Jayne Steven R.

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Jayne

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Steven R.

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0000-0001-7999-0147

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Corrigendum to “Formation and erosion of the seasonal thermocline in the Kuroshio Extension Recirculation gyre” [Deep-Sea Res. II 85 (2013) 62–74]

(Elsevier, 2016-08-08) Cronin, Meghan F. ; Bond, Nicholas A. ; Farrar, J. Thomas ; Ichikawa, Hiroshi ; Jayne, Steven R. ; Kawai, Yoshimi ; Konda, Masanori ; Qiu, Bo ; Rainville, Luc ; Tomita, Hiroyuki
The interaction of recirculation gyres and a deep boundary current

(American Meteorological Society, 2018-03-06) Le Bras, Isabela A. ; Jayne, Steven R. ; Toole, John M.

Motivated by the proximity of the Northern Recirculation Gyre and the deep western boundary current in the North Atlantic, an idealized model is used to investigate how recirculation gyres and a deep flow along a topographic slope interact. In this two-layer quasigeostrophic model, an unstable jet imposed in the upper layer generates barotropic recirculation gyres. These are maintained by an eddy-mean balance of potential vorticity (PV) in steady state. The authors show that the topographic slope can constrain the northern recirculation gyre meridionally and that the gyre’s adjustment to the slope leads to increased eddy PV fluxes at the base of the slope. When a deep current is present along the topographic slope in the lower layer, these eddy PV fluxes stir the deep current and recirculation gyre waters. Increased proximity to the slope dampens the eddy growth rate within the unstable jet, altering the geometry of recirculation gyre forcing and leading to a decrease in overall eddy PV fluxes. These mechanisms may shape the circulation in the western North Atlantic, with potential feedbacks on the climate system.
The Kuroshio Extension and its recirculation gyres

( 2009-07-01) Jayne, Steven R. ; Hogg, Nelson G. ; Waterman, Stephanie N. ; Rainville, Luc ; Donohue, Kathleen A. ; Watts, D. Randolph ; Tracey, Karen L. ; McClean, Julie L. ; Maltrud, Mathew E. ; Qiu, Bo ; Chen, Shuiming ; Hacker, Peter

This paper reports on the strength and structure of the Kuroshio Extension and its recirculation gyres. In the time average, quasi-permanent recirculation gyres are found to the north and south of the Kuroshio Extension jet. The characteristics of recirculation gyres are determined from the combined observations from the Kuroshio Extension System Study (KESS) field program program (June 2004 – June 2006) and include current meters, pressure and current recording inverted echo sounders, and sub-surface floats. The position and strength of the recirculation gyres simulated by a high-resolution numerical model are found to be consistent with the observations. The circulation pattern that is revealed is of a complex system of multiple recirculation gyres that are embedded in the crests and troughs of the quasi-permanent meanders of the Kuroshio Extension. At the location of the KESS array, the Kuroshio Extension jet and its recirculation gyres transport of about 114 Sv. This represents a 2.7-fold increase in the transport of the current compared to the Kuroshio’s transport at Cape Ashizuri before it separates from the coast and flows eastward into the open ocean. This enhancement in the current’s transport comes from the development of the flanking recirculation gyres. Estimates from an array of inverted echo sounders and a high-resolution ocean general circulation model are of similar magnitude.
Eddy–mean flow interaction in the Kuroshio Extension region

(American Meteorological Society, 2011-06) Waterman, Stephanie N. ; Hogg, Nelson G. ; Jayne, Steven R.

