scholarly journals Using stable isotopes as tracers of water masses and nutrient cycling processes in the Gulf of Maine

2020 ◽  
Vol 206 ◽  
pp. 104210
Author(s):  
Nina M. Whitney ◽  
Alan D. Wanamaker ◽  
Megan E. Switzer ◽  
Neal R. Pettigrew
Keyword(s):  
Stable Isotopes ◽  
Nutrient Cycling ◽  
Gulf Of Maine ◽  
Water Masses

scholarly journals Tracing subarctic Pacific water masses with benthic foraminiferal stable isotopes during the LGM and late Pleistocene

2016 ◽  
Vol 125-126 ◽  
pp. 84-95 ◽  
Author(s):  
Mea S. Cook ◽  
A. Christina Ravelo ◽  
Alan Mix ◽  
Ian M. Nesbitt ◽  
Nari V. Miller
Keyword(s):  
Stable Isotopes ◽  
Late Pleistocene ◽  
Water Masses ◽  
Pacific Water ◽  
Subarctic Pacific

scholarly journals Water masses and nutrient sources to the Gulf of Maine

2015 ◽  
Vol 73 (3) ◽  
pp. 93-122 ◽  
Author(s):  
David W. Townsend ◽  
Neal R. Pettigrew ◽  
Maura A. Thomas ◽  
Mark G. Neary ◽  
Dennis J. McGillicuddy ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Deep Water ◽  
Gulf Of Maine ◽  
Volume Transport ◽  
Water Masses ◽  
Scotian Shelf ◽  
Nutrient Sources ◽  
The North ◽  
Freshwater Fluxes ◽  
The North Atlantic Oscillation

The Gulf of Maine, a semienclosed basin on the continental shelf of the northwest Atlantic Ocean, is fed by surface and deep water flows from outside the gulf: Scotian Shelf Water (SSW) from the Nova Scotian shelf that enters the gulf at the surface and slope water that enters at depth and along the bottom through the Northeast Channel. There are two distinct types of slope water, Labrador Slope Water (LSW) and Warm Slope Water (WSW); it is these deep water masses that are the major source of dissolved inorganic nutrients to the gulf. It has been known for some time that the volume inflow of slope waters of either type to the Gulf of Maine is variable, that it covaries with the magnitude of inflowing SSW, and that periods of greater inflows of SSW have become more frequent in recent years, accompanied by reduced slope water inflows. We present here analyses of a 10-year record of data collected by moored sensors in Jordan Basin in the interior Gulf of Maine, and in the Northeast Channel, along with recent and historical hydrographic and nutrient data that help reveal the nature of SSW and slope water inflows. We show that proportional inflows of nutrient-rich slope waters and nutrient-poor SSWs alternate episodically with one another on timescales of months to several years, creating a variable nutrient field on which the biological productivities of the Gulf of Maine and Georges Bank depend. Unlike decades past, more recent inflows of slope waters of either type do not appear to be correlated with the North Atlantic Oscillation (NAO), which had been shown earlier to influence the relative proportions of the two types of slope waters that enter the gulf, WSW and LSW. We suggest that of greater importance than the NAO in recent years are recent increases in freshwater fluxes to the Labrador Sea, which may intensify the volume transport of the inshore, continental shelf limb of the Labrador Current and its continuation as the Nova Scotia Current. The result is more frequent, episodic influxes of colder, fresher, less dense, and low-nutrient SSW into the Gulf of Maine and concomitant reductions in the inflow of deep, nutrient-rich slope waters. We also discuss evidence that modified Gulf Stream ring water may have penetrated to Jordan Basin in the summer of 2013.

Overview of nutrient cycling in the sub-Arctic Atlantic regions: insights from nitrate & silicon isotopes

2021 ◽  
Author(s):  
Margot Debyser ◽  
Robyn Tuerena ◽  
Raja Ganeshram ◽  
Laetitia Pichevin
Keyword(s):  
Stable Isotopes ◽  
Nutrient Cycling ◽  
Primary Production ◽  
Silicic Acid ◽  
North Atlantic ◽  
Nutrient Budget ◽  
The Arctic ◽  
Silicon Isotopes ◽  
The North ◽  
The North Atlantic

<p>The environmental consequences of rapid climate change are already becoming apparent in the Arctic. Polar amplification has led to major loss of sea ice, increasing freshwater run-off and a poleward intrusion of Atlantic waters, thereby affecting biogeochemical cycles. Additionally, while primary production in the Arctic has increased by >50% over the last two decades (Lewis et al., 2020), it is still unclear whether Arctic nutrient budgets can sustain this increase on the long-term. Increased primary production in the central Arctic has the potential to reduce nutrient concentrations of Arctic outflow waters and modify their nutrient ratios, having consequences for the Atlantic nutrient budget.</p><p>Primary production in the Arctic is principally nitrogen-limited as a result of benthic denitrification on Arctic shelves. This is contrasted by silicon limitation in water masses originating from the Atlantic basin. To untangle the complexities of dual nutrient limitation and to gain insights into the role of Arctic outflows in controlling nutrient export to the North Atlantic, we examine the cycling of both major nutrients, nitrate and silicic acid, in key Arctic seas and straits. Using stable isotopes of dissolved nitrate and silicic acid, we provide new insights into the  mechanisms and factors that control nutrient cycling in the Arctic Ocean: nutrient origins, transformation during transport, as well as the relative contribution of primary production, remineralisation and regeneration to water column inventories.</p><p>In this study, measurements of nutrient stoichiometry and stable isotopes of dissolved nitrate and silicic acid profiles are presented across the Fram Strait, Labrador Sea (AR7W transect), and the Iceland Basin and Irminger Sea (the Extended Ellett line and the OSNAP-East program). The measured variability in nutrient isotope signatures across the Arctic gateways brings to light the contribution of Arctic-sourced freshwater to the North Atlantic and its potential impact to the North Atlantic nutrient budget with future changes to primary production in these key regions.</p>

Nutrient cycling in a tropical montane rainforest under a supply-limited weathering regime traced by elemental mass balances and Mg stable isotopes

2018 ◽  
Vol 497 ◽  
pp. 74-87 ◽  
Author(s):  
Jan A. Schuessler ◽  
Friedhelm von Blanckenburg ◽  
Julien Bouchez ◽  
David Uhlig ◽  
Tilak Hewawasam
Keyword(s):  
Stable Isotopes ◽  
Nutrient Cycling ◽  
Mass Balances ◽  
Elemental Mass ◽  
Montane Rainforest ◽  
Tropical Montane Rainforest
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