Effects of stopping the Mediterranean Outflow on the southern polar region

The extent to which the southern polar region is sensitive to the stopping of the Mediterranean Outflow is investigated by using a global ocean-atmosphere coupled model. Two experimental runs, one(named the control run) with and the other(named the NMOW run) without exchanges of heat and salinity between the Mediterranean Sea and the Atlantic Ocean, are carried out in order to simulate the presence and absence of the outflow. Large responses in the sea surface temperature are found in both the northern North Atlantic and the Southern Ocean. For the NMOW run, the response in the Southern Ocean shows general decreases in sea surface temperature and salinity over a millenial timescale. Sea-ice thickness mostly increases, but is reduced in regions associated with increased sea surface temperature. The freshening of the Southern Ocean brings about a decrease in the density difference between the southern polar regions and the tropics. Consequently, the meridional overturning which transports Antarctic Bottom Water decreases

Infectious virus shedding duration reflects secretory IgA antibody response latency after SARS-CoV-2 infection

新型コロナウイルス排出と粘膜抗体の関係を解明 --呼吸器ウイルスのヒト間伝播を制御・予防する第一歩--. 京都大学プレスリリース. 2023-12-25.Articles: Infectious virus shedding duration reflects secretory IgA antibody response latency after SARS-CoV-2 infection. 京都大学プレスリリース. 2023-12-25.Infectious virus shedding from individuals infected with severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) is used to estimate human-to-human transmission risk. Control of SARS-CoV-2 transmission requires identifying the immune correlates that protect infectious virus shedding. Mucosal immunity prevents infection by SARS-CoV-2, which replicates in the respiratory epithelium and spreads rapidly to other hosts. However, whether mucosal immunity prevents the shedding of the infectious virus in SARS-CoV-2-infected individuals is unknown. We examined the relationship between viral RNA shedding dynamics, duration of infectious virus shedding, and mucosal antibody responses during SARS-CoV-2 infection. Anti-spike secretory IgA antibodies (S-IgA) reduced viral RNA load and infectivity more than anti-spike IgG/IgA antibodies in infected nasopharyngeal samples. Compared with the IgG/IgA response, the anti-spike S-IgA post-infection responses affected the viral RNA shedding dynamics and predicted the duration of infectious virus shedding regardless of the immune history. These findings highlight the importance of anti-spike S-IgA responses in individuals infected with SARS-CoV-2 for preventing infectious virus shedding and SARS-CoV-2 transmission. Developing medical countermeasures to shorten S-IgA response time may help control human-to-human transmission of SARS-CoV-2 infection and prevent future respiratory virus pandemics

Some characteristics of summer ocean structure off the Queen Maud Land, Antarctica

The hydrographic data of FUJI (Japanese Antarctic Research Expedition : JARE) obtained in the austral summers of 1966-1969 and 1973-1975 in a sector of 60°-70°S and 30°W-15°E, where the Weddell polynya appeared during the winters of 1973-1977,are examined for finding out the influence of a winter polynya on summer ocean structure, in comparison with the cruise-12 data of the ARA ISLAS ORCADAS obtained in the same sector in the austral summer of 1977. The vertical profiles of temperature, salinity and sigma-t at station 75-7 (67°27′S, 2°04′E) on February 26,1975,for the JARE-16 show anomalous characteristics featuring the absence of water below 0℃, both the weak minimum and the weak maximum temperature profile, a high-salinity water at the depth where the temperature is minimum, and a shallow picnocline. These features, which reveal the upward movement of saline water, are different from the anomalous features at station 115 of the cruise of the ISLAS ORCADAS, where the sinking of the cooled surface water occurred, as explained by GORDON (J. Phys. Oceanogr., 8,600,1978) and KILLWORTH (J. Phys. Oceanogr., 9,531,1979). The same features as the profiles at stations 75-7 and 115 are found at stations 118 and 125 respectively in the ISLAS ORCADAS data. These four stations were located near the margin of the polynya in the preceding winter, and both types of anomalous features reveal that strong convection, which occurred locally in the polynya area in the preceding winter, influences summer ocean structure

Convective mixing and sea ice formation in the Weddell-Enderby Basin in 1974 and 1975

The formation of sea ice in the Weddell-Enderby Basin is examined using a one-dimensional convective mixing model. Oceanographic data obtained in late summer of 1974 and 1975 aboard the icebreaker FUJI are used as the initial conditions in the model. The results by the present model indicate that no sea ice forms in the Weddell Polynya region in 1974 and 1975. The major oceanographic criterion for sea ice formation in the winter is salinity of water in a mixed layer in the preceding summer; high salinity gives no sea-ice formation, which is due to an upward heat flux from deep water by deep convection

Characteristics of mid-depth water in summer off Queen Maud-Enderby Lands, Antarctica

Summer oceanographic conditions off Queen Maud-Enderby Lands are examined using temperature, salinity and dissolved-oxygen data from 177 hydrographic stations. The most characteristic feature of the area covered is the presence of a mid-depth water. It is composed of three distinct water masses : less saline, oxygen-rich water at a nearly freezing temperature; warm, saline, oxygen-poor water; and a third water which has properties between the above two. Finally, the regional distribution of the characteristic water masses and their sources are discussed