Archive for ocean-atmosphere

Antarctic Ocean CO2 helped end the ice age

Posted by mmaheigan 
· Tuesday, April 2nd, 2019 

Many scientists have long hypothesized that the ocean around Antarctica was responsible for changing CO2 levels during ice ages, but lacked definitive evidence. A new study in Nature provides the most direct evidence of this process to date and provides crucial evidence of the mechanisms—including changing sea ice cover and bipolar seesaw (warming in the Southern Hemisphere during cooling in the Northern Hemisphere) events—that controlled CO2 and climate during the ice ages.

Using samples of fossil deep-sea corals collected from 1000 m in the Drake Passage (Figure 1a), the authors were able to reconstruct the CO2 content of the deep ocean. They found that the deep ocean CO2 record was the “mirror image” of CO2 in the atmosphere (Figure 1b), with the ocean storing CO2 during an ice age and releasing it back to the atmosphere during deglaciation. CO2 rise during the last ice age occurred in a series of steps and jumps associated with intervals of rapid climate change.

a
a
b
b

As well as helping scientists better understand the ice ages, the new findings also provide context to current CO2 rise and climate change. Although the CO2 rise that helped end the last ice age was dramatic in geological terms, CO2 rise due to human activity over the last 100 years is even larger and about 100 times faster. CO2 rise at the end of the ice age helped drive major melting of ice sheets resulting in sea level rise of >100 meters. These results bolster the idea that if we want to prevent dangerous levels of global warming and sea level rise in the future, we need to reduce CO2 emissions as quickly as possible

Authors:
J. W. B. Rae (University of St Andrews, UK)
A. Burke (University of St Andrews, UK)
L. F. Robinson (University of Bristol, UK)
J. F. Adkins (California Institute of Technology)
T. Chen (University of Bristol, UK, Nanjing University, China)
C. Cole (University of St Andrews, UK)
R. Greenop (University of St Andrews, UK)
T. Li (University of Bristol, UK, Nanjing University, China)
E. F. M. Littley (University of St Andrews, UK)
D. C. Nita (University of St Andrews, UK, Babes-Bolyai University, Romania)
J. A. Stewart (University of St Andrews, UK, University of Bristol, UK)
B. J. Taylor (University of St Andrews, UK)

Constraints on glacial overturning circulation and export production lead to answers about the carbon cycle

Posted by mmaheigan 
· Friday, January 4th, 2019 

One of the biggest unsolved mysteries in climate science concerns the dynamics and feedbacks of the ice age carbon dioxide (CO2) cycle.

At the height of the Pleistocene ice ages, the atmospheric CO2 concentration was about 1/3 lower than during the warm interglacial periods. Most scientists think that the CO2 that was missing from the atmosphere was in the deep ocean, but how and why remains unclear. In a study published in Earth and Planetary Science Letters, we compared different computer simulations of the ice age ocean with δ13C, radiocarbon (14C), and δ15N data from sea floor sediments.

We find that a weak and shallow Atlantic Meridional Overturning Circulation (6-9 Sv, or approximately half of today’s overturning rate) best reproduces the glacial sediment isotope data. Increasing the atmospheric soluble iron flux in the model’s Southern Ocean intensifies export production, carbon storage, and further improves agreement with glacial δ13C and δ15N reconstructions.

Figure Caption: Depth profiles of global mean δ13C, calculated using only grid boxes for which there exists Last Glacial Maximum data. Blue: Weak Atlantic circulation; Red: Strong Atlantic circulation; Green: Collapsed Atlantic circulation; Dashed: Extra iron in the Southern Ocean; Orange: Last Glacial Maximum Data.

Our best-fitting simulation (blue, dashed line in the figure) is a significant improvement over previous studies and suggests that both circulation and export production changes were necessary to maximize carbon storage in the glacial ocean. These findings provide an equilibrium glacial state, consistent with a combination of proxies, that can be used as a basis for simulations covering the last deglaciation time period. Understanding the different states that the global climate system can transit, and the characteristics of the transitions, is crucial to project possible outcomes of current climate change processes.

