river, the Jiulong River (JR), China. The aim of the study is to elucidate the relevance of anthropogenic perturbation on the fluxes of dissolved metals such as molybdenum from land to ocean. Our study shows a large spatial variability of dissolved Mo across tributary to main stream of the JR. Particularly, dissolved Mo was generally low (average: 5 ± 1 nM) in the "pristine" JR headwaters, and elevated (19 ± 6 nM) along the lower river continuum. Sporadically high levels of dissolved Mo occurred in the upper North River (77 ± 19 nM), as a result of mining activities locally. Significant correlations of dissolved Mo with total dissolved solids (TDS) and dissolved strontium (Sr) were observed in the whole JR (Mo = 1.4* TDS -1.7, R 2  = 0.86, p < .01; Mo = 1.2*Sr - 2.2, R 2  = 0.70, p < .01, logarithmic scales). This indicates that dissolved Mo is mobilized mainly along with other major ions such as Sr during similar mineral dissolution processes. From the "pristine" headwaters to the mouth of the JR, riverine Mo fluxes at the mouth of the JR has elevated by at least 3 times due to human perturbation. Compiled historic data regarding metal fluxes from world rivers further confirmed that small and medium rivers are relatively more sensitive to human perturbation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Distribution of Dissolved Zinc in the Western and Central Subarctic North Pacific

NASA Astrophysics Data System (ADS)

Kim, Taejin; Obata, Hajime; Nishioka, Jun; Gamo, Toshitaka

2017-09-01

We investigated the biogeochemical cycling of dissolved zinc (Zn) in the western and central subarctic North Pacific during the GEOTRACES GP 02 cruise. The relationship between dissolved Zn and silicate in the subarctic North Pacific plotted as a concave curve. Values of Zn* were strongly positive in the intermediate waters (26.6-27.5 σθ) of both the western and the central subarctic North Pacific. There was a distinct kink in the relationship between dissolved Zn and soluble reactive phosphorus (SRP) at the transition from shallow to intermediate water, which is similar to what has been reported for other open oceans. The high Zn:SRP ratio and high Zn* in the intermediate water suggest that intermediate water masses play an important role in the decoupling of dissolved Zn and silicate in the subarctic North Pacific, which implies that the biogeochemical processes that control dissolved Zn and silicate in the intermediate water are different from those in other oceanic regions.

Nitrogen and Phosphorous Flow in Atlantic Forest Covered Watersheds on the Oceanic and Continental Slopes at Serra dos Órgãos mountain, Southeast of Brazil

NASA Astrophysics Data System (ADS)

Vidal, M. M.; De Souza, P.; De Mello, W. Z.; Damaceno, I.; Bourseau, L.; Rodrigues, R. D. A.; Mattos, B. B.

2017-12-01

Concentration of nutrients above natural levels are found even at remote or protected environments due to atmospheric transportation from biomass burning emissions, urban and industrial areas. This study evaluate N and P atmospheric deposition at the oceanic and continental slopes of Serra dos Órgãos mountain, which are influenced by the pollutants emission from the Metropolitan Region of Rio de Janeiro. Flux of dissolved forms of N and P were measured in three watersheds in headwaters of Piabanha basin, southeastern Brazil, to understand the dynamics of the biogeochemical processes of these elements, related to anthropic influences of atmospheric inputs and export via stream flow. Samples of bulk precipitation (weekly; n=47) and stream water (monthly; n=13) were collected along one year (Sept 2014 - Sept 2015). During that period the annual rainfall in the oceanic slope (2163 mm) was the double of the continental one. It is important to stress that the rainfall in the oceanic slope was 13 % and 28% in 2014/15, respectively, lower than the long term average. Atmospheric deposition of total dissolved nitrogen (TDN) on the oceanic and continental slopes were, respectively, 15 and 8.6 kg N ha-1 year-1. The TDN outputs by stream water were 5-7 times lower in oceanic slope and 28 times lower on the continental one. The relative contribution of dissolved organic nitrogen (DON; 65%-70%) was higher than the one of dissolved inorganic nitrogen (DIN; 30-35%) to TDN deposition. Atmospheric deposition of total dissolved phosphorus (TDP) in oceanic and continental slopes were 1.4 and 0.95 kg P ha-1 year-1. Dissolved Organic Phosphorus (DOP; 89-96%) was higher than the inorganic one (PO43-; 5-11%). TDP outputs were 2-4 times lower, regarding to atmospheric contribution. The contribution of DOP (73-77 %) was higher than DIP (23-27 %). Results show variations in quantities and forms of N and P species due to natural and anthropogenic processes which contribute to the cycling of these elements in the Serra dos Órgãos. TDN atmospheric contribution on oceanic slope, as well as the DON/DIN ratio, was higher than found on previous studies on the same area.The differences between inputs and outputs of N and P balance can be attributed to factors, including biogeochemical and physical processes, and to an underestimation of stream flows in annual scale.

Simulation of annual biogeochemical cycles of nutrient balance, phytoplankton bloom(s), and DO in Puget Sound using an unstructured grid model

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

Khangaonkar, Tarang; Sackmann, Brandon; Long, Wen

2012-08-14

Nutrient pollution from rivers, nonpoint source runoff, and nearly 100 wastewater discharges is a potential threat to the ecological health of Puget Sound with evidence of hypoxia in some basins. However, the relative contributions of loads entering Puget Sound from natural and anthropogenic sources, and the effects of exchange flow from the Pacific Ocean are not well understood. Development of a quantitative model of Puget Sound is thus presented to help improve our understanding of the annual biogeochemical cycles in this system using the unstructured grid Finite-Volume Coastal Ocean Model framework and the Integrated Compartment Model (CE-QUAL-ICM) water quality kinetics.more » Results based on 2006 data show that phytoplankton growth and die-off, succession between two species of algae, nutrient dynamics, and dissolved oxygen in Puget Sound are strongly tied to seasonal variation of temperature, solar radiation, and the annual exchange and flushing induced by upwelled Pacific Ocean waters. Concentrations in the mixed outflow surface layer occupying approximately 5–20 m of the upper water column show strong effects of eutrophication from natural and anthropogenic sources, spring and summer algae blooms, accompanied by depleted nutrients but high dissolved oxygen levels. The bottom layer reflects dissolved oxygen and nutrient concentrations of upwelled Pacific Ocean water modulated by mixing with biologically active surface outflow in the Strait of Juan de Fuca prior to entering Puget Sound over the Admiralty Inlet. The effect of reflux mixing at the Admiralty Inlet sill resulting in lower nutrient and higher dissolved oxygen levels in bottom waters of Puget Sound than the incoming upwelled Pacific Ocean water is reproduced. Finally, by late winter, with the reduction in algal activity, water column constituents of interest, were renewed and the system appeared to reset with cooler temperature, higher nutrient, and higher dissolved oxygen waters from the Pacific Ocean.« less

Behavioral Response of Hermit Crabs (Clibanarius digueti) to Dissolved Carbon Dioxide

NASA Astrophysics Data System (ADS)

Maier, H. J.

2016-02-01

CO2 induced ocean acidification is currently changing the population dynamics of marine organisms. This can involve increased stress in populations, and alteration in individual physiology, which can eventually be expressed through an organism's behavior. If sustained, CO2 induced ocean acidification has the potential to cause major impacts on marine food chains, including on services they provide. The purpose of this study was to understand whether and how ocean acidification affects the behavior of hermit crab Clibanarius digueti, a crustacean inhabiting the littoral zone. We hypothesized that an increase in dissolved carbonic acid would modify grazing and individual movement, because an increase in acidification alters the normal chemical composition of the water and potentially the physiology of C. digueti. A model tidal pool experiment consisting of two tanks (control and treatment) inhabited with seven living C. digueti was set up in the Ocean Biome of Biosphere-2. Each tank was also provided with uninhabited shells: two Turbo fluctuosa and four Cerithium sp. Gaseous CO2 was dissolved into the treatment tank and measured as dissolved CO2 by using a NaOH titration method. Additionally, water conditions were characterized for light and temperature. Two trials were run in this experiment with tanks and treatments interchanged in each trial. We found a marked treatment effect on C. digueti behavior. The population experiencing increased CO2 performed daily shell changes after first day of exposure for each of the 4-day trials, as compared to individuals unexposed to dissolved CO2, that experienced no shell changes. From this study we conclude that the behavior of C. Digueti can be a good indicator of changes in dissolved CO2. This would allow us to better interpret patterns in marine animal behavior in response to climate change.

Climate-driven disparities among ecological interactions threaten kelp forest persistence.

PubMed

Provost, Euan J; Kelaher, Brendan P; Dworjanyn, Symon A; Russell, Bayden D; Connell, Sean D; Ghedini, Giulia; Gillanders, Bronwyn M; Figueira, WillIAM; Coleman, Melinda A

2017-01-01

The combination of ocean warming and acidification brings an uncertain future to kelp forests that occupy the warmest parts of their range. These forests are not only subject to the direct negative effects of ocean climate change, but also to a combination of unknown indirect effects associated with changing ecological landscapes. Here, we used mesocosm experiments to test the direct effects of ocean warming and acidification on kelp biomass and photosynthetic health, as well as climate-driven disparities in indirect effects involving key consumers (urchins and rock lobsters) and competitors (algal turf). Elevated water temperature directly reduced kelp biomass, while their turf-forming competitors expanded in response to ocean acidification and declining kelp canopy. Elevated temperatures also increased growth of urchins and, concurrently, the rate at which they thinned kelp canopy. Rock lobsters, which are renowned for keeping urchin populations in check, indirectly intensified negative pressures on kelp by reducing their consumption of urchins in response to elevated temperature. Overall, these results suggest that kelp forests situated towards the low-latitude margins of their distribution will need to adapt to ocean warming in order to persist in the future. What is less certain is how such adaptation in kelps can occur in the face of intensifying consumptive (via ocean warming) and competitive (via ocean acidification) pressures that affect key ecological interactions associated with their persistence. If such indirect effects counter adaptation to changing climate, they may erode the stability of kelp forests and increase the probability of regime shifts from complex habitat-forming species to more simple habitats dominated by algal turfs. © 2016 John Wiley & Sons Ltd.

The influence of extratropical cloud phase and amount feedbacks on climate sensitivity

NASA Astrophysics Data System (ADS)

Frey, William R.; Kay, Jennifer E.

2018-04-01

Global coupled climate models have large long-standing cloud and radiation biases, calling into question their ability to simulate climate and climate change. This study assesses the impact of reducing shortwave radiation biases on climate sensitivity within the Community Earth System Model (CESM). The model is modified by increasing supercooled cloud liquid to better match absorbed shortwave radiation observations over the Southern Ocean while tuning to reduce a compensating tropical shortwave bias. With a thermodynamic mixed-layer ocean, equilibrium warming in response to doubled CO2 increases from 4.1 K in the control to 5.6 K in the modified model. This 1.5 K increase in equilibrium climate sensitivity is caused by changes in two extratropical shortwave cloud feedbacks. First, reduced conversion of cloud ice to liquid at high southern latitudes decreases the magnitude of a negative cloud phase feedback. Second, warming is amplified in the mid-latitudes by a larger positive shortwave cloud feedback. The positive cloud feedback, usually associated with the subtropics, arises when sea surface warming increases the moisture gradient between the boundary layer and free troposphere. The increased moisture gradient enhances the effectiveness of mixing to dry the boundary layer, which decreases cloud amount and optical depth. When a full-depth ocean with dynamics and thermodynamics is included, ocean heat uptake preferentially cools the mid-latitude Southern Ocean, partially inhibiting the positive cloud feedback and slowing warming. Overall, the results highlight strong connections between Southern Ocean mixed-phase cloud partitioning, cloud feedbacks, and ocean heat uptake in a climate forced by greenhouse gas changes.

Response to Comment on “Dissolved organic sulfur in the ocean: Biogeochemistry of a petagram inventory”

NASA Astrophysics Data System (ADS)

Koch, Boris P.; Ksionzek, Kerstin B.; Lechtenfeld, Oliver J.; McCallister, S. Leigh; Schmitt-Kopplin, Philippe; Geuer, Jana K.; Geibert, Walter

2017-05-01

Dittmar et al. proposed that mixing alone can explain our observed decrease in marine dissolved organic sulfur with age. However, their simple model lacks an explanation for the origin of sulfur-depleted organic matter in the deep ocean and cannot adequately reproduce our observed stoichiometric changes. Using radiocarbon age also implicitly models the preferential cycling of sulfur that they are disputing.

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.

Taking the metabolic pulse of the world's coral reefs.

PubMed

Cyronak, Tyler; Andersson, Andreas J; Langdon, Chris; Albright, Rebecca; Bates, Nicholas R; Caldeira, Ken; Carlton, Renee; Corredor, Jorge E; Dunbar, Rob B; Enochs, Ian; Erez, Jonathan; Eyre, Bradley D; Gattuso, Jean-Pierre; Gledhill, Dwight; Kayanne, Hajime; Kline, David I; Koweek, David A; Lantz, Coulson; Lazar, Boaz; Manzello, Derek; McMahon, Ashly; Meléndez, Melissa; Page, Heather N; Santos, Isaac R; Schulz, Kai G; Shaw, Emily; Silverman, Jacob; Suzuki, Atsushi; Teneva, Lida; Watanabe, Atsushi; Yamamoto, Shoji

2018-01-01

Worldwide, coral reef ecosystems are experiencing increasing pressure from a variety of anthropogenic perturbations including ocean warming and acidification, increased sedimentation, eutrophication, and overfishing, which could shift reefs to a condition of net calcium carbonate (CaCO3) dissolution and erosion. Herein, we determine the net calcification potential and the relative balance of net organic carbon metabolism (net community production; NCP) and net inorganic carbon metabolism (net community calcification; NCC) within 23 coral reef locations across the globe. In light of these results, we consider the suitability of using these two metrics developed from total alkalinity (TA) and dissolved inorganic carbon (DIC) measurements collected on different spatiotemporal scales to monitor coral reef biogeochemistry under anthropogenic change. All reefs in this study were net calcifying for the majority of observations as inferred from alkalinity depletion relative to offshore, although occasional observations of net dissolution occurred at most locations. However, reefs with lower net calcification potential (i.e., lower TA depletion) could shift towards net dissolution sooner than reefs with a higher potential. The percent influence of organic carbon fluxes on total changes in dissolved inorganic carbon (DIC) (i.e., NCP compared to the sum of NCP and NCC) ranged from 32% to 88% and reflected inherent biogeochemical differences between reefs. Reefs with the largest relative percentage of NCP experienced the largest variability in seawater pH for a given change in DIC, which is directly related to the reefs ability to elevate or suppress local pH relative to the open ocean. This work highlights the value of measuring coral reef carbonate chemistry when evaluating their susceptibility to ongoing global environmental change and offers a baseline from which to guide future conservation efforts aimed at preserving these valuable ecosystems.

Taking the metabolic pulse of the world’s coral reefs

PubMed Central

Andersson, Andreas J.; Langdon, Chris; Albright, Rebecca; Bates, Nicholas R.; Caldeira, Ken; Carlton, Renee; Corredor, Jorge E.; Dunbar, Rob B.; Enochs, Ian; Erez, Jonathan; Eyre, Bradley D.; Gattuso, Jean-Pierre; Gledhill, Dwight; Kayanne, Hajime; Kline, David I.; Koweek, David A.; Lantz, Coulson; Lazar, Boaz; Manzello, Derek; McMahon, Ashly; Meléndez, Melissa; Page, Heather N.; Santos, Isaac R.; Schulz, Kai G.; Shaw, Emily; Silverman, Jacob; Suzuki, Atsushi; Teneva, Lida; Watanabe, Atsushi; Yamamoto, Shoji

2018-01-01

Worldwide, coral reef ecosystems are experiencing increasing pressure from a variety of anthropogenic perturbations including ocean warming and acidification, increased sedimentation, eutrophication, and overfishing, which could shift reefs to a condition of net calcium carbonate (CaCO3) dissolution and erosion. Herein, we determine the net calcification potential and the relative balance of net organic carbon metabolism (net community production; NCP) and net inorganic carbon metabolism (net community calcification; NCC) within 23 coral reef locations across the globe. In light of these results, we consider the suitability of using these two metrics developed from total alkalinity (TA) and dissolved inorganic carbon (DIC) measurements collected on different spatiotemporal scales to monitor coral reef biogeochemistry under anthropogenic change. All reefs in this study were net calcifying for the majority of observations as inferred from alkalinity depletion relative to offshore, although occasional observations of net dissolution occurred at most locations. However, reefs with lower net calcification potential (i.e., lower TA depletion) could shift towards net dissolution sooner than reefs with a higher potential. The percent influence of organic carbon fluxes on total changes in dissolved inorganic carbon (DIC) (i.e., NCP compared to the sum of NCP and NCC) ranged from 32% to 88% and reflected inherent biogeochemical differences between reefs. Reefs with the largest relative percentage of NCP experienced the largest variability in seawater pH for a given change in DIC, which is directly related to the reefs ability to elevate or suppress local pH relative to the open ocean. This work highlights the value of measuring coral reef carbonate chemistry when evaluating their susceptibility to ongoing global environmental change and offers a baseline from which to guide future conservation efforts aimed at preserving these valuable ecosystems. PMID:29315312

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

Response to CO2 Transient Increase in the GISS Coupled Model: Regional Coolings in a Warming Climate

NASA Technical Reports Server (NTRS)

Russell, Gary L.; Rind, David

1999-01-01

The (GISS) Goddard Institute for Space Studies coupled atmosphere-ocean model is used to investigate the effect of increased atmospheric CO2 by comparing a compounded 1 percent CO2 increase experiment with a control simulation. After 70 years of integration, the global surface air temperature in the 1 percent CO2 experiment is 1.43 C warmer. In spite of this global warming, there are two distinct regions, the northern Atlantic Ocean and the southern Pacific Ocean, where the surface air temperature is up to 4 C cooler. This situation is maintained by two positive feedbacks: a local effect on convection in the South Pacific and a non-local impact on the meridional circulation in the North Atlantic. The poleward transport of latent energy and dry static energy by the atmosphere is greater in the 1 percent CO2 experiment, caused by warming and therefore increased water vapor and greater greenhouse capacity at lower latitudes. The larger atmospheric transports tend to reduce upward vertical fluxes of heat and moisture from the ocean surface at high latitudes, which has the effect of stabilizing the ocean, reducing both convection and the thermohaline circulation. With less convection, less warm water is brought up from below, and with a reduced North Atlantic thermohaline circulation (by 30 percent at time of CO2 doubling), the poleward energy transport by the oceans decreases. The colder water then leads to further reductions in evaporation, decreases of salinity at high latitudes, continued stabilization of the ocean, and maintenance of reduced convection and meridional overturning. Although sea ice decreases globally, it increases in the cooling regions which reduces the overall climate sensitivity; its effect is most pronounced in the Southern Hemisphere. Tropical warming has been observed over the past several decades; if modeling studies such as this and others which have produced similar effects are valid, these processes may already be beginning.

The distribution and stabilisation of dissolved Fe in deep-sea hydrothermal plumes

NASA Astrophysics Data System (ADS)

Bennett, Sarah A.; Achterberg, Eric P.; Connelly, Douglas P.; Statham, Peter J.; Fones, Gary R.; German, Christopher R.

2008-06-01

We have conducted a study of hydrothermal plumes overlying the Mid-Atlantic Ridge near 5° S to investigate whether there is a significant export flux of dissolved Fe from hydrothermal venting to the oceans. Our study combined measurements of plume-height Fe concentrations from a series of 6 CTD stations together with studies of dissolved Fe speciation in a subset of those samples. At 2.5 km down plume from the nearest known vent site dissolved Fe concentrations were ˜ 20 nM. This is much higher than would be predicted from a combination of plume dilution and dissolved Fe(II) oxidation rates, but consistent with stabilisation due to the presence of organic Fe complexes and Fe colloids. Using Competitive Ligand Exchange-Cathodic Stripping Voltammetry (CLE-CSV), stabilised dissolved Fe complexes were detected within the dissolved Fe fraction on the edges of one non-buoyant hydrothermal plume with observed ligand concentrations high enough to account for stabilisation of ˜ 4% of the total Fe emitted from the 5° S vent sites. If these results were representative of all hydrothermal systems, submarine venting could provide 12-22% of the global deep-ocean dissolved Fe budget.

Relevance of peat-draining rivers for the riverine input of dissolved iron into the ocean.

PubMed

Krachler, Regina; Krachler, Rudolf F; von der Kammer, Frank; Süphandag, Altan; Jirsa, Franz; Ayromlou, Shahram; Hofmann, Thilo; Keppler, Bernhard K

2010-05-01

Peat bogs have the ability to produce strong chelate ligands (humic and fulvic acids) which enhance the weathering rates of iron-silicate minerals and greatly increase the solubility of the essential trace metal iron in river water. Fluvial networks link peat bogs with the ocean, and thus terrestrial-derived fulvic-iron complexes fuel the ocean's biological productivity and biological carbon pump, but understanding this role is constrained by inconsistent observations regarding the behaviour of riverine iron in the estuarine mixing zone, where precipitation reactions remove iron from the water column. We applied a characterization of the colloidal iron carriers in peatland-draining rivers in North Scotland, using field-flow fractionation (FFF), in combination with end-member mixing experiments of river water sampled near the river mouth and coastal seawater using a (59)Fe radiotracer method. According to our results, the investigated river contributed "truly dissolved" Fe concentrations of about 3300nmolL(-1) to the ocean which is nearly two orders of magnitude higher than the dissolved iron contribution of the "average world" river ( approximately 40nmolL(-1)). Thus we conclude that peatland-draining rivers are important sources of dissolved iron to the ocean margins. We propose highly electrostatic and sterical stabilized iron-organic matter complexes in the size range of <2kDa to be responsible for iron transport across the estuarine mixing zone. Copyright 2010 Elsevier B.V. All rights reserved.

Temporal variability of dissolved iron species in the mesopelagic zone at Ocean Station PAPA

NASA Astrophysics Data System (ADS)

Schallenberg, Christina; Ross, Andrew R. S.; Davidson, Ashley B.; Stewart, Gillian M.; Cullen, Jay T.

2017-08-01

Deposition of atmospheric aerosols to the surface ocean is considered an important mechanism for the supply of iron (Fe) to remote ocean regions, but direct observations of the oceanic response to aerosol deposition are sparse. In the high nutrient, low chlorophyll (HNLC) subarctic Pacific Ocean we observed a dissolved Fe and Fe(II) anomaly at depth that is best explained as the result of aerosol deposition from Siberian forest fires in May 2012. Interestingly, there was no evidence of enhanced dFe concentrations in surface waters, nor was there a detectable phytoplankton bloom in response to the suspected aerosol deposition. Dissolved Fe (dFe) and Fe(II) showed the strongest enhancement in the subsurface oxygen deficient zone (ODZ), where oxygen concentrations <50 μmol kg-1 are prevalent. In the upper 200 m, dFe concentrations were at or below historic background levels, consistent with a short residence time of aerosol particles in surface waters and possible scavenging loss of dFe. Aerosol toxicity and/or dominance of particle scavenging over dissolution of Fe in the upper water column may have contributed to the lack of a strong phytoplankton response.

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.

Reduced interdecadal variability of Atlantic Meridional Overturning Circulation under global warming.

PubMed

Cheng, Jun; Liu, Zhengyu; Zhang, Shaoqing; Liu, Wei; Dong, Lina; Liu, Peng; Li, Hongli

2016-03-22

Interdecadal variability of the Atlantic Meridional Overturning Circulation (AMOC-IV) plays an important role in climate variation and has significant societal impacts. Past climate reconstruction indicates that AMOC-IV has likely undergone significant changes. Despite some previous studies, responses of AMOC-IV to global warming remain unclear, in particular regarding its amplitude and time scale. In this study, we analyze the responses of AMOC-IV under various scenarios of future global warming in multiple models and find that AMOC-IV becomes weaker and shorter with enhanced global warming. From the present climate condition to the strongest future warming scenario, on average, the major period of AMOC-IV is shortened from ∼50 y to ∼20 y, and the amplitude is reduced by ∼60%. These reductions in period and amplitude of AMOC-IV are suggested to be associated with increased oceanic stratification under global warming and, in turn, the speedup of oceanic baroclinic Rossby waves.

Impact of space dependent eddy mixing on large ocean circulation

NASA Astrophysics Data System (ADS)

Pradal, M. A. S.; Gnanadesikan, A.; Abernathey, R. P.

2016-02-01

Throughout the ocean, mesoscale eddies stir tracers such as heat, oxygen, helium, dissolved CO2, affecting their spatial distribution. Recent work (Gnanadesikan et al., 2013) showed that changes in eddy stirring could result in changes of the volume of hypoxic and anoxic waters, leading to drastic consequences for ocean biogeochemical cycles. The parameterization of mesocale eddies in global climate models (GCMs) is two parts, based on the formulations of Redi (1982) and Gent and McWilliams (1990) which are associated with mixing parameters ARedi and AGM respectively. Numerous studies have looked at the sensitivity of ESMs to changing AGM, either alone or in combination with an ARedi parameter taken to be equivalent to the value of the AGM. By contrast the impact of the Redi parameterization in isolation remains unexplored. In a previous article, Pradal and Gnanadesikan, 2014, described the sensitivity of the climate system to a six fold increase in the Redi parameter. They found that increasing the isopycnal mixing coefficient tended to warm the climate of the planet overall, through an increase of heat absorption linked to a destabilization of the halocline in subpolar regions (particularly the Southern Ocean). This previous work varied a globally constant Redi parameter from 400m2/s to 2400m2/s. New estimates from altimetry (Abernathey and Marshall, 2013) better constrain the spatial patterns and range for the ARedi parameter. Does such spatial variation matter, and if so, where does matter? Following Gnanadesikan et al. (2013) and Pradal and Gnanadesikan, 2014 this study examines this question with a suite of Earth System Models.

