Hydrographic characteristics along two XCTD sections between Africa and Antarctica during austral summer 2018

Using the Expendable CTDs (XCTDs) collected along two transects between Africa and Antarctica during 1–11 January (Cape Town−Prydz Bay, track-2) and 12-21 April 2018 (Prydz Bay−Cape Town, track-1), frontal locations are delineated and compared with the satellite-based maps of absolute dynamic topogr...

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Bibliographic Details
Published in:Polar Science
Format: Article in Journal/Newspaper
Language:English
Published: 2021
Subjects:
Southern ocean
Hydrological fronts
Baroclinic transport
Water mass
Chlorophyll-a
Southern Ocean
Austral
Prydz Bay
Indian
Antarc*
Antarctica
Polar Science
Online Access:https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=16872
http://id.nii.ac.jp/1291/00016742/
Description
Summary:Using the Expendable CTDs (XCTDs) collected along two transects between Africa and Antarctica during 1–11 January (Cape Town−Prydz Bay, track-2) and 12-21 April 2018 (Prydz Bay−Cape Town, track-1), frontal locations are delineated and compared with the satellite-based maps of absolute dynamic topography (MADT). The MADT maps revealed that the intensity of the Agulhas Current (AC) was 1.3 ms−1 during both periods; the southernmost limit of the Agulhas Retroflection (AR) was traced to 40°S, 20.5°E/42°S, 15°E on track-1/track-2. The vertical sections of temperature and salinity revealed the Agulhas anticyclonic eddy (AAE) whose core was detected at ~38.4°S/~37.6°S on track-1/track-2. The cumulative transport across track-2 was 50% higher than across track-1 which is attributed to deep-sea upwelling and its subsequent transport across the track-2 to the south of 50°S. On both transects, the winter water was detected up to 50°S in the upper 100 m. The highest AC transport in the upper 1000 m was detected at 37.75°S/38.28°S on track-1/track-2, which was related to the flow characteristics of the AC. The eddies that detached from the AC system transported nutrient-rich water southward which mixed with the ambient water resulting in peak chlorophyll-a concentration (Chl-a) exceeding 0.5 mg/m3 to the north of 42°S on both tracks. The shallow topographic features such as the Ob-Lena rise (54°S) and the southwest Indian Ridge (44°−46°S) also enhanced Chl-a by 39% on track-2.

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