The authors use data collected by a line of tall current meter moorings deployed across the axis of the Kuroshio Extension (KE) jet at the location of maximum time-mean eddy kinetic energy to characterize the mean jet structure, the eddy variability, and the nature of eddy–mean flow interactions observed during the Kuroshio Extension System Study (KESS). A picture of the 2-yr record mean jet structure is presented in both geographical and stream coordinates, revealing important contrasts in jet strength, width, vertical structure, and flanking recirculation structure. Eddy variability observed is discussed in the context of some of its various sources: jet meandering, rings, waves, and jet instability. Finally, various scenarios for eddy–mean flow interaction consistent with the observations are explored. It is shown that the observed cross-jet distributions of Reynolds stresses at the KESS location are consistent with wave radiation away from the jet, with the sense of the eddy feedback effect on the mean consistent with eddy driving of the observed recirculations. The authors consider these results in the context of a broader description of eddy–mean flow interactions in the larger KE region using KESS data in combination with in situ measurements from past programs in the region and satellite altimetry. This demonstrates important consistencies in the along-stream development of time-mean and eddy properties in the KE with features of an idealized model of a western boundary current (WBC) jet used to understand the nature and importance of eddy–mean flow interactions in WBC jet systems.
Targeted ocean sampling guidance for tropical cyclones

(John Wiley & Sons, 2017-05-13) Chen, Sue ; Cummings, James A. ; Schmidt, Jerome M. ; Sanabia, Elizabeth ; Jayne, Steven R.

A 3-D variational ocean data assimilation adjoint approach is used to examine the impact of ocean observations on coupled tropical cyclone (TC) model forecast error for three recent hurricanes: Isaac (2012), Hilda (2015), and Matthew (2016). In addition, this methodology is applied to develop an innovative ocean observation targeting tool validated using TC model simulations that assimilate ocean temperature observed by Airborne eXpendable Bathy Thermographs and Air-Launched Autonomous Micro-Observer floats. Comparison between the simulated targeted and real observation data assimilation impacts reveals a positive maximum mean linear correlation of 0.53 at 400–500 m, which implies some skill in the targeting application. Targeted ocean observation regions from these three hurricanes, however, show that the largest positive impacts in reducing the TC model forecast errors are sensitive to the initial prestorm ocean conditions such as the location and magnitude of preexisting ocean eddies, storm-induced ocean cold wake, and model track errors.
Autonomous and Lagrangian ocean observations for Atlantic tropical cyclone studies and forecasts

(Oceanography Society, 2017-06) Goni, Gustavo J. ; Todd, Robert E. ; Jayne, Steven R. ; Halliwell, George R. ; Glenn, Scott ; Dong, Jili ; Curry, Ruth G. ; Domingues, Ricardo ; Bringas, Francis ; Centurioni, Luca R. ; DiMarco, Steven F. ; Miles, Travis ; Morell, Julio M. ; Pomales, Luis ; Kim, Hyun-Sook ; Robbins, Pelle E. ; Gawarkiewicz, Glen G. ; Wilkin, John L. ; Heiderich, Joleen ; Baltes, Rebecca ; Cione, Joseph J. ; Seroka, Greg ; Knee, Kelly ; Sanabia, Elizabeth

The tropical Atlantic basin is one of seven global regions where tropical cyclones (TCs) commonly originate, intensify, and affect highly populated coastal areas. Under appropriate atmospheric conditions, TC intensification can be linked to upper-ocean properties. Errors in Atlantic TC intensification forecasts have not been significantly reduced during the last 25 years. The combined use of in situ and satellite observations, particularly of temperature and salinity ahead of TCs, has the potential to improve the representation of the ocean, more accurately initialize hurricane intensity forecast models, and identify areas where TCs may intensify. However, a sustained in situ ocean observing system in the tropical North Atlantic Ocean and Caribbean Sea dedicated to measuring subsurface temperature, salinity, and density fields in support of TC intensity studies and forecasts has yet to be designed and implemented. Autonomous and Lagrangian platforms and sensors offer cost-effective opportunities to accomplish this objective. Here, we highlight recent efforts to use autonomous platforms and sensors, including surface drifters, profiling floats, underwater gliders, and dropsondes, to better understand air-sea processes during high-wind events, particularly those geared toward improving hurricane intensity forecasts. Real-time data availability is key for assimilation into numerical weather forecast models.
The air-launched autonomous micro observer

