Ocean storage of anthropogenic CO2 from 1994 to 2007

A paper published in Science estimated the oceanic sink of the anthropogenic CO2 (Cant) over the period of 1994 to 2007 by comparing observations collected from global repeated hydrography cruises between 2003 and 2007 to those from the World Ocean Circulation Experiment (WOCE) and Joint Global Ocean Flux Study (JGOFS) program during the 1980s and early 1990s. The... Continue Reading →

Emergence of a shallow aragonite-undersaturated layer in the Southern Ocean

As the ocean absorbs anthropogenic CO2, its pH and carbonate ion concentration  decrease, thereby decreasing the ratio of the concentration of dissolved carbonate ions in the sea water to the concentration of dissolved ions in a saturated solution of aragonite (i.e., aragonite saturation state ΩAr). If ΩAr falls below the threshold ΩAr=1, ocean acidification makes it harder... Continue Reading →

Tropical ocean warming provides optimal growth condition for iron-limited cyanobacterium

Although the cyanobacterium (Trichodesmium) fixes as much as half of the nitrogen (N2) that supports tropical open-ocean ecosystem, its growth is limited by iron (Fe) availability. A study published in Nature Climate Change performed laboratory experiments to show that the optimum growth temperature of Fe-limited Trichodesmium is about 32°C, which is much higher than for Fe-replete cells (about... Continue Reading →

Ocean acidification may induce toxic algal bloom and disrupt the pelagic food web

A field experiment led by a team of scientists from GEOMAR Helmholtz Centre for Ocean Research Kiel and others (Riebesell et al., 2018) showed that the toxic microalga Vicicitus globosus, known for its wide geographical distribution and confirmed role in fish kills, has an advantage under ocean acidification, increasing its abundance in natural plankton communities at CO2 levels higher... Continue Reading →

Ocean carbon sink is dictated by natural variability on decadal time scales

Data-based estimates show that the global oceanic carbon flux has increased rapidly since around 2000 with little decadal variability during 1992-1999 (Rödenbeck et al., 2015). An article published in Geophysical Research Letters (Li and Ilyina, 2017) used large ensemble climate model simulations to show that the observed increase is much faster than simulated by their biogeochemical process model. By... Continue Reading →

Deglacial atmospheric CO2 increase caused by enhanced abyssal circulations in the Pacific Ocean

Paleo records indicate that during the last deglaciation period (19,000–9,000 years ago) atmospheric CO2 level increased by about 80 ppm. A new study published in Nature Geoscience analysed neodymium (Nd) isotope data in North Pacific sediment cores to find an increase in 14C age of North Pacific subsurface waters sourced from Antarctica indicating an enhanced abyssal overturning... Continue Reading →

Ship-based observations significantly underestimate carbon dioxide outgassing in the high-latitude Southern Ocean

It is widely believed that the Southern Ocean accounts for a significant portion of the oceanic uptake of anthropogenic carbon dioxide (CO2). However, flux estimates in this region are based on sparse ship-based observations that are strongly biased towards summer. A new study published in Geophysical Research Letters presented new estimates of Southern Ocean air‐sea CO2 fluxes based... Continue Reading →

Southern Hemisphere westerly winds and possible links to CO2 outgassing

Some model studies suggested that the current strengthening and poleward shift of the Southern Hemisphere (SH) westerly winds brought carbon-rich Circumpolar Deep Water (CDW) to the surface and reduced ΔpCO2, weakening the anthropocentric carbon sink (e.g., Mikaloff-Fletcher, 2015). A new study, which appeared in Nature Geoscience,  presented a 12,300-year reconstruction of SH westerly winds based on three... Continue Reading →

A coastal coccolithophore species (O. neapolitana) maintains pH homeostasis and switches carbon sources in response to ocean acidification

According to a new article published in Nature Communications, a coastal coccolithophore species (Ochrosphaera neapolitana), which has a unique mechanism for producing coccoliths, can maintains constant pH at the calcification site, regardless of CO2-induced changes in pH of the surrounding seawater. The authors of this study cultured a coccolithophore species (Ochrosphaera neapolitana), the most prolific ocean calcifiers in the ocean, under three pCO2-controlled... Continue Reading →

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