scholarly journals On the Abyssal Circulation in the Glacial Atlantic

2008 ◽  
Vol 38 (9) ◽  
pp. 2014-2037 ◽  
Author(s):  
Olivier Marchal ◽  
William B. Curry
Keyword(s):  
Ocean Circulation ◽  
Benthic Foraminifera ◽  
Dissolved Inorganic Carbon ◽  
World Ocean ◽  
Volume Transport ◽  
Time Interval ◽  
Organic C ◽  
Power Of The Test ◽  
Abyssal Circulation ◽  
Sediment Data

Abstract An inverse method is used to evaluate the information contained in sediment data for the Atlantic basin during the Last Glacial Maximum (defined here as the time interval 18–21 kyr before present). The data being considered are an updated compilation of the isotopic ratios 18O/16O (δ18O) and 13C/12C (δ13C) of fossil shells of benthic foraminifera (bottom-dwelling organisms). First, an estimate of the abyssal circulation in the modern Atlantic is obtained, which is consistent with (i) climatologies of temperature and salinity of the World Ocean Circulation Experiment, (ii) observational estimates of volume transport at specific locations, and (iii) the statements of a finite-difference geostrophic model. Second, estimates of water properties (δ18O of equilibrium calcite or δ18Oc and δ13C of dissolved inorganic carbon or δ13CDIC) derived from sediment data are combined with this circulation estimate to test their consistency with the modern flow. It is found that more than approximately 80% of water property estimates (δ18Oc or δ13CDIC) are compatible with the modern flow given their uncertainties. The consistency of glacial δ13CDIC estimates with the modern flow could be rejected after two assumptions are made: (i) the uncertainty in these estimates is ±0.1‰ (this uncertainty includes errors in sediment core chronology and oceanic representativity of benthic δ13C, which alone appears better than this value on average); and (ii) δ13CDIC in the glacial deep Atlantic was dominated by a balance between water advection and organic C remineralization. Measurements of δ13C on benthic foraminifera are clearly useful, but the current uncertainties in the distribution and budget of δ13CDIC in the glacial Atlantic must be reduced to increase the power of the test.

scholarly journals Two decades of inorganic carbon dynamics along the West Antarctic Peninsula

2015 ◽  
Vol 12 (22) ◽  
pp. 6761-6779 ◽  
Author(s):  
C. Hauri ◽  
S. C. Doney ◽  
T. Takahashi ◽  
M. Erickson ◽  
G. Jiang ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Ocean Circulation ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
World Ocean ◽  
Nutrient Utilization ◽  
Total Alkalinity ◽  
Data Set ◽  
Molar Ratios ◽  
Wide Range

Abstract. We present 20 years of seawater inorganic carbon measurements collected along the western shelf and slope of the Antarctic Peninsula. Water column observations from summertime cruises and seasonal surface underway pCO2 measurements provide unique insights into the spatial, seasonal, and interannual variability in this dynamic system. Discrete measurements from depths > 2000 m align well with World Ocean Circulation Experiment observations across the time series and underline the consistency of the data set. Surface total alkalinity and dissolved inorganic carbon data showed large spatial gradients, with a concomitant wide range of Ωarag (< 1 up to 3.9). This spatial variability was mainly driven by increasing influence of biological productivity towards the southern end of the sampling grid and meltwater input along the coast towards the northern end. Large inorganic carbon drawdown through biological production in summer caused high near-shore Ωarag despite glacial and sea-ice meltwater input. In support of previous studies, we observed Redfield behavior of regional C / N nutrient utilization, while the C / P (80.5 ± 2.5) and N / P (11.7 ± 0.3) molar ratios were significantly lower than the Redfield elemental stoichiometric values. Seasonal salinity-based predictions of Ωarag suggest that surface waters remained mostly supersaturated with regard to aragonite throughout the study. However, more than 20 % of the predictions for winters and springs between 1999 and 2013 resulted in Ωarag < 1.2. Such low levels of Ωarag may have implications for important organisms such as pteropods. Even though we did not detect any statistically significant long-term trends, the combination of on\\-going ocean acidification and freshwater input may soon induce more unfavorable conditions than the ecosystem experiences today.