(American Meteorological Society, 2022-04-01) Jayne, Steven R. ; Owens, W. Brechner ; Robbins, Pelle E. ; Ekholm, Alexander K. ; Bogue, Neil M. ; Sanabia, Elizabeth

The Air-Launched Autonomous Micro Observer (ALAMO) is a versatile profiling float that can be launched from an aircraft to make temperature and salinity observations of the upper ocean for over a year with high temporal sampling. Similar in dimensions and weight to an airborne expendable bathythermograph (AXBT), but with the same capability as Argo profiling floats, ALAMOs can be deployed from an A-sized (sonobuoy) launch tube, the stern ramp of a cargo plane, or the door of a small aircraft. Unlike an AXBT, however, the ALAMO float directly measures pressure, can incorporate additional sensors, and is capable of performing hundreds of ocean profiles compared to the single temperature profile provided by an AXBT. Upon deployment, the float parachutes to the ocean, releases the air-deployment package, and immediately begins profiling. Ocean profile data along with position and engineering information are transmitted via the Iridium satellite network, automatically processed, and then distributed by the Global Telecommunications System for use by the operational forecasting community. The ALAMO profiling mission can be modified using the two-way Iridium communications to change the profiling frequency and depth. Example observations are included to demonstrate the ALAMO’s utility.
The impact of abyssal mixing parameterizations in an ocean general circulation model

(American Meteorological Society, 2009-07) Jayne, Steven R.

A parameterization of vertical diffusivity in ocean general circulation models has been implemented in the ocean model component of the Community Climate System Model (CCSM). The parameterization represents the dynamics of the mixing in the abyssal ocean arising from the breaking of internal waves generated by the tides forcing stratified flow over rough topography. This parameterization is explored over a range of parameters and compared to the more traditional ad hoc specification of the vertical diffusivity. Diapycnal mixing in the ocean is thought to be one of the primary controls on the meridional overturning circulation and the poleward heat transport by the ocean. When compared to the traditional approach with uniform mixing, the new mixing parameterization has a noticeable impact on the meridional overturning circulation; while the upper limb of the meridional overturning circulation appears to be only weakly impacted by the transition to the new parameterization, the deep meridional overturning circulation is significantly strengthened by the change. The poleward ocean heat transport does not appear to be strongly affected by the mixing in the abyssal ocean for reasonable parameter ranges. The transport of the Antarctic Circumpolar Current through the Drake Passage is related to the amount of mixing in the deep ocean. The new parameterization is found to be energetically consistent with the known constraints on the ocean energy budget.
The air-sea response during Hurricane Irma's (2017) rapid intensification over the Amazon-Orinoco River plume as measured by atmospheric and oceanic observations

(American Geophysical Union, 2020-06-12) Rudzin, Johna E. ; Chen, Sue ; Sanabia, Elizabeth ; Jayne, Steven R.

Hurricane Irma (2017) underwent rapid intensification (RI) while passing over the Amazon‐Orinoco River plume in the tropical Atlantic. The freshwater discharge from the plume creates a vertical salinity gradient that suppresses turbulent heat flux from the cool, ocean subsurface. The stability within the plume reduces sea surface temperature (SST) cooling and promotes energetic air‐sea fluxes. Hence, it is hypothesized that this ocean feature may have facilitated Irma's RI through favorable upper ocean conditions. This hypothesis is validated using a collection of atmospheric and oceanic observations to quantify how the ocean response influences surface flux and atmospheric boundary layer thermodynamics during Hurricane Irma's RI over the river plume. Novel aircraft‐deployed oceanic profiling floats highlight the detailed evolution of the ocean response during Irma's passage over the river plume. Analyses include quantifying the ocean response and identifying how it influenced atmospheric boundary layer temperature, moisture, and equivalent potential temperature (θE). An atmospheric boundary layer recovery analysis indicates that surface fluxes were sufficient to support the enhanced boundary layer θE (moist entropy) observed, which promotes inner‐core convection and facilitates TC intensification. The implicit influence of salinity stratification on Irma's intensity during RI is assessed using theoretical intensity frameworks. Overall, the findings suggest that the salinity stratification sustained SST during Irma's passage, which promoted energetic air‐sea fluxes that aided in boundary layer recovery and facilitated Irma's intensity during RI. Examination of the air‐sea coupling over this river plume, corresponding atmospheric boundary layer response, and feedback on TC intensity was previously absent in literature.
Radium-based estimates of cesium isotope transport and total direct ocean discharges from the Fukushima Nuclear Power Plant accident