Constraints on oceanic methane emissions west of Svalbard from atmospheric in situ measurements and Lagrangian transport modeling

NASA Astrophysics Data System (ADS)

Pisso, Ignacio; Myhre, Cathrine Lund; Platt, Stephen Matthew; Eckhardt, Sabine; Hermansen, Ove; Schmidbauer, Norbert; Mienert, Jurgen; Vadakkepuliyambatta, Sunil; Bauguitte, Stephane; Pitt, Joseph; Allen, Grant; Bower, Keith; O'Shea, Sebastian; Gallagher, Martin; Percival, Carl; Pyle, John; Cain, Michelle; Stohl, Andreas

2017-04-01

Methane stored in seabed reservoirs such as methane hydrates can reach the atmosphere in the form of bubbles or dissolved in water. Hydrates could destabilize with rising temperature further increasing greenhouse gas emissions in a warming climate. To assess the impact of oceanic emissions from the area west of Svalbard, where methane hydrates are abundant, we used measurements collected with a research aircraft (FAAM) and a ship (Helmer Hansen) during the Summer 2014, and for Zeppelin Observatory for the full year. We present a model-supported analysis of the atmospheric CH4 mixing ratios measured by the different platforms. To address uncertainty about where CH4 emissions actually occur, we explored three scenarios: areas with known seeps, a hydrate stability model and an ocean depth criterion. We then used a budget analysis and a Lagrangian particle dispersion model to compare measurements taken upwind and downwind of the potential CH4 emission areas. We found small differences between the CH4 mixing ratios measured upwind and downwind of the potential emission areas during the campaign. By taking into account measurement and sampling uncertainties and by determining the sensitivity of the measured mixing ratios to potential oceanic emissions, we provide upper limits for the CH4 fluxes. The CH4 flux during the campaign was small, with an upper limit of 2.5 nmol / m s in the stability model scenario. The Zeppelin Observatory data for 2014 suggests CH4 fluxes from the Svalbard continental platform below 0.2 Tg/yr . All estimates are in the lower range of values previously reported.

Sea level change since 2005: importance of salinity

NASA Astrophysics Data System (ADS)

Llovel, W.; Purkey, S.; Meyssignac, B.; Kolodziejczyk, N.; Blazquez, A.; Bamber, J. L.

2017-12-01

Sea level rise is one of the most important consequences of the actual global warming. Global mean sea level has been rising at a faster rate since 1993 (over the satellite altimetry era) than previous decades. This rise is expected to accelerate over the coming decades and century. At global scale, sea level rise is caused by a combination of freshwater increase from land ice melting and land water changes (mass component) and ocean warming (thermal expansion). Estimating the causes is of great interest not only to understand the past sea level changes but also to validate projections based on climate models. In this study, we investigate the global mass contribution to recent sea level changes with an alternative approach by estimating the global ocean freshening. For that purpose, we consider the unprecedented amount of salinity measurements from Argo floats for the past decade (2005-2015). We compare our results to the ocean mass inferred by GRACE data and based on a sea level budget approach. Our results bring new constrains on the global water cycle (ocean freshening) and energy budget (ocean warming) as well as on the global ocean mass directly inferred from GRACE data.

Identifying Glacial Meltwater in the Amundsen Sea, Antarctica

NASA Astrophysics Data System (ADS)

Biddle, L. C.; Heywood, K. J.; Jenkins, A.; Kaiser, J.

2016-02-01

Pine Island Glacier, located in the Amundsen Sea, is losing mass rapidly due to relatively warm ocean waters melting its ice shelf from below. The resulting increase in meltwater production may be the root of the freshening in the Ross Sea over the last 30 years. Tracing the meltwater travelling away from the ice sheets is important in order to identify the regions most affected by the increased input of this water type. We use water mass characteristics (temperature, salinity, O2 concentration) derived from 105 CTD casts during the Ocean2ice cruise on RRS James Clark Ross in January-March 2014 to calculate meltwater fractions north of Pine Island Glacier. The data show maximum meltwater fractions at the ice front of up to 2.4 % and a plume of meltwater travelling away from the ice front along the 1027.7 kg m-3 isopycnal. We investigate the reliability of these results and attach uncertainties to the measurements made to ascertain the most reliable method of meltwater calculation in the Amundsen Sea. Processes such as atmospheric interaction and biological activity also affect the calculated apparent meltwater fractions. We analyse their effects on the reliability of the calculated meltwater fractions across the region using a bulk mixed layer model based on the one-dimensional Price-Weller-Pinkel model (Price et al., 1986). The model includes sea ice, dissolved oxygen concentrations and a simple respiration model, forced by NCEP climatology and an initial linear mixing profile between Winter Water (WW) and Circumpolar Deep Water (CDW). The model mimics the seasonal cycle of mixed layer warming and freshening and simulates how increases in sea ice formation and the influx of slightly cooler Lower CDW impact on the apparent meltwater fractions. These processes could result in biased meltwater signatures across the eastern Amundsen Sea.

Identifying glacial meltwater in the Amundsen Sea, Antarctica

NASA Astrophysics Data System (ADS)

Biddle, Louise; Heywood, Karen; Jenkins, Adrian; Kaiser, Jan

2016-04-01

Pine Island Glacier, located in the Amundsen Sea, is losing mass rapidly due to relatively warm ocean waters melting its ice shelf from below. The resulting increase in meltwater production may be the root of the freshening in the Ross Sea over the last 30 years. Tracing the meltwater travelling away from the ice sheets is important in order to identify the regions most affected by the increased input of this water type. We use water mass characteristics (temperature, salinity, O2 concentration) derived from 105 CTD casts during the Ocean2ice cruise on RRS James Clark Ross in January-March 2014 to calculate meltwater fractions north of Pine Island Glacier. The data show maximum meltwater fractions at the ice front of up to 2.4 % and a plume of meltwater travelling away from the ice front along the 1027.7 kg m-3 isopycnal. We investigate the reliability of these results and attach uncertainties to the measurements made to ascertain the most reliable method of meltwater calculation in the Amundsen Sea. Processes such as atmospheric interaction and biological activity also affect the calculated apparent meltwater fractions. We analyse their effects on the reliability of the calculated meltwater fractions across the region using a bulk mixed layer model based on the one-dimensional Price-Weller-Pinkel model (1986). The model includes sea ice, dissolved oxygen concentrations and a simple respiration model, forced by NCEP climatology and an initial linear mixing profile between Winter Water (WW) and Circumpolar Deep Water (CDW). The model mimics the seasonal cycle of mixed layer warming and freshening and simulates how increases in sea ice formation and the influx of slightly cooler Lower CDW impact on the apparent meltwater fractions. These processes could result in biased meltwater signatures across the eastern Amundsen Sea.

Deep Arctic Ocean warming during the last glacial cycle

USGS Publications Warehouse

Cronin, T. M.; Dwyer, G.S.; Farmer, J.; Bauch, H.A.; Spielhagen, R.F.; Jakobsson, M.; Nilsson, J.; Briggs, W.M.; Stepanova, A.

2012-01-01

In the Arctic Ocean, the cold and relatively fresh water beneath the sea ice is separated from the underlying warmer and saltier Atlantic Layer by a halocline. Ongoing sea ice loss and warming in the Arctic Ocean have demonstrated the instability of the halocline, with implications for further sea ice loss. The stability of the halocline through past climate variations is unclear. Here we estimate intermediate water temperatures over the past 50,000 years from the Mg/Ca and Sr/Ca values of ostracods from 31 Arctic sediment cores. From about 50 to 11 kyr ago, the central Arctic Basin from 1,000 to 2,500 m was occupied by a water mass we call Glacial Arctic Intermediate Water. This water mass was 1–2 °C warmer than modern Arctic Intermediate Water, with temperatures peaking during or just before millennial-scale Heinrich cold events and the Younger Dryas cold interval. We use numerical modelling to show that the intermediate depth warming could result from the expected decrease in the flux of fresh water to the Arctic Ocean during glacial conditions, which would cause the halocline to deepen and push the warm Atlantic Layer into intermediate depths. Although not modelled, the reduced formation of cold, deep waters due to the exposure of the Arctic continental shelf could also contribute to the intermediate depth warming.

Human-caused Indo-Pacific warm pool expansion

PubMed Central

Weller, Evan; Min, Seung-Ki; Cai, Wenju; Zwiers, Francis W.; Kim, Yeon-Hee; Lee, Donghyun

2016-01-01

The Indo-Pacific warm pool (IPWP) has warmed and grown substantially during the past century. The IPWP is Earth’s largest region of warm sea surface temperatures (SSTs), has the highest rainfall, and is fundamental to global atmospheric circulation and hydrological cycle. The region has also experienced the world’s highest rates of sea-level rise in recent decades, indicating large increases in ocean heat content and leading to substantial impacts on small island states in the region. Previous studies have considered mechanisms for the basin-scale ocean warming, but not the causes of the observed IPWP expansion, where expansion in the Indian Ocean has far exceeded that in the Pacific Ocean. We identify human and natural contributions to the observed IPWP changes since the 1950s by comparing observations with climate model simulations using an optimal fingerprinting technique. Greenhouse gas forcing is found to be the dominant cause of the observed increases in IPWP intensity and size, whereas natural fluctuations associated with the Pacific Decadal Oscillation have played a smaller yet significant role. Further, we show that the shape and impact of human-induced IPWP growth could be asymmetric between the Indian and Pacific basins, the causes of which remain uncertain. Human-induced changes in the IPWP have important implications for understanding and projecting related changes in monsoonal rainfall, and frequency or intensity of tropical storms, which have profound socioeconomic consequences. PMID:27419228

Human-caused Indo-Pacific warm pool expansion.

PubMed

Weller, Evan; Min, Seung-Ki; Cai, Wenju; Zwiers, Francis W; Kim, Yeon-Hee; Lee, Donghyun

2016-07-01

The Indo-Pacific warm pool (IPWP) has warmed and grown substantially during the past century. The IPWP is Earth's largest region of warm sea surface temperatures (SSTs), has the highest rainfall, and is fundamental to global atmospheric circulation and hydrological cycle. The region has also experienced the world's highest rates of sea-level rise in recent decades, indicating large increases in ocean heat content and leading to substantial impacts on small island states in the region. Previous studies have considered mechanisms for the basin-scale ocean warming, but not the causes of the observed IPWP expansion, where expansion in the Indian Ocean has far exceeded that in the Pacific Ocean. We identify human and natural contributions to the observed IPWP changes since the 1950s by comparing observations with climate model simulations using an optimal fingerprinting technique. Greenhouse gas forcing is found to be the dominant cause of the observed increases in IPWP intensity and size, whereas natural fluctuations associated with the Pacific Decadal Oscillation have played a smaller yet significant role. Further, we show that the shape and impact of human-induced IPWP growth could be asymmetric between the Indian and Pacific basins, the causes of which remain uncertain. Human-induced changes in the IPWP have important implications for understanding and projecting related changes in monsoonal rainfall, and frequency or intensity of tropical storms, which have profound socioeconomic consequences.

On the shortening of Indian summer monsoon season in a warming scenario

NASA Astrophysics Data System (ADS)

Sabeerali, C. T.; Ajayamohan, R. S.

2018-03-01

Assessing the future projections of the length of rainy season (LRS) has paramount societal impact considering its potential to alter the seasonal mean rainfall over the Indian subcontinent. Here, we explored the projections of LRS using both historical and Representative Concentration Pathways 8.5 (RCP8.5) simulations of the Coupled Model Intercomparison Project Phase5 (CMIP5). RCP8.5 simulations project shortening of the LRS of Indian summer monsoon by altering the timing of onset and withdrawal dates. Most CMIP5 RCP8.5 model simulations indicate a faster warming rate over the western tropical Indian Ocean compared to other regions of the Indian Ocean. It is found that the pronounced western Indian Ocean warming and associated increase in convection results in warmer upper troposphere over the Indian Ocean compared to the Indian subcontinent, reducing the meridional gradient in upper tropospheric temperature (UTT) over the Asian summer monsoon (ASM) domain. The weakening of the meridional gradient in UTT induces weakening of easterly vertical wind shear over the ASM domain during first and last phase of monsoon, facilitate delayed (advanced) monsoon onset (withdrawal) dates, ensues the shortening of LRS of the Indian summer monsoon in a warming scenario.

Arctic Sea Ice Basal Melt Onset Variability and Associated Ocean Surface Heating

NASA Astrophysics Data System (ADS)

Merrick, R. A.; Hutchings, J. K.

2015-12-01

The interannual and regional variability in Arctic sea ice melt has previously been characterized only in terms of surface melting. A focus on the variability in the onset of basal melt is additionally required to understand Arctic melt patterns. Monitoring basal melt provides a glimpse into the importance of ocean heating to sea ice melt. This warming is predominantly through seawater exposure due to lead opening and the associated solar warming at the ocean's surface. We present the temporal variability in basal melt onset observed by ice mass balance buoys throughout the Arctic Ocean since 2003, providing a different perspective than the satellite microwave data used to measure the onset of surface melt. We found that melt onset varies greatly, even for buoys deployed within 100km of each other. Therefore large volumes of data are necessary to accurately estimate the variability of basal melt onset. Once the variability of basal melt onset has been identified, we can investigate how this range has been changing as a response to atmospheric and oceanic warming, changes in ice morphology as well as the intensification of the ice albedo feedback.

Asynchronous marine-terrestrial signals of the last deglacial warming in East Asia associated with low- and high-latitude climate changes.

PubMed

Xu, Deke; Lu, Houyuan; Wu, Naiqin; Liu, Zhenxia; Li, Tiegang; Shen, Caiming; Wang, Luo

2013-06-11

A high-resolution multiproxy record, including pollen, foraminifera, and alkenone paleothermometry, obtained from a single core (DG9603) from the Okinawa Trough, East China Sea (ECS), provided unambiguous evidence for asynchronous climate change between the land and ocean over the past 40 ka. On land, the deglacial stage was characterized by rapid warming, as reflected by paleovegetation, and it began ca. 15 kaBP, consistent with the timing of the last deglacial warming in Greenland. However, sea surface temperature estimates from foraminifera and alkenone paleothermometry increased around 20-19 kaBP, as in the Western Pacific Warm Pool (WPWP). Sea surface temperatures in the Okinawa Trough were influenced mainly by heat transport from the tropical western Pacific Ocean by the Kuroshio Current, but the epicontinental vegetation of the ECS was influenced by atmospheric circulation linked to the northern high-latitude climate. Asynchronous terrestrial and marine signals of the last deglacial warming in East Asia were thus clearly related to ocean currents and atmospheric circulation. We argue that (i) early warming seawater of the WPWP, driven by low-latitude insolation and trade winds, moved northward via the Kuroshio Current and triggered marine warming along the ECS around 20-19 kaBP similar to that in the WPWP, and (ii) an almost complete shutdown of the Atlantic Meridional Overturning Circulation ca. 18-15 kaBP was associated with cold Heinrich stadial-1 and delayed terrestrial warming during the last deglacial warming until ca. 15 kaBP at northern high latitudes, and hence in East Asia. Terrestrial deglacial warming therefore lagged behind marine changes by ca. 3-4 ka.

Asynchronous marine-terrestrial signals of the last deglacial warming in East Asia associated with low- and high-latitude climate changes

PubMed Central

Xu, Deke; Lu, Houyuan; Wu, Naiqin; Liu, Zhenxia; Li, Tiegang; Shen, Caiming; Wang, Luo

2013-01-01

A high-resolution multiproxy record, including pollen, foraminifera, and alkenone paleothermometry, obtained from a single core (DG9603) from the Okinawa Trough, East China Sea (ECS), provided unambiguous evidence for asynchronous climate change between the land and ocean over the past 40 ka. On land, the deglacial stage was characterized by rapid warming, as reflected by paleovegetation, and it began ca. 15 kaBP, consistent with the timing of the last deglacial warming in Greenland. However, sea surface temperature estimates from foraminifera and alkenone paleothermometry increased around 20–19 kaBP, as in the Western Pacific Warm Pool (WPWP). Sea surface temperatures in the Okinawa Trough were influenced mainly by heat transport from the tropical western Pacific Ocean by the Kuroshio Current, but the epicontinental vegetation of the ECS was influenced by atmospheric circulation linked to the northern high-latitude climate. Asynchronous terrestrial and marine signals of the last deglacial warming in East Asia were thus clearly related to ocean currents and atmospheric circulation. We argue that (i) early warming seawater of the WPWP, driven by low-latitude insolation and trade winds, moved northward via the Kuroshio Current and triggered marine warming along the ECS around 20–19 kaBP similar to that in the WPWP, and (ii) an almost complete shutdown of the Atlantic Meridional Overturning Circulation ca. 18–15 kaBP was associated with cold Heinrich stadial-1 and delayed terrestrial warming during the last deglacial warming until ca. 15 kaBP at northern high latitudes, and hence in East Asia. Terrestrial deglacial warming therefore lagged behind marine changes by ca. 3–4 ka. PMID:23720306

Warming and Ocean Acidification Effects on Phytoplankton--From Species Shifts to Size Shifts within Species in a Mesocosm Experiment.

PubMed

Sommer, Ulrich; Paul, Carolin; Moustaka-Gouni, Maria

2015-01-01

While the isolated responses of marine phytoplankton to climate warming and to ocean acidification have been studied intensively, studies on the combined effect of both aspects of Global Change are still scarce. Therefore, we performed a mesocosm experiment with a factorial combination of temperature (9 and 15 °C) and pCO2 (means: 439 ppm and 1040 ppm) with a natural autumn plankton community from the western Baltic Sea. Temporal trajectories of total biomass and of the biomass of the most important higher taxa followed similar patterns in all treatments. When averaging over the entire time course, phytoplankton biomass decreased with warming and increased with CO2 under warm conditions. The contribution of the two dominant higher phytoplankton taxa (diatoms and cryptophytes) and of the 4 most important species (3 diatoms, 1 cryptophyte) did not respond to the experimental treatments. Taxonomic composition of phytoplankton showed only responses at the level of subdominant and rare species. Phytoplankton cell sizes increased with CO2 addition and decreased with warming. Both effects were stronger for larger species. Warming effects were stronger than CO2 effects and tended to counteract each other. Phytoplankton communities without calcifying species and exposed to short-term variation of CO2 seem to be rather resistant to ocean acidification.

Atlantic-induced pan-tropical climate change over the past three decades

NASA Astrophysics Data System (ADS)

Li, Xichen; Xie, Shang-Ping; Gille, Sarah T.; Yoo, Changhyun

2016-03-01

During the past three decades, tropical sea surface temperature (SST) has shown dipole-like trends, with warming over the tropical Atlantic and Indo-western Pacific but cooling over the eastern Pacific. Competing hypotheses relate this cooling, identified as a driver of the global warming hiatus, to the warming trends in either the Atlantic or Indian Ocean. However, the mechanisms, the relative importance and the interactions between these teleconnections remain unclear. Using a state-of-the-art climate model, we show that the Atlantic plays a key role in initiating the tropical-wide teleconnection, and the Atlantic-induced anomalies contribute ~55-75% of the tropical SST and circulation changes during the satellite era. The Atlantic warming drives easterly wind anomalies over the Indo-western Pacific as Kelvin waves and westerly anomalies over the eastern Pacific as Rossby waves. The wind changes induce an Indo-western Pacific warming through the wind-evaporation-SST effect, and this warming intensifies the La Niña-type response in the tropical Pacific by enhancing the easterly trade winds and through the Bjerknes ocean dynamical processes. The teleconnection develops into a tropical-wide SST dipole pattern. This mechanism, supported by observations and a hierarchy of climate models, reveals that the tropical ocean basins are more tightly connected than previously thought.

A century of ocean warming on Florida Keys coral reefs: historic in situ observations

USGS Publications Warehouse

Kuffner, Ilsa B.; Lidz, Barbara H.; Hudson, J. Harold; Anderson, Jeffery S.

2015-01-01

There is strong evidence that global climate change over the last several decades has caused shifts in species distributions, species extinctions, and alterations in the functioning of ecosystems. However, because of high variability on short (i.e., diurnal, seasonal, and annual) timescales as well as the recency of a comprehensive instrumental record, it is difficult to detect or provide evidence for long-term, site-specific trends in ocean temperature. Here we analyze five in situ datasets from Florida Keys coral reef habitats, including historic measurements taken by lighthouse keepers, to provide three independent lines of evidence supporting approximately 0.8 °C of warming in sea surface temperature (SST) over the last century. Results indicate that the warming observed in the records between 1878 and 2012 can be fully accounted for by the warming observed in recent decades (from 1975 to 2007), documented using in situ thermographs on a mid-shore patch reef. The magnitude of warming revealed here is similar to that found in other SST datasets from the region and to that observed in global mean surface temperature. The geologic context and significance of recent ocean warming to coral growth and population dynamics are discussed, as is the future prognosis for the Florida reef tract.

Mechanistic insights into a hydrate contribution to the Paleocene-Eocene carbon cycle perturbation from coupled thermohydraulic simulations

NASA Astrophysics Data System (ADS)

Minshull, T. A.; Marín-Moreno, H.; Armstrong McKay, D. I.; Wilson, P. A.

2016-08-01

During the Paleocene-Eocene Thermal Maximum (PETM), the carbon isotopic signature (δ13C) of surface carbon-bearing phases decreased abruptly by at least 2.5 to 3.0‰. This carbon isotope excursion (CIE) has been attributed to widespread methane hydrate dissociation in response to rapid ocean warming. We ran a thermohydraulic modeling code to simulate hydrate dissociation due to ocean warming for various PETM scenarios. Our results show that hydrate dissociation in response to such warming can be rapid but suggest that methane release to the ocean is modest and delayed by hundreds to thousands of years after the onset of dissociation, limiting the potential for positive feedback from emission-induced warming. In all of our simulations at least half of the dissociated hydrate methane remains beneath the seabed, suggesting that the pre-PETM hydrate inventory needed to account for all of the CIE is at least double that required for isotopic mass balance.

Mechanical robustness of the calcareous tubeworm Hydroides elegans: warming mitigates the adverse effects of ocean acidification.

PubMed

Li, Chaoyi; Meng, Yuan; He, Chong; Chan, Vera B S; Yao, Haimin; Thiyagarajan, V

2016-01-01

Development of antifouling strategies requires knowledge of how fouling organisms would respond to climate change associated environmental stressors. Here, a calcareous tube built by the tubeworm, Hydroides elegans, was used as an example to evaluate the individual and interactive effects of ocean acidification (OA), warming and reduced salinity on the mechanical properties of a tube. Tubeworms produce a mechanically weaker tube with less resistance to simulated predator attack under OA (pH 7.8). Warming (29°C) increased tube volume, tube mineral density and the tube's resistance to a simulated predatory attack. A weakening effect by OA did not make the removal of tubeworms easier except for the earliest stage, in which warming had the least effect. Reduced salinity (27 psu) did not affect tubes. This study showed that both mechanical analysis and computational modeling can be integrated with biofouling research to provide insights into how fouling communities might develop in future ocean conditions.

Species traits and climate velocity explain geographic range shifts in an ocean-warming hotspot.

PubMed

Sunday, Jennifer M; Pecl, Gretta T; Frusher, Stewart; Hobday, Alistair J; Hill, Nicole; Holbrook, Neil J; Edgar, Graham J; Stuart-Smith, Rick; Barrett, Neville; Wernberg, Thomas; Watson, Reg A; Smale, Dan A; Fulton, Elizabeth A; Slawinski, Dirk; Feng, Ming; Radford, Ben T; Thompson, Peter A; Bates, Amanda E

2015-09-01

Species' ranges are shifting globally in response to climate warming, with substantial variability among taxa, even within regions. Relationships between range dynamics and intrinsic species traits may be particularly apparent in the ocean, where temperature more directly shapes species' distributions. Here, we test for a role of species traits and climate velocity in driving range extensions in the ocean-warming hotspot of southeast Australia. Climate velocity explained some variation in range shifts, however, including species traits more than doubled the variation explained. Swimming ability, omnivory and latitudinal range size all had positive relationships with range extension rate, supporting hypotheses that increased dispersal capacity and ecological generalism promote extensions. We find independent support for the hypothesis that species with narrow latitudinal ranges are limited by factors other than climate. Our findings suggest that small-ranging species are in double jeopardy, with limited ability to escape warming and greater intrinsic vulnerability to stochastic disturbances. © 2015 John Wiley & Sons Ltd/CNRS.

A possible cause of the AO polarity reversal from winter to summer in 2010 and its relation to hemispheric extreme summer weather

NASA Astrophysics Data System (ADS)

Otomi, Yuriko; Tachibana, Yoshihiro; Nakamura, Tetsu

2013-04-01

In 2010, the Northern Hemisphere, in particular Russia and Japan, experienced an abnormally hot summer characterized by record-breaking warm temperatures and associated with a strongly positive Arctic Oscillation (AO), that is, low pressure in the Arctic and high pressure in the midlatitudes. In contrast, the AO index the previous winter and spring (2009/2010) was record-breaking negative. The AO polarity reversal that began in summer 2010 can explain the abnormally hot summer. The winter sea surface temperatures (SST) in the North Atlantic Ocean showed a tripolar anomaly pattern—warm SST anomalies over the tropics and high latitudes and cold SST anomalies over the midlatitudes—under the influence of the negative AO. The warm SST anomalies continued into summer 2010 because of the large oceanic heat capacity. A model simulation strongly suggested that the AO-related summertime North Atlantic oceanic warm temperature anomalies remotely caused blocking highs to form over Europe, which amplified the positive summertime AO. Thus, a possible cause of the AO polarity reversal might be the "memory" of the negative winter AO in the North Atlantic Ocean, suggesting an interseasonal linkage of the AO in which the oceanic memory of a wintertime negative AO induces a positive AO in the following summer. Understanding of this interseasonal linkage may aid in the long-term prediction of such abnormal summer events.