scholarly journals Assessment of the representation of Antarctic Bottom Water properties in the ECCO2 reanalysis

Ocean Science ◽  
2014 ◽  
Vol 10 (6) ◽  
pp. 923-946 ◽  
Author(s):  
M. Azaneu ◽  
R. Kerr ◽  
M. M. Mata
Keyword(s):  
Southern Ocean ◽  
Ocean Circulation ◽  
Bottom Water ◽  
Potential Temperature ◽  
World Ocean ◽  
Volume Transport ◽  
Weddell Sea ◽  
Antarctic Bottom Water ◽  
Water Properties ◽  
The Absolute

Abstract. We analyzed the ability of the Estimating the Circulation and Climate of the Ocean – Phase II (ECCO2) reanalysis to represent the hydrographic properties and variability of Antarctic Bottom Water (AABW) in the Southern Ocean. We used a 20-year (1992–2011) observational database to perform comparisons of hydrographic properties and reanalysis output for the same time period. Four case studies based on current meter data and the AABW volume transport estimates previously reported in the literature were also evaluated. The opening and maintenance of an oceanic polynya in the Weddell Sea sector is observed after 2004 in the reanalysis product. Moreover, intense deep water production due to deep convection occurs, which leads to a scenario in which the Weddell Sea is flooded with AABW. For this reason, our analyses focused on the period that was identified as more reliable (1992–2004). The main Southern Ocean oceanographic features, as well as the characteristic shape of the regional potential temperature–salinity (θ–S) diagrams, are coincident with observations. However, the reanalysis output produces surface waters that are generally denser than observations due to the reproduction of waters that are generally saltier than expected, which probably resulted from the strong seasonality of sea ice concentrations. Bottom waters are warmer and less dense, while intermediate waters are statistically closest to the observations. The differences in bottom water properties are partially due to the inability of the reanalysis to properly reproduce the formation and export of dense waters from the shelf and the consequent absence of the densest AABW variety for most of the analyzed period. Despite differences in the absolute values, the upper AABW limit (γn ≥ 28.27 kg m−3) and AABW occupied area estimates are coincident with the observations in the World Ocean Circulation Experiment (WOCE) repeat sections SR2 and SR4. Moreover, the AABW volume export and current velocity variability are correlated with the observed time series in the most important region of dense water export (i.e., the Weddell Sea). Despite the consistency in terms of variability, the absolute volume transport and velocity estimates are underrepresented in all cases.

scholarly journals Decadal Changes in Bomb-Produced Radiocarbon in the Pacific Ocean from the 1990s to 2000s

Radiocarbon ◽  
2013 ◽  
Vol 55 (3) ◽  
pp. 1641-1650 ◽  
Author(s):  
Yuichiro Kumamoto ◽  
Akihiko Murata ◽  
Takeshi Kawano ◽  
Shuichi Watanabe ◽  
Masao Fukasawa
Keyword(s):  
Pacific Ocean ◽  
Ocean Circulation ◽  
Dissolved Inorganic Carbon ◽  
World Ocean ◽  
Temporal Changes ◽  
Turnover Time ◽  
Subtropical Region ◽  
The North ◽  
The Pacific ◽  
The Pacific Ocean

In the 2000s, radiocarbon in dissolved inorganic carbon was measured during 7 revisit cruises along the lines of the World Ocean Circulation Experiment in the Pacific Ocean. Comparison of 14C data along these lines from the 1990s and 2000s revealed decadal changes of 14C concentration in the thermocline, most of which were due to temporal changes in the bomb-produced 14C. Vertical profiles and vertical-integrated inventories of the bomb 14C in the subarctic and equatorial regions did not change appreciably. In the southern subtropical region, 14C decreased in the upper thermocline from the surface to ∼500 m depth. In contrast, 14C increased in the lower thermocline below ∼500 m depth. The opposing directions in 14C change resulted in small temporal changes in the total inventory of bomb 14C. On the other hand, the water-column inventory significantly decreased in the northwestern subtropical region due to the 14C decrease in the upper thermocline. These decadal changes in bomb 14C indicate that the turnover time of thermocline circulation in the northwestern subtropical region is faster than that in the southern subtropical region, and imply an interbasin transport of bomb 14C from the North Pacific to other basins.

