![]() N and P drawdown events during December-March are influenced by the winter and spring Southern Annular Mode (SAM) phase, where nutrient utilization is enhanced in a stabilized upper water column as a consequence of SAM-driven winter sea ice and spring wind dynamics. These different drawdown patterns are shaped by different sets of physical and climate forcing mechanisms. Si EOF2 captures a drawdown event during November-December, which is correlated to Chl EOF2. The second most common seasonal patterns of nitrate and phosphate (N and P EOF2) capture prolonged drawdown events during December-March, which are correlated to Chl EOF1. The leading modes of nutrients (N, P, and Si empirical orthogonal functions 1, EOF1) represent overall negative anomalies throughout growing seasons, showing a mixed signal of variability in the initial levels and drawdown thereafter (low-frequency dynamics). We analyzed 20 years (1993-2013) of observations of dissolved inorganic macronutrients (nitrate, N phosphate, P and silicate, Si) and chlorophyll a (Chl) at Palmer Station, Antarctica (64.8°S, 64.1°W) to elucidate how large-scale climate and local physical forcing affect the interannual variability in the seasonal phytoplankton bloom and associated drawdown of nutrients. By measuring the received waveform at multiple distant sites around the globe, we can pinpoint the source lightning location, compare the changes in field strength and spectrum as a function of distance from the source, and evaluate modal propagation effects in the VLF range (that are not apparent in the ELF range).Ĭlimate forcing for dynamics of dissolved inorganic nutrients at Palmer Station, Antarctica: An interdecadal (1993-2013) analysis The ELF and VLF waves excited by the lightning discharge propagate to great distances in the earth-ionosphere waveguide, and in fact propagate around the Earth multiple times. These powerful lightning discharges are likely responsible for a significant level of energetic coupling between the troposphere, the ionosphere, and the magnetosphere. The Q-burst is characterized by a large increase in amplitude above the background at the Schumann Resonance modes and is believed to result from especially powerful cloud-to-ground lightning discharges. As a result, using this multi-site global network of ELF/VLF receivers, we are able to easily detect a particular type of ELF transient that propagates around the world multiple times, known as the Q-burst. Such remote locations afford the unique opportunity to record signals that are essentially unperturbed by power line noise. We present the first analysis of data from the recently deployed broadband ELF (5-500 Hz) B-field receiver at Palmer Station, Antarctica together with observations at similar receivers located at Sondrestromfjord, Greenland and Arrival Heights, Antarctica. In this paper, we compare and contrast the onset times and durations calculated using multiple different methods, with each method applied to the same 22 conjugate LEP events.ĮLF Transients and Q-bursts Detected Around the Globe: First results from Palmer Station, Antarctica The onset times and onset durations can be calculated using a number of different methods, however. In each case, the GLD360 dataset from Vaisala is used to determine the hemisphere of the causative lightning flash, and this is compared with the hemisphere in which the LEP event is detected first. In the southern hemisphere, the NPM transmitter signal (21.4 kHz, Laulaulei, Hawii) is tracked at Palmer station, Antarctica. ![]() LEP events were detected in the northern hemisphere using the VLF remote sensing method by tracking the NAA transmitter signal (24.0 kHz, Cutler, Maine) at Tuscaloosa, Alabama. ![]() After removing overlapping events and unclear (or not well-defined) events, 22 conjugate LEP events remain and are used to statistically analyze the hemispheric dependence of LEP onset time. Conjugate LEP Events at Palmer Station, Antarctica: Hemisphere-Dependent Timingĭuring March 2015, a large number of lightning-induced electron precipitation (LEP) events were simultaneously observed using very low frequency receivers in both the northern and southern hemispheres.
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