High‐frequency forward scattering from the arctic canopy: Experiment and high‐frequency modeling

1994 ◽  
Vol 96 (5) ◽  
pp. 2956-2964 ◽  
Author(s):  
K. L. Williams ◽  
D. E. Funk
Keyword(s):  
High Frequency ◽  
Forward Scattering ◽  
The Arctic

Lena River biogeochemistry resolved by a high frequency monitoring: comparing a wet and a dry year

2021 ◽  
Author(s):  
Bennet Juhls ◽  
Anne Morgenstern ◽  
Pier Paul Overduin
Keyword(s):  
Organic Carbon ◽  
High Frequency ◽  
Monitoring Program ◽  
The Arctic ◽  
Lena River ◽  
O Isotopes ◽  
The Arctic Ocean ◽  
Frequency Monitoring ◽  
Biogeochemical Parameters ◽  
Doc Flux

<p>River biogeochemistry at any location integrates environmental processes over a definable upstream area of the river watershed. Therefore, biogeochemical parameters of river water are powerful indicators of the climate change impact on the entire watershed and smaller parts of it.</p><p>The current warming of the Siberian Arctic is changing atmospheric forcing, precipitation, subsurface water storage, and runoff from rivers to the Arctic Ocean. A number of studies predict an increase of organic carbon export by rivers into the Arctic Ocean with further warming of the Arctic. Major potential drivers for this increase are the rise of river discharge and permafrost thaw, which mobilizes organic matter.</p><p>Here, we present results of high frequency monitoring program of the Lena River waters in the central part of its delta at the Laptev Sea. For the first time, a number of biogeochemical parameters such as dissolved organic carbon (DOC), coloured dissolved organic matter, electrical conductivity, temperature, and d<sup>18</sup>O isotopes were measured at an interval of every few days throughout the entire season. Currently, the data set comprises two complete years from the spring 2018 until the spring 2020, which were characterized by extremely high and low summer discharges, respectively. While 2018 to 2019 was the fourth highest on record from 1936 to present, resulting in an annual DOC flux of 6.8 Tg C yr<sup>-1</sup>, 2019 was the sixth lowest discharge year with a significantly lower DOC flux of 4.5 Tg C yr<sup>-1</sup>. Endmember analysis using electrical conductivity and d<sup>18</sup>O isotopes showed that rainwater transported less DOC in 2019 (1.5 Tg C) than in 2018 (2.9 Tg C) although the winter base flow and the snow and ice meltwater transported similar amounts.</p><p>The biogeochemical response of the Lena River water provides us with new insights into the catchment processes, including permafrost thaw and potential mobilization of previously frozen organic carbon. Our new monitoring program will serve 1) as a baseline to measure future changes and 2) as a training dataset to project changes under future climate scenarios.</p>

scholarly journals Towards improving the physical basis for ice-dynamics models

1997 ◽  
Vol 25 ◽  
pp. 177-182 ◽  
Author(s):  
J. A. Richter-Menge
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
The Arctic ◽  
Frequency Content ◽  
Ice Dynamics ◽  
Relative Significance ◽  
Thermally Induced ◽  
Induced Stress ◽  
Dynamics Models

In situ measurements of ice stress were made on a multi-year floe in the Alaskan Beaufort Sea over a 6 month period, beginning in October 1993. The data suggest that, in this region of the Arctic during this experiment, there were two main sources of stress: a thermally induced stress caused by changes in air temperature, and a stress generated by ice motion. Due to the natural damping of the snow and ice above the sensor, the thermally-induced stresses are low frequency (order of days). Stresses associated with periods of ice motion have both a high-frequency (order of hours), and low-frequency, content. The relative significance of these sources of stress is seasonal, reflecting the changes in the strength and continuity of the pack.

High‐frequency acoustic variability in the Arctic

1985 ◽  
Vol 77 (2) ◽  
pp. 465-481 ◽  
Author(s):  
M. Schulkin ◽  
G. R. Garrison ◽  
T. Wen
Keyword(s):  
High Frequency ◽  
The Arctic ◽  
Acoustic Variability

Experimental demonstration of a high-frequency forward scattering acoustic barrier in a dynamic coastal environment

2010 ◽  
Vol 127 (6) ◽  
pp. 3430-3439 ◽  
Author(s):  
Karim G. Sabra ◽  
Stephane Conti ◽  
Philippe Roux ◽  
Tuncay Akal ◽  
William A. Kuperman ◽  
...  
Keyword(s):  
High Frequency ◽  
Coastal Environment ◽  
Forward Scattering ◽  
Experimental Demonstration

scholarly journals Narwhals react to ship noise and airgun pulses embedded in background noise

2021 ◽  
Vol 17 (11) ◽  
Author(s):  
Outi M. Tervo ◽  
Susanna B. Blackwell ◽  
Susanne Ditlevsen ◽  
Alexander S. Conrad ◽  
Adeline L. Samson ◽  
...  
Keyword(s):  
High Frequency ◽  
Background Noise ◽  
Site Fidelity ◽  
Anthropogenic Activities ◽  
The Arctic ◽  
Exposure Study ◽  
Sound Exposure ◽  
Monodon Monoceros ◽  
Exposure Levels ◽  
Extreme Sensitivity

Anthropogenic activities are increasing in the Arctic, posing a threat to niche-conservative species with high seasonal site fidelity, such as the narwhal Monodon monoceros . In this controlled sound exposure study, six narwhals were live-captured and instrumented with animal-borne tags providing movement and behavioural data, and exposed to concurrent ship noise and airgun pulses. All narwhals reacted to sound exposure with reduced buzzing rates, where the response was dependent on the magnitude of exposure defined as 1/distance to ship. Buzzing rate was halved at 12 km from the ship, and whales ceased foraging at 7–8 km. Effects of exposure could be detected at distances > 40 km from the ship.At only a few kilometres from the ship, the received high-frequency cetacean weighted sound exposure levels were below background noise indicating extreme sensitivity of narwhals towards sound disturbance and demonstrating their ability to detect signals embedded in background noise. The narwhal's reactions to sustained disturbance may have a plethora of consequences both at individual and population levels. The observed reactions of the whales demonstrate their auditory sensitivity but also emphasize, that anthropogenic activities in pristine narwhal habitats needs to be managed carefully if healthy narwhal populations are to be maintained.

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