Ice ages in the North Pacific Ocean and the Southern Ocean were marked by low productivity. Accumulating evidence indicates that strong stratification restricted the supply of nutrients from the deep ocean to the algae of the sunlit surface in these regions.
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Haug, G., Sigman, D. Polar twins. Nature Geosci 2, 91–92 (2009). https://doi.org/10.1038/ngeo423
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DOI: https://doi.org/10.1038/ngeo423
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