(Copernicus Publications on behalf of the European Geosciences Union, 2013-03-28) Charette, Matthew A. ; Breier, Crystaline F. ; Henderson, Paul B. ; Pike, Steven M. ; Rypina, Irina I. ; Jayne, Steven R. ; Buesseler, Ken O.

Radium has four naturally occurring isotopes that have proven useful in constraining water mass source, age, and mixing rates in the coastal and open ocean. In this study, we used radium isotopes to determine the fate and flux of runoff-derived cesium from the Fukushima Dai-ichi Nuclear Power Plant (FNPP). During a June 2011 cruise, the highest cesium (Cs) concentrations were found along the eastern shelf of northern Japan, from Fukushima south, to the edge of the Kuroshio Current, and in an eddy ~ 130 km from the FNPP site. Locations with the highest cesium also had some of the highest radium activities, suggesting much of the direct ocean discharges of Cs remained in the coastal zone 2–3 months after the accident. We used a short-lived Ra isotope (223Ra, t1/2 = 11.4 d) to derive an average water mass age (Tr) in the coastal zone of 32 days. To ground-truth the Ra age model, we conducted a direct, station-by-station comparison of water mass ages with a numerical oceanographic model and found them to be in excellent agreement (model avg. Tr = 27 days). From these independent Tr values and the inventory of Cs within the water column at the time of our cruise, we were able to calculate an offshore 134Cs flux of 3.9–4.6 × 1013 Bq d−1. Radium-228 (t1/2 = 5.75 yr) was used to derive a vertical eddy diffusivity (Kz) of 0.7 m2 d−1 (0.1 cm2 s−1); from this Kz and 134Cs inventory, we estimated a 134Cs flux across the pycnocline of 1.8 × 104 Bq d−1 for the same time period. On average, our results show that horizontal mixing loss of Cs from the coastal zone was ~ 109 greater than vertical exchange below the surface mixed layer. Finally, a mixing/dilution model that utilized our Ra-based and oceanographic model water mass ages produced a direct ocean discharge of 134Cs from the FNPP of 11–16 PBq at the time of the peak release in early April 2011. Our results can be used to calculate discharge of other water-soluble radionuclides that were released to the ocean directly from the Fukushima NPP.
On the future of Argo: A global, full-depth, multi-disciplinary array

