Tidal and subtidal transport in short, tidally-driven estuaries with low rates of freshwater input

2021 ◽  
pp. 104453
Author(s):  
Lauren Ross ◽  
Sohaib Alahmed ◽  
Sean M.C. Smith ◽  
Gwyneth Roberts
Keyword(s):  
Freshwater Input ◽  
Tidally Driven

scholarly journals Middle Holocene Coastal Environmental and Climate Change on the Southern Coast of Korea

2020 ◽  
Vol 11 (1) ◽  
pp. 230
Author(s):  
Hoil Lee ◽  
Jin-Young Lee ◽  
Seungwon Shin
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Stable Carbon Isotopes ◽  
Asian Summer Monsoon ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Freshwater Input ◽  
Reclaimed Land ◽  
Middle Holocene ◽  
Southwest Coast

We obtained a 15 m drill core from Deukryang Bay on the southwest coast of Korea, which is now an area of reclaimed land used for agriculture. We investigated changes in the depositional environment and hydrological climate responses to sea level changes using sedimentary facies, radiocarbon ages, grain-size analysis, total organic carbon (TOC), total sulfur (TS), and stable carbon isotopes (δ13C). Sediment deposition began at 12,000 cal yr BP and was divided into four stages based on changes from fluvial to intertidal environments related to Holocene marine transgression events. Stage 1 (>10,000 cal yr BP) is represented by fluvial sediments; Stage 2 (10,000–7080 cal yr BP) is represented by the deposition of mud facies in an intertidal zone in response to sea level rise; Stage 3 (7080–3300 cal yr BP) was a period of gradually descending sea level following the Holocene maximum sea level and is characterized by gradual changes in TOC, TS, and C/S ratios compared with the mud facies of Stage 2. Stage 4 (3300 to present) was deposited in a supratidal zone and contains low TS and an abundance of TOC. Based on our TS and C/S ratio results, the south coast of Korea was mainly affected by sea level rise between 7000 and 3000 cal yr BP, during the middle Holocene. At 3000 cal yr BP, sea level began to stabilize or gradually decrease. In addition, changes in δ13C values are clearly observed since ca. 5000 cal yr BP, in particular, large hydrological changes via freshwater input are confirmed in 4000–3000 cal yr BP. We consider these shifts in freshwater input indicators of an increased influence of El Niño and La Niña conditions, related to the weakening of the East Asian Summer Monsoon (EASM) and changes in sea surface temperature (SST) of the Western Pacific Ocean during the middle Holocene climatic optimum (between 7800 and 5000 cal yr BP). The cooling periods of SST in East Asia between 8400 and 6600 cal yr BP reported from the west coast of Korea are related closely to changes in vegetation (as evidenced by δ13C) from 7700 cal yrs BP to the present in the southwest coast of Korea. We interpret the freshwater input events at 4000–3000 cal yr BP to be related to changes in SST in response to the weakening of the EASM on the southwest coast of Korea. However, additional research is needed to study the southward migration effect of the westerly jet related to SST and atmospheric circulation controlling terrestrial climate in the middle Holocene.

Channel head dynamics: capelin (Mallotus villosus) aggregation in the tidally driven upwelling system of the Saguenay - St. Lawrence Marine Park's whale feeding ground

2002 ◽  
Vol 59 (2) ◽  
pp. 197-210 ◽  
Author(s):  
Yvan Simard ◽  
Diane Lavoie ◽  
François J Saucier
Keyword(s):  
Circulation Model ◽  
Feeding Strategies ◽  
Total Biomass ◽  
Balaenoptera Acutorostrata ◽  
Mallotus Villosus ◽  
Tidal Dynamics ◽  
Lawrence Estuary ◽  
Fin Whale ◽  
Capelin Mallotus Villosus ◽  
Tidally Driven

Capelin (Mallotus villosus) tridimensional distribution at the head of the Laurentian Channel in the St. Lawrence estuary was investigated using 38- and 120-kHz acoustic surveys in the summers of 1994, 1995, 1997, and 1998. The results are interpreted with the help of a high-resolution tridimensional tidal circulation model. Total biomasses were small (93–4583 t) and showed rapid fluctuations, whereas mesoscale distribution was more constant. Capelin tended to occupy the very end of the channel head, especially the slopes and shallows surrounding the basins. This pattern did not coincide with the krill distribution, but the two total biomass series were significantly correlated. Capelin tidal dynamics is characterized by herding of capelin against the channel head slopes by the starting flooding currents, followed by an upwelling over the sills and shallows during maximum flood currents, and a return to the channel by the surface outflow during ebb. Each side of the channel head has a distinct capelin retention tidal cycle involving passive advection, swimming, and the two-layer estuarine circulation. This capelin distribution and tidal dynamics closely match the local fin whale (Balaenoptera physalus) and minke whale (Balaenoptera acutorostrata) distributions observed from the whale-watching fleet and typical tidal feeding strategies at the channel head.

