Increasing poleward intrusion of the Circumpolar Deep Water and its impact on the changing ocean-biogeochemistry of the Southern Ocean

A study published in Nature Geoscience (Bronselaer et al., 2020) analyzed new observations from autonomous floats with ocean-biogeochemical sensors (Bio-Argo) along with historical shipboard ocean measurements to document changes in Southern Ocean physical and ocean-biogeochemical variables (i.e., temperature, salinity, pH, concentrations of nitrate, dissolved inorganic carbon and oxygen) during the last two decades. Due to... Continue Reading →

Pantropical response to global warming and the emergence of a La Nina-like mean state trend

During the past century, the tropical Pacific Ocean has warmed significantly less than the other tropical oceans  in response to increasing greenhouse gases (GHGs). This La Nina-like warming trend in the observations is in stark contrast to the El Nino-like warming trend projected by the Coupled Model Intercomparison Project (CMIP) models for both the 20th... Continue Reading →

Atlantic Multidecadal Oscillation (AMO) modulates North Atlantic atmospheric blocking

Atmospheric blocking over the high-latitude North Atlantic blocks the westerly jet stream, causing the eastward propagation of weather systems to stall for 7 days or so. An earlier study  by Häkkinen et al. (2011) used the 20th century atmospheric reanalysis product of NOAA (20CR) to show that the wintertime blocking frequency over high latitude North Atlantic covaries... Continue Reading →

Recent warming of the tropical Indian Ocean may sustain the AMOC from slowing down

A recent study published in Nature Climate Change used a series of coupled ocean-atmosphere model simulations to demonstrate that the tropical Indian Ocean (TIO) warming reduces rainfall over the tropical Atlantic by strengthening the Walker circulation (i.e., increased ascending motion over TIO and increased subsidence over tropical Atlantic). This increases salinity of the upper tropical Atlantic Ocean.... Continue Reading →

Recent recovery of the Antarctic Bottom Water and its contribution to the Global Meridional Overturning Circulation

The lower limb of the Global Meridional Overturning Circulation (GMOC) is supplied by  the sinking of the heavy water mass that forms around the Antarctica, known as the Antarctic Bottom Water (AABW).  Repeat hydrographic data along the Atlantic, Pacific and Indian Ocean sections observed during the mid 1990s, 2000s and 2010s indicate that the volume... Continue Reading →

North Atlantic Ocean gyre circulation dictates the interannual sea level variability along the U.S. Southeast and Gulf Coasts

Interannual and longer time-scale sea level changes are relatively small amplitude. However,  they can provide background conditions favorable for the occurrence of extreme sea levels that represent a threat for coastal communities, especially in low-lying and flood-vulnerable regions. A new study accepted in Geophysical Research Letters identified the dominant mode of the ocean gyre-scale sea surface height... 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 →

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 →

Recent intensification of Amazonian flooding extremes is linked to the tropical Atlantic warming and tropical Pacific cooling

The Amazonian River basin hosts the one of the major global deep tropical convective systems, and thus drives the global Hadley and Walker circulations and the global hydrological cycle. Changes in the water cycle and deep convection activity in this region are, however, largely affected by remote oceans, especially the tropical Pacific, via the Walker circulation.... Continue Reading →

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