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Direct link to page: Processes determining the marine alkalinity and carbonate saturation distributions. Biogeosciences11 24DOI: We estimate the Arctic receives approximately twice the riverine alkalinity per unit area as the Atlantic, and 8 times that of the other oceans. We show regional variations in surface carbonate saturation are due to temperature changes driving CO2 fluxes and, to a http://hookupsguide.info/online-hookup/47334733z-dating-47334733l.php extent, freshwater cycling.

Calcium carbonate cycling plays a tertiary role. The relationship of Weddell polynya and open-ocean deep convection to the Southern Hemisphere westerlies.

Radiocarbon Hookup Reservoir Effects And Calibration

This small learn more here of applied wind stress is viewed as a stand-in for the stronger zonal winds that developed in the mid s following a long interval of relatively weak zonal winds between and Following the strengthening of the westerlies in our model, the cyclonic Weddell gyre intensifies, raising relatively warm Weddell Sea Deep Water to the surface.

The raised warm water then melts sea ice or prevents it from forming to produce the Weddell polynya. Within the polynya, large heat loss to the air causes surface water to become cold and sink to the bottom via open-ocean deep convection. Thus, the underlying layers cool down, the warm-water supply to the surface eventually stops, and the polynya can not be maintained anymore.

During Radiocarbon Hookup Reservoir Effects And Calibration year-long model simulation we observe two Weddell polynya events. The second one occurs a few years after the first one disappears; it is much weaker and persists for less time than the first one because the underlying layer is cooler. Based on our model simulations, we hypothesize that the Weddell polynya and open-ocean deep convection were responses to the stronger SH westerlies that followed a prolonged weak phase of the Southern Annular Mode.

Seasonal radiocarbon and oxygen isotopes in a Galapagos coral: Calibration with climate indices. Nutrient conditions in the subpolar North Atlantic during the last glacial period reconstructed from foraminifera-bound nitrogen isotopes. Paleoceanography28DOI: Moreover, nutrient consumption in the North Atlantic surface impacts the atmospheric concentration of carbon dioxide.

This is consistent with stronger light limitation associated with a deeper summer surface mixed layer, perhaps related to the formation of Glacial North Atlantic Intermediate Water previously suggested to have occurred near the core site. This suggests that increased water column stratification during Heinrich events, presumably due to surface freshening, reduced the nutrient supply from below and led to nearly complete nitrate consumption in the summertime mixed layer.

Global calcite cycling constrained by sediment preservation controls. We first drive a comprehensive 1-D model for sediment calcite preservation with globally gridded field observations and satellite-based syntheses. We then reformulate this model into a simpler five-parameter box model, and combine it with algorithms for surface calcite export and water column dissolution for a single expression for the vertical calcite balance. The resulting metamodel is optimized to fit the observed distributions of calcite burial flux.

We quantify the degree to which calcite export, saturation state, organic carbon respiration, and lithogenic sedimentation modulate the burial of calcite.

Predicted values are highly correlated with the quantity of mid-depth water which flows out of the Pacific to the south. Similar displacements were invoked to shift bomb 14 C from the Antarctic circumpolar region into the southern temperate zone. It is unstable and weakly radioactive.

Radiocarbon Hookup Reservoir Effects And Calibration Relative to organic carbon export, we find surface calcite export skewed geographically toward relatively warm, oligotrophic areas dominated by small, prokaryotic phytoplankton. We assess century-scale projected impacts of warming and acidification on calcite export, finding high sensitive to inferred saturation state controls. With respect to long term glacial cycling, our analysis supports the hypothesis that strong glacial abyssal stratification drives the lysocline towards much closer correspondence with the saturation horizon.

North Atlantic ventilation of "southern-sourced" deep water in the glacial ocean. This water is commonly referred to as "southern-sourced", because click to see more its apparent entry into the Atlantic basin from the south, prompting the inference that it was ventilated at the Southern Ocean surface.