scholarly journals Tidally-driven interannual variation in extreme sea level probabilities in the Gulf of Maine

2020 ◽  
Author(s):  
Hannah Baranes ◽  
Jonathan Woodruff ◽  
Stefan Talke ◽  
Robert Kopp ◽  
Richard Ray ◽  
...  
Keyword(s):  
Sea Level ◽  
Interannual Variation ◽  
Gulf Of Maine ◽  
Tidally Driven

Tidally Driven Dispersion of a Deep-Sea Sediment Plume Originating from Seafloor Disturbance in the DISCOL Area (SE-Pacific Ocean)

Geosciences ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 8
Author(s):  
Matthias Baeye ◽  
Kaveh Purkiani ◽  
Henko de de Stigter ◽  
Benjamin Gillard ◽  
Michael Fettweis ◽  
...  
Keyword(s):  
Optical Sensors ◽  
Fine Particles ◽  
Transport Model ◽  
Manganese Nodule ◽  
Background Concentration ◽  
Plume Dispersion ◽  
Suspended Particulate Matter Concentration ◽  
Deep Sea Sediment ◽  
Suspended Particulate ◽  
Tidally Driven

The purpose of the study was to measure in situ the background suspended particulate matter concentration (SPMC) in the DISCOL area (SE Pacific) and its increase due to mechanical mobilization of the seabed. The disturbance experiment imitated future manganese nodule exploitations and was designed to measure the sediment plume generated by such activities. In the direct vicinity of the disturbance, landers equipped with acoustic and optical sensors measured the current velocities and the SPMC. The SPMC at the disturbance was easily up to 10 mg/L and thus about 200 times higher than the background concentration. The downstream sediment plume, measured by the lander, had a SPMC of about 1 mg/L. After tide reversal, the sediment plume was recorded a second time. A sediment transport model reproduced the plume dispersion. After rapid settling of the coarser fraction, a plume of hardly settling fine particles remained in suspension (and no deposition–resuspension cycles). The transport was controlled by the tides and by the vertical velocity component that resulted from bathymetrical differences. The plume may continue to disperse up to 100+ days (up to hundreds of km) depending on the particle size and until background concentration is reached.

scholarly journals Population irruption of the clam Meretrix morphina in Lake St Lucia, South Africa

2017 ◽  
Vol 113 (7/8) ◽  
Author(s):  
Nelson A. F. Miranda ◽  
Nasreen Peer ◽  
Renzo Perissinotto ◽  
Nicola K. Carrasco ◽  
Salome Jones ◽  
...  
Keyword(s):  
South Africa ◽  
South African ◽  
East Coast ◽  
Severe Drought ◽  
Freshwater Input ◽  
Large Populations ◽  
Ocean Region ◽  
West Indian Ocean ◽  
First Time ◽  
Eastern Seaboard

The thick-shelled clam Meretrix morphina, previously referred to as Meretrix meretrix, now occurs in the west Indian Ocean region, along the eastern seaboard of Africa, from the Red Sea to the Mlalazi Estuary, close to the Tugela River. Its presence in South Africa is only of recent recording. Meretrix morphina was detected for the first time in Lake St Lucia in 2000. The population declined and was not detected from 2005 until 2011, most likely as a result of a severe drought that resulted in widespread desiccation and hypersalinity in the lake. The system then experienced increased freshwater input resulting in lower salinities from 2011 until 2014, during which time M. morphina reappeared and their population gradually increased. In 2015, M. morphina became abundant in St Lucia, attaining unprecedented densities of 447 ind./m2. Biomass, expressed as a fresh weight, varied in the different basins of St Lucia, ranging from 195 g/m2 at Lister’s Point to 1909.8 g/m2 at Catalina Bay. However, in 2016, when drought conditions returned, M. morphina disappeared. This species appears to thrive under brackish salinities and high temperatures. It is able to establish large populations with high biomass and can become dominant. However, M. morphina is sensitive to desiccation and hypersaline conditions. This clam has substantial commercial value and is exploited along the African east coast, particularly in Mozambique. In future, it may feature more prominently in South African estuaries. However, the ecology of M. morphina is still largely unknown.

