The refreezing of melt ponds on Arctic sea ice

The presence of melt ponds on the surface of Arctic sea ice significantly reduces its albedo, inducing a positive feedback leading to sea ice thinning. While the role of melt ponds in enhancing the summer melt of sea ice is well known, their impact on suppressing winter freezing of sea ice has, hitherto, received less attention. Melt ponds freeze by forming an ice lid at the upper surface, which insulates them from the atmosphere and traps pond water between the underlying sea ice and the ice lid. The pond water is a store of latent heat, which is released during refreezing. Until a pond freezes completely, there can be minimal ice growth at the base of the underlying sea ice. In this work, we present a model of the refreezing of a melt pond that includes the heat and salt balances in the ice lid, trapped pond, and underlying sea ice. The model uses a two-stream radiation model to account for radiative scattering at phase boundaries. Simulations and related sensitivity studies suggest that trapped pond water may survive for over a month. We focus on the role that pond salinity has on delaying the refreezing process and retarding basal sea ice growth. We estimate that for a typical sea ice pond coverage in autumn, excluding the impact of trapped ponds in models overestimates ice growth by up to 265 million km3, an overestimate of 26%

Incorporation of a physically based melt pond scheme into the sea ice component of a climate model

The extent and thickness of the Arctic sea ice cover has decreased dramatically in the past few decades with minima in sea ice extent in September 2005 and 2007. These minima have not been predicted in the IPCC AR4 report, suggesting that the sea ice component of climate models should more realistically represent the processes controlling the sea ice mass balance. One of the processes poorly represented in sea ice models is the formation and evolution of melt ponds. Melt ponds accumulate on the surface of sea ice from snow and sea ice melt and their presence reduces the albedo of the ice cover, leading to further melt. Toward the end of the melt season, melt ponds cover up to 50% of the sea ice surface. We have developed a melt pond evolution theory. Here, we have incorporated this melt pond theory into the Los Alamos CICE sea ice model, which has required us to include the refreezing of melt ponds. We present results showing that the presence, or otherwise, of a representation of melt ponds has a significant effect on the predicted sea ice thickness and extent. We also present a sensitivity study to uncertainty in the sea ice permeability, number of thickness categories in the model representation, meltwater redistribution scheme, and pond albedo. We conclude with a recommendation that our melt pond scheme is included in sea ice models, and the number of thickness categories should be increased and concentrated at lower thicknesses

Processes controlling surface, bottom and lateral melt of Arctic sea ice in a state of the art sea ice model

We present a modelling study of processes controlling the summer melt of the Arctic sea ice cover. We perform a sensitivity study and focus our interest on the thermodynamics at the ice–atmosphere and ice–ocean interfaces. We use the Los Alamos community sea ice model CICE, and additionally implement and test three new parametrization schemes: (i) a prognostic mixed layer; (ii) a three equation boundary condition for the salt and heat flux at the ice–ocean interface; and (iii) a new lateral melt parametrization. Recent additions to the CICE model are also tested, including explicit melt ponds, a form drag parametrization and a halodynamic brine drainage scheme. The various sea ice parametrizations tested in this sensitivity study introduce a wide spread in the simulated sea ice characteristics. For each simulation, the total melt is decomposed into its surface, bottom and lateral melt components to assess the processes driving melt and how this varies regionally and temporally. Because this study quantifies the relative importance of several processes in driving the summer melt of sea ice, this work can serve as a guide for future research priorities

Modelling the fate of surface melt on the Larsen C Ice Shelf

Surface melt lakes lower the albedo of ice shelves, leading to additional surface melting. This can substantially alter the surface energy balance and internal temperature and density profiles of the ice shelf. Evidence suggests that melt lakes also played a pivotal role in the sudden collapse of the Larsen B Ice Shelf in 2002. Here a recently developed, high-physical-fidelity model accounting for the development cycle of melt lakes is applied to the Larsen C Ice Shelf, Antarctica’s most northern ice shelf and one where melt lakes have been observed. We simulate current conditions on the ice shelf using weather station and reanalysis data and investigate the impacts of potential future increases in precipitation and air temperature on melt lake formation, for which concurrent increases lead to an increase in lake depth. Finally, we assess the viability in future crevasse propagation through the ice shelf due to surface meltwater accumulation