A possible cause of the AO polarity reversal from winter to summer in 2010 and its relation to hemispheric extreme hot summer

NASA Astrophysics Data System (ADS)

Tachibana, Yoshihiro; Otomi, Yuriko; Nakamura, Tetsu

2013-04-01

In 2010, the Northern Hemisphere, in particular Russia and Japan, experienced an abnormally hot summer characterized by record-breaking warm temperatures and associated with a strongly positive Arctic Oscillation (AO), that is, low pressure in the Arctic and high pressure in the midlatitudes. In contrast, the AO index the previous winter and spring (2009/2010) was record-breaking negative. The AO polarity reversal that began in summer 2010 can explain the abnormally hot summer. The winter sea surface temperatures (SST) in the North Atlantic Ocean showed a tripolar anomaly pattern—warm SST anomalies over the tropics and high latitudes and cold SST anomalies over the midlatitudes—under the influence of the negative AO. The warm SST anomalies continued into summer 2010 because of the large oceanic heat capacity. A model simulation strongly suggested that the AO-related summertime North Atlantic oceanic warm temperature anomalies remotely caused blocking highs to form over Europe, which amplified the positive summertime AO. Thus, a possible cause of the AO polarity reversal might be the "memory" of the negative winter AO in the North Atlantic Ocean, suggesting an interseasonal linkage of the AO in which the oceanic memory of a wintertime negative AO induces a positive AO in the following summer. Understanding of this interseasonal linkage may aid in the long-term prediction of such abnormal summer events.

Contrasting Heat Budget Dynamics During Two La Niña Marine Heat Wave Events Along Northwestern Australia

NASA Astrophysics Data System (ADS)

Xu, Jiangtao; Lowe, Ryan J.; Ivey, Gregory N.; Jones, Nicole L.; Zhang, Zhenling

2018-02-01

Two marine heat wave events along Western Australia (WA) during the alternate austral summer periods of 2010/2011 and 2012/2013, both linked to La Niña conditions, severely impacted marine ecosystems over more than 12° of latitude, which included the unprecedented bleaching of many coral reefs. Although these two heat waves were forced by similar large-scale climate drivers, the warming patterns differed substantially between events. The central coast of WA (south of 22°S) experienced greater warming in 2010/2011, whereas the northwestern coast of WA experienced greater warming in 2012/2013. To investigate how oceanic and atmospheric heat exchange processes drove these different spatial patterns, an analysis of the ocean heat budget was conducted by integrating remote sensing observations, in situ mooring data, and a high-resolution (˜1 km) ocean circulation model (Regional Ocean Modeling System). The results revealed substantial spatial differences in the relative contributions made by heat advection and air-sea heat exchange between the two heat wave events. During 2010/2011, anomalous warming driven by heat advection was present throughout the region but was much stronger south of 22°S where the poleward-flowing Leeuwin Current strengthens. During 2012/2013, air-sea heat exchange had a much more positive (warming) influence on sea surface temperatures (especially in the northwest), and when combined with a more positive contribution of heat advection in the north, this can explain the regional differences in warming between these two La Niña-associated marine heat wave events.

Insights into Ocean Acidification During the Middle Eocene Climatic Optimum from Boron Isotopes at Southern Ocean Site 738

NASA Astrophysics Data System (ADS)

Moebius, I.; Hoenisch, B.; Friedrich, O.

2015-12-01

The Middle Eocene Climatic Optimum (MECO) is a ~650-kyr interval of global warming, with a brief ~50 ky long peak warming interval, and an abrupt termination. Deep sea and surface ocean temperature evolution across this interval are fairly well constrained, but thus far we have little understanding of the mechanisms responsible for the gradual warming and rapid recovery. Carbonate mass accumulation rates suggest a shoaling of the carbonate compensation depth, and studies on alkenones indicate increasing atmospheric CO2 levels during the MECO. This suggests an increase in surface ocean CO2, and consequently ocean acidification. However, the severity and timing of the proposed ocean acidification with respect to the onset, peak warming and the termination are currently not well resolved. The boron isotopic composition (δ11B) recorded in planktic foraminifer shells offers an opportunity to infer oceanic pH across this interval. We are working on a boron isotope reconstruction from Southern Ocean IODP site 738 and South Atlantic IODP site 1263, covering 42.0 to 38.5 Ma. These sites are characterized by good carbonate preservation and well-defined age models have been established. Additionally, ecology, nutrient content and bottom-water oxygenation have been shown to change significantly across the event towards a more eutrophic, periodically oxygen-depleted environment supporting different biological communities. We selected the planktic foraminifera species Acarinina spinuloinflata for this study because it is symbiont-bearing, suggesting a near-surface habitat and little vertical migration in the water column, and because of its abundance in the samples. δ11B data will be translated to surface ocean pH and atmospheric pCO2 will be approximated to refine knowledge about the carbon cycle during this time. Parallel analysis of two core sites will help to evaluate the tenacity of the data.

Continental shelves as potential resource of rare earth elements.

PubMed

Pourret, Olivier; Tuduri, Johann

2017-07-19

The results of this study allow the reassessment of the rare earth elements (REE) external cycle. Indeed, the river input to the oceans has relatively flat REE patterns without cerium (Ce) anomalies, whereas oceanic REE patterns exhibit strong negative Ce anomalies and heavy REE enrichment. Indeed, the processes at the origin of seawater REE patterns are commonly thought to occur within the ocean masses themselves. However, the results from the present study illustrate that seawater-like REE patterns already occur in the truly dissolved pool of river input. This leads us to favor a partial or complete removal of the colloidal REE pool during estuarine mixing by coagulation, as previously shown for dissolved humic acids and iron. In this latter case, REE fractionation occurs because colloidal and truly dissolved pools have different REE patterns. Thus, the REE patterns of seawater could be the combination of both intra-oceanic and riverine processes. In this study, we show that the Atlantic continental shelves could be considered potential REE traps, suggesting further that shelf sediments could potentially become a resource for REE, similar to metalliferous deep sea sediments.

The ocean's role in polar climate change: asymmetric Arctic and Antarctic responses to greenhouse gas and ozone forcing

PubMed Central

Marshall, John; Armour, Kyle C.; Scott, Jeffery R.; Kostov, Yavor; Hausmann, Ute; Ferreira, David; Shepherd, Theodore G.; Bitz, Cecilia M.

2014-01-01

In recent decades, the Arctic has been warming and sea ice disappearing. By contrast, the Southern Ocean around Antarctica has been (mainly) cooling and sea-ice extent growing. We argue here that interhemispheric asymmetries in the mean ocean circulation, with sinking in the northern North Atlantic and upwelling around Antarctica, strongly influence the sea-surface temperature (SST) response to anthropogenic greenhouse gas (GHG) forcing, accelerating warming in the Arctic while delaying it in the Antarctic. Furthermore, while the amplitude of GHG forcing has been similar at the poles, significant ozone depletion only occurs over Antarctica. We suggest that the initial response of SST around Antarctica to ozone depletion is one of cooling and only later adds to the GHG-induced warming trend as upwelling of sub-surface warm water associated with stronger surface westerlies impacts surface properties. We organize our discussion around ‘climate response functions’ (CRFs), i.e. the response of the climate to ‘step’ changes in anthropogenic forcing in which GHG and/or ozone-hole forcing is abruptly turned on and the transient response of the climate revealed and studied. Convolutions of known or postulated GHG and ozone-hole forcing functions with their respective CRFs then yield the transient forced SST response (implied by linear response theory), providing a context for discussion of the differing warming/cooling trends in the Arctic and Antarctic. We speculate that the period through which we are now passing may be one in which the delayed warming of SST associated with GHG forcing around Antarctica is largely cancelled by the cooling effects associated with the ozone hole. By mid-century, however, ozone-hole effects may instead be adding to GHG warming around Antarctica but with diminished amplitude as the ozone hole heals. The Arctic, meanwhile, responding to GHG forcing but in a manner amplified by ocean heat transport, may continue to warm at an accelerating rate. PMID:24891392

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.

An investigation of CMIP5 model biases in simulating the impacts of central Pacific El Niño on the East Asian summer monsoon

NASA Astrophysics Data System (ADS)

Feng, Juan; Chen, Wen; Gong, Hainan; Ying, Jun; Jiang, Wenping

2018-06-01

The delayed impacts of the central Pacific (CP) El Niño on the East Asian summer monsoon (EASM) are evaluated by comparing historical runs from Coupled Model Intercomparison Project Phase 5 models against reanalysis data. In observations, an anomalous western North Pacific anticyclone (WNPAC), linking CP El Niño to the EASM, forms due to the transition of sea surface temperature (SST) warming into SST cooling over the CP, which generates a WNPAC through a Gill-Matsuno response. In comparison with the observational result, only one-third of the models (i.e., the type-I models) capture a weaker and smaller WNPAC, whereas the other two-thirds (i.e., the type-II models) fail to reproduce a WNPAC. The simulation biases in both of type-I models and type-II models mainly arise from an unrealistic, long-lasting CP El Niño warming, which causes a north Indian Ocean SST warming bias in models through air-sea interaction process. This north Indian Ocean SST warming generates the WNPAC through capacitor effects, which is different from the WNPAC formation mechanism in observations. This discrepancy leads to simulation biases in type-I models. In type-II models, the unrealistic CP El Niño warming persists into summer, which produces an anomalous cyclone over the central-western Pacific. The opposite effect of the CP and north Indian Ocean SST warming on the WNP atmospheric circulation leads to disappearance of the WNPAC. Hence, large simulation biases are produced in type-II models. Further analysis demonstrates the slow decay of CP El Niño is caused by the unrealistically simulated climatological SST, which creates strong warm meridional oceanic advection and results in a sustained CP El Niño warming.

The ocean's role in polar climate change: asymmetric Arctic and Antarctic responses to greenhouse gas and ozone forcing.

PubMed

Marshall, John; Armour, Kyle C; Scott, Jeffery R; Kostov, Yavor; Hausmann, Ute; Ferreira, David; Shepherd, Theodore G; Bitz, Cecilia M

2014-07-13

In recent decades, the Arctic has been warming and sea ice disappearing. By contrast, the Southern Ocean around Antarctica has been (mainly) cooling and sea-ice extent growing. We argue here that interhemispheric asymmetries in the mean ocean circulation, with sinking in the northern North Atlantic and upwelling around Antarctica, strongly influence the sea-surface temperature (SST) response to anthropogenic greenhouse gas (GHG) forcing, accelerating warming in the Arctic while delaying it in the Antarctic. Furthermore, while the amplitude of GHG forcing has been similar at the poles, significant ozone depletion only occurs over Antarctica. We suggest that the initial response of SST around Antarctica to ozone depletion is one of cooling and only later adds to the GHG-induced warming trend as upwelling of sub-surface warm water associated with stronger surface westerlies impacts surface properties. We organize our discussion around 'climate response functions' (CRFs), i.e. the response of the climate to 'step' changes in anthropogenic forcing in which GHG and/or ozone-hole forcing is abruptly turned on and the transient response of the climate revealed and studied. Convolutions of known or postulated GHG and ozone-hole forcing functions with their respective CRFs then yield the transient forced SST response (implied by linear response theory), providing a context for discussion of the differing warming/cooling trends in the Arctic and Antarctic. We speculate that the period through which we are now passing may be one in which the delayed warming of SST associated with GHG forcing around Antarctica is largely cancelled by the cooling effects associated with the ozone hole. By mid-century, however, ozone-hole effects may instead be adding to GHG warming around Antarctica but with diminished amplitude as the ozone hole heals. The Arctic, meanwhile, responding to GHG forcing but in a manner amplified by ocean heat transport, may continue to warm at an accelerating rate.

A model of the methane cycle, permafrost, and hydrology of the Siberian continental margin

DOE PAGES

Archer, D.

2014-06-03

A two-dimensional model of a passive continental margin was adapted to the simulation of the methane cycle on Siberian continental shelf and slope, attempting to account for the impacts of glacial/interglacial cycles in sea level, alternately exposing the continental shelf to freezing conditions with deep permafrost formation during glacial times, and immersion in the ocean in interglacial times. The model is used to gauge the impact of the glacial cycles, and potential anthropogenic warming in the deep future, on the atmospheric methane emission flux, and the sensitivities of that flux to processes such as permafrost formation and terrestrial organic carbonmore » (Yedoma) deposition. Hydrological forcing drives a freshening and ventilation of pore waters in areas exposed to the atmosphere, which is not quickly reversed by invasion of seawater upon submergence, since there is no analogous saltwater pump. This hydrological pump changes the salinity enough to affect the stability of permafrost and methane hydrates on the shelf. Permafrost formation inhibits bubble transport through the sediment column, by construction in the model. The impact of permafrost on the methane budget is to replace the bubble flux by offshore groundwater flow containing dissolved methane, rather than accumulating methane for catastrophic release when the permafrost seal fails during warming. By far the largest impact of the glacial/interglacial cycles on the atmospheric methane flux is attenuation by dissolution of bubbles in the ocean when sea level is high. Methane emissions are highest during the regression (soil freezing) part of the cycle, rather than during transgression (thawing). The model-predicted methane flux to the atmosphere in response to a warming climate is small, relative to the global methane production rate, because of the ongoing flooding of the continental shelf. A slight increase due to warming could be completely counteracted by sea level rise on geologic time scales, decreasing the efficiency of bubble transit through the water column. The methane cycle on the shelf responds to climate change on a long time constant of thousands of years, because hydrate is excluded thermodynamically from the permafrost zone by water limitation, leaving the hydrate stability zone at least 300 m below the sediment surface.« less

TOPEX/El Nino Watch - El Nino Warm Water Pool Decreasing, Jan, 08, 1998

NASA Technical Reports Server (NTRS)

1998-01-01

This image of the Pacific Ocean was produced using sea surface height measurements taken by the U.S.-French TOPEX/Poseidon satellite. The image shows sea surface height relative to normal ocean conditions on Jan. 8, 1998, and sea surface height is an indicator of the heat content of the ocean. The volume of the warm water pool related to the El Nino has decreased by about 40 percent since its maximum in early November, but the area of the warm water pool is still about one and a half times the size of the continental United States. The volume measurements are computed as the sum of all the sea surface height changes as compared to normal ocean conditions. In addition, the maximum water temperature in the eastern tropical Pacific, as measured by the National Oceanic and Atmospheric Administration (NOAA), is still higher than normal. Until these high temperatures diminish, the El Nino warm water pool still has great potential to disrupt global weather because the high water temperatures directly influence the atmosphere. Oceanographers believe the recent decrease in the size of the warm water pool is a normal part of El Nino's natural rhythm. TOPEX/Poseidon has been tracking these fluctuations of the El Nino warm pool since it began in early 1997. These sea surface height measurements have provided scientists with their first detailed view of how El Nino's warm pool behaves because the TOPEX/Poseidon satellite measures the changing sea surface height with unprecedented precision. In this image, the white and red areas indicate unusual patterns of heat storage; in the white areas, the sea surface is between 14 and 32 centimeters (6 to 13 inches) above normal; in the red areas, it's about 10 centimeters (4 inches) above normal. The green areas indicate normal conditions, while purple (the western Pacific) means at least 18 centimeters (7 inches) below normal sea level.

The El Nino phenomenon is thought to be triggered when the steady westward blowing trade winds weaken and even reverse direction. This change in the winds allows a large mass of warm water (the red and white area) that is normally located near Australia to move eastward along the equator until it reaches the coast of South America. The displacement of so much warm water affects evaporation, where rain clouds form and, consequently, alters the typical atmospheric jet stream patterns around the world. Using these global data, limited regional measurements from buoys and ships, and a forecasting model of the ocean-atmosphere system, the National Centers for Environmental Prediction (NCEP) of the National Oceanic and Atmospheric Administration, (NOAA), has issued an advisory indicating the presence of a strong El Nino condition throughout the winter.

For more information, please visit the TOPEX/Poseidon project web page at http://topex-www.jpl.nasa.gov

Ocean warming ameliorates the negative effects of ocean acidification on Paracentrotus lividus larval development and settlement.

PubMed

García, Eliseba; Clemente, Sabrina; Hernández, José Carlos

2015-09-01

Ocean warming and acidification both impact marine ecosystems. All organisms have a limited body temperature range, outside of which they become functionally constrained. Beyond the absolute extremes of this range, they cannot survive. It is hypothesized that some stressors can present effects that interact with other environmental variables, such as ocean acidification (OA) that have the potential to narrow the thermal range where marine species are functional. An organism's response to ocean acidification can therefore be highly dependent on thermal conditions. This study evaluated the combined effects of predicted ocean warming conditions and acidification, on survival, development, and settlement, of the sea urchin Paracentrotus lividus. Nine combined treatments of temperature (19.0, 20.5 and 22.5 °C) and pH (8.1, 7.7 and 7.4 units) were carried out. All of the conditions tested were either within the current natural ranges of seawater pH and temperature or are within the ranges that have been predicted for the end of the century, in the sampling region (Canary Islands). Our results indicated that the negative effects of low pH on P. lividus larval development and settlement will be mitigated by a rise in seawater temperature, up to a thermotolerance threshold. Larval development and settlement performance of the sea urchin P. lividus was enhanced by a slight increase in temperature, even under lowered pH conditions. However, the species did show negative responses to the levels of ocean warming and acidification that have been predicted for the turn of the century. Copyright © 2015 Elsevier Ltd. All rights reserved.

The ocean-atmosphere response to wind-induced thermocline changes in the tropical South Western Indian Ocean

NASA Astrophysics Data System (ADS)

Manola, Iris; Selten, F. M.; de Ruijter, W. P. M.; Hazeleger, W.

2015-08-01

In the Indian Ocean basin the sea surface temperatures (SSTs) are most sensitive to changes in the oceanic depth of the thermocline in the region of the Seychelles Dome. Observational studies have suggested that the strong SST variations in this region influence the atmospheric evolution around the basin, while its impact could extend far into the Pacific and the extra-tropics. Here we study the adjustments of the coupled atmosphere-ocean system to a winter shallow doming event using dedicated ensemble simulations with the state-of-the-art EC-Earth climate model. The doming creates an equatorial Kelvin wave and a pair of westward moving Rossby waves, leading to higher SST 1-2 months later in the Western equatorial Indian Ocean. Atmospheric convection is strengthened and the Walker circulation responds with reduced convection over Indonesia and cooling of the SST in that region. The Pacific warm pool convection shifts eastward and an oceanic Kelvin wave is triggered at thermocline depth. The wave leads to an SST warming in the East Equatorial Pacific 5-6 months after the initiation of the Seychelles Dome event. The atmosphere responds to this warming with weak anomalous atmospheric convection. The changes in the upper tropospheric divergence in this sequence of events create large-scale Rossby waves that propagate away from the tropics along the atmospheric waveguides. We suggest to repeat these types of experiments with other models to test the robustness of the results. We also suggest to create the doming event in June so that the East-Pacific warming occurs in November when the atmosphere is most sensitive to SST anomalies and El Niño could possibly be triggered by the doming event under suitable conditions.

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

Archer, D.

A two-dimensional model of a sediment column, with Darcy fluid flow, biological and thermal methane production, and permafrost and methane hydrate formation, is subjected to glacial–interglacial cycles in sea level, alternately exposing the continental shelf to the cold atmosphere during glacial times and immersing it in the ocean in interglacial times. The glacial cycles are followed by a "long-tail" 100 kyr warming due to fossil fuel combustion. The salinity of the sediment column in the interior of the shelf can be decreased by hydrological forcing to depths well below sea level when the sediment is exposed to the atmosphere. Theremore » is no analogous advective seawater-injecting mechanism upon resubmergence, only slower diffusive mechanisms. This hydrological ratchet is consistent with the existence of freshwater beneath the sea floor on continental shelves around the world, left over from the last glacial period. The salt content of the sediment column affects the relative proportions of the solid and fluid H 2O-containing phases, but in the permafrost zone the salinity in the pore fluid brine is a function of temperature only, controlled by equilibrium with ice. Ice can tolerate a higher salinity in the pore fluid than methane hydrate can at low pressure and temperature, excluding methane hydrate from thermodynamic stability in the permafrost zone. The implication is that any methane hydrate existing today will be insulated from anthropogenic climate change by hundreds of meters of sediment, resulting in a response time of thousands of years. The strongest impact of the glacial–interglacial cycles on the atmospheric methane flux is due to bubbles dissolving in the ocean when sea level is high. When sea level is low and the sediment surface is exposed to the atmosphere, the atmospheric flux is sensitive to whether permafrost inhibits bubble migration in the model. If it does, the atmospheric flux is highest during the glaciating, sea level regression (soil-freezing) part of the cycle rather than during deglacial transgression (warming and thawing). The atmospheric flux response to a warming climate is small, relative to the rest of the methane sources to the atmosphere in the global budget, because of the ongoing flooding of the continental shelf. The increased methane flux due to ocean warming could be completely counteracted by a sea level rise of tens of meters on millennial timescales due to the loss of ice sheets, decreasing the efficiency of bubble transit through the water column. The model results give no indication of a mechanism by which methane emissions from the Siberian continental shelf could have a significant impact on the near-term evolution of Earth's climate, but on millennial timescales the release of carbon from hydrate and permafrost could contribute significantly to the fossil fuel carbon burden in the atmosphere–ocean–terrestrial carbon cycle.« less

Multidecadal-scale adjustment of the ocean mixed layer heat budget in the tropics: examining ocean reanalyses

NASA Astrophysics Data System (ADS)

Cook, Kerry H.; Vizy, Edward K.; Sun, Xiaoming

2018-03-01

Distributions of ocean mixed layer temperature trends and trends in the net heat flux from the atmosphere differ, indicating the important role of the transport of heat within the ocean for determining temperature trends. Annual-mean, linear trends in the components of the tropical ocean mixed layer heat budget for 1980-2015 are diagnosed in 4 ocean reanalyses to improve our physical understanding of multidecadal-scale SST trends. The well-known temperature trend in the tropical Pacific, with cooling in the east and warming in the west, is reproduced in each reanalysis with high statistical significance. Cooling in the east is associated with negative trends in the net heat flux from the atmosphere and enhanced equatorial upwelling related to a strengthening of the subtropical cells. Negative trends in the net heat flux also occur in the western tropical Pacific, but advective warming associated with a strengthening and shoaling of the equatorial undercurrent overwhelms these negative trends. The strengthening of the equatorial undercurrent is consistent with enhanced easterly wind stress, which is applied to the ocean reanalyses, and differential sea level trends that enhance the negative zonal height gradient across the Pacific. The Pacific North Equatorial countercurrent is also strengthening in all 4 reanalyses in association with a strengthening of the sea level trough at 10°N in the central and eastern Pacific. All 4 ocean reanalyses produce warming of 0.1-0.3 K/decade in the North Atlantic with statistical significance levels ranging from below 90-99%. The Atlantic is similar to the Pacific in having the equatorial undercurrent strengthening, but indications of shoaling are less consistent in the reanalyses and the North Equatorial Countercurrent in the Atlantic is not strengthening. Large-scale ocean mixed layer warming trends in the Indian Ocean in the reanalyses are interrupted by some regional cooling close to the equator. Net surface heat flux trends are mostly negative, indicating increasing heat fluxes from the ocean to the atmosphere. Wind stress trends applied to the ocean reanalyses are weak, but trends in the Indian Ocean equatorial undercurrent are strong. Since the Indian monsoon climate introduces strong seasonality, the annual analysis may not be adequate for studying physical processes in this ocean basin.

Role of the Indonesian Throughflow in controlling regional mean climate and rainfall variability

NASA Astrophysics Data System (ADS)

England, Matthew H.; Santoso, Agus; Phipps, Steven; Ummenhofer, Caroline

2017-04-01

The role of the Indonesian Throughflow (ITF) in controlling regional mean climate and rainfall is examined using a coupled ocean-atmosphere general circulation model. Experiments employing both a closed and open ITF are equilibrated to steady state and then 200 years of natural climatic variability is assessed within each model run, with a particular focus on the Indian Ocean region. Opening of the ITF results in a mean Pacific-to-Indian throughflow of 21 Sv (1 Sv = 106 m3 sec-1), which advects warm west Pacific waters into the east Indian Ocean. This warm signature is propagated westward by the mean ocean flow, however it never reaches the west Indian Ocean, as an ocean-atmosphere feedback in the tropics generates a weakened trade wind field that is reminiscent of the negative phase of the Indian Ocean Dipole (IOD). This is in marked contrast to the Indian Ocean response to an open ITF when examined in ocean-only model experiments; which sees a strengthening of both the Indian Ocean South Equatorial Current and the Agulhas Current. The coupled feedback in contrast leads to cooler conditions over the west Indian Ocean, and an anomalous zonal atmospheric pressure gradient that enhances the advection of warm moist air toward south Asia and Australia. This leaves the African continent significantly drier, and much of Australia and southern Asia significantly wetter, in response to the opening of the ITF. Given the substantial interannual variability that the ITF exhibits in the present-day climate system, and the restriction of the ITF gateway in past climate eras, this could have important implications for understanding past and present regional rainfall patterns around the Indian Ocean and over neighbouring land-masses.

Increased frequency of extreme Indian Ocean Dipole events due to greenhouse warming.

PubMed

Cai, Wenju; Santoso, Agus; Wang, Guojian; Weller, Evan; Wu, Lixin; Ashok, Karumuri; Masumoto, Yukio; Yamagata, Toshio

2014-06-12

The Indian Ocean dipole is a prominent mode of coupled ocean-atmosphere variability, affecting the lives of millions of people in Indian Ocean rim countries. In its positive phase, sea surface temperatures are lower than normal off the Sumatra-Java coast, but higher in the western tropical Indian Ocean. During the extreme positive-IOD (pIOD) events of 1961, 1994 and 1997, the eastern cooling strengthened and extended westward along the equatorial Indian Ocean through strong reversal of both the mean westerly winds and the associated eastward-flowing upper ocean currents. This created anomalously dry conditions from the eastern to the central Indian Ocean along the Equator and atmospheric convergence farther west, leading to catastrophic floods in eastern tropical African countries but devastating droughts in eastern Indian Ocean rim countries. Despite these serious consequences, the response of pIOD events to greenhouse warming is unknown. Here, using an ensemble of climate models forced by a scenario of high greenhouse gas emissions (Representative Concentration Pathway 8.5), we project that the frequency of extreme pIOD events will increase by almost a factor of three, from one event every 17.3 years over the twentieth century to one event every 6.3 years over the twenty-first century. We find that a mean state change--with weakening of both equatorial westerly winds and eastward oceanic currents in association with a faster warming in the western than the eastern equatorial Indian Ocean--facilitates more frequent occurrences of wind and oceanic current reversal. This leads to more frequent extreme pIOD events, suggesting an increasing frequency of extreme climate and weather events in regions affected by the pIOD.