 

Authors:
Juan Muglia (Oregon State University)
Luke C. Skinner (Godwin Laboratory for Palaeoclimate Research, University of Cambridge)
Andreas Schmittner (Oregon State University)

Filter by Keyword

abundance acidification africa air-sea interactions alkalinity allometry ammonium AMOC anoxia anoxic Antarctic anthropogenic carbon aragonite saturation arctic arsenic Atlantic Atlantic modeling atmospheric CO2 atmospheric nitrogen deposition authigenic carbonates autonomous platforms bacteria BATS benthic bgc argo bio-optical bioavailability biogeochemical cycles biogeochemical models biogeochemistry biological pump biological uptake biophysics bloom blooms blue carbon bottom water boundary layer buffer capacity C14 CaCO3 calcification calcite carbon-climate feedback carbon-sulfur coupling carbon cycle carbon dioxide carbon sequestration Caribbean CCA CCS changing marine ecosystems changing ocean chemistry chemoautotroph chesapeake bay chl a chlorophyll circulation climate change CO2 coastal darkening coastal ocean cobalt Coccolithophores community composition conservation cooling effect copepod coral reefs currents cyclone DCM decomposers decomposition deep convection deep ocean deep sea coral deoxygenation depth diagenesis diatoms DIC diel migration dimethylsulfide dinoflagellate dissolved inorganic carbon dissolved organic carbon DOC DOM domoic acid dust DVM earth system models ecosystem state eddy Education Ekman transport emissions ENSO enzyme equatorial regions error ESM estuarine and coastal carbon fluxes estuary euphotic zone eutrophication evolution export EXPORTS extreme events extreme weather events faecal pellets filter feeders filtration rates fire fish Fish carbon fisheries floats fluid dynamics fluorescence food webs forams freshening freshwater frontal zone functional role future oceans geochemistry geoengineering GEOTRACES glaciers gliders global carbon budget global warming go-ship grazing greenhouse gas Greenland groundwater Gulf of Maine Gulf of Mexico Gulf Stream gyre harmful algal bloom high latitude human food human impact hurricane hydrothermal hypoxia ice age ice cores ice cover industrial onset inverse circulation iron iron fertilization isotopes jellies katabatic winds kelvin waves krill kuroshio land-ocean continuum larvaceans lateral transport LGM lidar ligands light light attenuation mangroves marine heatwave marine snowfall marshes Mediterranean meltwater mesopelagic mesoscale metagenome metals methane microbes microlayer microorganisms microscale microzooplankton midwater mixed layer mixed layers mixotrophy modeling mode water molecular diffusion MPT multi-decade NAAMES NASA NCP net community production new technology nitrate nitrogen nitrogen fixation nitrous oxide north atlantic north pacific nutricline nutrient budget nutrient cycling nutrient limitation nutrients OA ocean-atmosphere ocean acidification ocean carbon uptake and storage ocean color ocean observatories ODZ oligotrophic omics OMZ open ocean optics organic particles overturning circulation oxygen pacific paleoceanography particle flux pCO2 PDO peat pelagic pH phenology phosphorus photosynthesis physical processes physiology phytoplankton plankton POC polar regions pollutants prediction primary productivity Prochlorococcus proteins pteropods pycnocline radioisotopes remineralization remote sensing residence time resource management respiration resuspension rivers rocky shore Rossby waves Ross Sea ROV salinity salt marsh satell satellite scale seafloor seagrass sea ice sea level rise seasonal patterns sea spray seaweed sediments sensors shelf system shells ship-based observations shorelines silicate sinking particles size SOCCOM soil carbon southern ocean south pacific spatial covariations speciation SST subduction submesoscale subpolar subtropical sulfate surface surface ocean Synechococcus teleconnections temperate temperature temporal covariations thermocline thermohaline thorium tidal time-series time of emergence top predators total alkalinity trace elements trace metals trait-based transfer efficiency transient features trophic transfer tropical turbulence twilight zone upper ocean upper water column upwelling US CLIVAR validation velocity gradient ventilation vertical flux vertical migration vertical transport volcano water clarity water quality western boundary currents wetlands winter mixing zooplankton

Copyright © 2021 - OCB Project Office, Woods Hole Oceanographic Institution, 266 Woods Hole Rd, MS #25, Woods Hole, MA 02543 USA Phone: 508-289-2838  •  Fax: 508-457-2193  •  Email: ocb_news@us-ocb.org

link to nsflink to noaalink to WHOI

Funding for the Ocean Carbon & Biogeochemistry Project Office is provided by the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA). The OCB Project Office is housed at the Woods Hole Oceanographic Institution.