(Frontiers Media, 2019-08-02) Roemmich, Dean ; Alford, Matthew H. ; Claustre, Hervé ; Johnson, Kenneth S. ; King, Brian ; Moum, James N. ; Oke, Peter ; Owens, W. Brechner ; Pouliquen, Sylvie ; Purkey, Sarah G. ; Scanderbeg, Megan ; Suga, Koushirou ; Wijffels, Susan E. ; Zilberman, Nathalie ; Bakker, Dorothee ; Baringer, Molly O. ; Belbeoch, Mathieu ; Bittig, Henry C. ; Boss, Emmanuel S. ; Calil, Paulo H. R. ; Carse, Fiona ; Carval, Thierry ; Chai, Fei ; Conchubhair, Diarmuid Ó. ; d’Ortenzio, Fabrizio ; Dall'Olmo, Giorgio ; Desbruyeres, Damien ; Fennel, Katja ; Fer, Ilker ; Ferrari, Raffaele ; Forget, Gael ; Freeland, Howard ; Fujiki, Tetsuichi ; Gehlen, Marion ; Geenan, Blair ; Hallberg, Robert ; Hibiya, Toshiyuki ; Hosoda, Shigeki ; Jayne, Steven R. ; Jochum, Markus ; Johnson, Gregory C. ; Kang, KiRyong ; Kolodziejczyk, Nicolas ; Körtzinger, Arne ; Le Traon, Pierre-Yves ; Lenn, Yueng-Djern ; Maze, Guillaume ; Mork, Kjell Arne ; Morris, Tamaryn ; Nagai, Takeyoshi ; Nash, Jonathan D. ; Naveira Garabato, Alberto C. ; Olsen, Are ; Pattabhi Rama Rao, Eluri ; Prakash, Satya ; Riser, Stephen C. ; Schmechtig, Catherine ; Schmid, Claudia ; Shroyer, Emily L. ; Sterl, Andreas ; Sutton, Philip J. H. ; Talley, Lynne D. ; Tanhua, Toste ; Thierry, Virginie ; Thomalla, Sandy J. ; Toole, John M. ; Troisi, Ariel ; Trull, Thomas W. ; Turton, Jon ; Velez-Belchi, Pedro ; Walczowski, Waldemar ; Wang, Haili ; Wanninkhof, Rik ; Waterhouse, Amy F. ; Waterman, Stephanie N. ; Watson, Andrew J. ; Wilson, Cara ; Wong, Annie P. S. ; Xu, Jianping ; Yasuda, Ichiro

The Argo Program has been implemented and sustained for almost two decades, as a global array of about 4000 profiling floats. Argo provides continuous observations of ocean temperature and salinity versus pressure, from the sea surface to 2000 dbar. The successful installation of the Argo array and its innovative data management system arose opportunistically from the combination of great scientific need and technological innovation. Through the data system, Argo provides fundamental physical observations with broad societally-valuable applications, built on the cost-efficient and robust technologies of autonomous profiling floats. Following recent advances in platform and sensor technologies, even greater opportunity exists now than 20 years ago to (i) improve Argo’s global coverage and value beyond the original design, (ii) extend Argo to span the full ocean depth, (iii) add biogeochemical sensors for improved understanding of oceanic cycles of carbon, nutrients, and ecosystems, and (iv) consider experimental sensors that might be included in the future, for example to document the spatial and temporal patterns of ocean mixing. For Core Argo and each of these enhancements, the past, present, and future progression along a path from experimental deployments to regional pilot arrays to global implementation is described. The objective is to create a fully global, top-to-bottom, dynamically complete, and multidisciplinary Argo Program that will integrate seamlessly with satellite and with other in situ elements of the Global Ocean Observing System (Legler et al., 2015). The integrated system will deliver operational reanalysis and forecasting capability, and assessment of the state and variability of the climate system with respect to physical, biogeochemical, and ecosystems parameters. It will enable basic research of unprecedented breadth and magnitude, and a wealth of ocean-education and outreach opportunities.
The Arctic Ocean spices up

(American Meteorological Society, 2016-04-05) Timmermans, Mary-Louise ; Jayne, Steven R.

The contemporary Arctic Ocean differs markedly from midlatitude, ice-free, and relatively warm oceans in the context of density-compensating temperature and salinity variations. These variations are invaluable tracers in the midlatitudes, revealing essential fundamental physical processes of the oceans, on scales from millimeters to thousands of kilometers. However, in the cold Arctic Ocean, temperature variations have little effect on density, and a measure of density-compensating variations in temperature and salinity (i.e., spiciness) is not appropriate. In general, temperature is simply a passive tracer, which implies that most of the heat transported in the Arctic Ocean relies entirely on the ocean dynamics determined by the salinity field. It is shown, however, that as the Arctic Ocean warms up, temperature will take on a new role in setting dynamical balances. Under continued warming, there exists the possibility for a regime shift in the mechanisms by which heat is transported in the Arctic Ocean. This may result in a cap on the storage of deep-ocean heat, having profound implications for future predictions of Arctic sea ice.
Variations of the North Pacific Subtropical Mode Water from direct observations

(American Meteorological Society, 2014-04-15) Rainville, Luc ; Jayne, Steven R. ; Cronin, Meghan F.

