You Are In The Old Site Archive - Click Here To See The Main Site With Current Stories

Southern Ocean Carbon Dioxide Mystery Solved

04.02.2016 12:56 Age: 1 year

Why did concentrations of atmospheric greenhouse gases drop to a level that allowed the Earth to slip into a period of glaciation some 20,000 years ago? Sediment samples from the seafloor suggest more carbon dioxide was dissolved in the deep Southern Ocean at times when levels in the atmosphere were low

Click to enlarge. From the paper. Researchers have found that bottom waters of the Southern Ocean had very low levels of oxygen during the last ice age, indicating high uptake of carbon dioxide. Here, dissolved Southern Ocean bottom-water oxygen in modern times. Brighter colors indicate more oxygen; dots show sites where researchers sampled sediments to measure past oxygen levels. Courtesy: authors and Nature


by Kevin Krajick, Columbia University22


No single mechanism can account for the full amplitude of past atmospheric carbon dioxide (CO22 concentration before the Last Glacial Maximum, have remained unclear. Here we present sedimentary redox-sensitive trace-metal records from the Antarctic Zone of the Southern Ocean that provide a reconstruction of transient changes in deep ocean oxygenation and, by inference, respired carbon storage throughout the last glacial cycle. Our data suggest that respired carbon was removed from the abyssal Southern Ocean during the Northern Hemisphere cold phases of the deglaciation, when atmospheric CO22 concentration and abyssal Southern Ocean oxygenation was maintained throughout most of the past 80,000 years. This suggests that on millennial timescales deep ocean circulation and iron fertilization in the Southern Ocean played a consistent role in modifying atmospheric CO2 concentration.




Columbia University news release here.