Abrupt CO2 release to the atmosphere under glacial and early interglacial climate conditions

Science ◽  
2020 ◽  
Vol 369 (6506) ◽  
pp. 1000-1005
Author(s):  
C. Nehrbass-Ahles ◽  
J. Shin ◽  
J. Schmitt ◽  
B. Bereiter ◽  
F. Joos ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Intertropical Convergence Zone ◽  
Meridional Overturning Circulation ◽  
Before Present ◽  
Freshwater Input ◽  
Warm Climate ◽  
Climate Conditions ◽  
Carbon Dioxide Release ◽  
Meridional Overturning ◽  
Co2 Release

Pulse-like carbon dioxide release to the atmosphere on centennial time scales has only been identified for the most recent glacial and deglacial periods and is thought to be absent during warmer climate conditions. Here, we present a high-resolution carbon dioxide record from 330,000 to 450,000 years before present, revealing pronounced carbon dioxide jumps (CDJ) under cold and warm climate conditions. CDJ come in two varieties that we attribute to invigoration or weakening of the Atlantic meridional overturning circulation (AMOC) and associated northward and southward shifts of the intertropical convergence zone, respectively. We find that CDJ are pervasive features of the carbon cycle that can occur during interglacial climate conditions if land ice masses are sufficiently extended to be able to disturb the AMOC by freshwater input.

Estimating tidally driven mixing in the deep ocean

2002 ◽  
Vol 29 (23) ◽  
pp. 21-1-21-4 ◽  
Author(s):  
L. C. St. Laurent ◽  
H. L. Simmons ◽  
S. R. Jayne
Keyword(s):  
Deep Ocean ◽  
Tidally Driven

scholarly journals Kū Hou Kuapā: Cultural Restoration Improves Water Budget and Water Quality Dynamics in Heʻeia Fishpond

2018 ◽  
Author(s):  
Paula Mohlenkamp ◽  
Charles Kaiaka Beebe ◽  
Margaret A. McManus ◽  
Angela Hiʻilei Kawelo ◽  
Keliʻiahonui Kotubetey ◽  
...  
Keyword(s):  
Water Quality ◽  
Exchange Rates ◽  
Positive Impact ◽  
Discharge Rate ◽  
Quality Parameters ◽  
Stream Discharge ◽  
Bacterial Indicator ◽  
Average Abundance ◽  
Tidally Driven ◽  
The Impact

In Hawaiʻi, the transition from customary subsistence flooded taro agroecosystems, which regulate stream discharge rate trapping sediment and nutrients, to a plantation-style economy (c. the 1840s) led to nearshore sediment deposition - smothering coral reefs and destroying adjacent coastal fisheries and customary fishpond mariculture. To mitigate sediment transport, Rhizophora mangle was introduced in estuaries across Hawai’i (c. 1902) further altering fishpond ecosystems. Here, we examine the impact of cultural restoration between 2012-2018 at Heʻeia Fishpond, a 600-800-year-old walled fishpond. Fishpond water quality was assessed by calculating water exchange rates, residence times, salinity distribution, and abundance of microbial indicators prior to and after restoration. We hypothesized that R. mangle removal and concomitant reconstruction of sluice gates would increase mixing and decrease bacterial indicator abundance in the fishpond. We find that Heʻeia Fishpond’s physical environment is primarily tidally driven; wind forcing and river flux are secondary drivers. Post-restoration, two gates in the northeastern region account for >80% of relative flux in the fishpond. Increase in exchange rates during spring and neap tide and shorter minimum water residence time corresponded with the reconstruction of a partially obstructed 56 m gap together with the installation of an additional sluice gate in the fishpond wall. Lower mean salinities post-restoration suggests increased freshwater influx due to R. mangle removal. Spatial distribution of microbial bio-indicator species inversely correlated with salinity. Average abundance of Enterococcus and Bacteroidales did not significantly change after restoration efforts, however, average abundance of a biomarker specific to birds nesting in the mangroves decreased significantly after restoration. This study demonstrates the positive impact of biocultural restoration regimes on water flushing and water quality parameters, encouraging the prospect of revitalizing this and other culturally and economically significant sites for sustainable aquaculture in the future.

scholarly journals Heterogeneous timing of freshwater input into Kobbefjord, a low‐Arctic Fjord in Greenland

2021 ◽  
Author(s):  
Jakob Abermann ◽  
Kirsty Langley ◽  
Sille M. Myreng ◽  
Kerstin Rasmussen ◽  
Dorthe Petersen
Keyword(s):  
Freshwater Input ◽  
Arctic Fjord ◽  
Low Arctic
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