Simulation of Water Age and Residence Time in New York Bight

2010 ◽  
Vol 40 (5) ◽  
pp. 965-982 ◽  
Author(s):  
Weifeng G. Zhang ◽  
John L. Wilkin ◽  
Oscar M. E. Schofield
Keyword(s):  
New York ◽  
Surface Water ◽  
Time Scales ◽  
Residence Time ◽  
Surface Waters ◽  
River Discharge ◽  
Long Island ◽  
Water Age ◽  
New York Bight ◽  
Island Coast

Abstract The time scales on which river inflows disperse in the coastal ocean are relevant to a host of biogeochemical and environmental processes. These time scales are examined in a modeling study of the Hudson River plume on its entry to the New York Bight (NYB). Constituent-oriented age and residence-time theory is applied to compute two time scales: mean age, which is calculated from the ratio of two model tracers, and residence time, which is calculated using the adjoint of the tracer conservation equation. Spatial and temporal variability associated with river discharge and wind is investigated. High river discharge lowers surface water age and shortens residence time in the apex of the NYB. Easterly winds increase surface water age and extend the duration waters along the Long Island coast remain in the NYB apex. Southerly winds increase age along the New Jersey coast but drive a decrease in age of offshore surface waters and prolong the time that surface waters close to the New Jersey coast stay in the NYB apex. Residence time along the Long Island coast is high in spring and summer because of the retention of water north of the Hudson shelf valley. Patterns of modeled surface water age and an age proxy computed from the ratio of satellite-measured irradiance in two channels show qualitative agreement. A least squares fit gives a statistically significant empirical relationship between the band ratio and modeled mean age for NYB waters.

scholarly journals Pathways for Methane Emissions and Oxidation that Influence the Net Carbon Balance of a Subtropical Cypress Swamp

2020 ◽  
Vol 8 ◽  
Author(s):  
Nicholas D. Ward ◽  
Thomas S. Bianchi ◽  
Jonathan B. Martin ◽  
Carlos J. Quintero ◽  
Henrique O. Sawakuchi ◽  
...  
Keyword(s):  
Surface Water ◽  
Time Scales ◽  
Surface Waters ◽  
Methane Flux ◽  
Methane Emissions ◽  
Molar Ratio ◽  
Sediment Layer ◽  
Wetland Site ◽  
Organic Carbon Burial ◽  
Methane Fluxes

We evaluated the major pathways for methane emissions from wetlands to the atmosphere at four wetland sites in the Big Cypress National Preserve in southwest Florida. Methane oxidation was estimated based on the δ13C-CH4 of surface water, porewater, and bubbles to evaluate mechanisms that limit surface water emissions. Spatially-scaled methane fluxes were then compared to organic carbon burial rates. The pathway with the lowest methane flux rate was diffusion from surface waters (3.50 ± 0.22 mmol m−2 d−1). Microbial activity in the surface water environment and/or shallow oxic sediment layer oxidized 26 ± 3% of the methane delivered from anerobic sediments to the surface waters. The highest rates of diffusion were observed at the site with the lowest extent of oxidation. Ebullition flux rates were 2.2 times greater than diffusion and more variable (7.79 ± 1.37 mmol m−2 d−1). Methane fluxes from non-inundated soils were 1.6 times greater (18.4 ± 5.14 mmol m−2 d−1) than combined surface water fluxes. Methane flux rates from cypress knees (emergent cypress tree root structures) were 3.7 and 2.3 times higher (42.0 ± 6.33 mmol m−2 d−1) than from surface water and soils, respectively. Cypress knee flux rates were highest at the wetland site with the highest porewater methane partial pressure, suggesting that the emergent root structures allow methane produced in anaerobic sediment layers to bypass oxidation in aerobic surface waters or shallow sediments. Scaled across the four wetlands, emissions from surface water diffusion, ebullition, non-inundated soils, and knees contributed to 14 ± 2%, 25 ± 6%, 34 ± 10%, and 26 ± 5% of total methane emissions, respectively. When considering only the three wetlands with cypress knees present, knee emissions contributed to 39 ± 5% of the total scaled methane emissions. Finally, the molar ratio of CH4 emissions to OC burial ranged from 0.03 to 0.14 in the wetland centers indicating that all four wetland sites are net sources of atmospheric warming potential on 20–100 yr timescales, but net sinks over longer time scales (500 yr) with the exception of one wetland site that was a net source even over 500 yr time scales.

