Remote sensing observations of ocean physical and biological properties in the region of the Southern Ocean Iron Experiment (SOFeX)

Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 111 (2006): C06026, doi:10.1029/2005JC003289.Satellite remote sensing estimates of surface chlorophyll, temperature, wind speed, and sea ice cover are examined in the region of the Southern Ocean Iron Experiment (SOFeX). Our objectives are to place SOFeX into a regional context and highlight regional mesoscale spatial and monthly temporal variability. SOFeX fertilized two patches with iron, one south of the Antarctic Polar front (PF) and one north of the PF but south of the Subantarctic Front (SAF). Satellite observable phytoplankton blooms developed in both patches. The spring sea-ice retreat near the south patch site was delayed in the 2001-2002 season, in turn delaying the naturally occurring, modest spring bloom in this region. Ambient surface chlorophyll concentrations for the area surrounding the southern patch during January 2002 are low (mean 0.26 mg/m3) compared with climatological January values (0.42 mg/m3). Regions east and west at similar latitudes exhibited higher mean chlorophyll concentrations (0.79 and 0.74 mg/m3, respectively). These modest phytoplankton blooms were likely stimulated by melting sea-ice via changes in the light-mixing regime and release of iron, and were smaller in magnitude than the iron-induced bloom within the SOFeX southern patch (> 3 mg/m3). Iron inputs from melting ice may drive much of the natural spatial and temporal variability within the seasonal ice zone. Mean chlorophyll concentrations surrounding the SOFeX northern patch site were similar to climatological values during the SOFeX season. The northern patch was stretched into a long, thin filament along the southern boundary of the SAF, likely increasing the mixing/dilution rate with surrounding waters.S. Doney and K. Moore were supported by NASA grant NAG5-12520 from the NASA Ocean Biogeochemistry Program

NASA ION (Interplanetary Overlay Network) Developer Course Materials

The Delay/Disruption Tolerant Networking Project created open-source software, the Interplanetary Overlay Network (ION), as an implementation of the Bundle Protocol. To aid users in understanding the architecture of ION and how best to use it, the DTN Project developed a course

A Critical Race Analysis of the Hiring Process for Head Coaches in NCAA College Football

In this article, we respond to Singer’s (2005) challenge to sport management scholars to consider race-based epistemologies in conducting certain kinds of research in the field, as we use critical race theory (CRT) as a framework to analyze the Black Coaches & Administrators (BCA) Hiring Report Card (HRC) (Harrison & Yee, 2009). The BCA HRC was created as a result of the access discrimination that has historically taken place in college sport (Brooks & Althouse, 2000; Cunningham & Sagas, 2005), which has consequently contributed to the under-representation of racial minorities in the head coach position in college football. The HRC places the hiring process of predominantly white institutions of higher education (PWIHE) under public scrutiny, with the ultimate goal of changing the decision-making process when these institutions hire head football coaches. This article utilizes CRT to support and justify the conception of the HRC, and also applies CRT principles to the five grading criteria of the HRC as a way to better understand what has been occurring in the hiring process for head football coaches at PWIHE. Implications for research and practice related to the head coach hiring process in college football are discussed

A Reinforcement Learning Based Control Approach for Propofol-Induced Burst Suppression

High-dose propofol is being investigated for its potential antidepressant effect. Propofol is titrated to induce burst suppression, a specific EEG pattern. However, propofol is difficult to dose due to uncertainty in each patient’s pharmacokinetics (PK) and pharmacodynamics (PD), and the lack of a commercially available monitor of propofol concentration. Clinicians currently infer the proper drug dose after observing the EEG response to the given dose. In this report we share our development of an automated controller to optimally administer propofol-induced burst suppression. We designed a deep deterministic policy gradient (DDPG) algorithm, which includes two deep neural networks and relates a 2-dimensional action space with a 3-dimensional state space. Our DDPG prototype did not satisfy our minimum training criteria. However, we share our diagnosis of current limitations in training a DDPG-based RL agent to administer propofol to PK-PD-simulated in silico patients. We also discuss potential solutions to improve RL agent training and performance