scholarly journals Two decades of inorganic carbon dynamics along the Western Antarctic Peninsula

2015 ◽  
Vol 12 (9) ◽  
pp. 6929-6969 ◽  
Author(s):  
C. Hauri ◽  
S. C. Doney ◽  
T. Takahashi ◽  
M. Erickson ◽  
G. Jiang ◽  
...  
Keyword(s):  
Ocean Acidification ◽  
Interannual Variability ◽  
Antarctic Peninsula ◽  
Ocean Circulation ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
World Ocean ◽  
Data Set ◽  
Wide Range ◽  
Melt Water

Abstract. We present 20 years of seawater inorganic carbon measurements collected along the western shelf and slope of the Antarctic Peninsula. Water column observations from summertime cruises and seasonal surface underway pCO2 measurements provide unique insights into the spatial, seasonal and interannual variability of the dynamic system. The discrete measurements from depths > 2000 m align well with World Ocean Circulation Experiment observations across the time-series and underline the consistency of the data set. Analysis shows large spatial gradients in surface alkalinity and dissolved inorganic carbon content, with a concomitant wide range of Ωarag from values < 1 up to 3.9. This spatial variability was mainly driven by increasing influence of biological productivity towards the southern end of the sampling grid and melt water input along the coast towards the northern end. Large inorganic carbon drawdown through biological production in summer caused high near-shore Ωarag despite glacial and sea-ice melt water input. In support of previous studies, we observed Redfield behavior of regional C / N nutrient utilization, while the C / P (80.5 ± 2.5) and N / P (11.7 ± 0.3) molar ratios were significantly lower than the Redfield elemental stoichiometric values. Seasonal predictions of Ωarag suggest that surface waters remained mostly supersaturated with regard to aragonite throughout the study. However, more than a third of the predictions for winters between 1999 and 2013 resulted in Ωarag < 1.3. Such low levels of Ωarag may have implications for important organisms such as pteropods. Despite large interannual variability, surface pCO2 measurements indicate a statistically significant increasing trend of up to 23 μatm per decade in fall and spring and a concomitant decreasing pH, pointing towards first signs of ocean acidification in the region. The combination of ongoing ocean acidification and freshwater input may soon provoke more unfavorable conditions than what the ecosystem experiences today.

ON EVALUATION OF THE ROLE OF THERMAL AND WIND FACTORS FOR A PHYSICAL MODEL OF THE WORLD OCEAN GENERAL CIRCULATION SYSTEM

2019 ◽  
Vol 47 (3) ◽  
pp. 80-91
Author(s):  
V. G. Neiman
Keyword(s):  
Physical Model ◽  
Ocean Circulation ◽  
General Circulation ◽  
World Ocean ◽  
Circulation System ◽  
The Public ◽  
The World ◽  
Almost All ◽  
Conceptual Foundations

The main content of the work consists of certain systematization and addition of longexisting, but eventually deformed and partly lost qualitative ideas about the role of thermal and wind factors that determine the physical mechanism of the World Ocean’s General Circulation System (OGCS). It is noted that the conceptual foundations of the theory of the OGCS in one form or another are contained in the works of many well-known hydrophysicists of the last century, but the aggregate, logically coherent description of the key factors determining the physical model of the OGCS in the public literature is not so easy to find. An attempt is made to clarify and concretize some general ideas about the two key blocks that form the basis of an adequate physical model of the system of oceanic water masses motion in a climatic scale. Attention is drawn to the fact that when analyzing the OGCS it is necessary to take into account not only immediate but also indirect effects of thermal and wind factors on the ocean surface. In conclusion, it is noted that, in the end, by the uneven flow of heat to the surface of the ocean can be explained the nature of both external and almost all internal factors, in one way or another contributing to the excitation of the general, or climatic, ocean circulation.

scholarly journals Tropical cyclones cumulatively control regional carbon fluxes in Everglades mangrove wetlands (Florida, USA)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Xiaochen Zhao ◽  
Victor H. Rivera-Monroy ◽  
Luis M. Farfán ◽  
Henry Briceño ◽  
Edward Castañeda-Moya ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Functional Role ◽  
Net Primary Productivity ◽  
Dissolved Inorganic Carbon ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Neotropical Region ◽  
Limited Information ◽  
Organic C ◽  
Wide Range