Mooring measurements from the Kuroshio Extension System Study (June 2004–June 2006) and from the ongoing Kuroshio Extension Observatory (June 2004–present) are combined with float measurements of the Argo network to study the variability of the North Pacific Subtropical Mode Water (STMW) across the entire gyre, on time scales from days, to seasons, to a decade. The top of the STMW follows a seasonal cycle, although observations reveal that it primarily varies in discrete steps associated with episodic wind events. The variations of the STMW bottom depth are tightly related to the sea surface height (SSH), reflecting mesoscale eddies and large-scale variations of the Kuroshio Extension and recirculation gyre systems. Using the observed relationship between SSH and STMW, gridded SSH products and in situ estimates from floats are used to construct weekly maps of STMW thickness, providing nonbiased estimates of STMW total volume, annual formation and erosion volumes, and seasonal and interannual variability for the past decade. Year-to-year variations are detected, particularly a significant decrease of STMW volume in 2007–10 primarily attributable to a smaller volume formed. Variability of the heat content in the mode water region is dominated by the seasonal cycle and mesoscale eddies; there is only a weak link to STMW on interannual time scales, and no long-term trends in heat content and STMW thickness between 2002 and 2011 are detected. Weak lagged correlations among air–sea fluxes, oceanic heat content, and STMW thickness are found when averaged over the northwestern Pacific recirculation gyre region.
Ocean observations in support of studies and forecasts of tropical and extratropical cyclones

(Frontiers Media, 2019-07-29) Domingues, Ricardo ; Kuwano-Yoshida, Akira ; Chardon-Maldonado, Patricia ; Todd, Robert E. ; Halliwell, George R. ; Kim, Hyun-Sook ; Lin, I.-I. ; Sato, Katsufumi ; Narazaki, Tomoko ; Shay, Lynn Keith ; Miles, Travis ; Glenn, Scott ; Zhang, Jun A. ; Jayne, Steven R. ; Centurioni, Luca R. ; Le Hénaff, Matthieu ; Foltz, Gregory R. ; Bringas, Francis ; Ali, M. M. ; DiMarco, Steven F. ; Hosoda, Shigeki ; Fukuoka, Takuya ; LaCour, Benjamin ; Mehra, Avichal ; Sanabia, Elizabeth ; Gyakum, John R. ; Dong, Jili ; Knaff, John A. ; Goni, Gustavo J.

Over the past decade, measurements from the climate-oriented ocean observing system have been key to advancing the understanding of extreme weather events that originate and intensify over the ocean, such as tropical cyclones (TCs) and extratropical bomb cyclones (ECs). In order to foster further advancements to predict and better understand these extreme weather events, a need for a dedicated observing system component specifically to support studies and forecasts of TCs and ECs has been identified, but such a system has not yet been implemented. New technologies, pilot networks, targeted deployments of instruments, and state-of-the art coupled numerical models have enabled advances in research and forecast capabilities and illustrate a potential framework for future development. Here, applications and key results made possible by the different ocean observing efforts in support of studies and forecasts of TCs and ECs, as well as recent advances in observing technologies and strategies are reviewed. Then a vision and specific recommendations for the next decade are discussed.
Calibrated CTD measurements of salinity and oxygen and Niskin bottle water samples collected from the R/V Ka'imikai-o-Kanaloa KOK1108 cruise from June 5 to June 16, 2011 (Fukushima Radionuclide Levels project)

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2012-07-12) Jayne, Steven R. ; Buesseler, Ken O.