Here, we propose that this deep Atlantic water mass actually included a large fraction of North Atlantic-venitlated water, the chemical characteristics of which were altered by recirculation in the deep Southern and Indo-Pacific Oceans.

In an ocean model sensitivity experiment that reduces Antarctic Bottom Water formation and weakens its overturning circulation, we find that a much greater fraction of NADW is transported into the Southern Ocean without contacting the surface and is entrained and mixed into the southern-sourced deep water that spreads into the global abyssal ocean.

Impact of Antarctic Circumpolar Current development on late Paleogene ocean structure. Science, DOI: We show that the modern four-layer ocean structure surface, intermediate, deep, and bottom waters developed during the early Oligocene as a consequence of the ACC.

GFDL - Geophysical Fluid Dynamics Laboratory

The control of atmospheric pCO 2 by ocean ventilation change: Radiocarbon Hookup Reservoir Effects And Calibration effect of the oceanic storage of biogenic carbon. Assuming that the inventory of carbon is conserved in the ocean-atmosphere system i. The large uncertainty ranges in atmospheric pCO2 arise from uncertainty in how surface productivity responds to circulation change.

The Last Glacial Termination. We here offer a comprehensive hypothesis of how Earth emerged from the last global ice age. A prerequisite was the check this out of very large Northern Hemisphere ice sheets, whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation.

The Southern Hemisphere westerlies shifted poleward during each northern stadial, producing pulses of ocean upwelling and warming that together accounted for much of the termination in the Southern Ocean and Antarctica.

Rising atmospheric CO2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres. We also consider elements of observational measures rendering information to help evaluate simulations and to guide development priorities. Temperature differences between the hemispheres and ice age climate variability.

Atmospheric CO2 also rose and fell, but again, the CO2 changes are rather small in relation to the warming and cooling. So, how did the Earth manage to warm and cool by so much? Here we argue that, for the big transitions at least, the Earth did not warm and cool as a single entity.

Rather, the south warmed instead at the expense of a cooler north through massive redistributions of heat that were set off by the orbital forcing. Oceanic CO2 was vented up to the atmosphere by the same redistributions. The north then warmed later in response to higher CO2 and a reduced albedo from smaller ice sheets.

This form of north-south displacement is actually very familiar, as it is readily observed during the Younger Dryas interval 13, years ago and in the various millennial-scale events over the last 90, years.

Ocean overturning since the Late Cretaceous: Inferences from a new benthic foraminiferal isotope compilation. These records are also widely used as a general climate indicator for comparison with local and more specific marine and terrestrial climate proxy records.

It provides more accurate dating within sites than previous methods, which usually derived either from stratigraphy or from typologies e. In this way, an individual random fluctuation becomes one of the big link seen in the Antarctic ice cores. Journal of Geophysical Research91 C1214, Post navigation Previous Post - Previous post:

We propose that these transitions reflect alterations in a first-order characteristic of ocean circulation: The role of wind-driven upwelling, possibly associated with a Tethyan Circumequatorial Current, in controlling Late Cretaceous interior ocean heterogeneity should be the subject of further research. Journal of Climate22 24DOI: One approach taken in previous idealized modeling studies of gateway effects has been to alter modern boundary conditions, whereby the Drake Passage becomes closed.

Here, the authors follow this approach but vary atmospheric pCO 2 over a range of values when comparing gateway configurations. They find a significantly greater sensitivity of Antarctic temperatures to Southern Ocean gateway changes when atmospheric pCO 2 is high than when concentrations are low and the ambient climate is cool.

In particular, the closure of the Drake Passage DP gap is a necessary condition for the existence of ice-free Antarctic conditions at high CO 2 concentrations in this coupled climate model. The absence of the Radiocarbon Hookup Reservoir Effects And Calibration Circumpolar Current ACC is particularly conducive to warm Antarctic conditions at higher CO 2 concentrations, which is markedly different from previous simulations conducted under present-day CO 2 conditions.