AbstractMangroves are the most blue-carbon rich coastal wetlands contributing to the reduction of atmospheric CO2 through photosynthesis (sequestration) and high soil organic carbon (C) storage. Globally, mangroves are increasingly impacted by human and natural disturbances under climate warming, including pervasive pulsing tropical cyclones. However, there is limited information assessing cyclone’s functional role in regulating wetlands carbon cycling from annual to decadal scales. Here we show how cyclones with a wide range of integrated kinetic energy (IKE) impact C fluxes in the Everglades, a neotropical region with high cyclone landing frequency. Using long-term mangrove Net Primary Productivity (Litterfall, NPPL) data (2001–2018), we estimated cyclone-induced litterfall particulate organic C (litter-POC) export from mangroves to estuarine waters. Our analysis revealed that this lateral litter-POC flux (71–205 g C m−2 year−1)—currently unaccounted in global C budgets—is similar to C burial rates (69–157 g C m−2 year−1) and dissolved inorganic carbon (DIC, 61–229 g C m−2 year−1) export. We proposed a statistical model (PULITER) between IKE-based pulse index and NPPL to determine cyclone’s impact on mangrove role as C sink or source. Including the cyclone’s functional role in regulating mangrove C fluxes is critical to developing local and regional climate change mitigation plans.

scholarly journals A Time History of Pre- and Post-Bomb Radiocarbon in the Barents Sea Derived from Arcto-Norwegian Cod Otoliths

Radiocarbon ◽  
2001 ◽  
Vol 43 (2B) ◽  
pp. 843-855 ◽  
Author(s):  
John M Kalish ◽  
Reidar Nydal ◽  
Kjell H Nedreaas ◽  
George S Burr ◽  
Gro L Eine
Keyword(s):  
Time Series ◽  
Ocean Circulation ◽  
General Circulation ◽  
Barents Sea ◽  
Dissolved Inorganic Carbon ◽  
Time History ◽  
General Circulation Models ◽  
Fine Tuning ◽  
Birth Date ◽  
The Barents Sea

Radiocarbon measured in seawater dissolved inorganic carbon (DIC) can be used to investigate ocean circulation, atmosphere/ocean carbon flux, and provide powerful constraints for the fine-tuning of general circulation models (GCMs). Time series of 14C in seawater are derived most frequently from annual bands of hermatypic corals. However, this proxy is unavailable in temperate and polar oceans. Fish otoliths, calcium carbonate auditory, and gravity receptors in the membranous labyrinths of teleost fishes, can act as proxies for 14C in most oceans and at most depths. Arcto-Norwegian cod otoliths are suited to this application due to the well-defined distribution of this species in the Barents Sea, the ability to determine ages of individual Arcto-Norwegian cod with a high level of accuracy, and the availability of archived otoliths collected for fisheries research over the past 60 years. Using measurements of 14C derived from Arcto-Norwegian cod otoliths, we present the first pre- and post-bomb time series (1919–1992) of 14C from polar seas and consider the significance of these data in relation to ocean circulation and atmosphere/ocean flux of 14C. The data provide evidence for a minor Suess effect of only 0.2‰ per year between 1919 and 1950. Bomb 14C was evident in the Barents Sea as early as 1957 and the highest 14C value was measured in an otolith core from a cod with a birth date of 1967. The otolith 14C data display key features common to records of 14C obtained from a Georges Bank mollusc and corals from the tropical and subtropical North Atlantic.

scholarly journals An Eddy-Permitting Southern Ocean State Estimate

2010 ◽  
Vol 40 (5) ◽  
pp. 880-899 ◽  
Author(s):  
Matthew R. Mazloff ◽  
Patrick Heimbach ◽  
Carl Wunsch
Keyword(s):  
Southern Ocean ◽  
General Circulation Model ◽  
General Circulation ◽  
Microwave Radiometer ◽  
World Ocean ◽  
Circulation Model ◽  
Great Majority ◽  
Drake Passage ◽  
Volume Transport ◽  
Intermediate Cell