Warming increases nutrient mobilization and gaseous nitrogen removal from sediments across cascade reservoirs.

PubMed

Zhou, Xingpeng; Chen, Nengwang; Yan, Zhihao; Duan, Shuiwang

2016-12-01

Increases in water temperature, as a result of climate change, may influence biogeochemical cycles, sediment-water fluxes and consequently environmental sustainability. Effects of rising temperature on dynamics of nitrate, nitrite, ammonium, dissolved inorganic nitrogen (DIN), dissolved reactive phosphorus (DRP), dissolved organic carbon (DOC) and gaseous nitrogen (N 2 and N 2 O) were examined in a subtropical river (the Jiulong River, southeast China) by microcosm experiments. Slurry sediments and overlying water were collected from three continuous cascade reservoirs, and laboratory incubations were performed at four temperature gradients (5 °C, 15 °C, 25 °C and 35 °C). Results indicated: (1) warming considerably increased sediment ammonium, DIN and DOC fluxes to overlying water; (2) warming increased retention of nitrate, and to a lesser extent, nitrite, corresponding to increases in N 2 and N 2 O emission; (3) DRP was retained but released from Fe/Al-P enriched sediments at high temperature (35 °C) due to enhanced coupled transformation of carbon and nitrogen with oxygen deficiency. Using relationships between sediment fluxes and temperature, a projected 2.3°C-warming in future would increase ammonium flux from sediment by 7.0%-16.8%, while increasing nitrate flux into sediment by 8.9%-28.6%. Moreover, substrates (e.g., grain size, carbon availability) influenced nutrient delivery and cycling across cascade reservoirs. This study highlights that warming would increase bioreactive nutrient (i.e., ammonium and phosphate) mobilization with limited gaseous N removal from sediments, consequently deteriorating water quality and increasing eutrophication with future climate change. Copyright © 2016 Elsevier Ltd. All rights reserved.

Observed temperature trends in the Indian Ocean over 1960-1999 and associated mechanisms

NASA Astrophysics Data System (ADS)

Alory, Gaël; Wijffels, Susan; Meyers, Gary

2007-01-01

The linear trends in oceanic temperature from 1960 to 1999 are estimated using the new Indian Ocean Thermal Archive (IOTA), a compilation of historical temperature profiles. Widespread surface warming is found, as in other data sets, and reproduced in IPCC climate model simulations for the 20th century. This warming is particularly large in the subtropics, and extends down to 800 m around 40-50°S. Models suggest the deep-reaching subtropical warming is related to a 0.5° southward shift of the subtropical gyre driven by a strengthening of the westerly winds, and associated with an upward trend in the Southern Annular Mode index. In the tropics, IOTA shows a subsurface cooling corresponding to a shoaling of the thermocline and increasing vertical stratification. Most models suggest this trend in the tropical Indian thermocline is likely associated with the observed weakening of the Pacific trade winds and transmitted to the Indian Ocean by the Indonesian throughflow.

Multi-sensor Improved Sea-Surface Temperature (MISST) for IOOS - Navy Component

DTIC Science & Technology

2013-09-30

application and data fusion techniques. 2. Parameterization of IR and MW retrieval differences, with consideration of diurnal warming and cool-skin effects...associated retrieval confidence, standard deviation (STD), and diurnal warming estimates to the application user community in the new GDS 2.0 GHRSST...including coral reefs, ocean modeling in the Gulf of Mexico, improved lake temperatures, numerical data assimilation by ocean models, numerical

Mitigating Local Causes of Ocean Acidification with Existing Laws

EPA Science Inventory

The oceans continue to absorb CO2 in step with the increasing atmospheric concentration of CO2. The dissolved CO2 reacts with seawater to form carbonic acid (H2CO3) and liberate hydrogen ions, causing the pH of the oceans to decrease. Ocean acidification is thus an inevitable a...

TRMM-observed summer warm rain over the tropical and subtropical Pacific Ocean: Characteristics and regional differences

NASA Astrophysics Data System (ADS)

Qin, Fang; Fu, Yunfei

2016-06-01

Based on the merged measurements from the TRMM Precipitation Radar and Visible and Infrared Scanner, refined characteristics (intensity, frequency, vertical structure, and diurnal variation) and regional differences of the warm rain over the tropical and subtropical Pacific Ocean (40ffiS-40ffiN, 120ffiE-70ffiW) in boreal summer are investigated for the period 1998-2012. The results reveal that three warm rain types (phased, pure, and mixed) exist over these regions. The phased warm rain, which occurs during the developing or declining stage of precipitation weather systems, is located over the central to western Intertropical Convergence Zone, South Pacific Convergence Zone, and Northwest Pacific. Its occurrence frequency peaks at midnight and minimizes during daytime with a 5.5-km maximum echo top. The frequency of this warm rain type is about 2.2%, and it contributes to 40% of the regional total rainfall. The pure warm rain is characterized by typical stable precipitation with an echo top lower than 4 km, and mostly occurs in Southeast Pacific. Although its frequency is less than 1.3%, this type of warm rain accounts for 95% of the regional total rainfall. Its occurrence peaks before dawn and it usually disappears in the afternoon. For the mixed warm rain, some may develop into deep convective precipitation, while most are similar to those of the pure type. The mixed warm rain is mainly located over the ocean east of Hawaii. Its frequency is 1.2%, but this type of warm rain could contribute to 80% of the regional total rainfall. The results also uncover that the mixed and pure types occur over the regions where SST ranges from 295 to 299 K, accompanied by relatively strong downdrafts at 500 hPa. Both the mixed and pure warm rains happen in a more unstable atmosphere, compared with the phased warm rain.

An examination of the role of particles in oceanic mercury cycling

NASA Astrophysics Data System (ADS)

Lamborg, Carl H.; Hammerschmidt, Chad R.; Bowman, Katlin L.

2016-11-01

Recent models of global mercury (Hg) cycling have identified the downward flux of sinking particles in the ocean as a prominent Hg removal process from the ocean. At least one of these models estimates the amount of anthropogenic Hg in the ocean to be about 400 Mmol, with deep water formation and sinking fluxes representing the largest vectors by which pollutant Hg is able to penetrate the ocean interior. Using data from recent cruises to the Atlantic, we examined the dissolved and particulate partitioning of Hg in the oceanic water column as a cross-check on the hypothesis that sinking particle fluxes are important. Interestingly, these new data suggest particle-dissolved partitioning (Kd) that is approximately 20× greater than previous estimates, which thereby challenges certain assumptions about the scavenging and active partitioning of Hg in the ocean used in earlier models. For example, the new particle data suggest that regenerative scavenging is the most likely mechanism by which the association of Hg and particles occurs. This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

Oceanographic Setting Dominates Methane Transport Through the Water Column in the Shallow Area West of Prins Karls Forland, Arctic Ocean

NASA Astrophysics Data System (ADS)

Silyakova, A.; Jansson, P.; Serov, P.; Graves, C. A.; Niemann, H.; Grundger, F.; Ferre, B.; Mienert, J.

2016-02-01

The area west of Prins Karls Forland (PKF, West Spitsbergen) in the Arctic Ocean, restricted to 90 m water depth, is known for a large amount of shallow active gas flares. Gas flares are streams of bubbles that contain mostly methane, which is a potent greenhouse gas. The important questions for many areas with discovered gas flares are: Does this gas reach the atmosphere? What controls the vertical and horizontal distribution of dissolved methane away from the source on the seafloor? Is all dissolved methane detected above gas flares released from those flares or does it partially originate from other areas (eg. Storfjorden, or area of deeper flares on the PKF slope)? The present study is based on two repeated oceanographic surveys conducted in the summers of 2014 and 2015. During the surveys, we sampled 64 CTD stations in a grid above a 30 x 15 km area with active methane flares. Vertical profiles of temperature (T) and salinity (S), as well as TS diagrams indicate very different oceanographic settings during the two surveys. Warm and saline Atlantic waters originating from the West Spitsbergen Current prevailed during the 2014 campaign. In 2015, in contrast, waters were distinctly less saline and cooler. These waters originate from the East-Spitsbergen current that flows northwards over the shelf from the Barents Sea around the southern tip of Spitsbergen. The water mass was furthermore influenced by local sources from the fjords. In both years, we observed strong vertical gradients in the distribution of dissolved methane in the water column above gas flares, with only 4% methane concentrations at the sea surface when compared to bottom waters. However, the circulation of the dominant water masses mainly controlled the horizontal distribution of methane in the water column in the specific year. We discuss oceanographic processes and mechanisms responsible for methane transport and transformation in the study area. This study is funded by CAGE (Centre for Arctic Gas Hydrate, Environment and Climate), Norwegian Research Council grant no. 223259.

Pan-arctic trends in terrestrial dissolved organic matter from optical measurements

USGS Publications Warehouse

Mann, Paul J.; Spencer, Robert G.M.; Hernes, Peter J.; Six, Johan; Aiken, George R.; Tank, Suzanne E.; McClelland, James W.; Butler, Kenna D.; Dyda, Rachael Y.; Holmes, Robert M.

2016-01-01

Climate change is causing extensive warming across Arctic regions resulting in permafrost degradation, alterations to regional hydrology and shifting amounts and composition of dissolved organic matter (DOM) transported by streams and rivers. Here, we characterize the DOM composition and optical properties of the six largest Arctic rivers draining into the Arctic Ocean to examine the ability of optical measurements to provide meaningful insights into terrigenous carbon export patterns and biogeochemical cycling. The chemical composition of aquatic DOM varied with season, spring months were typified by highest lignin phenol and dissolved organic carbon (DOC) concentrations with greater hydrophobic acid content, and lower proportions of hydrophilic compounds, relative to summer and winter months. Chromophoric DOM (CDOM) spectral slope (S275–295) tracked seasonal shifts in DOM composition across river basins. Fluorescence and parallel factor analysis identified seven components across the six Arctic rivers. The ratios of “terrestrial humic-like” vs. “marine humic-like” fluorescent components co-varied with lignin monomer ratios over summer and winter months, suggesting fluorescence may provide information on the age and degradation state of riverine DOM. CDOM absorbance (a350) proved a sensitive proxy for lignin phenol concentrations across all six river basins and over the hydrograph, enabling for the first time the development of a single pan-arctic relationship between a350 and terrigenous DOC (R2 = 0.93). Combining this lignin proxy with high-resolution monitoring of a350, pan-arctic estimates of annual lignin flux were calculated to range from 156 to 185 Gg, resulting in shorter and more constrained estimates of terrigenous DOM residence times in the Arctic Ocean (spanning 7 months to 2½ years). Furthermore, multiple linear regression models incorporating both absorbance and fluorescence variables proved capable of explaining much of the variability in lignin composition across rivers and seasons. Our findings suggest that synoptic, high-resolution optical measurements can provide improved understanding of northern high-latitude organic matter cycling and flux, and prove an important technique for capturing future climate-driven changes.

Pan-arctic trends in terrestrial dissolved organic matter from optical measurements

USGS Publications Warehouse

Mann, Paul J.; Spencer, Robert G. M.; Hernes, Peter J.; Six, Johan; Aiken, George R.; Tank, Suzanne E.; McClelland, James W.; Butler, Kenna D.; Dyda, Rachael Y.; Holmes, Robert M.

2016-01-01

Climate change is causing extensive warming across Arctic regions resulting in permafrost degradation, alterations to regional hydrology and shifting amounts and composition of dissolved organic matter (DOM) transported by streams and rivers. Here, we characterize the DOM composition and optical properties of the six largest Arctic rivers draining into the Arctic Ocean to examine the ability of optical measurements to provide meaningful insights into terrigenous carbon export patterns and biogeochemical cycling. The chemical composition of aquatic DOM varied with season, spring months were typified by highest lignin phenol and dissolved organic carbon (DOC) concentrations with greater hydrophobic acid content, and lower proportions of hydrophilic compounds, relative to summer and winter months. Chromophoric DOM (CDOM) spectral slope (S275–295) tracked seasonal shifts in DOM composition across river basins. Fluorescence and parallel factor analysis identified seven components across the six Arctic rivers. The ratios of “terrestrial humic-like” vs. “marine humic-like” fluorescent components co-varied with lignin monomer ratios over summer and winter months, suggesting fluorescence may provide information on the age and degradation state of riverine DOM. CDOM absorbance (a350) proved a sensitive proxy for lignin phenol concentrations across all six river basins and over the hydrograph, enabling for the first time the development of a single pan-arctic relationship between a350 and terrigenous DOC (R2 = 0.93). Combining this lignin proxy with high-resolution monitoring of a350, pan-arctic estimates of annual lignin flux were calculated to range from 156 to 185 Gg, resulting in shorter and more constrained estimates of terrigenous DOM residence times in the Arctic Ocean (spanning 7 months to 2½ years). Furthermore, multiple linear regression models incorporating both absorbance and fluorescence variables proved capable of explaining much of the variability in lignin composition across rivers and seasons. Our findings suggest that synoptic, high-resolution optical measurements can provide improved understanding of northern high-latitude organic matter cycling and flux, and prove an important technique for capturing future climate-driven changes.

Project CLIMPEAT - Influence of global warming and drought on the carbon sequestration and biodiversity of Sphagnum peatlands

NASA Astrophysics Data System (ADS)

Lamentowicz, M.; Buttler, A.; Mitchell, E. A. D.; Chojnicki, B.; Słowińska, S.; Słowiński, M.

2012-04-01

Northern peatlands represent a globally significant pool of carbon and are subject to the highest rates of climate warming, and most of these peatlands are in continental settings. However, it is unclear if how fast peatlands respond to past and present changes in temperature and surface moisture in continental vs. oceanic climate settings. The CLIMPEAT project brings together scientists from Poland and Switzerland. Our goal is to assess the past and present vulnerability to climate change of Sphagnum peatland plant and microbial communities, peat organic matter transformations and carbon sequestration using a combination of field and mesocosm experiments simulating warming and water table changes and palaeoecological studies. Warming will be achieved using ITEX-type "Open-Top Chambers". The field studies are conducted in Poland, at the limit between oceanic and continental climates, and are part of a network of projects also including field experiments in the French Jura (sub-oceanic) and in Siberia (continental). We will calibrate the response of key biological (plants, testate amoebae) and geochemical (isotopic composition of organic compounds, organic matter changes) proxies to warming and water table changes and use these proxies to reconstruct climate changes during the last 1000 years.

The Footprint of the Inter-decadal Pacific Oscillation in Indian Ocean Sea Surface Temperatures

NASA Astrophysics Data System (ADS)

Dong, Lu; Zhou, Tianjun; Dai, Aiguo; Song, Fengfei; Wu, Bo; Chen, Xiaolong

2016-02-01

Superimposed on a pronounced warming trend, the Indian Ocean (IO) sea surface temperatures (SSTs) also show considerable decadal variations that can cause regional climate oscillations around the IO. However, the mechanisms of the IO decadal variability remain unclear. Here we perform numerical experiments using a state-of-the-art, fully coupled climate model in which the external forcings with or without the observed SSTs in the tropical eastern Pacific Ocean (TEP) are applied for 1871-2012. Both the observed timing and magnitude of the IO decadal variations are well reproduced in those experiments with the TEP SSTs prescribed to observations. Although the external forcings account for most of the warming trend, the decadal variability in IO SSTs is dominated by internal variability that is induced by the TEP SSTs, especially the Inter-decadal Pacific Oscillation (IPO). The IPO weakens (enhances) the warming of the external forcings by about 50% over the IO during IPO’s cold (warm) phase, which contributes about 10% to the recent global warming hiatus since 1999. The decadal variability in IO SSTs is modulated by the IPO-induced atmospheric adjustment through changing surface heat fluxes, sea surface height and thermocline depth.

The Footprint of the Inter-decadal Pacific Oscillation in Indian Ocean Sea Surface Temperatures.

PubMed

Dong, Lu; Zhou, Tianjun; Dai, Aiguo; Song, Fengfei; Wu, Bo; Chen, Xiaolong

2016-02-17

Superimposed on a pronounced warming trend, the Indian Ocean (IO) sea surface temperatures (SSTs) also show considerable decadal variations that can cause regional climate oscillations around the IO. However, the mechanisms of the IO decadal variability remain unclear. Here we perform numerical experiments using a state-of-the-art, fully coupled climate model in which the external forcings with or without the observed SSTs in the tropical eastern Pacific Ocean (TEP) are applied for 1871-2012. Both the observed timing and magnitude of the IO decadal variations are well reproduced in those experiments with the TEP SSTs prescribed to observations. Although the external forcings account for most of the warming trend, the decadal variability in IO SSTs is dominated by internal variability that is induced by the TEP SSTs, especially the Inter-decadal Pacific Oscillation (IPO). The IPO weakens (enhances) the warming of the external forcings by about 50% over the IO during IPO's cold (warm) phase, which contributes about 10% to the recent global warming hiatus since 1999. The decadal variability in IO SSTs is modulated by the IPO-induced atmospheric adjustment through changing surface heat fluxes, sea surface height and thermocline depth.

Ocean forcing of Ice Sheet retreat in central west Greenland from LGM to the early Holocene

NASA Astrophysics Data System (ADS)

Jennings, Anne E.; Andrews, John T.; Ó Cofaigh, Colm; Onge, Guillaume St.; Sheldon, Christina; Belt, Simon T.; Cabedo-Sanz, Patricia; Hillaire-Marcel, Claude

2017-08-01

Three radiocarbon dated sediment cores from trough mouth fans on the central west Greenland continental slope were studied to determine the timing and processes of Greenland Ice Sheet (GIS) retreat from the shelf edge during the last deglaciation and to test the role of ocean forcing (i.e. warm ocean water) thereon. Analyses of lithofacies, quantitative x-ray diffraction mineralogy, benthic foraminiferal assemblages, the sea-ice biomarker IP25, and δ18 O of the planktonic foraminifera Neogloboquadrina pachyderma sinistral from sediments in the interval from 17.5-10.8 cal ka BP provide consistent evidence for ocean and ice sheet interactions during central west Greenland (CWG) deglaciation. The Disko and Uummannaq ice streams both retreated from the shelf edge after the last glacial maximum (LGM) under the influence of subsurface, warm Atlantic Water. The warm subsurface water was limited to depths below the ice stream grounding lines during the LGM, when the GIS terminated as a floating ice shelf in a sea-ice covered Baffin Bay. The deeper Uummannaq ice stream retreated first (ca. 17.1 cal ka BP), while the shallower Disko ice stream retreated at ca. 16.2 cal ka BP. The grounding lines were protected from accelerating mass loss (calving) by a buttressing ice shelf and by landward shallowing bathymetry on the outer shelf. Calving retreat was delayed until ca. 15.3 cal ka BP in the Uummannaq Trough and until 15.1 cal ka BP in the Disko Trough, during another interval of ocean warming. Instabilities in the Laurentide, Innuitian and Greenland ice sheets with outlets draining into northern Baffin Bay periodically released cold, fresh water that enhanced sea ice formation and slowed GIS melt. During the Younger Dryas, the CWG records document strong cooling, lack of GIS meltwater, and an increase in iceberg rafted material from northern Baffin Bay. The ice sheet remained in the cross-shelf troughs until the early Holocene, when it retreated rapidly by calving and strong melting under the influence of atmosphere and ocean warming and a steep reverse slope toward the deep fjords. We conclude that ocean warming played an important role in the palaeo-retreat dynamics of the GIS during the last deglaciation.

A synthesis of light absorption properties of the Pan-Arctic Ocean: application to semi-analytical estimates of dissolved organic carbon concentrations from space

NASA Astrophysics Data System (ADS)

Matsuoka, A.; Babin, M.; Doxaran, D.; Hooker, S. B.; Mitchell, B. G.; Bélanger, S.; Bricaud, A.

2013-11-01

The light absorption coefficients of particulate and dissolved materials are the main factors determining the light propagation of the visible part of the spectrum and are, thus, important for developing ocean color algorithms. While these absorption properties have recently been documented by a few studies for the Arctic Ocean (e.g., Matsuoka et al., 2007, 2011; Ben Mustapha et al., 2012), the datasets used in the literature were sparse and individually insufficient to draw a general view of the basin-wide spatial and temporal variations in absorption. To achieve such a task, we built a large absorption database at the pan-Arctic scale by pooling the majority of published datasets and merging new datasets. Our results showed that the total non-water absorption coefficients measured in the Eastern Arctic Ocean (EAO; Siberian side) are significantly higher than in the Western Arctic Ocean (WAO; North American side). This higher absorption is explained by higher concentration of colored dissolved organic matter (CDOM) in watersheds on the Siberian side, which contains a large amount of dissolved organic carbon (DOC) compared to waters off North America. In contrast, the relationship between the phytoplankton absorption (aφ(λ)) and chlorophyll a (chl a) concentration in the EAO was not significantly different from that in the WAO. Because our semi-analytical CDOM absorption algorithm is based on chl a-specific aφ(λ) values (Matsuoka et al., 2013), this result indirectly suggests that CDOM absorption can be appropriately derived not only for the WAO but also for the EAO using ocean color data. Derived CDOM absorption values were reasonable compared to in situ measurements. By combining this algorithm with empirical DOC vs. CDOM relationships, a semi-analytical algorithm for estimating DOC concentrations for coastal waters at the Pan-Arctic scale is presented and applied to satellite ocean color data.

A Synthesis of Light Absorption Properties of the Arctic Ocean: Application to Semi-analytical Estimates of Dissolved Organic Carbon Concentrations from Space

NASA Technical Reports Server (NTRS)

Matsuoka, A.; Babin, M.; Doxaran, D.; Hooker, S. B.; Mitchell, B. G.; Belanger, S.; Bricaud, A.

2014-01-01

The light absorption coefficients of particulate and dissolved materials are the main factors determining the light propagation of the visible part of the spectrum and are, thus, important for developing ocean color algorithms. While these absorption properties have recently been documented by a few studies for the Arctic Ocean [e.g., Matsuoka et al., 2007, 2011; Ben Mustapha et al., 2012], the datasets used in the literature were sparse and individually insufficient to draw a general view of the basin-wide spatial and temporal variations in absorption. To achieve such a task, we built a large absorption database at the pan-Arctic scale by pooling the majority of published datasets and merging new datasets. Our results showed that the total non-water absorption coefficients measured in the Eastern Arctic Ocean (EAO; Siberian side) are significantly higher 74 than in the Western Arctic Ocean (WAO; North American side). This higher absorption is explained 75 by higher concentration of colored dissolved organic matter (CDOM) in watersheds on the Siberian 76 side, which contains a large amount of dissolved organic carbon (DOC) compared to waters off 77 North America. In contrast, the relationship between the phytoplankton absorption (a()) and chlorophyll a (chl a) concentration in the EAO was not significantly different from that in the WAO. Because our semi-analytical CDOM absorption algorithm is based on chl a-specific a() values [Matsuoka et al., 2013], this result indirectly suggests that CDOM absorption can be appropriately erived not only for the WAO but also for the EAO using ocean color data. Derived CDOM absorption values were reasonable compared to in situ measurements. By combining this algorithm with empirical DOC versus CDOM relationships, a semi-analytical algorithm for estimating DOC concentrations for coastal waters at the Pan-Arctic scale is presented and applied to satellite ocean color data.

Simulating global and local surface temperature changes due to Holocene anthropogenic land cover change

NASA Astrophysics Data System (ADS)

He, F.; Vavrus, S. J.; Kutzbach, J. E.; Ruddiman, W. F.; Kaplan, J. O.; Krumhardt, K. M.

2015-12-01

Surface albedo changes from anthropogenic land cover change (ALCC) represent the second-largest negative radiative forcing behind aerosol during the industrial era. Using a new reconstruction of ALCC during the Holocene era by Kaplan et al. [2011], we quantify the local and global temperature response induced by Holocene ALCC in the Community Climate System Model, version 4 (CCSM4). With 1-degree resolution of the CCSM4 slab-ocean model,we find that Holocene ALCC cause a global cooling of 0.17 °C due to the biogeophysical effects of land-atmosphere exchange of momentum, moisture, radiative and heat fluxes. On the global scale, the biogeochemical effects of Holocene ALCC from carbon emissions dominate the biogeophysical effects by causing 0.9 °C global warming. The net effects of Holocene ALCC amount to a global warming of 0.73 °C during the pre-industrial era, which is comparable to the ~0.8 °C warming during industrial times. On local to regional scales, such as parts of Europe, North America and Asia, the biogeophysical effects of Holocene ALCC are significant and comparable to the biogeochemical effect. The lack of ocean dynamics in the 1° CCSM4 slab-ocean simulations could underestimate the climate sensitivity because of the lack of feedbacks from ocean heat transport [Kutzbach et al., 2013; Manabe and Bryan, 1985]. In 1° CCSM4 fully coupled simulations, the climate sensitivity is ~65% larger than the 1° CCSM4 slab-ocean simulations during the Holocene (5.3 °C versus 3.2 °C) [Kutzbach et al., 2013]. With this greater climate sensitivity, the biogeochemical effects of Holocene ALCC could have caused a global warming of ~1.5 °C, and the net biogeophysical and biogeochemical effects of Holocene ALCC could cause a global warming of 1.2 °C during the preindustrial era in our simulations, which is 50% higher than the global warming of ~0.8 °C during industrial times.

Imbalanced nutrient recycling in a warmer ocean driven by differential response of extracellular enzymatic activities.