Variability in the mechanisms controlling Southern Ocean phytoplankton bloom phenology in an ocean model and satellite observations

Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 31 (2017): 922–940, doi:10.1002/2016GB005615.A coupled global numerical simulation (conducted with the Community Earth System Model) is used in conjunction with satellite remote sensing observations to examine the role of top-down (grazing pressure) and bottom-up (light, nutrients) controls on marine phytoplankton bloom dynamics in the Southern Ocean. Phytoplankton seasonal phenology is evaluated in the context of the recently proposed “disturbance-recovery” hypothesis relative to more traditional, exclusively “bottom-up” frameworks. All blooms occur when phytoplankton division rates exceed loss rates to permit sustained net population growth; however, the nature of this decoupling period varies regionally in Community Earth System Model. Regional case studies illustrate how unique pathways allow blooms to emerge despite very poor division rates or very strong grazing rates. In the Subantarctic, southeast Pacific small spring blooms initiate early cooccurring with deep mixing and low division rates, consistent with the disturbance-recovery hypothesis. Similar systematics are present in the Subantarctic, southwest Atlantic during the spring but are eclipsed by a subsequent, larger summer bloom that is coincident with shallow mixing and the annual maximum in division rates, consistent with a bottom-up, light limited framework. In the model simulation, increased iron stress prevents a similar summer bloom in the southeast Pacific. In the simulated Antarctic zone (70°S–65°S) seasonal sea ice acts as a dominant phytoplankton-zooplankton decoupling agent, triggering a delayed but substantial bloom as ice recedes. Satellite ocean color remote sensing and ocean physical reanalysis products do not precisely match model-predicted phenology, but observed patterns do indicate regional variability in mechanism across the Atlantic and Pacific.NDSEG Graduate Fellowship; National Aeronautics and Space Administration Ocean Biology and Biogeochemistry Program Grant Number: NNX14L86G; NSF Poloar Programs Award Grant Number: 1440435; National Aeronautics and Space Administration Grant Number: NNX14AL86G; NDSEG; National Science Foundation Grant Number: 14404352017-11-3

Natural variability in a stable, 1000-yr global coupled climate-carbon cycle simulation

Author Posting. © American Meteorological Society 2006. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 19 (2006): 3033–3054, doi:10.1175/JCLI3783.1.A new 3D global coupled carbon–climate model is presented in the framework of the Community Climate System Model (CSM-1.4). The biogeochemical module includes explicit land water–carbon coupling, dynamic carbon allocation to leaf, root, and wood, prognostic leaf phenology, multiple soil and detrital carbon pools, oceanic iron limitation, a full ocean iron cycle, and 3D atmospheric CO2 transport. A sequential spinup strategy is utilized to minimize the coupling shock and drifts in land and ocean carbon inventories. A stable, 1000-yr control simulation [global annual mean surface temperature ±0.10 K and atmospheric CO2 ± 1.2 ppm (1σ)] is presented with no flux adjustment in either physics or biogeochemistry. The control simulation compares reasonably well against observations for key annual mean and seasonal carbon cycle metrics; regional biases in coupled model physics, however, propagate clearly into biogeochemical error patterns. Simulated interannual-to-centennial variability in atmospheric CO2 is dominated by terrestrial carbon flux variability, ±0.69 Pg C yr−1 (1σ global net annual mean), which in turn reflects primarily regional changes in net primary production modulated by moisture stress. Power spectra of global CO2 fluxes are white on time scales beyond a few years, and thus most of the variance is concentrated at high frequencies (time scale 20 yr), global net ocean CO2 flux is strongly anticorrelated (0.7–0.95) with the net CO2 flux from land; the ocean tends to damp (20%–25%) slow variations in atmospheric CO2 generated by the terrestrial biosphere. The intrinsic, unforced natural variability in land and ocean carbon storage is the “noise” that complicates the detection and mechanistic attribution of contemporary anthropogenic carbon sinks.This work was supported by NCAR, NSF ATM-9987457, NASA EOS-IDS Grant NAG5-9514, NASA Carbon Cycle Program Grant NAG5-11200, Lawrence Berkeley National Laboratory LDRD, and the WHOI Ocean and Climate Change Institute