New multivariate metrics help better monitor and predict global coral breaching events

Key factors that affect regional coral bleaching have been well studied and documented. These include extreme warm temperatures, the duration of extreme cold temperatures, and temperature bimodality (i.e., the exposure of corals to two distinct temperature regimes). However, some of these factors are more important than others in different regions because there are complex and interactive responses to... Continue Reading →

Enhanced carbon sequestration by the North Atlantic Ocean during the Last Glacial Maximum

According to Redfield stoichiometry, marine organisms incorporate and release PO4 and Dissolved Inorganic Carbon (DIC) in a relatively fixed proportion. Additionally, PO4 in the ocean is not affected by air-sea exchange. Therefore, PO4 and DIC in the ocean can be used to estimate biology-driven versus air-sea flux-driven oceanic DIC redistributions. Applying this method to sediment core data, a new paper... Continue Reading →

Deep Indo-Pacific Oceans are still in the Little Ice Age

The Little Ice Age (LIA) is a period of cold global average surface temperatures from around 1600 to 1850, following the Medieval Warm Period (950 ~ 1250). A new study published in Science suggested that since the ocean adjusts to the surface thermal anomalies with the time scales of 100 ~ 1,000 years, some parts of the... Continue Reading →

Glacial weakening of the AMOC and the associated increase in deep ocean carbon deposit

During the mid-Pleistocene between 1,250 and 700 kyr ago (ka), Earth’s climate oscillated between warmer interglacial periods and cooler glacial periods with reduced and expanded polar ice sheets, respectively. Paleo records indicate that the Atlantic meridional overturning circulation (AMOC)  was relatively weaker during glacial periods likely due to reduced evaporation and increased freshwater input from glaciers to the... Continue Reading →

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 →

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