PubMed

Ayo, Begoña; Abad, Naiara; Artolozaga, Itxaso; Azua, Iñigo; Baña, Zuriñe; Unanue, Marian; Gasol, Josep M; Duarte, Carlos M; Iriberri, Juan

2017-10-01

Ocean oligotrophication concurrent with warming weakens the capacity of marine primary producers to support marine food webs and act as a CO 2 sink, and is believed to result from reduced nutrient inputs associated to the stabilization of the thermocline. However, nutrient supply in the oligotrophic ocean is largely dependent on the recycling of organic matter. This involves hydrolytic processes catalyzed by extracellular enzymes released by bacteria, which temperature dependence has not yet been evaluated. Here, we report a global assessment of the temperature-sensitivity, as represented by the activation energies (E a ), of extracellular β-glucosidase (βG), leucine aminopeptidase (LAP) and alkaline phosphatase (AP) enzymatic activities, which enable the uptake by bacteria of substrates rich in carbon, nitrogen, and phosphorus, respectively. These E a were calculated from two different approaches, temperature experimental manipulations and a space-for-time substitution approach, which generated congruent results. The three activities showed contrasting E a in the subtropical and tropical ocean, with βG increasing the fastest with warming, followed by LAP, while AP showed the smallest increase. The estimated activation energies predict that the hydrolysis products under projected warming scenarios will have higher C:N, C:P and N:P molar ratios than those currently generated, and suggest that the warming of oceanic surface waters leads to a decline in the nutrient supply to the microbial heterotrophic community relative to that of carbon, particularly so for phosphorus, slowing down nutrient recycling and contributing to further ocean oligotrophication. © 2017 John Wiley & Sons Ltd.

Early ice retreat and ocean warming may induce copepod biogeographic boundary shifts in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Feng, Zhixuan; Ji, Rubao; Campbell, Robert G.; Ashjian, Carin J.; Zhang, Jinlun

2016-08-01

Early ice retreat and ocean warming are changing various facets of the Arctic marine ecosystem, including the biogeographic distribution of marine organisms. Here an endemic copepod species, Calanus glacialis, was used as a model organism, to understand how and why Arctic marine environmental changes may induce biogeographic boundary shifts. A copepod individual-based model was coupled to an ice-ocean-ecosystem model to simulate temperature- and food-dependent copepod life history development. Numerical experiments were conducted for two contrasting years: a relatively cold and normal sea ice year (2001) and a well-known warm year with early ice retreat (2007). Model results agreed with commonly known biogeographic distributions of C. glacialis, which is a shelf/slope species and cannot colonize the vast majority of the central Arctic basins. Individuals along the northern boundaries of this species' distribution were most susceptible to reproduction timing and early food availability (released sea ice algae). In the Beaufort, Chukchi, East Siberian, and Laptev Seas where severe ocean warming and loss of sea ice occurred in summer 2007, relatively early ice retreat, elevated ocean temperature (about 1-2°C higher than 2001), increased phytoplankton food, and prolonged growth season created favorable conditions for C. glacialis development and caused a remarkable poleward expansion of its distribution. From a pan-Arctic perspective, despite the great heterogeneity in the temperature and food regimes, common biogeographic zones were identified from model simulations, thus allowing a better characterization of habitats and prediction of potential future biogeographic boundary shifts.

Causes of the large warm bias in the Angola-Benguela Frontal Zone in the Norwegian Earth System Model

NASA Astrophysics Data System (ADS)

Koseki, Shunya; Keenlyside, Noel; Demissie, Teferi; Toniazzo, Thomas; Counillon, Francois; Bethke, Ingo; Ilicak, Mehmet; Shen, Mao-Lin

2018-06-01

We have investigated the causes of the sea surface temperature (SST) bias in the Angola-Benguela Frontal Zone (ABFZ) of the southeastern Atlantic Ocean simulated by the Norwegian Earth System Model (NorESM). Similar to other coupled-models, NorESM has a warm SST bias in the ABFZ of up to 8 °C in the annual mean. Our analysis of NorESM reveals that a cyclonic surface wind bias over the ABFZ drives a locally excessively strong southward (0.05 m/s (relative to observation)) Angola Current displacing the ABFZ southward. A series of uncoupled stand-alone atmosphere and ocean model simulations are performed to investigate the cause of the coupled model bias. The stand-alone atmosphere model driven with observed SST exhibits a similar cyclonic surface circulation bias; while the stand-alone ocean model forced with the reanalysis data produces a warm SST in the ABFZ with a magnitude approximately half of that in the coupled NorESM simulation. An additional uncoupled sensitivity experiment shows that the atmospheric model's local negative surface wind curl generates anomalously strong Angola Current at the ocean surface. Consequently, this contributes to the warm SST bias in the ABFZ by 2 °C (compared to the reanalysis forced simulation). There is no evidence that local air-sea feedbacks among wind stress curl, SST, and sea level pressure (SLP) affect the ABFZ SST bias. Turbulent surface heat flux differences between coupled and uncoupled experiments explain the remaining 2 °C warm SST bias in NorESM. Ocean circulation, upwelling and turbulent heat flux errors all modulate the intensity and the seasonality of the ABFZ errors.

Can multi-generational exposure to ocean warming and acidification lead to the adaptation of life history and physiology in a marine metazoan?

PubMed

Gibbin, Emma M; Chakravarti, Leela J; Jarrold, Michael D; Christen, Felix; Turpin, Vincent; Massamba N'Siala, Gloria; Blier, Pierre U; Calosi, Piero

2017-02-15

Ocean warming and acidification are concomitant global drivers that are currently threatening the survival of marine organisms. How species will respond to these changes depends on their capacity for plastic and adaptive responses. Little is known about the mechanisms that govern plasticity and adaptability or how global changes will influence these relationships across multiple generations. Here, we exposed the emerging model marine polychaete Ophryotrocha labronica to conditions simulating ocean warming and acidification, in isolation and in combination over five generations to identify: (i) how multiple versus single global change drivers alter both juvenile and adult life-history traits; (ii) the mechanistic link between adult physiological and fitness-related life-history traits; and (iii) whether the phenotypic changes observed over multiple generations are of plastic and/or adaptive origin. Two juvenile (developmental rate; survival to sexual maturity) and two adult (average reproductive body size; fecundity) life-history traits were measured in each generation, in addition to three physiological (cellular reactive oxygen species content, mitochondrial density, mitochondrial capacity) traits. We found that multi-generational exposure to warming alone caused an increase in juvenile developmental rate, reactive oxygen species production and mitochondrial density, decreases in average reproductive body size and fecundity, and fluctuations in mitochondrial capacity, relative to control conditions. Exposure to ocean acidification alone had only minor effects on juvenile developmental rate. Remarkably, when both drivers of global change were present, only mitochondrial capacity was significantly affected, suggesting that ocean warming and acidification act as opposing vectors of stress across multiple generations. © 2017. Published by The Company of Biologists Ltd.

INTERACTIONS BETWEEN OCEAN ACIDIFICATION AND WARMING ON THE MORTALITY AND DISSOLUTION OF CORALLINE ALGAE(1).

PubMed

Diaz-Pulido, Guillermo; Anthony, Kenneth R N; Kline, David I; Dove, Sophie; Hoegh-Guldberg, Ove

2012-02-01

Coralline algae are among the most sensitive calcifying organisms to ocean acidification as a result of increased atmospheric carbon dioxide (pCO2 ). Little is known, however, about the combined impacts of increased pCO2 , ocean acidification, and sea surface temperature on tissue mortality and skeletal dissolution of coralline algae. To address this issue, we conducted factorial manipulative experiments of elevated CO2 and temperature and examined the consequences on tissue survival and skeletal dissolution of the crustose coralline alga (CCA) Porolithon (=Hydrolithon) onkodes (Heydr.) Foslie (Corallinaceae, Rhodophyta) on the southern Great Barrier Reef (GBR), Australia. We observed that warming amplified the negative effects of high pCO2 on the health of the algae: rates of advanced partial mortality of CCA increased from <1% to 9% under high CO2 (from 400 to 1,100 ppm) and exacerbated to 15% under warming conditions (from 26°C to 29°C). Furthermore, the effect of pCO2 on skeletal dissolution strongly depended on temperature. Dissolution of P. onkodes only occurred in the high-pCO2 treatment and was greater in the warm treatment. Enhanced skeletal dissolution was also associated with a significant increase in the abundance of endolithic algae. Our results demonstrate that P. onkodes is particularly sensitive to ocean acidification under warm conditions, suggesting that previous experiments focused on ocean acidification alone have underestimated the impact of future conditions on coralline algae. Given the central role that coralline algae play within coral reefs, these conclusions have serious ramifications for the integrity of coral-reef ecosystems. © 2011 Phycological Society of America.

Ocean-atmosphere coupling at the Brazil-Malvinas Confluence region based on in situ, satellite and numerical model data

NASA Astrophysics Data System (ADS)

Casagrande, F.; Souza, R.; Pezzi, L.

2013-05-01

In the Southwest Atlantic close to 40oS, the meeting of two ocean currents with distinct characteristics, the Brazil Current (BC), warm and saline, and the Malvinas Current (MC), cold and low salinity, resulting in strong activity marked by the formation of mesoscale eddies, this region is known as Brazil Malvinas Confluence (BMC). The INTERCONF project (Ocean Atmosphere Interaction over the region of CBM) perfoms since the 2002 data collection in situ radiosondes and XBTs onboard the Oceanographic Support Ship Ary Rongel during its trajectory of Brazil to the Antarctic continent. This paper analyzes the thermal contrast and ocean atmosphere coupling on the ocean front from the INTERCONF data, and compares the results to satellite data (QuikSCAT) and numerical models (Eta-CPTEC / INPE). The results indicate that the Sea Surface Temperature (SST) is driving the atmosphere, on the warm waters of the BC occurs an intensification of the winds and heat fluxes, and the reverse occurs on the cold waters of the MC. The data collected in 2009 include the presence of a warm core eddy (42 oS to 43.1 oS) which recorded higher values of heat fluxes and wind speed in relation to its surroundings. On the warm core eddy wind speed recorded was about 10 m.s-1, while on the BC and MC was approximately 7 m.s-1 and 2 m.s-1, respectively. Satellite data and numerical model tends to overestimate the wind speed data in the region in relation to data collected in situ. The heat flux data from the numerical model tend to increase over the warm waters and cold waters on the decline, though the amounts recorded by the model have low correlation.

Diverse stoichiometry of dissolved trace metals in the Indian Ocean

PubMed Central

Thi Dieu Vu, Huong; Sohrin, Yoshiki

2013-01-01

Trace metals in seawater are essential to organisms and important as tracers of various processes in the ocean. However, we do not have a good understanding of the global distribution and cycling of trace metals, especially in the Indian Ocean. Here we report the first simultaneous, full-depth, and basin-scale section-distribution of dissolved (D) Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in the Indian Ocean. Our data reveal widespread co-limitation for phytoplankton production by DFe and occurrence of redox-related processes. The stoichiometry of the DM/phosphorus ratio agrees within a factor of 5 between deep waters in the Indian and Pacific, whereas it shows variability up to a factor of 300 among water masses within the Indian Ocean. This indicates that a consistent mechanism controls the stoichiometry in the deep waters, which are significantly depleted in Mn, Fe, and Co compared to requirements for phytoplankton.

Lambert-Beer law in ocean waters: optical properties of water and of dissolved/suspended material, optical energy budgets.

PubMed

Stavn, R H

1988-01-15

The role of the Lambert-Beer law in ocean optics is critically examined. The Lambert-Beer law and the three-parameter model of the submarine light field are used to construct an optical energy budget for any hydrosol. It is further applied to the analytical exponential decay coefficient of the light field and used to estimate the optical properties and effects of the dissolved/suspended component in upper ocean layers. The concepts of the empirical exponential decay coefficient (diffuse attenuation coefficient) of the light field and a constant exponential decay coefficient for molecular water are analyzed quantitatively. A constant exponential decay coefficient for water is rejected. The analytical exponential decay coefficient is used to analyze optical gradients in ocean waters.

GLOBAL WARMING. Recent hiatus caused by decadal shift in Indo-Pacific heating.

PubMed

Nieves, Veronica; Willis, Josh K; Patzert, William C

2015-07-31

Recent modeling studies have proposed different scenarios to explain the slowdown in surface temperature warming in the most recent decade. Some of these studies seem to support the idea of internal variability and/or rearrangement of heat between the surface and the ocean interior. Others suggest that radiative forcing might also play a role. Our examination of observational data over the past two decades shows some significant differences when compared to model results from reanalyses and provides the most definitive explanation of how the heat was redistributed. We find that cooling in the top 100-meter layer of the Pacific Ocean was mainly compensated for by warming in the 100- to 300-meter layer of the Indian and Pacific Oceans in the past decade since 2003. Copyright © 2015, American Association for the Advancement of Science.

Dissolved organic carbon in Alaskan boreal forest: sources, chemical characteristics, and biodegradability

Treesearch

Kimberly P. Wickland; Jason C. Neff; George R. Aiken

2007-01-01

The fate of terrestrially-derived dissolved organic carbon (DOC) is important to carbon (C) cycling in both terrestrial and aquatic environments, and recent evidence suggests that climate warming is influencing DOC dynamics in northern ecosystems. To understand what determines the fate of terrestrial DOC, it is essential to quantify the chemical nature and potential...

Impact of the ocean diurnal cycle on the North Atlantic mean sea surface temperatures in a regionally coupled model

NASA Astrophysics Data System (ADS)

Guemas, Virginie; Salas-Mélia, David; Kageyama, Masa; Giordani, Hervé; Voldoire, Aurore

2013-03-01

This study investigates the mechanisms by which the ocean diurnal cycle can affect the ocean mean state in the North Atlantic region. We perform two ocean-atmosphere regionally coupled simulations (20°N-80°N, 80°W-40°E) using the CNRMOM1D ocean model coupled to the ARPEGE4 atmospheric model: one with a 1 h coupling frequency (C1h) and another with a 24 h coupling frequency (C24h). The comparison between both experiments shows that accounting for the ocean diurnal cycle tends to warm up the surface ocean at high latitudes and cool it down in the subtropics during the boreal summer season (June-August). In the subtropics, the leading cause for the formation of the negative surface temperature anomalies is the fact that the nocturnal entrainment heat flux overcompensates the diurnal absorption of solar heat flux. Both in the subtropics and in the high latitudes, the surface temperature anomalies are involved in a positive feedback loop: the cold (warm) surface anomalies favour a decrease (increase) in evaporation, a decrease (increase) in tropospheric humidity, a decrease (increase) in downwelling longwave radiative flux which in turn favours the surface cooling (warming). Furthermore, the decrease in meridional sea surface temperature gradient affects the large-scale atmospheric circulation by a decrease in the zonal mean flow.

An Integrated Assessment Model for Helping the United States Sea Scallop (Placopecten magellanicus) Fishery Plan Ahead for Ocean Acidification and Warming

PubMed Central

2015-01-01

Ocean acidification, the progressive change in ocean chemistry caused by uptake of atmospheric CO2, is likely to affect some marine resources negatively, including shellfish. The Atlantic sea scallop (Placopecten magellanicus) supports one of the most economically important single-species commercial fisheries in the United States. Careful management appears to be the most powerful short-term factor affecting scallop populations, but in the coming decades scallops will be increasingly influenced by global environmental changes such as ocean warming and ocean acidification. In this paper, we describe an integrated assessment model (IAM) that numerically simulates oceanographic, population dynamic, and socioeconomic relationships for the U.S. commercial sea scallop fishery. Our primary goal is to enrich resource management deliberations by offering both short- and long-term insight into the system and generating detailed policy-relevant information about the relative effects of ocean acidification, temperature rise, fishing pressure, and socioeconomic factors on the fishery using a simplified model system. Starting with relationships and data used now for sea scallop fishery management, the model adds socioeconomic decision making based on static economic theory and includes ocean biogeochemical change resulting from CO2 emissions. The model skillfully reproduces scallop population dynamics, market dynamics, and seawater carbonate chemistry since 2000. It indicates sea scallop harvests could decline substantially by 2050 under RCP 8.5 CO2 emissions and current harvest rules, assuming that ocean acidification affects P. magellanicus by decreasing recruitment and slowing growth, and that ocean warming increases growth. Future work will explore different economic and management scenarios and test how potential impacts of ocean acidification on other scallop biological parameters may influence the social-ecological system. Future empirical work on the effect of ocean acidification on sea scallops is also needed. PMID:25945497

An Integrated Assessment Model for Helping the United States Sea Scallop (Placopecten magellanicus) Fishery Plan Ahead for Ocean Acidification and Warming.

PubMed

Cooley, Sarah R; Rheuban, Jennie E; Hart, Deborah R; Luu, Victoria; Glover, David M; Hare, Jonathan A; Doney, Scott C

2015-01-01

Ocean acidification, the progressive change in ocean chemistry caused by uptake of atmospheric CO2, is likely to affect some marine resources negatively, including shellfish. The Atlantic sea scallop (Placopecten magellanicus) supports one of the most economically important single-species commercial fisheries in the United States. Careful management appears to be the most powerful short-term factor affecting scallop populations, but in the coming decades scallops will be increasingly influenced by global environmental changes such as ocean warming and ocean acidification. In this paper, we describe an integrated assessment model (IAM) that numerically simulates oceanographic, population dynamic, and socioeconomic relationships for the U.S. commercial sea scallop fishery. Our primary goal is to enrich resource management deliberations by offering both short- and long-term insight into the system and generating detailed policy-relevant information about the relative effects of ocean acidification, temperature rise, fishing pressure, and socioeconomic factors on the fishery using a simplified model system. Starting with relationships and data used now for sea scallop fishery management, the model adds socioeconomic decision making based on static economic theory and includes ocean biogeochemical change resulting from CO2 emissions. The model skillfully reproduces scallop population dynamics, market dynamics, and seawater carbonate chemistry since 2000. It indicates sea scallop harvests could decline substantially by 2050 under RCP 8.5 CO2 emissions and current harvest rules, assuming that ocean acidification affects P. magellanicus by decreasing recruitment and slowing growth, and that ocean warming increases growth. Future work will explore different economic and management scenarios and test how potential impacts of ocean acidification on other scallop biological parameters may influence the social-ecological system. Future empirical work on the effect of ocean acidification on sea scallops is also needed.

Decadal slowdown in global air temperature rise triggered by variability in the Atlantic Meridional Overturning Circulation

NASA Astrophysics Data System (ADS)

England, Matthew H.

2015-04-01

Various explanations have been proposed for the recent slowdown in global surface air temperature (SAT) rise, either involving enhanced ocean heat uptake or reduced radiation reaching Earth's surface. Among the mechanisms postulated involving enhanced ocean heat uptake, past work has argued for both a Pacific and Atlantic origin, with additional contributions from the Southern Ocean. Here we examine the mechanisms driving 'hiatus' periods originating out of the Atlantic Ocean. We show that while Atlantic-driven hiatuses are entirely plausible and consistent with known climate feedbacks associated with variability in the Atlantic Meridional Overturning Circulation (AMOC), the present climate state is configured to enhance global-average SAT, not reduce it. We show that Atlantic hiatuses are instead characterised by anomalously cool fresh oceanic conditions in the North Atlantic, with the atmosphere advecting the cool temperature signature zonally. Compared to the 1980s and 1990s, however, the mean climate since 2001 has been characterised by a warm saline North Atlantic, suggesting the AMOC cannot be implicated as a direct driver of the current hiatus. We further discuss the impacts of a warm tropical Atlantic on the unprecedented trade wind acceleration in the Pacific Ocean, and propose that this is the main way that the Atlantic has contributed to the present "false pause" in global warming.

CMIP5 Historical Simulations (1850-2012) with GISS ModelE2

NASA Technical Reports Server (NTRS)

Miller, Ronald Lindsay; Schmidt, Gavin A.; Nazarenko, Larissa S.; Tausnev, Nick; Bauer, Susanne E.; DelGenio, Anthony D.; Kelley, Max; Lo, Ken K.; Ruedy, Reto; Shindell, Drew T.;

Possible signals of poleward surface ocean heat transport, of Arctic basal ice melt, and of the twentieth century solar maximum in the 1904-2012 Isle of Man daily timeseries

NASA Astrophysics Data System (ADS)

Matthews, J. B.; Matthews, J. B. R.

2014-01-01

This is the second of two papers on observational timeseries of top of ocean heat capture. The first reports hourly and daily meridional central tropical Pacific top 3 m timeseries showing high Southern Hemisphere evaporation (2.67 m yr-1) and Northern Hemisphere trapped heat (12 MJ m-2 day-1). We suggested that wind drift/geostrophic stratified gyre circulation transported warm water to the Arctic and led to three phases of Arctic basal ice melt and fluxes of brackish nutrient-rich waters to north Atlantic on centennial timescales. Here we examine daily top metre 1904-2012 timeseries at Isle of Man west coast ~54° N for evidence of tropical and polar surface waters. We compare these to Central England (CET) daily land-air temperatures and to Arctic floating ice heat content and extent. We find three phases of ocean surface heating consistent with basal icemelt buffering greenhouse gas warming until a regime shift post-1986 led to the modern surface temperature rise of ~1 °C in 20 yr. Three phases were: warming +0.018 °C yr-1 from 1904-1939, slight cooling -0.002 °C yr-11940-86 and strong warming +0.037 °C yr-1 1986-2012. For the same periods CET land-air showed: warming +0.015 °C yr-1, slight cooling -0.004 °C yr-1, about half SST warming at +0.018 °C yr-1. The mid-century cooling and a 1959/1963 hot/cold event is consistent with sunspot/solar radiation maximum 1923-2008 leading to record volumes of Arctic ice meltwater and runoff that peaked in 1962/3 British Isles extreme cold winter. The warming Arctic resulted in wind regime and surface water regime shifts post 1986. This coincides with the onset of rapid Arctic annual ice melt. Continued heat imbalance is likely to lead to tidewater glacier basal icemelt and future sealevel rise after remaining relatively stable over 4000 yr. Our work needs confirmation by further fieldwork concentrating on the dynamics and thermodynamics of ocean top 3 m that controls the 93 % anthropogenic global warming in the oceans. This may be done most cost-effectively through focussed multidisciplinary scientific research adaptively managed and funded.

Importance of ocean mesoscale variability for air-sea interactions in the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Putrasahan, D. A.; Kamenkovich, I.; Le Hénaff, M.; Kirtman, B. P.

2017-06-01

Mesoscale variability of currents in the Gulf of Mexico (GoM) can affect oceanic heat advection and air-sea heat exchanges, which can influence climate extremes over North America. This study is aimed at understanding the influence of the oceanic mesoscale variability on the lower atmosphere and air-sea heat exchanges. The study contrasts global climate model (GCM) with 0.1° ocean resolution (high resolution; HR) with its low-resolution counterpart (1° ocean resolution with the same 0.5° atmosphere resolution; LR). The LR simulation is relevant to current generation of GCMs that are still unable to resolve the oceanic mesoscale. Similar to observations, HR exhibits positive correlation between sea surface temperature (SST) and surface turbulent heat flux anomalies, while LR has negative correlation. For HR, we decompose lateral advective heat fluxes in the upper ocean into mean (slowly varying) and mesoscale-eddy (fast fluctuations) components. We find that the eddy flux divergence/convergence dominates the lateral advection and correlates well with the SST anomalies and air-sea latent heat exchanges. This result suggests that oceanic mesoscale advection supports warm SST anomalies that in turn feed surface heat flux. We identify anticyclonic warm-core circulation patterns (associated Loop Current and rings) which have an average diameter of 350 km. These warm anomalies are sustained by eddy heat flux convergence at submonthly time scales and have an identifiable imprint on surface turbulent heat flux, atmospheric circulation, and convective precipitation in the northwest portion of an averaged anticyclone.

Effect of the tropical Pacific and Indian Ocean warming since the late 1970s on wintertime Northern Hemispheric atmospheric circulation and East Asian climate interdecadal changes

NASA Astrophysics Data System (ADS)

Chu, Cuijiao; Yang, Xiu-Qun; Sun, Xuguang; Yang, Dejian; Jiang, Yiquan; Feng, Tao; Liang, Jin

2018-04-01

Observation reveals that the tropical Pacific-Indian Ocean (TPIO) has experienced a pronounced interdecadal warming since the end of the 1970s. Meanwhile, the wintertime midlatitude Northern Hemispheric atmospheric circulation and East Asian climate have also undergone substantial interdecadal changes. The effect of the TPIO warming on these interdecadal changes are identified by a suite of AMIP-type atmospheric general circulation model experiments in which the model is integrated from September 1948 to December 1999 with prescribed historical, observed realistic sea surface temperature (SST) in a specific region and climatological SST elsewhere. Results show that the TPIO warming reproduces quite well the observed Northern Hemispheric wintertime interdecadal changes, suggesting that these interdecadal changes primarily originate from the TPIO warming. However, each sub-region of TPIO has its own distinct contribution. Comparatively, the tropical central-eastern Pacific (TCEP) and tropical western Pacific (TWP) warming makes dominant contributions to the observed positive-phase PNA-like interdecadal anomaly over the North Pacific sector, while the tropical Indian Ocean (TIO) warming tends to cancel these contributions. Meanwhile, the TIO and TWP warming makes dominant contributions to the observed positive NAO-like interdecadal anomaly over the North Atlantic sector as well as the interdecadal anomalies over the Eurasian sector, although the TWP warming's contribution is relatively small. These remote responses are directly attributed to the TPIO warming-induced tropical convection, rainfall and diabatic heating increases, in which the TIO warming has the most significant effect. Moreover, the TPIO warming excites a Gill-type pattern anomaly over the tropical western Pacific, with a low-level anticyclonic circulation anomaly over the Philippine Sea. Of three sub-regions, the TIO warming dominates such a pattern, although the TWP warming tends to cancel this effect. The anticyclonic circulation anomaly intensifies the southwesterly flow that transfers more moisture from the Bay of Bengal to East Asia and considerably increases the winter precipitation over the southern East Asia. This is strongly supported by the observational fact that there has been a significant interdecadal increase of winter precipitation over the southern China since the end of the 1970s.

