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Larry P. Atkinson

Bio: Larry P. Atkinson is an academic researcher from Old Dominion University. The author has contributed to research in topics: Gulf Stream & Continental shelf. The author has an hindex of 47, co-authored 129 publications receiving 6835 citations. Previous affiliations of Larry P. Atkinson include University of Washington & Skidaway Institute of Oceanography.


Papers
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Book ChapterDOI
TL;DR: In this paper, it was shown that the effective transport of active N and P from land to the shelf through very large rivers is reduced to 292 · 109 moles y-1 of N and 13 · 109moles y -1 of P.
Abstract: Five large rivers that discharge on the western North Atlantic continental shelf carry about 45% of the nitrogen (N) and 70% of the phosphorus (P) that others estimate to be the total flux of these elements from the entire North Atlantic watershed, including North, Central and South America, Europe, and Northwest Africa. We estimate that 61 · 109 moles y-1 of N and 20 · 109 moles y-1 of P from the large rivers are buried with sediments in their deltas, and that an equal amount of N and P from the large rivers is lost to the shelf through burial of river sediments that are deposited directly on the continental slope. The effective transport of active N and P from land to the shelf through the very large rivers is thus reduced to 292 · 109 moles y-1 of N and 13 · 109 moles y-1 of P.

787 citations

Journal ArticleDOI
TL;DR: In this paper, an Empirical Mode Decomposition/Hilbert-Huang Transformation (EMD/HHT) method was used to separate long-term trends from oscillating modes.
Abstract: [1] Recent studies indicate that the rates of sea level rise (SLR) along the U.S. mid-Atlantic coast have accelerated in recent decades, possibly due to a slowdown of the Atlantic Meridional Overturning Circulation (AMOC) and its upper branch, the Gulf Stream (GS). We analyzed the GS elevation gradient obtained from altimeter data, the Florida Current transport obtained from cable measurements, the North Atlantic Oscillation (NAO) index, and coastal sea level obtained from 10 tide gauge stations in the Chesapeake Bay and the mid-Atlantic coast. An Empirical Mode Decomposition/Hilbert-Huang Transformation (EMD/HHT) method was used to separate long-term trends from oscillating modes. The coastal sea level variations were found to be strongly influenced by variations in the GS on timescales ranging from a few months to decades. It appears that the GS has shifted from a 6–8 year oscillation cycle to a continuous weakening trend since about 2004 and that this trend may be responsible for recent acceleration in local SLR. The correlation between long-term changes in the coastal sea level and changes in the GS strength was extremely high (R = −0.85 with more than 99.99% confidence that the correlation is not zero). The impact of the GS on SLR rates over the past decade seems to be larger in the southern portion of the mid-Atlantic Bight near Cape Hatteras and is reduced northward along the coast. The study suggests that regional coastal sea level rise projections due to climate change must take into account the impact of spatial changes in ocean dynamics.

321 citations

Book
01 Jan 2010
TL;DR: In this paper, the authors examined human impacts on Global Biogeochemical cycling via the Coastal Zone and Ocean Margins, and the biogeochemical transformation of Silicon along the Land-Ocean Continuum and Implications for the Global Carbon Cycle.
Abstract: Perspectives and Regional Syntheses.- Biogeochemistry of Continental Margins in a Global Context.- Eastern Boundary Current Systems.- Western Boundary Currents.- Indian Ocean Margins.- Subpolar Margins.- Polar Margins.- Marginal Seas.- Tropical Margins.- Arising Issues and New Approaches.- Examining Human Impacts on Global Biogeochemical Cycling Via the Coastal Zone and Ocean Margins.- Biogeochemical Transformations of Silicon Along the Land-Ocean Continuum and Implications for the Global Carbon Cycle1.- Submarine Groundwater Discharge (SGD) and Associated Nutrient Fluxes to the Coastal Ocean.- Coupled Circulation/Biogeochemical Models to Estimate Carbon Flux1.- Cross-Boundary Fluxes and Global Synthesis.- Cross-Boundary Exchanges of Carbon and Nitrogen in Continental Margins1.- Carbon-Nitrogen-Phosphorus Fluxes in the Coastal Zone: The LOICZ Approach to Global Assessment.- Sediment and Carbon Accumulation on Continental Shelves1.- Global Synthesis1.