Interactions between wind-blown snow redistribution and melt ponds in a coupled ocean–sea ice model

Introducing a parameterization of the interactions between wind-driven snow depth changes and melt pond evolution allows us to improve large scale models. In this paper we have implemented an explicit melt pond scheme and, for the first time, a wind dependant snow redistribution model and new snow thermophysics into a coupled ocean–sea ice model. The comparison of long-term mean statistics of melt pond fractions against observations demonstrates realistic melt pond cover on average over Arctic sea ice, but a clear underestimation of the pond coverage on the multi-year ice (MYI) of the western Arctic Ocean. The latter shortcoming originates from the concealing effect of persistent snow on forming ponds, impeding their growth. Analyzing a second simulation with intensified snow drift enables the identification of two distinct modes of sensitivity in the melt pond formation process. First, the larger proportion of wind-transported snow that is lost in leads directly curtails the late spring snow volume on sea ice and facilitates the early development of melt ponds on MYI. In contrast, a combination of higher air temperatures and thinner snow prior to the onset of melting sometimes make the snow cover switch to a regime where it melts entirely and rapidly. In the latter situation, seemingly more frequent on first-year ice (FYI), a smaller snow volume directly relates to a reduced melt pond cover. Notwithstanding, changes in snow and water accumulation on seasonal sea ice is naturally limited, which lessens the impacts of wind-blown snow redistribution on FYI, as compared to those on MYI. At the basin scale, the overall increased melt pond cover results in decreased ice volume via the ice-albedo feedback in summer, which is experienced almost exclusively by MYI

Impact of melt ponds on Arctic sea ice simulations from 1990 to 2007

The extent and thickness of the Arctic sea ice cover has decreased dramatically in the past few decades with minima in sea ice extent in September 2007 and 2011 and climate models did not predict this decline. One of the processes poorly represented in sea ice models is the formation and evolution of melt ponds. Melt ponds form on Arctic sea ice during the melting season and their presence affects the heat and mass balances of the ice cover, mainly by decreasing the value of the surface albedo by up to 20%. We have developed a melt pond model suitable for forecasting the presence of melt ponds based on sea ice conditions. This model has been incorporated into the Los Alamos CICE sea ice model, the sea ice component of several IPCC climate models. Simulations for the period 1990 to 2007 are in good agreement with observed ice concentration. In comparison to simulations without ponds, the September ice volume is nearly 40% lower. Sensitivity studies within the range of uncertainty reveal that, of the parameters pertinent to the present melt pond parameterization and for our prescribed atmospheric and oceanic forcing, variations of optical properties and the amount of snowfall have the strongest impact on sea ice extent and volume. We conclude that melt ponds will play an increasingly important role in the melting of the Arctic ice cover and their incorporation in the sea ice component of Global Circulation Models is essential for accurate future sea ice forecasts

Skillful spring forecasts of September Arctic sea ice extent using passive microwave sea ice observations

In this study, we demonstrate skillful spring forecasts of detrended September Arctic sea ice extent using passive microwave observations of sea ice concentration (SIC) and melt onset (MO). We compare these to forecasts produced using data from a sophisticated melt pond model, and find similar to higher skill values, where the forecast skill is calculated relative to linear trend persistence. The MO forecasts shows the highest skill in March–May, while the SIC forecasts produce the highest skill in June–August, especially when the forecasts are evaluated over recent years (since 2008). The high MO forecast skill in early spring appears to be driven primarily by the presence and timing of open water anomalies, while the high SIC forecast skill appears to be driven by both open water and surface melt processes. Spatial maps of detrended anomalies highlight the drivers of the different forecasts, and enable us to understand regions of predictive importance. Correctly capturing sea ice state anomalies, along with changes in open water coverage appear to be key processes in skillfully forecasting summer Arctic sea ice