Reduced interdecadal variability of Atlantic Meridional Overturning Circulation under global warming

PubMed Central

Cheng, Jun; Liu, Zhengyu; Zhang, Shaoqing; Liu, Wei; Dong, Lina; Liu, Peng; Li, Hongli

2016-01-01

Interdecadal variability of the Atlantic Meridional Overturning Circulation (AMOC-IV) plays an important role in climate variation and has significant societal impacts. Past climate reconstruction indicates that AMOC-IV has likely undergone significant changes. Despite some previous studies, responses of AMOC-IV to global warming remain unclear, in particular regarding its amplitude and time scale. In this study, we analyze the responses of AMOC-IV under various scenarios of future global warming in multiple models and find that AMOC-IV becomes weaker and shorter with enhanced global warming. From the present climate condition to the strongest future warming scenario, on average, the major period of AMOC-IV is shortened from ∼50 y to ∼20 y, and the amplitude is reduced by ∼60%. These reductions in period and amplitude of AMOC-IV are suggested to be associated with increased oceanic stratification under global warming and, in turn, the speedup of oceanic baroclinic Rossby waves. PMID:26951654

Can increased poleward oceanic heat flux explain the warm Cretaceous climate?

NASA Astrophysics Data System (ADS)

Schmidt, Gavin A.; Mysak, Lawrence A.

1996-10-01

The poleward transport of heat in the mid-Cretaceous (100 Ma) is examined using an idealized coupled ocean-atmosphere model. The oceanic component consists of two zonally averaged basins representing the proto-Pacific and proto-Indian oceans and models the dynamics of the meridional thermohaline circulation. The atmospheric component is a simple energy and moisture balance model which includes the diffusive meridional transport of sensible heat and moisture. The ocean model is spun up with a variety of plausible Cretaceous surface temperature and salinity profiles, and a consistent atmosphere is objectively derived based on the resultant sea surface temperature and the surface heat and freshwater fluxes. The coupled model does not exhibit climate drift. Multiple equilibria of the coupled model are found that break the initial symmetry of the ocean circulation; several of these equilibria have one-cell (northern or southern sinking) thermohaline circulation patterns. Two main classes of circulation are found: circulations where the densest water is relatively cool and is formed at the polar latitudes and circulations where the densest water is warm, but quite saline, and the strongest sinking occurs at the tropics. In all cases, significant amounts of warm, saline bottom water are formed in the proto-Indian basin which modify the deepwater characteristics in the larger (proto-Pacific) basin. Temperatures in the deep ocean are warm, 10°-17°C, in agreement with benthic foraminiferal oxygen isotope data. The poleward transport of heat in the modeled Cretaceous oceans is larger than in some comparable models of the present day thermohaline circulation and significantly larger than estimates of similar processes in the present-day ocean. It is consistently larger in the polar sinking cases when compared with that seen in the tropical sinking cases, but this represents an increase of only 10%. The largest increase over present-day model transports is in the atmospheric latent heat transport, where an increased hydrological cycle (especially in the tropical sinking cases) contributes up to an extra 1 PW of poleward heat transport. Better constraints on the oceanic deepwater circulation during this period are necessary before the meridional circulation can be unambiguously described.

Orbital-scale Central Arctic Ocean Temperature Records from Benthic Foraminiferal δ18O and Ostracode Mg/Ca Ratios

NASA Astrophysics Data System (ADS)

Keller, K.; Cronin, T. M.; Dwyer, G. S.; Farmer, J. R.; Poirier, R. K.; Schaller, M. F.

2017-12-01

Orbital-scale climate variability is often amplified in the polar region, for example in changes in seawater temperature, sea-ice cover, deep-water formation, ecosystems, heat storage and carbon cycling. Yet, the relationship between the Arctic Ocean and global climate remains poorly understood due largely to limited orbital-scale paleoclimate records, the complicated nature of sea-ice response to climate and limited abundance of deep sea biological proxies. Here we reconstruct central Arctic Ocean bottom temperatures over the last 600 kyr using ostracode Mg/Ca ratios (genus Krithe) and benthic foraminiferal oxygen isotope ratios (δ18Obf - I. teretis, O. tener, P. bulloides, C. reniforme, C. wuellerstorfi) in six sediment cores recovered from the Mendeleev and Northwind Ridges (700- 2726 m water depth). We examined glacial-interglacial cycles in Arctic seawater temperatures and Arctic δ18Obf chronostratigraphy to reconcile effects of changing bottom water temperature, ice volume and regional hydrography on δ18Obf records. Results show lower ( 10-12 mmol/mol) interglacial and higher ( 16-23 mmol/mol) glacial Mg/Ca ratios, signifying intermediate depth ocean warming during glacials of up to 2 ºC. These temperature maxima are likely related to a deepening of the halocline and the corresponding deeper influence of warm Atlantic water. Glacial-interglacial δ18Obf ranges are smaller in the Arctic ( 0.8-1‰ VPDB) than in the global ocean ( 1.8 ‰). However, when the distinct glacial-interglacial temperature histories of the Arctic (glacial warming) and global ocean (glacial cooling) are accounted for, both Arctic and global ocean seawater δ18O values (δ18Osw) exhibit similar 1.2-1.3 ‰ glacial-interglacial ranges. Thus, Arctic δ18Obf confirms glacial Arctic warming inferred from ostracode Mg/Ca. This study will discuss the strengths and limitations of applying paired Mg/Ca and oxygen isotope proxies in reconstructing more robust paleoceanographic changes in the Arctic Ocean.

Microwave Limb Sounder/El Nino Watch - Water Vapor Measurement, October, 1997

NASA Technical Reports Server (NTRS)

1997-01-01

This image shows atmospheric water vapor in Earth's upper troposphere, about 10 kilometers (6 miles) above the surface, as measured by the Microwave Limb Sounder (MLS) instrument flying aboard the Upper Atmosphere Research Satellite. These data collected in early October 1997 indicate the presence of El Nino by showing a shift of humidity from west to east (blue and red areas) along the equatorial Pacific Ocean. El Nino is the term used when the warmest equatorial Pacific Ocean water is displaced toward the east. The areas of high atmospheric moisture correspond to areas of very warm ocean water. Warmer water evaporates at a higher rate and the resulting warm moist air then rises, forming tall cloud towers. In the tropics, the warm water and the resulting tall cloud towers typically produce large amounts of rain. The MLS instrument, developed at NASA's Jet Propulsion Laboratory, measures humidity at the top of these clouds, which are very moist. This rain is now occurring in the eastern Pacific Ocean and has left Indonesia (deep blue region) unusually dry, resulting in the current drought in that region. This image also shows moisture moving north into Mexico, an effect of several hurricanes spawned by the warm waters of El Nino.

Long-term effects of warming and ocean acidification are modified by seasonal variation in species responses and environmental conditions

PubMed Central

Godbold, Jasmin A.; Solan, Martin

2013-01-01

Warming of sea surface temperatures and alteration of ocean chemistry associated with anthropogenic increases in atmospheric carbon dioxide will have profound consequences for a broad range of species, but the potential for seasonal variation to modify species and ecosystem responses to these stressors has received little attention. Here, using the longest experiment to date (542 days), we investigate how the interactive effects of warming and ocean acidification affect the growth, behaviour and associated levels of ecosystem functioning (nutrient release) for a functionally important non-calcifying intertidal polychaete (Alitta virens) under seasonally changing conditions. We find that the effects of warming, ocean acidification and their interactions are not detectable in the short term, but manifest over time through changes in growth, bioturbation and bioirrigation behaviour that, in turn, affect nutrient generation. These changes are intimately linked to species responses to seasonal variations in environmental conditions (temperature and photoperiod) that, depending upon timing, can either exacerbate or buffer the long-term directional effects of climatic forcing. Taken together, our observations caution against over emphasizing the conclusions from short-term experiments and highlight the necessity to consider the temporal expression of complex system dynamics established over appropriate timescales when forecasting the likely ecological consequences of climatic forcing. PMID:23980249

Ocean warming and acidification synergistically increase coral mortality

PubMed Central

Prada, F.; Caroselli, E.; Mengoli, S.; Brizi, L.; Fantazzini, P.; Capaccioni, B.; Pasquini, L.; Fabricius, K. E.; Dubinsky, Z.; Falini, G.; Goffredo, S.

2017-01-01

Organisms that accumulate calcium carbonate structures are particularly vulnerable to ocean warming (OW) and ocean acidification (OA), potentially reducing the socioeconomic benefits of ecosystems reliant on these taxa. Since rising atmospheric CO2 is responsible for global warming and increasing ocean acidity, to correctly predict how OW and OA will affect marine organisms, their possible interactive effects must be assessed. Here we investigate, in the field, the combined temperature (range: 16–26 °C) and acidification (range: pHTS 8.1–7.4) effects on mortality and growth of Mediterranean coral species transplanted, in different seasonal periods, along a natural pH gradient generated by a CO2 vent. We show a synergistic adverse effect on mortality rates (up to 60%), for solitary and colonial, symbiotic and asymbiotic corals, suggesting that high seawater temperatures may have increased their metabolic rates which, in conjunction with decreasing pH, could have led to rapid deterioration of cellular processes and performance. The net calcification rate of the symbiotic species was not affected by decreasing pH, regardless of temperature, while in the two asymbiotic species it was negatively affected by increasing acidification and temperature, suggesting that symbiotic corals may be more tolerant to increasing warming and acidifying conditions compared to asymbiotic ones. PMID:28102293

Dissolved Organic Matter (DOM) Export from Watersheds to Coastal Oceans

NASA Astrophysics Data System (ADS)

Chen, R. F.; Gardner, G. B.; Peri, F.

2016-02-01

Dissolved organic matter (DOM) from terrestrial plants and soils is transported by surface waters and groundwaters to coastal ocean waters. Along the way, photochemical and biological degradation can remove DOM, and in situ processes such as phytoplankton leaching and sediment sources can add to the DOM in the river water. Wetlands, especially coastal wetlands can add significant amounts of DOM that is carried by rivers and is exported through estuaries to coastal systems. We will present observational data from a variety of coastal systems (San Francisco Bay, Boston Harbor, Chesapeake Bay, Hudson River, the Mississippi River, and a small salt marsh in the Gulf of Mexico). High resolution measurements of chromophoric dissolved organic matter (CDOM) can be correlated with dissolved organic carbon (DOC) so can be used to estimate DOC in specific systems and seasons. Gradients in CDOM/DOC combined with water fluxes can be used to estimate DOC fluxes from a variety of coastal watersheds to coastal systems. Influences of land use, system size, residence time, DOM quality, and photochemical and biological degradation will be discussed. The significance of coastal wetlands in the land-to-ocean export of DOC will be emphasized.

Moderate ocean warming mitigates, but more extreme warming exacerbates the impacts of zinc from engineered nanoparticles on a marine larva.

PubMed

Mos, Benjamin; Kaposi, Katrina L; Rose, Andrew L; Kelaher, Brendan; Dworjanyn, Symon A

2017-09-01

There is growing concern about the combined effects of multiple human-induced stressors on biodiversity. In particular, there are substantial knowledge gaps about the combined effects of existing stressors (e.g. pollution) and predicted environmental stress from climate change (e.g. ocean warming). We investigated the impacts of ocean warming and engineered nanoparticles (nano-zinc oxide, nZnO) on larvae of a cosmopolitan tropical sea urchin, Tripneustes gratilla. Larval T. gratilla were exposed to all combinations of three temperatures, 25, 27 and 29 °C (current SST and near-future predicted warming of +2 and + 4 °C) and six concentrations of nZnO (0, 0.001, 0.01, 0.1, 1 and 10 mg nZnO·L -1 ). These stressors had strong interactive effects on fertilization, gastrulation and normal development of 5 day old larvae. High concentrations of nZnO had a negative effect, but this impact was less pronounced for sea urchins reared at their preferred temperature of 27 °C compared to 25 or 29 °C. Larval growth was also impacted by combined stress of elevated temperature and nZnO. Subsequent measurement of the dissolution and aggregation of nZnO particles and the direct effect of Zn 2+ ions on larvae, suggest the negative effects of nZnO on larval development and growth were most likely due to Zn 2+ ions. Our results demonstrate that marine larvae may be more resilient to stressors at optimal temperatures and highlight the potential for ocean warming to exacerbate the effects of pollution on marine larvae. Copyright © 2017 Elsevier Ltd. All rights reserved.

Precipitation overrides warming in mediating soil nitrogen pools in an alpine grassland ecosystem on the Tibetan Plateau.

PubMed

Lin, Li; Zhu, Biao; Chen, Chengrong; Zhang, Zhenhua; Wang, Qi-Bing; He, Jin-Sheng

2016-08-16

Soils in the alpine grassland store a large amount of nitrogen (N) due to slow decomposition. However, the decomposition could be affected by climate change, which has profound impacts on soil N cycling. We investigated the changes of soil total N and five labile N stocks in the topsoil, the subsoil and the entire soil profile in response to three years of experimental warming and altered precipitation in a Tibetan alpine grassland. We found that warming significantly increased soil nitrate N stock and decreased microbial biomass N (MBN) stock. Increased precipitation reduced nitrate N, dissolved organic N and amino acid N stocks, but increased MBN stock in the topsoil. No change in soil total N was detected under warming and altered precipitation regimes. Redundancy analysis further revealed that soil moisture (26.3%) overrode soil temperature (10.4%) in explaining the variations of soil N stocks across the treatments. Our results suggest that precipitation exerted stronger influence than warming on soil N pools in this mesic and high-elevation grassland ecosystem. This indicates that the projected rise in future precipitation may lead to a significant loss of dissolved soil N pools by stimulating the biogeochemical processes in this alpine grassland.

Precipitation overrides warming in mediating soil nitrogen pools in an alpine grassland ecosystem on the Tibetan Plateau

PubMed Central

Lin, Li; Zhu, Biao; Chen, Chengrong; Zhang, Zhenhua; Wang, Qi-Bing; He, Jin-Sheng

2016-01-01

Soils in the alpine grassland store a large amount of nitrogen (N) due to slow decomposition. However, the decomposition could be affected by climate change, which has profound impacts on soil N cycling. We investigated the changes of soil total N and five labile N stocks in the topsoil, the subsoil and the entire soil profile in response to three years of experimental warming and altered precipitation in a Tibetan alpine grassland. We found that warming significantly increased soil nitrate N stock and decreased microbial biomass N (MBN) stock. Increased precipitation reduced nitrate N, dissolved organic N and amino acid N stocks, but increased MBN stock in the topsoil. No change in soil total N was detected under warming and altered precipitation regimes. Redundancy analysis further revealed that soil moisture (26.3%) overrode soil temperature (10.4%) in explaining the variations of soil N stocks across the treatments. Our results suggest that precipitation exerted stronger influence than warming on soil N pools in this mesic and high-elevation grassland ecosystem. This indicates that the projected rise in future precipitation may lead to a significant loss of dissolved soil N pools by stimulating the biogeochemical processes in this alpine grassland. PMID:27527683

Frequency of Tropical Ocean Deep Convection and Global Warming

NASA Astrophysics Data System (ADS)

Aumann, H. H.; Behrangi, A.; Ruzmaikin, A.

2017-12-01

The average of 36 CMIP5 models predicts about 3K of warming and a 4.7% increase in precipitation for the tropical oceans with a doubling of the CO2 by the end of this century. For this scenario we evaluate the increase in the frequency of Deep Convective Clouds (DCC) in the tropical oceans. We select only DCC which reach or penetrate the tropopause in the 15 km AIRS footprint. The evaluation is based on Probability Distribution Functions (PDFs) of the current temperatures of the tropical oceans, those predicted by the mean of the CMIP5 models and the PDF of the DCC process. The PDF of the DCC process is derived from the Atmospheric Infrared Sounder (AIRS) between the years 2003 and 2016. During this time the variability due Enso years provided a 1 K p-p change in the mean tropical SST. The key parameter is the SST associated with the onset of the DCC process. This parameter shifts only 0.5 K for each K of warming of the oceans. As a result the frequency of DCC is expected to increases by the end of this century by about 50% above the current frequency.

Improved estimates of ocean heat content from 1960 to 2015.

PubMed

Cheng, Lijing; Trenberth, Kevin E; Fasullo, John; Boyer, Tim; Abraham, John; Zhu, Jiang

2017-03-01

Earth's energy imbalance (EEI) drives the ongoing global warming and can best be assessed across the historical record (that is, since 1960) from ocean heat content (OHC) changes. An accurate assessment of OHC is a challenge, mainly because of insufficient and irregular data coverage. We provide updated OHC estimates with the goal of minimizing associated sampling error. We performed a subsample test, in which subsets of data during the data-rich Argo era are colocated with locations of earlier ocean observations, to quantify this error. Our results provide a new OHC estimate with an unbiased mean sampling error and with variability on decadal and multidecadal time scales (signal) that can be reliably distinguished from sampling error (noise) with signal-to-noise ratios higher than 3. The inferred integrated EEI is greater than that reported in previous assessments and is consistent with a reconstruction of the radiative imbalance at the top of atmosphere starting in 1985. We found that changes in OHC are relatively small before about 1980; since then, OHC has increased fairly steadily and, since 1990, has increasingly involved deeper layers of the ocean. In addition, OHC changes in six major oceans are reliable on decadal time scales. All ocean basins examined have experienced significant warming since 1998, with the greatest warming in the southern oceans, the tropical/subtropical Pacific Ocean, and the tropical/subtropical Atlantic Ocean. This new look at OHC and EEI changes over time provides greater confidence than previously possible, and the data sets produced are a valuable resource for further study.

Improved estimates of ocean heat content from 1960 to 2015

PubMed Central

Cheng, Lijing; Trenberth, Kevin E.; Fasullo, John; Boyer, Tim; Abraham, John; Zhu, Jiang

2017-01-01

Earth’s energy imbalance (EEI) drives the ongoing global warming and can best be assessed across the historical record (that is, since 1960) from ocean heat content (OHC) changes. An accurate assessment of OHC is a challenge, mainly because of insufficient and irregular data coverage. We provide updated OHC estimates with the goal of minimizing associated sampling error. We performed a subsample test, in which subsets of data during the data-rich Argo era are colocated with locations of earlier ocean observations, to quantify this error. Our results provide a new OHC estimate with an unbiased mean sampling error and with variability on decadal and multidecadal time scales (signal) that can be reliably distinguished from sampling error (noise) with signal-to-noise ratios higher than 3. The inferred integrated EEI is greater than that reported in previous assessments and is consistent with a reconstruction of the radiative imbalance at the top of atmosphere starting in 1985. We found that changes in OHC are relatively small before about 1980; since then, OHC has increased fairly steadily and, since 1990, has increasingly involved deeper layers of the ocean. In addition, OHC changes in six major oceans are reliable on decadal time scales. All ocean basins examined have experienced significant warming since 1998, with the greatest warming in the southern oceans, the tropical/subtropical Pacific Ocean, and the tropical/subtropical Atlantic Ocean. This new look at OHC and EEI changes over time provides greater confidence than previously possible, and the data sets produced are a valuable resource for further study. PMID:28345033

Improved estimates of ocean heat content from 1960 to 2015

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

Cheng, Lijing; Trenberth, Kevin E.; Fasullo, John

Earth’s energy imbalance (EEI) drives the ongoing global warming and can best be assessed across the historical record (that is, since 1960) from ocean heat content (OHC) changes. An accurate assessment of OHC is a challenge, mainly because of insufficient and irregular data coverage. We provide here updated OHC estimates with the goal of minimizing associated sampling error. We performed a subsample test, in which subsets of data during the datarich Argo era are colocated with locations of earlier ocean observations, to quantify this error. Our results provide a new OHC estimate with an unbiased mean sampling error and withmore » variability on decadal and multidecadal time scales (signal) that can be reliably distinguished fromsampling error (noise) with signal-to-noise ratios higher than 3. The inferred integrated EEI is greater than that reported in previous assessments and is consistent with a reconstruction of the radiative imbalance at the top of atmosphere starting in 1985. We found that changes in OHC are relatively small before about 1980; since then, OHC has increased fairly steadily and, since 1990, has increasingly involved deeper layers of the ocean. In addition,OHC changes in sixmajor oceans are reliable on decadal timescales. All ocean basins examined have experienced significant warming since 1998, with the greatest warming in the southern oceans, the tropical/subtropical Pacific Ocean, and the tropical/subtropical Atlantic Ocean. This new look at OHC and EEI changes over time provides greater confidence than previously possible, and the data sets produced are a valuable resource for further study.« less

Improved estimates of ocean heat content from 1960 to 2015

DOE PAGES

Cheng, Lijing; Trenberth, Kevin E.; Fasullo, John; ...

2017-03-10

Earth’s energy imbalance (EEI) drives the ongoing global warming and can best be assessed across the historical record (that is, since 1960) from ocean heat content (OHC) changes. An accurate assessment of OHC is a challenge, mainly because of insufficient and irregular data coverage. We provide here updated OHC estimates with the goal of minimizing associated sampling error. We performed a subsample test, in which subsets of data during the datarich Argo era are colocated with locations of earlier ocean observations, to quantify this error. Our results provide a new OHC estimate with an unbiased mean sampling error and withmore » variability on decadal and multidecadal time scales (signal) that can be reliably distinguished fromsampling error (noise) with signal-to-noise ratios higher than 3. The inferred integrated EEI is greater than that reported in previous assessments and is consistent with a reconstruction of the radiative imbalance at the top of atmosphere starting in 1985. We found that changes in OHC are relatively small before about 1980; since then, OHC has increased fairly steadily and, since 1990, has increasingly involved deeper layers of the ocean. In addition,OHC changes in sixmajor oceans are reliable on decadal timescales. All ocean basins examined have experienced significant warming since 1998, with the greatest warming in the southern oceans, the tropical/subtropical Pacific Ocean, and the tropical/subtropical Atlantic Ocean. This new look at OHC and EEI changes over time provides greater confidence than previously possible, and the data sets produced are a valuable resource for further study.« less

Impact of the GeoMIP G1 sunshade geoengineering experiment on the Atlantic meridional overturning circulation

NASA Astrophysics Data System (ADS)

Hong, Yu; Moore, John C.; Jevrejeva, Svetlana; Ji, Duoying; Phipps, Steven J.; Lenton, Andrew; Tilmes, Simone; Watanabe, Shingo; Zhao, Liyun

2017-03-01

We analyze the multi-earth system model responses of ocean temperatures and the Atlantic Meridional Overturning Circulation (AMOC) under an idealized solar radiation management scenario (G1) from the Geoengineering Model Intercomparison Project. All models simulate warming of the northern North Atlantic relative to no geoengineering, despite geoengineering substantially offsetting the increases in mean global ocean temperatures. Increases in the temperature of the North Atlantic Ocean at the surface (˜0.25 K) and at a depth of 500 m (˜0.10 K) are mainly due to a 10 Wm-2 reduction of total heat flux from ocean to atmosphere. Although the AMOC is slightly reduced under the solar dimming scenario, G1, relative to piControl, it is about 37% stronger than under abrupt4 × CO2 . The reduction of the AMOC under G1 is mainly a response to the heat flux change at the northern North Atlantic rather than to changes in the water flux and the wind stress. The AMOC transfers heat from tropics to high latitudes, helping to warm the high latitudes, and its strength is maintained under solar dimming rather than weakened by greenhouse gas forcing acting alone. Hence the relative reduction in high latitude ocean temperatures provided by solar radiation geoengineering, would tend to be counteracted by the correspondingly active AMOC circulation which furthermore transports warm surface waters towards the Greenland ice sheet, warming Arctic sea ice and permafrost.

Non-additive effects of ocean acidification in combination with warming on the larval proteome of the Pacific oyster, Crassostrea gigas.

PubMed

Harney, Ewan; Artigaud, Sébastien; Le Souchu, Pierrick; Miner, Philippe; Corporeau, Charlotte; Essid, Hafida; Pichereau, Vianney; Nunes, Flavia L D

2016-03-01

Increasing atmospheric carbon dioxide results in ocean acidification and warming, significantly impacting marine invertebrate larvae development. We investigated how ocean acidification in combination with warming affected D-veliger larvae of the Pacific oyster Crassostrea gigas. Larvae were reared for 40h under either control (pH8.1, 20 °C), acidified (pH7.9, 20 °C), warm (pH8.1, 22 °C) or warm acidified (pH7.9, 22 °C) conditions. Larvae in acidified conditions were significantly smaller than in the control, but warm acidified conditions mitigated negative effects on size, and increased calcification. A proteomic approach employing two-dimensional electrophoresis (2-DE) was used to quantify proteins and relate their abundance to phenotypic traits. In total 12 differentially abundant spots were identified by nano-liquid chromatography-tandem mass spectrometry. These proteins had roles in metabolism, intra- and extra-cellular matrix formations, stress response, and as molecular chaperones. Seven spots responded to reduced pH, four to increased temperature, and six to acidification and warming. Reduced abundance of proteins such as ATP synthase and GAPDH, and increased abundance of superoxide dismutase, occurred when both pH and temperature changes were imposed, suggesting altered metabolism and enhanced oxidative stress. These results identify key proteins that may be involved in the acclimation of C. gigas larvae to ocean acidification and warming. Increasing atmospheric CO2 raises sea surface temperatures and results in ocean acidification, two climatic variables known to impact marine organisms. Larvae of calcifying species may be particularly at risk to such changing environmental conditions. The Pacific oyster Crassostrea gigas is ecologically and commercially important, and understanding its ability to acclimate to climate change will help to predict how aquaculture of this species is likely to be impacted. Modest, yet realistic changes in pH and/or temperature may be more informative of how populations will respond to contemporary climate change. We showed that concurrent acidification and warming mitigates the negative effects of pH alone on size of larvae, but proteomic analysis reveals altered patterns of metabolism and an increase in oxidative stress suggesting non-additive effects of the interaction between pH and temperature on protein abundance. Thus, even small changes in climate may influence development, with potential consequences later in life. Copyright © 2015 Elsevier B.V. All rights reserved.

Suspended sediment concentration and optical property observations of mixed-turbidity, coastal waters through multispectral ocean color inversion

EPA Science Inventory

Multispectral satellite ocean color data from high-turbidity areas of the coastal ocean contain information about the surface concentrations and optical properties of suspended sediments and colored dissolved organic matter (CDOM). Empirical and semi-analytical inversion algorit...

