Wyniki wyszukiwania - Biblioteka Nauki

Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl

Ograniczanie wyników

Znaleziono wyników: 3

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: primary productivity

Sortuj według:

Ogranicz wyniki do:

Inconsistent response of biophysical characteristics in the western Bay of Bengal associated with positive Indian Ocean dipole

100%

Seelanki V. , Nigam T. , Pant V.

2022

tom No. 64 (4)

595--614

The Bay of Bengal (BoB) is known to have high primary productivity at its western margin during the Indian summer monsoon season (June–September). This higher coastal productivity is mainly caused due to the near-surface nutrient availability maintained by the local coastal upwelling process. The surface winds in the Indian Ocean significantly vary during El-Niño/La-Niña and Indian Ocean dipole (IOD). The current study examines the sea surface temperature (SST) and Chlorophyll-a (Chl-a) anomalies in the western BoB for the period of 18 years (2000 to 2017), using a coupled regional ocean biophysical model. All considered positive IOD (pIOD) years show discrete behavior of biophysical features in the western BoB. The co-occurrence years of pIOD and El-Niño modes are associated with contrast biophysical anomalies. In the analyzed pIOD events, the years 2006 and 2012 show an enhancement in the Chl-a anomalies whereas, the other two years (2015 and 2017) experience Chl-a decrement. The western BoB was anomalously warmer during the 2015 and 2017 pIOD years compared to the other two pIOD years (2006, 2012). This inconsistent response of biophysical features associated with pIOD years is investigated in terms of local surface flux (momentum, heat, and freshwater) changes over the western BoB. The combined impact of local surface flux changes during the individual years remains the major contributing factor affecting the upper-ocean stratification. Ultimately, the stratification changes are responsible for the observed inconsistent response of biophysical features by significantly altering the upper-ocean mixing, upwelling, and nutrient availability in the western BoB.

Nutrient flux fuels the summer primary productivity in the oligotrophic waters of the Gulf of Aqaba, Red Sea

84%

Badran M. I. , Rasheed M. , Manasrah R. , Al-Najjar T.

nr 1

The thermohaline characteristics of the Gulf of Aqaba, Red Sea, depict a welldefined seasonal pattern of winter mixing from December to April and summer stratification from May to November. This thermohaline structure is a major controlling factor of the nutrient, chlorophyll a and primary productivity seasonal cycles. The nitrate and chlorophyll a concentration records generated down to 200 m at a vertical resolution of 25 m – weekly during 1994, 1995 and every two weeks from April 1997 through to December 2000 – are employed to assess the nitrogen flux across the summer thermocline of the Gulf of Aqaba. The flux calculations are based on a simple diffusion model that incorporates the physical stress eddy diffusivity factor Kz and a biological stress factor k. Both Kz and k are calculated using the Michaelis-Menten equation and the nitrate concentration gradient. The total nitrate flux of the Gulf of Aqaba during the seven summer months (May–November) is estimated at 0.52 moleN m−2. In relation to established primary productivity values (75.5 gC m−2 (May November)−1) and the generated chlorophyll a records, this yields an f fraction of new to total primary production of 0.50. This relatively high f value is discussed with respect to the geophysical characteristics of the Gulf of Aqaba and similar oceanic basins. The remaining 50% is accounted for by cross-sectional flow from the relatively nutrientrich coral reef coastal habitat and rapid recycling, triggered by high irradiance and water temperature.

Primary productivity off Western and Southern Portuguese waters

84%

Cavaco M. H. , Cabecadas G.

nr 1