This Establishing Radionuclide Levels in the Atlantic and Pacific Oceans Originating from the Fukushima Daiichi Nuclear Power Facility (Fukushima Radionuclide Levels) Niskin bottle samples dataset includes the following data: calibrated CTD measurements of salinity and oxygen and Niskin bottle water samples. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf'. A full dataset description is included in the supplemental file 'Dataset_description.pdf'.
Formation and erosion of the seasonal thermocline in the Kuroshio Extension Recirculation Gyre

(Elsevier Ltd., 2012-07-21) Cronin, Meghan F. ; Bond, Nicholas A. ; Farrar, J. Thomas ; Ichikawa, Hiroshi ; Jayne, Steven R. ; Kawai, Yoshimi ; Konda, Masanori ; Qiu, Bo ; Rainville, Luc ; Tomita, Hiroyuki

Data from the Kuroshio Extension Observatory (KEO) surface mooring are used to analyze the balance of processes affecting the upper ocean heat content and surface mixed layer temperature variations in the Recirculation Gyre (RG) south of the Kuroshio Extension (KE). Cold and dry air blowing across the KE and its warm RG during winter cause very large heat fluxes out of the ocean that result in the erosion of the seasonal thermocline in the RG. Some of this heat is replenished through horizontal heat advection, which may enable the seasonal thermocline to begin restratifying while the net surface heat flux is still acting to cool the upper ocean. Once the surface heat flux begins warming the ocean, restratification occurs rapidly due to the low thermal inertia of the shallow mixed layer depth. Enhanced diffusive mixing below the mixed layer tends to transfer some of the mixed layer heat downward, eroding and potentially modifying sequestered subtropical mode water and even the deeper waters of the main thermocline during winter. Diffusivity at the base of the mixed layer, estimated from the residual of the mixed layer temperature balance, is roughly 3×10−4 m2/s during the summer and up to two orders of magnitude larger during winter. The enhanced diffusivities appear to be due to large inertial shear generated by wind events associated with winter storms and summer tropical cyclones. The diffusivity's seasonality is likely due to seasonal variations in stratification just below the mixed layer depth, which is large during the summer when the seasonal thermocline is fully developed and low during the winter when the mixed layer extends to the top of the thermocline.
Dynamics of global ocean heat transport variability

(Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1999-02) Jayne, Steven R.

A state-of-the-art, high-resolution ocean general circulation model is used to estimate the time-dependent global ocean heat transport and investigate its dynamics. The north-south heat transport is the prime manifestation of the ocean’s role in global climate, but understanding of its variability has been fragmentary owing to uncertainties in observational analyses, limitations in models, and the lack of a convincing mechanism. These issues are addressed in this thesis. Technical problems associated with the forcing and sampling of the model, and the impact of high-frequency motions are discussed. Numerical schemes are suggested to remove the inertial energy to prevent aliasing when the model fields are stored for later analysis. Globally, the cross-equatorial, seasonal heat transport fluctuations are close to +4.5 x 1015 watts, the same amplitude as the seasonal, cross-equatorial atmospheric energy transport. The variability is concentrated within 200 of the equator and dominated by the annual cycle. The majority of it is due to wind-induced current fluctuations in which the time-varying wind drives Ekman layer mass transports that are compensated by depth-independent return flows. The temperature difference between the mass transports gives rise to the time-dependent heat transport. The rectified eddy heat transport is calculated from the model. It is weak in the central gyres, and strong in the western boundary currents, the Antarctic Circumpolar Current, and the equatorial region. It is largely confined to the upper 1000 meters of the ocean. The rotational component of the eddy heat transport is strong in the oceanic jets, while the divergent component is strongest in the equatorial region and Antarctic Circumpolar Current. The method of estimating the eddy heat transport from an eddy diffusivity derived from mixing length arguments and altimetry data, and the climatological temperature field, is tested and shown not to reproduce the model’s directly evaluated eddy heat transport. Possible reasons for the discrepancy are explored.
Fukushima-derived radionuclides in the ocean and biota off Japan