The Role of Ocean Eddies in the Southern Ocean Response to Observed Greenhouse Gas Forcing

NASA Astrophysics Data System (ADS)

Bilgen, S. I.; Kirtman, B. P.

2017-12-01

The Southern Ocean (SO) is crucial to understanding the possible future response to a changing climate. This is a principal region where energy is conveyed to the ocean by the westerly winds and it is here that mesoscale ocean eddies field dominate meridional heat and momentum transport. Compared to the Arctic, the Antarctic and the surrounding SO have a "delayed warming" anthropogenic greenhouse gas (GHG) response. Understanding the role of the ocean dynamics in modulating the mesoscale atmosphere-ocean interactions in the SO in a fully coupled regime is crucial to efforts aimed at predicting the consequences of the warming and variability to the climate system. The response of model run at multiple resolutions (eddy permitting, eddy resolving) to both GHG forcing and historical forcing are examined in NCAR CCSM4 with four experiments. The first simulation, 0.5° atmosphere coupled to ocean and sea ice components with 1° resolution (LR). The second simulation uses the identical atmospheric model but coupled to 0.1° ocean and sea ice component models (HR). For the third and fourth experiments, the global ocean is simulated for LR an HR models, and a climate change scenario are produced by applying a fixed (present-day) CO2 concentration. The analysis focuses on the last 55 years of two individual 155 year simulations. We discuss results from a set of state-of-art model experiments in comparison with observational estimates and explore mechanisms by examining sea surface temperature, westerly winds, surface heat flux, ocean heat transport. In LR simulations, the patterns and mechanisms of SO changes under GHG forcing are similar to those over the historical period: warming is damped southward of the ACC and enhanced to the north, however major changes between the HR simulations are explored. We find that in recent decades the Southern Annual Mode has shown a distinct upward trend, the result of an anthropogenic global warming. Also, HR simulations show that strengthening of the SAM and associated surface wind stress have been invoked to posit enhancement in the strength of the upwelling of the MOC, and increases eddy activity of the ACC. The results also indicate that eddy-permitting models are not able to capture the eddy-driven SST response since ocean dynamics is playing crucial role in the HR simulation but not in the LR models.

Diazotroph community structure in the deep oxygen minimum zone of the Costa Rica Dome.

PubMed

Cheung, Shunyan; Xia, Xiaomin; Guo, Cui; Liu, Hongbin

2016-03-01

Oxygen minimum zones (OMZs), characterized by depleted dissolved oxygen concentration in the intermediate depth of the water column, are predicted to expand under the influence of global warming. Recent studies in the Eastern Tropical South Pacific Ocean and Arabian Sea have reported that heterotrophic nitrogen fixation is active in the OMZs. In this study, we investigated the community structure of diazotrophs in the OMZ of the Costa Rica Dome (CRD) upwelling region in the Eastern Tropical North Pacific Ocean, using 454-pyrosequencing of nifH gene amplicons. Comparing diazotroph assemblages in different depth strata of the OMZ (200-1000 m in depth), we found a unique diazotroph community in the OMZ core, which was mainly dominated by methanotroph-like diazotrophs, suggesting a potential coupling of nitrogen cycle and methane assimilation. In addition, some OTUs revealed in this study, especially those belonging to the large sub-cluster Vibrio diazotrophicus , were reported to be abundant and expressing the nifH gene in other OMZs. Our results suggest that the unique hydrographic conditions in OMZs may support similar assemblages of diazotrophs, and heterotrophic nitrogen fixation could also be occurring in our studied region. Our study provides the first insight into the composition and distribution of putative diazotrophs in the CRD OMZ.

Fast Response of the Tropics to an Abrupt Loss of Arctic Sea Ice via Ocean Dynamics

NASA Astrophysics Data System (ADS)

Wang, Kun; Deser, Clara; Sun, Lantao; Tomas, Robert A.

2018-05-01

The role of ocean dynamics in the transient adjustment of the coupled climate system to an abrupt loss of Arctic sea ice is investigated using experiments with Community Climate System Model version 4 in two configurations: a thermodynamic slab mixed layer ocean and a full-depth ocean that includes both dynamics and thermodynamics. Ocean dynamics produce a distinct sea surface temperature warming maximum in the eastern equatorial Pacific, accompanied by an equatorward intensification of the Intertropical Convergence Zone and Hadley Circulation. These tropical responses are established within 25 years of ice loss and contrast markedly with the quasi-steady antisymmetric coupled response in the slab-ocean configuration. A heat budget analysis reveals the importance of anomalous vertical advection tied to a monotonic temperature increase below 200 m for the equatorial sea surface temperature warming maximum in the fully coupled model. Ocean dynamics also rapidly modify the midlatitude atmospheric response to sea ice loss.

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

A simple model of the effect of ocean ventilation on ocean heat uptake

NASA Astrophysics Data System (ADS)

Nadiga, Balu; Urban, Nathan

2017-11-01

Transport of water from the surface mixed layer into the ocean interior is achieved, in large part, by the process of ventilation-a process associated with outcropping isopycnals. Starting from such a configuration of outcropping isopycnals, we derive a simple model of the effect of ventilation on ocean uptake of anomalous radiative forcing. This model can be seen as an improvement of the popular anomaly-diffusing class of energy balance models (AD-EBM) that are routinely employed to analyze and emulate the warming response of both observed and simulated Earth system. We demonstrate that neither multi-layer, nor continuous-diffusion AD-EBM variants can properly represent both surface-warming and the vertical distribution of ocean heat uptake. The new model overcomes this deficiency. The simplicity of the models notwithstanding, the analysis presented and the necessity of the modification is indicative of the role played by processes related to the down-welling branch of global ocean circulation in shaping the vertical distribution of ocean heat uptake.

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.

Dissolved and colloidal copper in the tropical South Pacific

NASA Astrophysics Data System (ADS)

Roshan, Saeed; Wu, Jingfeng

2018-07-01

Copper (Cu) as a bioactive trace metal in the ocean has widely been studied in the context of chemical speciation. However, this trace metal is extremely understudied in the context of physical speciation (i.e., size- or molecular weight-partitioning), which may help in characterizing dissolved Cu species. In this study, we determine total dissolved Cu (<0.2 μm) distribution and its physical speciation along the US GEOTRACES 2013 cruise, a 4300-km east-west transect in the tropical South Pacific. The distribution of dissolved Cu is rather uniform horizontally and exhibits a linear increase with depth from surface to 2500-3000 m, below which it varies less significantly both vertically and horizontally. Dissolved Cu shows a strong correlation with silicate (SiO44-) in the upper 1500 m, which is in agreement with previous studies in other regions. This correlation is weaker but with higher slope at depths below 1500 m, which supports the sedimentary source hypothesis. Although hydrothermal activity at the East Pacific Rise (EPR) does not show a readily evident impact on the dissolved Cu distribution, high-quality data at 2300-2800 m allow for diagnosing a subtle westward decrease in the background-subtracted dissolved Cu component. This component of dissolved Cu poorly correlates with mantle-derived 3He (R2 = 0.41), indicating a possible hydrothermal source for dissolved Cu, in contrast to previous studies. For the first time in a major basin, we also determined the physical speciation of dissolved Cu, which shows that Cu species lighter than 10 kDa (Da = 1 g mol-1) dominate the pool of dissolved Cu (<0.2 μm) below 1000 m with a contribution of 61 ± 6% (fraction of total dissolved). 39 ± 6% of dissolved Cu at depths below 1000 m, thus, occurs in the pool of colloidal matter (10 kDa-0.2 μm). Moreover, using a suite of molecular weight cutoffs indicate that Cu species are distributed between two distinct molecular weight classes: the lighter than 5 kDa and heavier than 300 kDa classes, which form 53 ± 6% and 37 ± 7% of dissolved Cu at 2200-2800 m, respectively. The Cu species with molecular weight between 5 kDa and 300 kDa contribute only to 10 ± 12% of the pool at 2200-2800 m. These results offer new insights into structure, reactivity and bioavailability of oceanic Cu compounds. As an organic-dominating metal, Cu physical speciation may also shed light on size-reactivity spectrum of dissolved organic matter (DOM) in the deep ocean.

Seasonality in ocean microbial communities.

PubMed

Giovannoni, Stephen J; Vergin, Kevin L

2012-02-10

Ocean warming occurs every year in seasonal cycles that can help us to understand long-term responses of plankton to climate change. Rhythmic seasonal patterns of microbial community turnover are revealed when high-resolution measurements of microbial plankton diversity are applied to samples collected in lengthy time series. Seasonal cycles in microbial plankton are complex, but the expansion of fixed ocean stations monitoring long-term change and the development of automated instrumentation are providing the time-series data needed to understand how these cycles vary across broad geographical scales. By accumulating data and using predictive modeling, we gain insights into changes that will occur as the ocean surface continues to warm and as the extent and duration of ocean stratification increase. These developments will enable marine scientists to predict changes in geochemical cycles mediated by microbial communities and to gauge their broader impacts.

Bracketing mid-pliocene sea surface temperature: maximum and minimum possible warming

USGS Publications Warehouse

Dowsett, Harry

2004-01-01

Estimates of sea surface temperature (SST) from ocean cores reveal a warm phase of the Pliocene between about 3.3 and 3.0 Mega-annums (Ma). Pollen records from land based cores and sections, although not as well dated, also show evidence for a warmer climate at about the same time. Increased greenhouse forcing and altered ocean heat transport is the leading candidates for the underlying cause of Pliocene global warmth. However, despite being a period of global warmth, there exists considerable variability within this interval. Two new SST reconstructions have been created to provide a climatological error bar for warm peak phases of the Pliocene. These data represent the maximum and minimum possible warming recorded within the 3.3 to 3.0 Ma interval.

Winter cold of eastern continental boundaries induced by warm ocean waters.

PubMed

Kaspi, Yohai; Schneider, Tapio

2011-03-31

In winter, northeastern North America and northeastern Asia are both colder than other regions at similar latitudes. This has been attributed to the effects of stationary weather systems set by elevated terrain (orography), and to a lack of maritime influences from the prevailing westerly winds. However, the differences in extent and orography between the two continents suggest that further mechanisms are involved. Here we show that this anomalous winter cold can result in part from westward radiation of large-scale atmospheric waves--nearly stationary Rossby waves--generated by heating of the atmosphere over warm ocean waters. We demonstrate this mechanism using simulations with an idealized general circulation model, with which we show that the extent of the cold region is controlled by properties of Rossby waves, such as their group velocity and its dependence on the planetary rotation rate. Our results show that warm ocean waters contribute to the contrast in mid-latitude winter temperatures between eastern and western continental boundaries not only by warming western boundaries, but also by cooling eastern boundaries.

Climatic regulation of the neurotoxin domoic acid

PubMed Central

McKibben, S. Morgaine; Peterson, William; Wood, A. Michelle; Trainer, Vera L.; Hunter, Matthew; White, Angelicque E.

2017-01-01

Domoic acid is a potent neurotoxin produced by certain marine microalgae that can accumulate in the foodweb, posing a health threat to human seafood consumers and wildlife in coastal regions worldwide. Evidence of climatic regulation of domoic acid in shellfish over the past 20 y in the Northern California Current regime is shown. The timing of elevated domoic acid is strongly related to warm phases of the Pacific Decadal Oscillation and the Oceanic Niño Index, an indicator of El Niño events. Ocean conditions in the northeast Pacific that are associated with warm phases of these indices, including changes in prevailing currents and advection of anomalously warm water masses onto the continental shelf, are hypothesized to contribute to increases in this toxin. We present an applied domoic acid risk assessment model for the US West Coast based on combined climatic and local variables. Evidence of regional- to basin-scale controls on domoic acid has not previously been presented. Our findings have implications in coastal zones worldwide that are affected by this toxin and are particularly relevant given the increased frequency of anomalously warm ocean conditions. PMID:28069959

Salinity bias on the foraminifera Mg/Ca thermometry: Correction procedure and implications for past ocean hydrographic reconstructions

NASA Astrophysics Data System (ADS)

Mathien-Blard, Elise; Bassinot, Franck

2009-12-01

Mg/Ca in foraminiferal calcite has recently been extensively used to estimate past oceanic temperatures. Here we show, however, that the Mg/Ca temperature relationship of the planktonic species Globigerinoides ruber is significantly affected by seawater salinity, with a +1 psu change in salinity resulting in a +1.6°C bias in Mg/Ca temperature calculations. If not accounted for, such a bias could lead, for instance, to systematic overestimations of Mg/Ca temperatures during glacial periods, when global ocean salinity had significantly increased compared to today. We present here a correction procedure to derive unbiased sea surface temperatures (SST) and δ18Osw from G. ruber TMg/Ca and δ18Of measurements. This correction procedure was applied to a sedimentary record to reconstruct hydrographic changes since the Last Glacial Maximum (LGM) in the Western Pacific Warm Pool. While uncorrected TMg/Ca data indicate a 3°C warming of the Western Pacific Warm Pool since the LGM, the salinity-corrected SST result in a stronger warming of 4°C.

Global Surface Temperature Anomalies and Attribution

NASA Astrophysics Data System (ADS)

Pietrafesa, L. J.

2017-12-01

We study Non-Stationary, Non-Linear time series of global surface temperatures from 1850 to 2016, and via an empirical, mathematical methodology, we reveal the buried, internal modes of variability of planetary temperatures over the past 167 years, and find periods of cooling and warming, both in the ocean and the atmosphere over land, with multiple modes of variability; seasonal, annual, inter-annual, multi-year, decadal, multi-decadal, centennial and overall warming trends in the ocean, atmosphere and the combination therein. The oceanic rate of warming is less than two thirds of that of the atmosphere. While our findings on overall trends of fossil fuel burning and planetary temperatures are only visually correlative, by employing a mathematical methodology well known in ergonomics, this study causally links the upward rise in planetary surface temperature from the latter part of the 19th Century and into the 21st Century, to the contemporaneous upward rise in fossil fuel burning and suggests that if present fossil fuel burning is not curtailed there will be continued warming of the planet in the future.

How important are intertidal ecosystems for global biogeochemical cycles? Molecular and isotopic evidence for major outwelling of photo-bleached dissolved organic matter from mangroves.

NASA Astrophysics Data System (ADS)

Dittmar, T.; Cooper, W. T.; Koch, B. P.; Kattner, G.

2006-05-01

Organic matter, which is dissolved in low concentrations in the vast waters of the oceans, contains a total amount of carbon similar to atmospheric carbon dioxide. To understand global biogeochemical cycles it is crucial to quantify the sources of marine dissolved organic carbon (DOC). We investigated the impact of mangroves, the dominant intertidal vegetation of the tropics, on marine DOC inventories. Stable carbon- isotopes, ultrahigh-resolution mass spectrometry (FTICRMS), lignin-derived phenols and proton nuclear magnetic resonance spectroscopy showed that mangroves are the main source of terrigenous DOC on the shelf off Northern Brazil. Sunlight efficiently destroyed aromatic molecules during transport offshore, removing about one third of mangrove-derived DOC. The remainder was refractory and may thus be distributed over the oceans. On a global scale, we estimate that mangroves account for more than 10 percent of the terrestrially- derived, refractory DOC transported to the ocean, while they cover less than 0.1 percent of the continents' surface.

Thorium distributions in high- and low-dust regions and the significance for iron supply

NASA Astrophysics Data System (ADS)

Hayes, Christopher T.; Rosen, Jeffrey; McGee, David; Boyle, Edward A.

2017-02-01

Thorium and uranium isotopes (232Th, 230Th, 238U, and 234U) were investigated to refine their use for estimating mineral dust deposition and Fe delivery to the ocean. U concentrations and isotope ratios were consistent with conservative behavior and can safely be described using published U-salinity relationships and global average seawater isotopic composition. Near Barbados, waters affected by the Amazon outflow contained elevated 232Th. This signals one region where the thorium-dust method is inaccurate because of a confounding continental input. Dissolved 232Th fluxes in this region suggest that Amazonian Fe supply to the adjacent open ocean is much larger than local atmospheric deposition. The colloidal content of dissolved Th south of Bermuda was found to be quite small (2-6%), similar to that found north of Hawaii, despite the order of magnitude higher dust deposition in the Atlantic. This finding supports the assumption that dissolved 232Th and 230Th are scavenged at the same rate despite their different sources and also sheds light on the increase of dissolved 232Th fluxes with integrated depth. Outside the region influenced by Amazon River waters, dissolved 232Th fluxes are compared with Bermudan aerosol Fe deposition to estimate that fractional Th solubility is around 20% in this region. Finally, new dissolved and soluble Fe, Mn, and Cr data from the subtropical North Pacific support the idea that Fe concentrations in the remote ocean are highly buffered, whereas 232Th has a larger dynamic range between high- and low-dust regions.

Tracking changes in ocean redox during the PETM using stable chromium isotopes

NASA Astrophysics Data System (ADS)

Dixon, S. K.; Parkinson, I. J.; Sexton, P.; Fehr, M.; James, R. H.; Peacock, C.

2012-12-01

Climate models predict a decline in oceanic dissolved oxygen under global warming conditions and observations suggest the expansion of tropical oxygen minimum zones is already underway1, with concern over the trend for future seawater oxygen levels. Therefore, previous deoxygenation events in the geological record may provide insight into the dynamics of changing oxygen levels in the Earth's oceans. One such event, is the Palaeocene-Eocene Thermal Maximum (PETM) at ~55Ma which represents a period of rapid global warming. Multiple lines of evidence suggest that at least on a local scale, near bottom anoxia occurred during the event2,3 and further understanding of changing redox conditions during this period may provide insight into future sea level oxygenation. To track seawater oxygenation during the PETM, we are utilising stable Cr isotope composition of marine carbonates, a new palaeo-redox proxy, which has shown potential when applied to modern and ancient carbonates 4,5. We present δ53Cr, trace element and REE data of foraminiferal ooze deposits over the PETM interval. Samples were taken from the North East Atlantic DSDP site 401, which preserves an exceptional and complete carbonate sequence over the interval, at a time when ocean acidification lead to massive sea floor carbonate dissolution6. Foraminifera were taken from the 63 - 150μm size fraction and planktic count data indicate that the relative proportions of dominant species do not change significantly over the event7. Systematic changes occur in REEs, Cr concentration and δ53Cr coincident with the onset of the negative δ13C excursion. The Cr concentrations of the carbonates decrease into the event, which suggests the sea level Cr concentration has fallen. We interpret this to reflect falling oxygen concentration in the seawater, leading to a decrease in aqueous Cr (VI) via precipitation of Cr out of the water column in the form of insoluble Cr (III) hydroxide. Additionally, we will demonstrate how stable Cr isotopes in carbonates respond to changes in ocean chemistry during the PETM. (1) Stramma et al. (2008). Science, 320, 655-658. (2) Dickson et al. (2012). Geology, 40, 639-642. (3) Dypvik et al. (2011). Palaeogeography, Palaeoclimatology, Palaeoecology, 302, 156-169. (4) Bonnand (2011). PhD thesis, The Open University ; (5) Frei et al. (2011). Earth and Planet. Sci. Lett., 312, 114-125. (6) Zachos et al. (2005). Science, 308, 1611-1615. (7) Pardo et al. (1997). Marine Micropaleontology, 29, 129-158.

Constraints on oceanic methane emissions west of Svalbard from atmospheric in situ measurements and Lagrangian transport modeling.

PubMed

Pisso, I; Myhre, C Lund; Platt, S M; Eckhardt, S; Hermansen, O; Schmidbauer, N; Mienert, J; Vadakkepuliyambatta, S; Bauguitte, S; Pitt, J; Allen, G; Bower, K N; O'Shea, S; Gallagher, M W; Percival, C J; Pyle, J; Cain, M; Stohl, A

2016-12-16

Methane stored in seabed reservoirs such as methane hydrates can reach the atmosphere in the form of bubbles or dissolved in water. Hydrates could destabilize with rising temperature further increasing greenhouse gas emissions in a warming climate. To assess the impact of oceanic emissions from the area west of Svalbard, where methane hydrates are abundant, we used measurements collected with a research aircraft (Facility for Airborne Atmospheric Measurements) and a ship (Helmer Hansen) during the Summer 2014 and for Zeppelin Observatory for the full year. We present a model-supported analysis of the atmospheric CH 4 mixing ratios measured by the different platforms. To address uncertainty about where CH 4 emissions actually occur, we explored three scenarios: areas with known seeps, a hydrate stability model, and an ocean depth criterion. We then used a budget analysis and a Lagrangian particle dispersion model to compare measurements taken upwind and downwind of the potential CH 4 emission areas. We found small differences between the CH 4 mixing ratios measured upwind and downwind of the potential emission areas during the campaign. By taking into account measurement and sampling uncertainties and by determining the sensitivity of the measured mixing ratios to potential oceanic emissions, we provide upper limits for the CH 4 fluxes. The CH 4 flux during the campaign was small, with an upper limit of 2.5 nmol m -2  s -1 in the stability model scenario. The Zeppelin Observatory data for 2014 suggest CH 4 fluxes from the Svalbard continental platform below 0.2 Tg yr -1 . All estimates are in the lower range of values previously reported.

Constraints on oceanic methane emissions west of Svalbard from atmospheric in situ measurements and Lagrangian transport modeling

PubMed Central

Myhre, C. Lund; Platt, S. M.; Eckhardt, S.; Hermansen, O.; Schmidbauer, N.; Mienert, J.; Vadakkepuliyambatta, S.; Bauguitte, S.; Pitt, J.; Allen, G.; Bower, K. N.; O'Shea, S.; Gallagher, M. W.; Percival, C. J.; Pyle, J.; Cain, M.; Stohl, A.

2016-01-01

Abstract Methane stored in seabed reservoirs such as methane hydrates can reach the atmosphere in the form of bubbles or dissolved in water. Hydrates could destabilize with rising temperature further increasing greenhouse gas emissions in a warming climate. To assess the impact of oceanic emissions from the area west of Svalbard, where methane hydrates are abundant, we used measurements collected with a research aircraft (Facility for Airborne Atmospheric Measurements) and a ship (Helmer Hansen) during the Summer 2014 and for Zeppelin Observatory for the full year. We present a model‐supported analysis of the atmospheric CH4 mixing ratios measured by the different platforms. To address uncertainty about where CH4 emissions actually occur, we explored three scenarios: areas with known seeps, a hydrate stability model, and an ocean depth criterion. We then used a budget analysis and a Lagrangian particle dispersion model to compare measurements taken upwind and downwind of the potential CH4 emission areas. We found small differences between the CH4 mixing ratios measured upwind and downwind of the potential emission areas during the campaign. By taking into account measurement and sampling uncertainties and by determining the sensitivity of the measured mixing ratios to potential oceanic emissions, we provide upper limits for the CH4 fluxes. The CH4 flux during the campaign was small, with an upper limit of 2.5 nmol m−2 s−1 in the stability model scenario. The Zeppelin Observatory data for 2014 suggest CH4 fluxes from the Svalbard continental platform below 0.2 Tg yr−1. All estimates are in the lower range of values previously reported. PMID:28261536

Constraints on oceanic methane emissions west of Svalbard from atmospheric in situ measurements and Lagrangian transport modeling

NASA Astrophysics Data System (ADS)

Pisso, I.; Myhre, C. Lund; Platt, S. M.; Eckhardt, S.; Hermansen, O.; Schmidbauer, N.; Mienert, J.; Vadakkepuliyambatta, S.; Bauguitte, S.; Pitt, J.; Allen, G.; Bower, K. N.; O'Shea, S.; Gallagher, M. W.; Percival, C. J.; Pyle, J.; Cain, M.; Stohl, A.

2016-12-01

Methane stored in seabed reservoirs such as methane hydrates can reach the atmosphere in the form of bubbles or dissolved in water. Hydrates could destabilize with rising temperature further increasing greenhouse gas emissions in a warming climate. To assess the impact of oceanic emissions from the area west of Svalbard, where methane hydrates are abundant, we used measurements collected with a research aircraft (Facility for Airborne Atmospheric Measurements) and a ship (Helmer Hansen) during the Summer 2014 and for Zeppelin Observatory for the full year. We present a model-supported analysis of the atmospheric CH4 mixing ratios measured by the different platforms. To address uncertainty about where CH4 emissions actually occur, we explored three scenarios: areas with known seeps, a hydrate stability model, and an ocean depth criterion. We then used a budget analysis and a Lagrangian particle dispersion model to compare measurements taken upwind and downwind of the potential CH4 emission areas. We found small differences between the CH4 mixing ratios measured upwind and downwind of the potential emission areas during the campaign. By taking into account measurement and sampling uncertainties and by determining the sensitivity of the measured mixing ratios to potential oceanic emissions, we provide upper limits for the CH4 fluxes. The CH4 flux during the campaign was small, with an upper limit of 2.5 nmol m-2 s-1 in the stability model scenario. The Zeppelin Observatory data for 2014 suggest CH4 fluxes from the Svalbard continental platform below 0.2 Tg yr-1. All estimates are in the lower range of values previously reported.

40 CFR Appendix B to Part 80 - Test Methods for Lead in Gasoline

Code of Federal Regulations, 2014 CFR

2014-07-01

... one liter. 4.6 Iodine Solution—Dissolve and dilute 3.0 g iodine crystals with Toluene to 100 ml. 4.7...): Dissolve and dilute 3.0 g iodine crystals (American Chemical Society) with toluene (Burdick & Jackson Lab... and aligned according to Section 7 and the instrument has had substantial time for warm-up. 8.2Auto...

40 CFR Appendix B to Part 80 - Test Methods for Lead in Gasoline

Code of Federal Regulations, 2010 CFR

2010-07-01

... one liter. 4.6 Iodine Solution—Dissolve and dilute 3.0 g iodine crystals with Toluene to 100 ml. 4.7...): Dissolve and dilute 3.0 g iodine crystals (American Chemical Society) with toluene (Burdick & Jackson Lab... and aligned according to Section 7 and the instrument has had substantial time for warm-up. 8.2Auto...