Acidity of and the concentrations of major and minor metals in the surface waters of bryophyte assemblages from 20 North American bogs and fens

2000 ◽  
Vol 78 (6) ◽  
pp. 718-727 ◽  
Author(s):  
Steven F Mullen ◽  
Jan A Janssens ◽  
Eville Gorham
Keyword(s):  
New York ◽  
Surface Water ◽  
Species Diversity ◽  
Surface Waters ◽  
Chemical Properties ◽  
Elemental Abundance ◽  
Secondary Axis ◽  
Alkaline Earths ◽  
Primary Axis ◽  
Components Analysis

One hundred and thirty-five samples of surface water, associated with bryophyte plots distributed across 20 wetlands in Newfoundland, Nova Scotia, Ontario, Alaska, Maine, Minnesota, and New York, were analyzed for pH and 11 elements, several of them seldom measured in wetlands. The overall order of elemental abundance was the following: Ca, Si, Na, Mg, Fe, K, Al, Mn, Sr, Ba, and Ti. Principal-components analysis of the pH and elemental chemistries of the water samples revealed seven subcategories that could be recognized as belonging to maritime and continental ombrotrophic bogs and poor, rich, and calcareous rich fens. The primary axis related to pH and the concentrations of alkaline earths, as well as to Si. The secondary axis segregated an unusual group of Alaskan fens; it was related mainly to Fe and Mn, and to a lesser degree Al and K. The tertiary axis separated maritime from continental bogs and was related chiefly to Na. The distribution of bryophyte species, most of them widespread in bogs and fens elsewhere, was most clearly related to pH and Ca concentration. As expected, many species exhibited narrow ranges of these chemical properties, whereas many others were widely distributed.Key words: mosses, peatlands, species diversity, water chemistry.

The Effect of Wind on the Dispersal of the Hudson River Plume

2007 ◽  
Vol 37 (7) ◽  
pp. 1878-1897 ◽  
Author(s):  
Byoung-Ju Choi ◽  
John L. Wilkin
Keyword(s):  
New York ◽  
River Discharge ◽  
Bottom Topography ◽  
Hudson River ◽  
River Plume ◽  
Wind Forcing ◽  
High Discharge ◽  
New York Bight ◽  
York Bight ◽  
Freshwater Export

Abstract The dispersal of the Hudson River plume in response to idealized wind forcing is studied using a three-dimensional model. The model domain includes the Hudson River and its estuary, with a realistic coastline and bottom topography of the New York Bight. Steady low river discharge typical of mean conditions and a high-discharge event representative of the spring freshet are considered. Without wind forcing the plume forms a southward coastally trapped current at low river discharge and a large recirculating bulge of low-salinity water during a high-discharge event. Winds affect the freshwater export through the mouth of the estuary, which is the trajectory the plume takes upon entering the waters of the Mid-Atlantic Bight inner shelf, and the rate at which freshwater drains downstream. The dispersal trajectory is also influenced by the particular geography of the coastline in the apex of the New York Bight. Northward wind causes offshore displacement of a previously formed coastally trapped plume and drives a new plume along the Long Island coast. Southward wind induces a strong coastal jet that efficiently drains freshwater to the south. Eastward wind aids freshwater export from the estuary and favors the accumulation of freshwater in the recirculating bulge outside the mouth of Raritan Bay. Westward wind delays freshwater export from Raritan Bay. The momentum balance of the modeled plume shows that buoyancy and wind forces largely determine the pattern of horizontal freshwater dispersal, including the spreading of freshwater over ambient, more saline water and the bulge formation.

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