(National Academy of Sciences, 2012-04-02) Buesseler, Ken O. ; Jayne, Steven R. ; Fisher, Nicholas S. ; Rypina, Irina I. ; Baumann, Hannes ; Baumann, Zofia ; Breier, Crystaline F. ; Douglass, Elizabeth M. ; George, Jennifer ; Macdonald, Alison M. ; Miyamoto, Hiroomi ; Nishikawa, Jun ; Pike, Steven M. ; Yoshida, Sachiko
Formation of Subtropical Mode Water in a high-resolution ocean simulation of the Kuroshio Extension region

( 2007-03-09) Rainville, Luc ; Jayne, Steven R. ; McClean, Julie L. ; Maltrud, Mathew E.

A high-resolution numerical model is used to examine the formation and variability of the North Pacific Subtropical ModeWater (STMW) over a 3-year period. The STMW distribution is found to be highly variable in both space and time, a characteristic often unexplored because of sparse observations or the use of coarse resolution simulations. Its distribution is highly dependent on eddies, and where it was renewed during the previous winter. Although the potential vorticity fluxes associated with down-front winds can be of the same order of magnitude or even greater than the diabatic ones due to air-sea temperature differences, the latter dominate the potential vorticity budget on regional and larger scales. Air-sea fluxes, however, are dominated by a few strong wind events, emphasizing the importance of short time scales in the formation of mode waters. In the Kuroshio Extension region, both advection and mixing play important roles to remove the STMW from the formation region.
Short-term dispersal of Fukushima-derived radionuclides off Japan : modeling efforts and model-data intercomparison

(Copernicus Publications on behalf of the European Geosciences Union, 2013-07-24) Rypina, Irina I. ; Jayne, Steven R. ; Yoshida, Sachiko ; Macdonald, Alison M. ; Douglass, Elizabeth M. ; Buesseler, Ken O.

The Great East Japan Earthquake and tsunami that caused a loss of power at the Fukushima nuclear power plants (FNPP) resulted in emission of radioactive isotopes into the atmosphere and the ocean. In June of 2011, an international survey measuring a variety of radionuclide isotopes, including 137Cs, was conducted in surface and subsurface waters off Japan. This paper presents the results of numerical simulations specifically aimed at interpreting these observations and investigating the spread of Fukushima-derived radionuclides off the coast of Japan and into the greater Pacific Ocean. Together, the simulations and observations allow us to study the dominant mechanisms governing this process, and to estimate the total amount of radionuclides in discharged coolant waters and atmospheric airborne radionuclide fallout. The numerical simulations are based on two different ocean circulation models, one inferred from AVISO altimetry and NCEP/NCAR reanalysis wind stress, and the second generated numerically by the NCOM model. Our simulations determine that > 95% of 137Cs remaining in the water within ~600 km of Fukushima, Japan in mid-June 2011 was due to the direct oceanic discharge. The estimated strength of the oceanic source is 16.2 ± 1.6 PBq, based on minimizing the model-data mismatch. We cannot make an accurate estimate for the atmospheric source strength since most of the fallout cesium had left the survey area by mid-June. The model explained several key features of the observed 137Cs distribution. First, the absence of 137Cs at the southernmost stations is attributed to the Kuroshio Current acting as a transport barrier against the southward progression of 137Cs. Second, the largest 137Cs concentrations were associated with a semi-permanent eddy that entrained 137Cs-rich waters, collecting and stirring them around the eddy perimeter. Finally, the intermediate 137Cs concentrations at the westernmost stations are attributed to younger, and therefore less Cs-rich, coolant waters that continued to leak from the reactor in June of that year.

Jayne Steven R.

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