40 CFR Appendix B to Part 80 - Test Methods for Lead in Gasoline

Code of Federal Regulations, 2013 CFR

2013-07-01

... one liter. 4.6 Iodine Solution—Dissolve and dilute 3.0 g iodine crystals with Toluene to 100 ml. 4.7...): Dissolve and dilute 3.0 g iodine crystals (American Chemical Society) with toluene (Burdick & Jackson Lab... and aligned according to Section 7 and the instrument has had substantial time for warm-up. 8.2Auto...

40 CFR Appendix B to Part 80 - Test Methods for Lead in Gasoline

Code of Federal Regulations, 2011 CFR

2011-07-01

... one liter. 4.6 Iodine Solution—Dissolve and dilute 3.0 g iodine crystals with Toluene to 100 ml. 4.7...): Dissolve and dilute 3.0 g iodine crystals (American Chemical Society) with toluene (Burdick & Jackson Lab... and aligned according to Section 7 and the instrument has had substantial time for warm-up. 8.2Auto...

40 CFR Appendix B to Part 80 - Test Methods for Lead in Gasoline

Code of Federal Regulations, 2012 CFR

2012-07-01

... one liter. 4.6 Iodine Solution—Dissolve and dilute 3.0 g iodine crystals with Toluene to 100 ml. 4.7...): Dissolve and dilute 3.0 g iodine crystals (American Chemical Society) with toluene (Burdick & Jackson Lab... and aligned according to Section 7 and the instrument has had substantial time for warm-up. 8.2Auto...

The Effect of Increased Temperatures and Ultraviolet Radiation on Dissolved Oxygen in Ecosystems Primarily Comprised of "Euglena"

ERIC Educational Resources Information Center

Carpenter, Matt

2009-01-01

The purpose of this study was to determine whether increased levels of UV radiation and temperatures from global warming have a significant impact on dissolved oxygen (DO) output from the alga, "Euglena," which affects other organisms in the ecosystem. The original hypothesis stated that if temperature was increased along with exposure time to…

Ancient Oceans Had Less Oxygen

ERIC Educational Resources Information Center

King, Angela G.

2004-01-01

The amount of dissolved oxygen in the oceans in the mid-Proterozoic period has evolutionary implications since essential trace metals are redox sensitive. The findings suggest that there is global lack of oxygen in seawater.

Patterns of Indian Ocean Sea-Level Change in a Warming Climate

DTIC Science & Technology

2010-08-01

distribution is unlimited. 13. SUPPLEMENTARY NOTES 20110415461 14 ABSTRACT Global sea level has risen during the past decades as a result of thermal...expansion of the warming ocean and freshwater addition from melting continental icel However, sea-level rise is not globally uniforml, 2, 3, 4, 5...7320 Division Head Ruth H. Preller, 7300 Security. Code 1226 Office of Counsel,Code 1008.3 ADOR/Director NCST E. R. Franchi , 7000 Public

The history and future trends of ocean warming-induced gas hydrate dissociation in the SW Barents Sea

NASA Astrophysics Data System (ADS)

Vadakkepuliyambatta, Sunil; Chand, Shyam; Bünz, Stefan

2017-01-01

The Barents Sea is a major part of the Arctic where the Gulf Stream mixes with the cold Arctic waters. Late Cenozoic uplift and glacial erosion have resulted in hydrocarbon leakage from reservoirs, evolution of fluid flow systems, shallow gas accumulations, and hydrate formation throughout the Barents Sea. Here we integrate seismic data observations of gas hydrate accumulations along with gas hydrate stability modeling to analyze the impact of warming ocean waters in the recent past and future (1960-2060). Seismic observations of bottom-simulating reflectors (BSRs) indicate significant thermogenic gas input into the hydrate stability zone throughout the SW Barents Sea. The distribution of BSR is controlled primarily by fluid flow focusing features, such as gas chimneys and faults. Warming ocean bottom temperatures over the recent past and in future (1960-2060) can result in hydrate dissociation over an area covering 0.03-38% of the SW Barents Sea.

Large-amplitude internal waves sustain coral health during thermal stress

NASA Astrophysics Data System (ADS)

Schmidt, Gertraud M.; Wall, Marlene; Taylor, Marc; Jantzen, Carin; Richter, Claudio

2016-09-01

Ocean warming is a major threat for coral reefs causing widespread coral bleaching and mortality. Potential refugia are thus crucial for coral survival. Exposure to large-amplitude internal waves (LAIW) mitigated heat stress and ensured coral survival and recovery during and after an extreme heat anomaly. The physiological status of two common corals, Porites lutea and Pocillopora meandrina, was monitored in host and symbiont traits, in response to LAIW-exposure throughout the unprecedented 2010 heat anomaly in the Andaman Sea. LAIW-exposed corals of both species survived and recovered, while LAIW-sheltered corals suffered partial and total mortality in P. lutea and P. meandrina, respectively. LAIW are ubiquitous in the tropics and potentially generate coral refuge areas. As thermal stress to corals is expected to increase in a warming ocean, the mechanisms linking coral bleaching to ocean dynamics will be crucial to predict coral survival on a warming planet.

Keeping the ocean warm

NASA Astrophysics Data System (ADS)

Nimmo, Francis

2017-12-01

More than 20 GW of power are necessary to balance the heat emitted by Enceladus and avoid the freezing of its internal ocean. A very porous core undergoing tidal heating can generate the required power to maintain a liquid ocean and drive hydrothermal activity.

Photochemical Mineralization of Terrigenous DOC to Dissolved Inorganic Carbon in Ocean

NASA Astrophysics Data System (ADS)

Aarnos, Hanna; Gélinas, Yves; Kasurinen, Ville; Gu, Yufei; Puupponen, Veli-Mikko; Vähätalo, Anssi V.

2018-02-01

When terrigenous dissolved organic carbon (tDOC) rich in chromophoric dissolved organic matter (tCDOM) enters the ocean, solar radiation mineralizes it partially into dissolved inorganic carbon (DIC). This study addresses the amount and the rates of DIC photoproduction from tDOC and the area of ocean required to photomineralize tDOC. We collected water samples from 10 major rivers, mixed them with artificial seawater, and irradiated them with simulated solar radiation to measure DIC photoproduction and the photobleaching of tCDOM. The linear relationship between DIC photoproduction and tCDOM photobleaching was used to estimate the amount of photoproduced DIC from the tCDOM fluxes of the study rivers. Solar radiation was estimated to mineralize 12.5 ± 3.7 Tg C yr-1 (10 rivers)-1 or 18 ± 8% of tDOC flux. The irradiation experiments also approximated typical apparent spectral quantum yields for DIC photoproduction (ϕλ) over the entire lifetime of the tCDOM. Based on ϕλs and the local solar irradiances in river plumes, the annual areal DIC photoproduction rates from tDOC were calculated to range from 52 ± 4 (Lena River) to 157 ± 2 mmol C m-2 yr-1 (Mississippi River). When the amount of photoproduced DIC was divided by the areal rate, 9.6 ± 2.5 × 106 km2 of ocean was required for the photomineralization of tDOC from the study rivers. Extrapolation to the global tDOC flux yields 45 (31-58) Tg of photoproduced DIC per year in the river plumes that cover 34 (25-43) × 106 km2 of the ocean.

Global Warming Threatens National Interests in the Arctic

DTIC Science & Technology

2009-03-26

Global warming has impacted the Arctic Ocean by significantly reducing the extent of the summer ice cover allowing greater access to the region...increased operations in the Arctic region, and DoD must continue to research and develop new and alternate energy sources for its forces. Global warming is

Variability in organic carbon reactivity across lake residence time and trophic gradients

NASA Astrophysics Data System (ADS)

Evans, Chris D.; Futter, Martyn N.; Moldan, Filip; Valinia, Salar; Frogbrook, Zoe; Kothawala, Dolly N.

2017-11-01

The transport of dissolved organic carbon from land to ocean is a large dynamic component of the global carbon cycle. Inland waters are hotspots for organic matter turnover, via both biological and photochemical processes, and mediate carbon transfer between land, oceans and atmosphere. However, predicting dissolved organic carbon reactivity remains problematic. Here we present in situ dissolved organic carbon budget data from 82 predominantly European and North American water bodies with varying nutrient concentrations and water residence times ranging from one week to 700 years. We find that trophic status strongly regulates whether water bodies act as net dissolved organic carbon sources or sinks, and that rates of both dissolved organic carbon production and consumption can be predicted from water residence time. Our results suggest a dominant role of rapid light-driven removal in water bodies with a short water residence time, whereas in water bodies with longer residence times, slower biotic production and consumption processes are dominant and counterbalance one another. Eutrophication caused lakes to transition from sinks to sources of dissolved organic carbon. We conclude that rates and locations of dissolved organic carbon processing and associated CO2 emissions in inland waters may be misrepresented in global carbon budgets if temporal and spatial reactivity gradients are not accounted for.

Continuous flux of dissolved black carbon from a vanished tropical forest biome

NASA Astrophysics Data System (ADS)

Dittmar, T.; Rezende, C. E.; Manecki, M.; Niggemann, J.; Coelho Ovalle, A. R.; Bernardes, M. C.

2012-04-01

Humans have extensively used fire as a tool to shape Earth's vegetation. One of the biggest events in this context was the destruction of Brazilian's Atlantic forest, once among the largest tropical forest biomes on Earth. We estimate that the slash-and-burn practice produced 200 to 500 million tons of black carbon from the 1850' to 1973. The fate of this charred organic matter is unknown. Here we show continuous runoff of dissolved black carbon from the cleared forest biome, more than 35 years after the widespread burning of the forest ended. During the 11-year observation period (1997-2008) of this study, on average 0.04 to 0.08 tons of dissolved black carbon were annually exported per square kilometer land. We estimate an annual runoff of 48,000 to 97,000 tons dissolved black carbon from the former Atlantic forest biome. Dissolved black carbon was mobilized by water percolating through the soil during the rainy season. During base flow conditions, dissolved organic carbon (DOC) did not contain black carbon, whereas at peak flow up to 6% of DOC was combustion-derived. If runoff was the only removal mechanism of black carbon from soils, even the highly condensed and presumably refractory component of black carbon would have a half-life of only 440 to 2300 years in the soil. In areas with higher precipitation, stronger runoff and consequently a shorter half-life can be expected. In the deep ocean, dissolved black carbon is virtually inert on this time scale. The disappearance of the Atlantic forest provides a worst-case scenario for tropical forests worldwide, most of which are cleared at increasing rate. Because of the comparably fast mobilization of dissolved black carbon from soils and its resistivity in the deep ocean, an increase of black carbon production on land may alter the size of the global pool of >12 Pg carbon of thermally altered DOC in the ocean on the long term.

An examination of the role of particles in oceanic mercury cycling.

PubMed

Lamborg, Carl H; Hammerschmidt, Chad R; Bowman, Katlin L

2016-11-28

Recent models of global mercury (Hg) cycling have identified the downward flux of sinking particles in the ocean as a prominent Hg removal process from the ocean. At least one of these models estimates the amount of anthropogenic Hg in the ocean to be about 400 Mmol, with deep water formation and sinking fluxes representing the largest vectors by which pollutant Hg is able to penetrate the ocean interior. Using data from recent cruises to the Atlantic, we examined the dissolved and particulate partitioning of Hg in the oceanic water column as a cross-check on the hypothesis that sinking particle fluxes are important. Interestingly, these new data suggest particle-dissolved partitioning ( K d ) that is approximately 20× greater than previous estimates, which thereby challenges certain assumptions about the scavenging and active partitioning of Hg in the ocean used in earlier models. For example, the new particle data suggest that regenerative scavenging is the most likely mechanism by which the association of Hg and particles occurs.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'. © 2016 The Author(s).

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.

The footprint of the inter-decadal Pacific oscillation in Indian Ocean sea surface temperatures

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

Dong, Lu; Zhou, Tianjun; Dai, Aiguo

Superimposed on a pronounced warming trend, the Indian Ocean (IO) sea surface temperatures (SSTs) also show considerable decadal variations that can cause regional climate oscillations around the IO. However, the mechanisms of the IO decadal variability remain unclear. Here we perform numerical experiments using a state-of-the-art, fully coupled climate model in which the external forcings with or without the observed SSTs in the tropical eastern Pacific Ocean (TEP) are applied for 1871–2012. Both the observed timing and magnitude of the IO decadal variations are well reproduced in those experiments with the TEP SSTs prescribed to observations. Although the external forcingsmore » account for most of the warming trend, the decadal variability in IO SSTs is dominated by internal variability that is induced by the TEP SSTs, especially the Inter-decadal Pacific Oscillation (IPO). The IPO weakens (enhances) the warming of the external forcings by about 50% over the IO during IPO’s cold (warm) phase, which contributes about 10% to the recent global warming hiatus since 1999. As a result, the decadal variability in IO SSTs is modulated by the IPO-induced atmospheric adjustment through changing surface heat fluxes, sea surface height and thermocline depth.« less

The footprint of the inter-decadal Pacific oscillation in Indian Ocean sea surface temperatures

DOE PAGES

Dong, Lu; Zhou, Tianjun; Dai, Aiguo; ...

2016-02-17

Superimposed on a pronounced warming trend, the Indian Ocean (IO) sea surface temperatures (SSTs) also show considerable decadal variations that can cause regional climate oscillations around the IO. However, the mechanisms of the IO decadal variability remain unclear. Here we perform numerical experiments using a state-of-the-art, fully coupled climate model in which the external forcings with or without the observed SSTs in the tropical eastern Pacific Ocean (TEP) are applied for 1871–2012. Both the observed timing and magnitude of the IO decadal variations are well reproduced in those experiments with the TEP SSTs prescribed to observations. Although the external forcingsmore » account for most of the warming trend, the decadal variability in IO SSTs is dominated by internal variability that is induced by the TEP SSTs, especially the Inter-decadal Pacific Oscillation (IPO). The IPO weakens (enhances) the warming of the external forcings by about 50% over the IO during IPO’s cold (warm) phase, which contributes about 10% to the recent global warming hiatus since 1999. As a result, the decadal variability in IO SSTs is modulated by the IPO-induced atmospheric adjustment through changing surface heat fluxes, sea surface height and thermocline depth.« less

Late Lutetian Thermal Maximum—Crossing a Thermal Threshold in Earth's Climate System?

NASA Astrophysics Data System (ADS)

Westerhold, T.; Röhl, U.; Donner, B.; Frederichs, T.; Kordesch, W. E. C.; Bohaty, S. M.; Hodell, D. A.; Laskar, J.; Zeebe, R. E.

2018-01-01

Recognizing and deciphering transient global warming events triggered by massive release of carbon into Earth's ocean-atmosphere climate system in the past are important for understanding climate under elevated pCO2 conditions. Here we present new high-resolution geochemical records including benthic foraminiferal stable isotope data with clear evidence of a short-lived (30 kyr) warming event at 41.52 Ma. The event occurs in the late Lutetian within magnetochron C19r and is characterized by a ˜2°C warming of the deep ocean in the southern South Atlantic. The magnitudes of the carbon and oxygen isotope excursions of the Late Lutetian Thermal Maximum are comparable to the H2 event (53.6 Ma) suggesting a similar response of the climate system to carbon cycle perturbations even in an already relatively cooler climate several million years after the Early Eocene Climate Optimum. Coincidence of the event with exceptionally high insolation values in the Northern Hemisphere at 41.52 Ma might indicate that Earth's climate system has a thermal threshold. When this tipping point is crossed, rapid positive feedback mechanisms potentially trigger transient global warming. The orbital configuration in this case could have caused prolonged warm and dry season leading to a massive release of terrestrial carbon into the ocean-atmosphere system initiating environmental change.

Decline of cold-water fish species in the Bay of Somme (English Channel, France) in response to ocean warming

NASA Astrophysics Data System (ADS)

Auber, Arnaud; Gohin, Francis; Goascoz, Nicolas; Schlaich, Ivan

2017-04-01

A growing number of studies have documented increasing dominance of warm-water fish species ("tropicalisation") in response to ocean warming. Such reorganization of communities is starting to occur in a multitude of local ecosystems, implying that tropicalisation of marine communities could become a global phenomenon. Using 32 years of trawl surveys in the Bay of Somme (English Channel, France), we aimed to investigate the existence of a tropicalisation in the fish community at the local scale of the estuary during the mid-1990s, a period where an exceptional temperature rise occurred in Northeast Atlantic. A long-term response occurred (with a major transition over 6 years) that was characterized by a marked diminution in the abundance of cold-water species in parallel to a temperature rise generated by the ocean-scale phenomenon, the Atlantic Multidecadal Oscillation, which switched from a cool to a warm phase during the late 1990s. Despite finding no significant increase in the dominance of warm-water species, the long-term diminution of cold-water species suggests that the restructuring of the fish community was mainly influenced by global-scale environmental conditions rather than local ones and that indirect effects may also occurred through biological interactions.

Indo-Pacific climate during the decaying phase of the 2015/16 El Niño: role of southeast tropical Indian Ocean warming

NASA Astrophysics Data System (ADS)

Chen, Zesheng; Du, Yan; Wen, Zhiping; Wu, Renguang; Wang, Chunzai

2018-06-01

This study investigates the influence of southeast tropical Indian Ocean (SETIO) sea surface temperature (SST) warming on Indo-Pacific climate during the decaying phase of the 2015/16 El Niño by using observations and model experiments. The results show that the SETIO SST warming in spring 2016 enhanced local convection and forced a "C-shape" wind anomaly pattern in the lower troposphere. The "C-shape" wind anomaly pattern over the eastern tropical Indian Ocean consists of anomalous westerly flow south of the equator and anomalous easterly flow north of the equator. The anomalous easterly flow then extended eastward into the western North Pacific (WNP) and facilitates the development or the maintenance of an anomalous anticyclone over the South China Sea (SCS). Correspondingly, the eastern part of the Bay of Bengal, the SCS and the WNP suffered less rainfall. Such precipitation features and the associated "C-shape" wind anomaly pattern shifted northward about five latitudes in summer 2016. Additionally, the SETIO warming can induce local meridional circulation anomalies, which directly affect Indo-Pacific climate. Numerical model experiments further confirm that the SETIO SST warming plays an important role in modulating Indo-Pacific climate.

The southeastern continental shelf of the United States as an atmospheric CO 2 source and an exporter of inorganic carbon to the ocean

NASA Astrophysics Data System (ADS)

Aleck Wang, Zhaohui; Cai, Wei-Jun; Wang, Yongchen; Ji, Hongwei

2005-10-01

The US southeastern continental shelf, also known as the South Atlantic Bight (SAB), is a strong source of CO 2 to the atmosphere, which is in direct contrast to recent reports regarding other major continental shelves. Both spatial (cross-shelf) and seasonal variations of the CO 2 system were pronounced in the SAB. Sea surface pCO 2 in winter was undersaturated relative to the atmosphere, while oversaturation of pCO 2 dominated the entire shelf water in all other seasons. Annually, the SAB releases CO 2 to the atmosphere at an average rate of 30 g C m -2 (2.5 mol C m -2). This system also discharges dissolved inorganic carbon to the open ocean (30 g C m -2 yr -1). Methods of estimating CO 2 flux and DIC flux are critically evaluated and compared. A carbon mass balance model in the SAB is presented based on inorganic carbon fluxes from this study and organic carbon fluxes from literature. The carbon budget is much closer to balance by using this carbon flux approach than by direct measurements of primary production and respiration. It is concluded that the SAB is a net heterotrophic system annually. Intensified heating, elevated input of inorganic carbon from coastal salt marshes, microbial respiration of marsh-exported organic carbon and the lack of annual spring blooms all contribute to maintaining the SAB as a strong CO 2 source to the atmosphere during the warm seasons. In winter, the primary factor that governs the CO 2 sink in the SAB is likely the cooling process. Strong heterotrophy during warm seasons also sustains the SAB to be an exporter of inorganic carbon to the open ocean annually. The SAB shelf functions differently from the East China Sea, the North Atlantic European Shelves, and the Mid-Atlantic Bight as a source or sink of atmospheric CO 2. The SAB is classified as a "marsh-dominated" shelf as compared to other shelves in terms of carbon dynamics. Further work to study carbon dynamics in coastal margins is warranted to interpret their roles in the global CO 2 budget.

Assessing and Upgrading Ocean Mixing for the Study of Climate Change

NASA Astrophysics Data System (ADS)

Howard, A. M.; Fells, J.; Lindo, F.; Tulsee, V.; Canuto, V.; Cheng, Y.; Dubovikov, M. S.; Leboissetier, A.

2016-12-01

Climate is critical. Climate variability affects us all; Climate Change is a burning issue. Droughts, floods, other extreme events, and Global Warming's effects on these and problems such as sea-level rise and ecosystem disruption threaten lives. Citizens must be informed to make decisions concerning climate such as "business as usual" vs. mitigating emissions to keep warming within bounds. Medgar Evers undergraduates aid NASA research while learning climate science and developing computer&math skills. To make useful predictions we must realistically model each component of the climate system, including the ocean, whose critical role includes transporting&storing heat and dissolved CO2. We need physically based parameterizations of key ocean processes that can't be put explicitly in a global climate model, e.g. vertical&lateral mixing. The NASA-GISS turbulence group uses theory to model mixing including: 1) a comprehensive scheme for small scale vertical mixing, including convection&shear, internal waves & double-diffusion, and bottom tides 2) a new parameterization for the lateral&vertical mixing by mesoscale eddies. For better understanding we write our own programs. To assess the modelling MATLAB programs visualize and calculate statistics, including means, standard deviations and correlations, on NASA-GISS OGCM output with different mixing schemes and help us study drift from observations. We also try to upgrade the schemes, e.g. the bottom tidal mixing parameterizations' roughness, calculated from high resolution topographic data using Gaussian weighting functions with cut-offs. We study the effects of their parameters to improve them. A FORTRAN program extracts topography data subsets of manageable size for a MATLAB program, tested on idealized cases, to visualize&calculate roughness on. Students are introduced to modeling a complex system, gain a deeper appreciation of climate science, programming skills and familiarity with MATLAB, while furthering climate science by improving our mixing schemes. We are incorporating climate research into our college curriculum. The PI is both a member of the turbulence group at NASA-GISS and an associate professor at Medgar Evers College of CUNY, an urban minority serving institution in central Brooklyn. Supported by NSF Award AGS-1359293.

Preliminary forecasts of Pacific bigeye tuna population trends under the A2 IPCC scenario

NASA Astrophysics Data System (ADS)

Lehodey, P.; Senina, I.; Sibert, J.; Bopp, L.; Calmettes, B.; Hampton, J.; Murtugudde, R.

2010-07-01

An improved version of the spatial ecosystem and population dynamics model SEAPODYM was used to investigate the potential impacts of global warming on tuna populations. The model included an enhanced definition of habitat indices, movements, and accessibility of tuna predators to different vertically migrant and non-migrant micronekton functional groups. The simulations covered the Pacific basin (model domain) at a 2° × 2° geographic resolution. The structure of the model allows an evaluation from multiple data sources, and parameterization can be optimized by adjoint techniques and maximum likelihood using fishing data. A first such optimized parameterization was obtained for bigeye tuna ( Thunnus obesus) in the Pacific Ocean using historical catch data for the last 50 years and a hindcast from a coupled physical-biogeochemical model driven by the NCEP atmospheric reanalysis. The parameterization provided very plausible biological parameter values and a good fit to fishing data from the different fisheries, both within and outside the time period used for optimization. We then employed this model to forecast the future of bigeye tuna populations in the Pacific Ocean. The simulation was driven by the physical-biogeochemical fields predicted from a global marine biogeochemistry - climate simulation. This global simulation was performed with the IPSL climate model version 4 (IPSL-CM4) coupled to the oceanic biogeochemical model PISCES and forced by atmospheric CO 2, from historical records over 1860-2000, and under the SRES A2 IPCC scenario for the 21st century (i.e. atmospheric CO 2 concentration reaching 850 ppm in the year 2100). Potential future changes in distribution and abundance under the IPCC scenario are presented but without taking into account any fishing effort. The simulation showed an improvement in bigeye tuna spawning habitat both in subtropical latitudes and in the eastern tropical Pacific (ETP) where the surface temperature becomes optimal for bigeye tuna spawning. The adult feeding habitat also improved in the ETP due to the increase of dissolved oxygen concentration in the sub-surface allowing adults to access deeper forage. Conversely, in the Western Central Pacific the temperature becomes too warm for bigeye tuna spawning. The decrease in spawning is compensated by an increase of larvae biomass in subtropical regions. However, natural mortality of older stages increased due to lower habitat values (too warm surface temperatures, decreasing oxygen concentration in the sub-surface and less food). This increased mortality and the displacement of surviving fish to the eastern region led to stable then declining adult biomass at the end of the century.

Committed warming inferred from observations and an energy balance model

NASA Astrophysics Data System (ADS)

Pincus, R.; Mauritsen, T.

2017-12-01

Due to the lifetime of CO2 and thermal inertia of the ocean, the Earth's climate is not equilibrated with anthropogenic forcing. As a result, even if fossil fuel emissions were to suddenly cease, some level of committed warming is expected due to past emissions. Here, we provide an observational-based quantification of this committed warming using the instrument record of global-mean warming, recently-improved estimates of Earth's energy imbalance, and estimates of radiative forcing from the fifth IPCC assessment report. Compared to pre-industrial levels, we find a committed warming of 1.5K [0.9-3.6, 5-95 percentile] at equilibrium, and of 1.3K [0.9-2.3] within this century. However, when assuming that ocean carbon uptake cancels remnant greenhouse gas-induced warming on centennial timescales, committed warming is reduced to 1.1K [0.7-1.8]. Conservatively, there is a 32% risk that committed warming already exceeds the 1.5K target set in Paris, and that this will likely be crossed prior to 2053. Regular updates of these observationally-constrained committed warming estimates, though simplistic, can provide transparent guidance as uncertainty regarding transient climate sensitivity inevitably narrows and understanding the limitations of the framework is advanced.