Experimental investigation of stray light from dust contamination in gravitational wave detectors

openStray light presents a significant challenge in the LIGO-Virgo interferometers, manifesting as excess noise in the low-frequency region and causing a loss in sensitivity both through increased measurement noise and disruption of control loops. This issue is expected to be even more critical in future interferometers, such as the Einstein Telescope (ET), which will have higher sensitivity in the low-frequency region. Therefore, effective monitoring and mitigation of stray light sources are crucial. This thesis focuses on understanding and controlling stray light contributions, primarily from surface roughness and dust particles deposited on optical components. The Bidirectional Scattering Distribution Function (BSDF) and Total Integrated Scattering (TIS) are utilized to model and characterize stray light sources. The Harvey-Shack model and its generalized form, along with Mie scattering theory, are applied to understand the scattering phenomena. The research included significant enhancements to a scattering measurement facility, including background noise optimization and the implementation of automated measurement procedures. Various samples, including baffle components from Virgo detectors, absorbent glass samples, and silicon wafers used in dust monitoring campaigns, were characterized using the improved facility for their scattering properties. The facility's future focus will be on supporting the dust monitoring campaign, with new wafers periodically exposed in various environments of the Virgo laboratories to monitor dust accumulation. These measurements will help validate BSDF estimates and improve the overall understanding of stray light contributions in gravitational wave detectors

A Romantic Comedy of Boats and Gardens: Selected Projects in Scenic Design and Technical Direction

When this play was given to me as one of my production assignments, I was both thrilled and terrified. I thoroughly enjoy Shakespeare, but I realized that this would also be the largest show of the year; it would be the only production to take place in the Morgan Theater, our largest and most challenging space. This was only my second time designing a realized production and I knew it would be a massive undertaking. However, I knew that having a realized Shakespeare design this early in my career would greatly help my portfolio. Also, my advisor told me that this could have been the best realized portfolio piece I could get during my time at Utah State, so I would need to make the most of it. In this piece especially, my advisor Shawn Fisher wanted me to focus on composition

Leadership and the creative process insights from the filmmaking industry

LAUREA MAGISTRALENell’attuale panorama economico in continua evoluzione, uno degli obiettivi primari per i leader di diverse organizzazioni è la comprensione dei processi da adottare al fine di favorire lo sviluppo di creatività ed innovazione all’interno delle proprie aziende e tra i propri dipendenti. Oggi il tema della creatività risulta più che mai attuale: Sternberg (2007) ha recentemente osservato che mentre in passato la creatività era percepita come una caratteristica opzionale della leadership, oggigiorno non è più considerabile opzionale, dal momento che i leader che mancano di creatività hanno meno probabilità di condurre le proprie aziende nel futuro. L’obiettivo di questa ricerca è quello di studiare la Leadership con riferimento ad un contesto specifico: l’Industria Cinematografica. In particolare, sono stati analizzati diversi casi di studio relativi a sei registi selezionati. È stato possibile concludere che diverse manifestazioni di leadership sono osservabili non solo all’interno dello stesso contesto, ma anche all’interno dello stesso processo creativo. Inoltre grazie ai dati raccolti è stato possibile identificare la struttura del processo creativo, e studiare la rilevanza di ogni sua fase.In today’s evolving and challenging economical context an essential goal for organizational leaders seems to be the comprehension of the process to foster creativity in their companies and in their employees. Nowadays this issue is the focus of interest of many studies and researches: Sternberg (2007) recently observed, while in the past creativity was often perceived as an optional feature of leadership, today it is no longer optional because leaders who lack creativity are unlikely to propel their organizations into the future. The goal of this research was to study Creative Leadership with reference to a specific context: the Filmmaking Industry. In particular, multiple case studies about six movie directors were studied and Directive, Integrative and Facilitative Creative Leadership traits were identified. From this study it was possible to understand that different manifestations of leadership can coexist in the same context and also in the same creative process. Moreover, the structure of the creative process was identified, and the relevance of each process’ stage was enlightened