Thesis--Massachusetts Institute of Technology. / Prepared under contract N00014-67-A-0204-0048 and grant NSF-GA30616 for Office of Naval Research. Includes bibliographical references (leaves 210-213).

Although it has long been known that cold dense waters from the Nordic Seas overflow the Wyville Thomson Ridge, the water masses' subsequent pathways and fate have been uncertain. This study conclusively places Wyville Thomson Ridge Overflow Water (WTOW) as an important water mass in the eastern subpolar North Atlantic for the first time. Using a variety of chemical tracer s (chlorofluorocarbons, oxygen, nutrients and aluminium) in conjunction with temperature and salinity, WTOW is traced southwards into the northern and central Rockall Trough as well as into the channels between the western banks. The overflow water has a clear temperature, salinity and chlorofluorocarbon (CFC-11 and CFC-12) signature. Additionally, levels of aluminium are elevated in WTOW suggesting that this element is potentially a useful and novel water mass tracer. The lower oxygen layer complicates the use of dissolved oxygen and nitrate as tracers in the mid water column. However, higher and lower concentrations respectively in the western trough reveal the presence of WTOW in this area. The overflow water does not appear to have a silicate or phosphate signature. Two branches of WTOW exist in the Rockall Trough: a slow-moving indistinct intermediate branch (600-1200 m) f ound in both the east and west of the basin; and a coherent deep branch (> 1200 m) that flows southward along the western banks of the trough. As well as having a large spatial footprint within the Rockall Trough, intermediate a nd deep WTOW are temporally persistent being present 65-75 % of the time between 1975 and 2008. The signature of WTOW at intermediate depths is absent from the Ellett Line record in the mid-1980s and early-1990s. As deep WTOW is still observed during these periods flow over the Wyville Thomson Ridge cannot have ceased. Instead, it is proposed that the strength of the Subpolar Gyre is an important driver in the temporal distribution of intermediate WTOW within the Rockall Trough. When the gyre is strong, such as in the mid-1980s and early-1990s, the mid water column is dominated by waters originating from the west which block the southward flow of intermediate WTOW. In contrast, when the gyre is weak, such as in the late-1990s and 2000s, subpolar waters lie further west enabling intermediate waters within the Rockall Trough to be dominated by the southern orig inating Mediterranean Overflow Water and the northern water mass of WTOW.

<p>Mismatches in the spatiotemporal variability of resource, resource users and management actions breeds inefficiency in the management of marine resources. To date, the spatiotemporal resolution and extent of fisheries management has been largely dictated by logistical and political constraints, and secondarily by the geographic range of the species or meta-population dynamics. Management units are rarely smaller than 1000 km2 in developed coastal fisheries, and management measures generally occur at resolutions larger than 100 km2. From a temporal perspective, the finest resolution of management measures is at best a month but more generally a year. As such, attempts to manage processes and patterns at sub-10 km, sub-1 month resolution often involve some level of spatiotemporal mismatch. To address the obvious spatiotemporal mismatch between a dynamic ocean and static management, to allow for a comprehensive implementation of ecosystem-based fisheries management, and to minimize inefficiency in our management of marine resources, we must seek to develop more dynamic management measures that allow managers to address scales, processes and patterns occurring under ten kilometers.</p><p>In this dissertation I apply point pattern processes, cumulative distribution functions, receiver operator characteristic curves, simulated annealing tools, regression models and clustering techniques to develop examples of two dynamic management measures and to compare the efficiency of static versus dynamic management measures. I show that autocorrelation analysis can inform the distances and times used in real-time closures based on move-on rules. Further, I identify optimum bottom temperature threshold values to separate individual species within the Northeast Multispecies Fishery from Atlantic cod. Results demonstrate that dynamic spatiotemporal management measures are widely applicable, and more effective and more efficient than static time-area closures. Unexpected trends in some results due to a changing climate indicate possible increasing thermal overlap between Atlantic cod and many other species in the fishery. Implications of scale in fisheries management and the importance of coarse scale (1 - 10km) ecological patterns to fisheries are discussed.</p> / Dissertation

I present herein an ensemble of ROCKE-3D aqua-planet simulations which I compare with the simulations presented in the work of Yang et al. (2019) and other similar works. The focus was on contrasting differences in the greenhouse effect between the models. In contrast to their work, I examined simulations with a dynamic ocean instead of a slab ocean, as well as the inclusion of dynamic sea ice for 2 out of 4 of them. A subset of the simulations examined prevented the formation of sea ice to make them more comparable to Yang et al. (2019), but they never reached radiative equilibrium and this made it difficult to utilize their results. When contrasting the sea ice simulations of ROCKE-3D with the CAM4_Wolf/ExoCAM simulation of Komacek &amp; Abbot(2019), I found that the inclusion of ocean heat transport through a dynamic ocean increases the ice-free region around the sub-tropics for the rapidly rotating aqua-planet around a G-star, thus, resulting in a lower Bond albedo and more surface warming. Supporting previous intercomparisons (Sergeevet al. 2021), ROCKE-3D produces less low- to midlevel clouds toward the equator/substellar point, compared to other models. Consequently, this leads to less cooling through the shortwave cloud radiative forcing. Lastly, I looked at the specific humidity. ROCKE-3D produced the highest stratospheric water vapor content in the M-star scenario, which suggests that ROCKE-3D is closer to the moist greenhouse limit of Kasting et al. (1993); although, the model is still far off. / I detta arbete så presenterar jag vattenplanet simulationer producerade med hjälp av ROCKE-3D, som jag sedan jämför med simulationerna som presenteras i Yang et al. (2019). Fokuset för jämförelsen låg på att jämföra skillnader gällande den producerade växthuseffekten. Alla simulationer utnyttjade ett dynamiskt hav i stället för ett enklare "platt hav", varav 2 utav 4 av dom simulationer som presenteras tillåter havsis att formas. De simulationer som inte tillät is uppnådde aldrig termisk jämvikt vilket gjorde det svårt att antyda något utifrån dom. Vid jämförelse av is-simulationerna som producerades av ROCKE-3D med de is-simulationer producerade med hjälp av CAM4/ExoCAM i Komacek &amp; Abbot (2019), så visades det sig att den is-fria regionen runtomkring de subtropiska områderna vart större för den snabbt roterande vattenplaneten runt en G-klassad stjärna om man inkluderar ett dynamiskt hav i stället för ett "platt hav". Vidare, så stödjer detta arbete dom resultat presenterade i Sergeev et al. (2021), där ROCKE-3D producerar mindre låg- och medelhöga molnformationer runtom ekvatorn/substellära regionen, jämfört med andra modeller. Vidare, så leder detta till en mindre kylningseffekt genom molnens reflektion av kortvågsstrålning. Sist, så undersökte jag den specifika fuktigheten, där ROCKE-3D visar på ett högre värde av stratosfärisk vattenånga i fallet av en tidsvattenlåst havsplanet runt en M-stjärna. Detta tyder på att ROCKE-3D är närmare den fuktiga växthusgränsen som presenteras i Kasting et al. (1993). Dock, så är den fortfarande långt ifrån att uppnås.