277 citations

Journal ArticleDOI
01 Apr 1981
TL;DR: In this paper, the effect of Gulf Stream frontal disturbances on low-frequency current and temperature variability, water exchange, and nutrient flux in the outer region of the Georgia shelf was analyzed using satellite, hydrographic and data from moored current meters.
Abstract: Satellite, hydrographic, and data from moored current meters are used to show the effect of Gulf Stream frontal disturbances on low-frequency current and temperature variability, water exchange, and nutrient flux in the outer region of the Georgia shelf. Perturbations of the Gulf Stream cyclonic front are commonly observed as folded wave patterns in routine satellite-derived analyses of the western boundary of the Gulf Stream between Cape Hatteras and Miami. The disturbances consist of southward-flowing warm filaments or streamers of near-surface Gulf Stream water, 15 to 20 m deep, which can extend 35 to 40 km over the outer shelf around a cold upwelled core. Downstream dimensions of the filaments reach 100 to 200 km in the region from Jupiter, Florida, to Charleston, South Carolina, 10 to 50 km south of Jupiter, and 200 to 300 km between Charleston and Cape Hatteras. The features are defined as cyclonic, cold-core frontal eddies due to their flow and water mass properties. They appear to form from amplified waves in the Gulf Stream cyclonic front on an annual average of one every two weeks but with considerable monthly variability. They can persist up to three weeks and travel to the north with the same phase speed as the waves, approx. 40 cm s−1. The cyclonic circulation in frontal eddies provides a means for rapid shelf-Gulf Stream water exchange. The eddies appear to control the residence time of the outer shelf waters, defined as the mean separation time between eddy events, or approx. two weeks. Upwelling in the cold core extended into the euphotic zone (45 m) and shoreward (35 to 40 km) beneath the southward-flowing warm filament in a bottom intrusion layer 20 m thick. The annual nitrogen input to the shelf waters by this process is estimated as 55,000 tons each year, about twice all other estimated nitrogen sources combined; it can support an annual carbon production by phytoplankton of 32 to 64 g C m−2y−1 with no nitrogen recycling.

245 citations

Journal ArticleDOI
TL;DR: In this article, satellite imagery and moored current and temperature records reveal a spatial pattern of preferred regions for growth and decay of frontal disturbances from Miami, Florida, to Cape Hatteras, North Carolina.
Abstract: Weekly period meanders and eddies are persistent features of Gulf Stream frontal dynamics from Miami, Florida, to Cape Hatteras, North Carolina. Satellite imagery and moored current and temperature records reveal a spatial pattern of preferred regions for growth and decay of frontal disturbances. Growth regions occur off Miami, Cape Canaveral, and Cape Fear due to baroclinic instability, and decay occurs in the confines of the Straits of Florida between Miami and Palm Beach, between 30° and 32°N where the stream approaches the topographic feature known as the Charleston bump and between 33°N and Cape Hatteras. Eddy decay regions are associated with elongation of frontal features, offshore transport of momentum and heat, and onshore transport of nutrients. Onshore transport of new nitrogen from the nutrient-bearing strata beneath the Gulf Stream indicates that frontal eddies serve as a “nutrient pump” for the shelf. New nitrogen flux to the shelf due to Gulf Stream input could support new production of 7.4×1012 g C yr−1 or about 8 million tons carbon per year if all nitrate were utilized. Calculations indicate that approximately 70% of this potential new production is realized, yielding an annual new production for the outer shelf of 4.3×1012 g C.

235 citations


Cited by
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Journal ArticleDOI
25 Jul 1997-Science
TL;DR: Human alteration of Earth is substantial and growing as discussed by the authors, between one-third and one-half of the land surface has been transformed by human action; the carbon dioxide concentration in the atmosphere has increased by nearly 30 percent since the beginning of the Industrial Revolution; more atmospheric nitrogen is fixed by humanity than by all natural terrestrial sources combined; more than half of all accessible surface fresh water is put to use by humanity; and about one-quarter of the bird species on Earth have been driven to extinction.
Abstract: Human alteration of Earth is substantial and growing. Between one-third and one-half of the land surface has been transformed by human action; the carbon dioxide concentration in the atmosphere has increased by nearly 30 percent since the beginning of the Industrial Revolution; more atmospheric nitrogen is fixed by humanity than by all natural terrestrial sources combined; more than half of all accessible surface fresh water is put to use by humanity; and about one-quarter of the bird species on Earth have been driven to extinction. By these and other standards, it is clear that we live on a human-dominated planet.

8,831 citations

Journal ArticleDOI
TL;DR: In this article, a review of available scientific evidence shows that human alterations of the nitrogen cycle have approximately doubled the rate of nitrogen input into the terrestrial nitrogen cycle, with these rates still increasing; increased concentrations of the potent greenhouse gas N 2O globally, and increased concentration of other oxides of nitrogen that drive the formation of photochemical smog over large regions of Earth.
Abstract: Nitrogen is a key element controlling the species composition, diversity, dynamics, and functioning of many terrestrial, freshwater, and marine ecosystems. Many of the original plant species living in these ecosystems are adapted to, and function optimally in, soils and solutions with low levels of available nitrogen. The growth and dynamics of herbivore populations, and ultimately those of their predators, also are affected by N. Agriculture, combustion of fossil fuels, and other human activities have altered the global cycle of N substantially, generally increasing both the availability and the mobility of N over large regions of Earth. The mobility of N means that while most deliberate applications of N occur locally, their influence spreads regionally and even globally. Moreover, many of the mobile forms of N themselves have environmental consequences. Although most nitrogen inputs serve human needs such as agricultural production, their environmental conse- quences are serious and long term. Based on our review of available scientific evidence, we are certain that human alterations of the nitrogen cycle have: 1) approximately doubled the rate of nitrogen input into the terrestrial nitrogen cycle, with these rates still increasing; 2) increased concentrations of the potent greenhouse gas N 2O globally, and increased concentrations of other oxides of nitrogen that drive the formation of photochemical smog over large regions of Earth; 3) caused losses of soil nutrients, such as calcium and potassium, that are essential for the long-term maintenance of soil fertility; 4) contributed substantially to the acidification of soils, streams, and lakes in several regions; and 5) greatly increased the transfer of nitrogen through rivers to estuaries and coastal oceans. In addition, based on our review of available scientific evidence we are confident that human alterations of the nitrogen cycle have: 6) increased the quantity of organic carbon stored within terrestrial ecosystems; 7) accelerated losses of biological diversity, especially losses of plants adapted to efficient use of nitrogen, and losses of the animals and microorganisms that depend on them; and 8) caused changes in the composition and functioning of estuarine and nearshore ecosystems, and contributed to long-term declines in coastal marine fisheries.

