Red Sea gravity currents cascade near-reef phytoplankton to the twilight zone
H. Niemann
C. Richter
H. Jonkers
M. I. Badran
Abstract
Cross-reef variations of sea water density, currents and phytoplankton pigments were investigated in the northern Gulf of Aqaba, Red Sea. Differential cooling of near- and offshore surface water during cold winter nights results in cross-shore gradients of density (sigma-t) triggering gravity currents which cascade downslope along sandy valleys. Two 4-wk deployments of 3-D acoustic current meters showed that cross-shore currents near the sea bed (35 and 90 m) were 2- to 5-fold higher than long-shore currents, inversely related to surface flow and highly correlated with seasonally detrended diel variations in seawater temperature. Cross-shore flow varied during the course of the night, with offshore pulses of up to 15 cm s(-1) associated with sudden temperature drops of similar to0.15degreesC. Spatial distribution of chl a pigments shows that phytoplankton enriched nearshore waters are entrained in the gravity currents to depths > 300 m. Gravity currents may therefore provide an important and previously overlooked pathway of reef-borne material to the food-impoverished deeper strata of the Red Sea.
Niemann H., Richter C., Jonkers H. and Badran M.I. (2004) Red Sea gravity currents cascade near-reef phytoplankton to the twilight zone. (269): 91-99. 10.3354/meps269091
@article{Niemann2004,
Title = {Red Sea gravity currents cascade near-reef phytoplankton to the twilight zone},
Author = {Niemann, H. and Richter, C. and Jonkers, H. and Badran, M. I.},
Editor = {},
Year = {2004},
Pages = {91-99},
Doi = {10.3354/meps269091},
Abstract = {Cross-reef variations of sea water density, currents and phytoplankton pigments were investigated in the northern Gulf of Aqaba, Red Sea. Differential cooling of near- and offshore surface water during cold winter nights results in cross-shore gradients of density (sigma-t) triggering gravity currents which cascade downslope along sandy valleys. Two 4-wk deployments of 3-D acoustic current meters showed that cross-shore currents near the sea bed (35 and 90 m) were 2- to 5-fold higher than long-shore currents, inversely related to surface flow and highly correlated with seasonally detrended diel variations in seawater temperature. Cross-shore flow varied during the course of the night, with offshore pulses of up to 15 cm s(-1) associated with sudden temperature drops of similar to0.15degreesC. Spatial distribution of chl a pigments shows that phytoplankton enriched nearshore waters are entrained in the gravity currents to depths > 300 m. Gravity currents may therefore provide an important and previously overlooked pathway of reef-borne material to the food-impoverished deeper strata of the Red Sea.},
}
TY - JOUR
AU - Niemann, H.
AU - Richter, C.
AU - Jonkers, H.
AU - Badran, M. I.
TI - Red Sea gravity currents cascade near-reef phytoplankton to the twilight zone
PY - 2004
SP - 91-99
DO - 10.3354/meps269091
AB - Cross-reef variations of sea water density, currents and phytoplankton pigments were investigated in the northern Gulf of Aqaba, Red Sea. Differential cooling of near- and offshore surface water during cold winter nights results in cross-shore gradients of density (sigma-t) triggering gravity currents which cascade downslope along sandy valleys. Two 4-wk deployments of 3-D acoustic current meters showed that cross-shore currents near the sea bed (35 and 90 m) were 2- to 5-fold higher than long-shore currents, inversely related to surface flow and highly correlated with seasonally detrended diel variations in seawater temperature. Cross-shore flow varied during the course of the night, with offshore pulses of up to 15 cm s(-1) associated with sudden temperature drops of similar to0.15degreesC. Spatial distribution of chl a pigments shows that phytoplankton enriched nearshore waters are entrained in the gravity currents to depths > 300 m. Gravity currents may therefore provide an important and previously overlooked pathway of reef-borne material to the food-impoverished deeper strata of the Red Sea.
ER -
