Cold versus warm water routes for the upper limb of the South Atlantic MOC

The surface water in the South Atlantic (σ2 < 35.7) is known to originate largely from the Indian Ocean via the Agulhas leakage (e.g., Beal et al., 2011; Gordon, 1986). It is carried northward below the surface mixed layer and brought to the surface via the equatorial Atlantic upwelling. Antarctic Intermediate Water (AAIW) that forms... 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 →

Why does the upper atmosphere cool with increasing carbon dioxide?

According to model simulations with increasing carbon dioxide in the atmosphere, the zonal mean temperature in the atmosphere get warmer in the troposphere (< 10km or > 100hPa) and colder in the stratosphere (10 ~ 50km or 100 ~ 1hPa). A simple explanation is that the amount of infrared heat radiated out to the space... Continue Reading →

Ocean-ice momentum flux reversal and the associated stabilization of the Beaufort Gyre and freshwater accumulation

Driven by the Beaufort High and associated wind-stress curl, the anticyclonic ocean gyre over the Canada Basin, as known as the Beaufort Gyre, is a dominant feature of the Arctic Ocean circulation. The Beaufort Gyre is the largest freshwater reservoir in the Arctic Ocean  (Proshutinsky et al., 2009) and also is a region of the largest summer sea... Continue Reading →

Global meridional overturning circulation revisited

Ocean tracers such as heat, salt and carbon are perpetually carried by the global meridional overturning circulation (GMOC) and redistributed between hemispheres and across ocean basins from their source regions. The GMOC is therefore a crucial component of the global heat, salt and carbon balances. In a new article accepted in Geophysical Research Letter, a... Continue Reading →

Natural variability in the Southern Ocean as a driver of the observed Antarctic sea-ice expansion trends

A team of scientists from Princeton University, NOAA-GFDL, and UCAR performed global climate model simulations, using a newly developed coupled ocean–atmosphere model SPEAR (Seamless System for Prediction and Earth System Research). When this model was driven with changes in past radiative forcing, the model simulation did not reproduce the observed increasing trends in sea-ice concentration around... Continue Reading →

Antarctic meltwater slows down global warming by more than a decade

A new study published in Nature used climate models to explore the effects of meltwater from the Antarctic ice sheets and ice shelves on global surface temperature under a warming climate. The study found that the increasing meltwater decreases the surface salinity of the Southern Ocean and thus increases the near-surface stratification, which in turn... Continue Reading →

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