5,729 citations

Journal ArticleDOI
TL;DR: In this article, a review of the available scientific information, they are confident that nonpoint pollution of surface waters with P and N could be reduced by reducing surplus nutrient flows in agricultural systems and processes, reducing agricultural and urban runoff by diverse methods, and reducing N emissions from fossil fuel burning, but rates of recovery are highly variable among water bodies.
Abstract: Agriculture and urban activities are major sources of phosphorus and nitrogen to aquatic ecosystems. Atmospheric deposition further contributes as a source of N. These nonpoint inputs of nutrients are difficult to measure and regulate because they derive from activities dispersed over wide areas of land and are variable in time due to effects of weather. In aquatic ecosystems, these nutrients cause diverse problems such as toxic algal blooms, loss of oxygen, fish kills, loss of biodiversity (including species important for commerce and recreation), loss of aquatic plant beds and coral reefs, and other problems. Nutrient enrichment seriously degrades aquatic ecosystems and impairs the use of water for drinking, industry, agriculture, recreation, and other purposes. Based on our review of the scientific literature, we are certain that (1) eutrophication is a widespread problem in rivers, lakes, estuaries, and coastal oceans, caused by overenrichment with P and N; (2) nonpoint pollution, a major source of P and N to surface waters of the United States, results primarily from agriculture and urban activity, including industry; (3) inputs of P and N to agriculture in the form of fertilizers exceed outputs in produce in the United States and many other nations; (4) nutrient flows to aquatic ecosystems are directly related to animal stocking densities, and under high livestock densities, manure production exceeds the needs of crops to which the manure is applied; (5) excess fertilization and manure production cause a P surplus to accumulate in soil, some of which is transported to aquatic ecosystems; and (6) excess fertilization and manure production on agricultural lands create surplus N, which is mobile in many soils and often leaches to downstream aquatic ecosystems, and which can also volatilize to the atmosphere, redepositing elsewhere and eventually reaching aquatic ecosystems. If current practices continue, nonpoint pollution of surface waters is virtually certain to increase in the future. Such an outcome is not inevitable, however, because a number of technologies, land use practices, and conservation measures are capable of decreasing the flow of nonpoint P and N into surface waters. From our review of the available scientific information, we are confident that: (1) nonpoint pollution of surface waters with P and N could be reduced by reducing surplus nutrient flows in agricultural systems and processes, reducing agricultural and urban runoff by diverse methods, and reducing N emissions from fossil fuel burning; and (2) eutrophication can be reversed by decreasing input rates of P and N to aquatic ecosystems, but rates of recovery are highly variable among water bodies. Often, the eutrophic state is persistent, and recovery is slow.

5,662 citations

Journal ArticleDOI
TL;DR: In this paper, the authors compared the natural and anthropogenic controls on the conversion of unreactive N2 to more reactive forms of nitrogen (Nr) and found that human activities increasingly dominate the N budget at the global and at most regional scales, and the terrestrial and open ocean N budgets are essentially dis-connected.
Abstract: This paper contrasts the natural and anthropogenic controls on the conversion of unreactive N2 to more reactive forms of nitrogen (Nr). A variety of data sets are used to construct global N budgets for 1860 and the early 1990s and to make projections for the global N budget in 2050. Regional N budgets for Asia, North America, and other major regions for the early 1990s, as well as the marine N budget, are presented to highlight the dominant fluxes of nitrogen in each region. Important findings are that human activities increasingly dominate the N budget at the global and at most regional scales, the terrestrial and open ocean N budgets are essentially dis- connected, and the fixed forms of N are accumulating in most environmental reservoirs. The largest uncertainties in our understanding of the N budget at most scales are the rates of natural biological nitrogen fixation, the amount of Nr storage in most environmental reservoirs, and the production rates of N2 by denitrification.

4,555 citations

Journal ArticleDOI
TL;DR: Pore water profiles of total CO 2, pH, PO 3−4, NO − 3 plus NO − 2, SO 2− 4, S 2−, Fe 2+ and Mn 2+ have been obtained in cores from pelagic sediments of the eastern equatorial Atlantic under waters of moderate to high productivity as mentioned in this paper.

3,045 citations