Abstract An eddy-permitting general circulation model of the Southern Ocean is fit by constrained least squares to a large observational dataset during 2005–06. Data used include Argo float profiles, CTD synoptic sections, Southern Elephant Seals as Oceanographic Samplers (SEaOS) instrument-mounted seal profiles, XBTs, altimetric observations [Envisat, Geosat, Jason-1, and Ocean Topography Experiment (TOPEX)/Poseidon], and infrared and microwave radiometer observed sea surface temperature. An adjoint model is used to determine descent directions in minimizing a misfit function, each of whose elements has been weighted by an estimate of the observational plus model error. The model is brought into near agreement with the data by adjusting its control vector, here consisting of initial and meteorological boundary conditions. Although total consistency has not yet been achieved, the existing solution is in good agreement with the great majority of the 2005 and 2006 Southern Ocean observations and better represents these data than does the World Ocean Atlas 2001 (WOA01) climatological product. The estimate captures the oceanic temporal variability and in this respect represents a major improvement upon earlier static inverse estimates. During the estimation period, the Drake Passage volume transport is 153 ± 5 Sv (1 Sv ≡ 106 m3 s−1). The Ross and Weddell polar gyre transports are 20 ± 5 Sv and 40 ± 8 Sv, respectively. Across 32°S there is a surface meridional overturning cell of 12 ± 12 Sv, an intermediate cell of 17 ± 12 Sv, and an abyssal cell of 13 ± 6 Sv. The northward heat and freshwater anomaly transports across 30°S are −0.3 PW and 0.7 Sv, with estimated uncertainties of 0.5 PW and 0.2 Sv. The net rate of wind work is 2.1 ± 1.1 TW. Southern Ocean theories involving short temporal- and spatial-scale dynamics may now be tested with a dynamically and thermodynamically realistic general circulation model solution that is known to be compatible with the modern observational datasets.

scholarly journals Linking the lithogenic, atmospheric, and biogenic cycles of silicate, carbonate, and organic carbon in the ocean

2009 ◽  
Vol 6 (4) ◽  
pp. 6579-6599
Author(s):  
S. V. Smith ◽  
J.-P. Gattuso
Keyword(s):  
Carbon Storage ◽  
Chemical Weathering ◽  
Dissolved Inorganic Carbon ◽  
North Pacific Ocean ◽  
Atmospheric Co2 ◽  
Molar Ratio ◽  
Co2 Uptake ◽  
Organic C ◽  
Co2 Gas ◽  
The Relationship

Abstract. Geochemical theory describes long term cycling of atmospheric CO2 between the atmosphere and rocks at the Earth surface in terms of rock weathering and precipitation of sedimentary minerals. Chemical weathering of silicate rocks takes up atmospheric CO2, releases cations and HCO3− to water, and precipitates SiO2, while CaCO3 precipitation consumes Ca2+ and HCO3− and releases one mole of CO2 to the atmosphere for each mole of CaCO3 precipitated. At steady state, according to this theory, the CO2 uptake and release should equal one another. In contradiction to this theory, carbonate precipitation in the present surface ocean releases only about 0.6 mol of CO2 per mole of carbonate precipitated. This is a result of the buffer effect described by Ψ, the molar ratio of net CO2 gas evasion to net CaCO3 precipitation from seawater in pCO2 equilibrium with the atmosphere. This asymmetry in CO2 flux between weathering and precipitation would quickly exhaust atmospheric CO2, posing a conundrum in the classical weathering and precipitation cycle. While often treated as a constant, Ψ actually varies as a function of salinity, pCO2, and temperature. Introduction of organic C reactions into the weathering-precipitation couplet largely reconciles the relationship. ψ in the North Pacific Ocean central gyre rises from 0.6 to 0.9, as a consequence of organic matter oxidation in the water column. ψ records the combined effect of CaCO3 and organic reactions and storage of dissolved inorganic carbon in the ocean, as well as CO2 gas exchange between the ocean and atmosphere. Further, in the absence of CaCO3 reactions, Ψ would rise to 1.0. Similarly, increasing atmospheric pCO2 over time, which leads to ocean acidification, alters the relationship between organic and inorganic C reactions and carbon storage in the ocean. Thus, the carbon reactions and ψ can cause large variations in oceanic carbon storage with little exchange with the atmosphere.

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