Radiocarbon dating organic materials, how radiocarbon gets there

The reason for this is the reduction of sea ice associated with higher CO 2. In other words, the authors find a significantly greater sensitivity of Antarctic temperatures to atmospheric CO 2 concentration when the DP is closed compared to when it is open.

The presence of a DP source inhibits a return to warmer and more Eocene-like Antarctic and deep ocean conditions, even under enhanced atmospheric greenhouse gas concentrations. De Boer, A M. Atlantic dominance of the meridional overturning circulation. Using an idealized geometry ocean general circulation model coupled to an energy moisture balance model, various climatic forcings are tested for their effect on the strength and structure of the overturning circulation.

Without winds or a high vertical diffusivity, the ocean does not support deep convection. A supply of mechanical energy through winds or mixing purposefully included or due to numerical diffusion starts the deep-water formation. Once deep convection and overturning set in, the distribution of convection centers is determined by the relative strength of the thermal and haline buoyancy forcing. In Radiocarbon Hookup Reservoir Effects And Calibration most thermally dominant state i.

The effect of a more vigorous hydrological cycle is to produce stronger salinity gradients, favoring the haline state of NA dominance. In contrast, a higher mean ocean temperature will increase the importance of temperature gradients because the thermal continue reading coefficient is higher in a warm ocean, leading to the thermally dominated state.

An increase in SO winds or global winds tends to weaken the salinity gradients, also pushing the ocean to the thermal state. Paleoobservations of more distributed sinking in warmer climates in the past suggest that mean ocean temperature and winds Radiocarbon Hookup Reservoir Effects And Calibration a more important role than the hydrological cycle in the overturning circulation over long time scales. Impact of oceanic circulation on biological carbon storage in the ocean and atmospheric p CO 2.

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We demonstrate that atmospheric CO 2 can be simply related to the amount of inorganic carbon stored in the ocean by the soft-tissue pump, which we term OCS soft. OCS soft is linearly related to the inventory of remineralized nutrient, which in turn is just the total nutrient inventory minus the preformed nutrient inventory.

In a system where total nutrient is conserved, atmospheric CO 2 can thus be simply related to the global inventory of preformed nutrient.

Radiocarbon Hookup Reservoir Effects And Calibration

Previous model simulations have explored how changes in the surface concentration of nutrients in deepwater formation regions change the global preformed nutrient inventory. We show that changes in physical forcing such as winds, vertical mixing, and lateral mixing can shift the balance of deepwater formation between the North Atlantic where preformed nutrients are low and the Southern Ocean where they are high.

Such changes in physical forcing can thus drive large changes in atmospheric CO 2even with minimal changes in surface nutrient learn more here. If Southern Ocean deepwater formation strengthens, the preformed nutrient inventory and thus atmospheric CO 2 increase.

An important consequence of these new insights is that the relationship between Radiocarbon Hookup Reservoir Effects And Calibration nutrient concentrations, biological export production, and atmospheric CO 2 is more complex than previously predicted.

Contrary to conventional wisdom, we show that OCS soft can increase and atmospheric CO 2 decrease, while surface nutrients show minimal change and export production decreases. Ocean circulation in a warming climate. Nature, DOI: Origin of the ,year timescale in Antarctic temperatures and atmospheric CO 2. It starts with fluctuations in the oceanic overturning around Antarctica that release CO 2 up to the atmosphere or trap it in the deep ocean.

Every 50, years one of these fluctuations coincides with a changeover in the burial of Radiocarbon Hookup Reservoir Effects And Calibration 3 in link deep ocean.

The changeover alters the atmospheric p CO 2 in a way that augments the tendency of the overturning.

The augmented overturning then enhances the tendency of the CaCO 3 burial, which augments the overturning, etc. In this way, an individual random fluctuation becomes one of the big transitions seen in the Antarctic ice cores. Alternating transitions toward the warm and cold states every 50, years produce the ,year timescale.