NLO QCD corrections to W+ W+ jj production in vector-boson fusion at the LHC

We present a next-to-leading-order QCD calculation for e+\nu e\mu+\nu\mu jj production in vector-boson fusion, i.e. the scattering of two positively charged W bosons at the LHC. We include the complete set of electroweak leading-order diagrams for the six-particle final state and quantitatively assess the size of the s-channel and interference contributions in VBF kinematics. The calculation uses the complex-mass scheme to describe the W-boson resonances and is implemented into a flexible Monte Carlo generator. Using a dynamical scale based on the transverse momenta of the jets, the QCD corrections stay below about 10% for all considered observables, while the residual scale dependence is at the level of 1%.Comment: 60 page

Impact of sea ice floe size distribution on seasonal fragmentation and melt of Arctic sea ice

Recent years have seen a rapid reduction in the summer Arctic sea ice extent. To both understand this trend and project the future evolution of the summer Arctic sea ice, a better understanding of the physical processes that drive the seasonal loss of sea ice is required. The marginal ice zone, here defined as regions with between 15 % and 80 % sea ice cover, is the region separating pack ice from the open ocean. Accurate modelling of this region is important to understand the dominant mechanisms involved in seasonal sea ice loss. Evolution of the marginal ice zone is determined by complex interactions between the atmosphere, sea ice, ocean, and ocean surface waves. Therefore, this region presents a significant modelling challenge. Sea ice floes span a range of sizes but sea ice models within climate models assume they adopt a constant size. Floe size influences the lateral melt rate of sea ice and momentum transfer between atmosphere, sea ice, and ocean, all important processes within the marginal ice zone. In this study, the floe size distribution is represented as a power law defined by an upper floe size cut-off, lower floe size cut-off, and power-law exponent. This distribution is also defined by a new tracer that varies in response to lateral melting, wave-induced break-up, freezing conditions, and advection. This distribution is implemented within a sea ice model coupled to a prognostic ocean mixed-layer model. We present results to show that the use of a power-law floe size distribution has a spatially and temporally dependent impact on the sea ice, in particular increasing the role of the marginal ice zone in seasonal sea ice loss. This feature is important in correcting existing biases within sea ice models. In addition, we show a much stronger model sensitivity to floe size distribution parameters than other parameters used to calculate lateral melt, justifying the focus on floe size distribution in model development. We also find that the attenuation rate of waves propagating under the sea ice cover modulates the impact of wave break-up on the floe size distribution. It is finally concluded that the model approach presented here is a flexible tool for assessing the importance of a floe size distribution in the evolution of sea ice and is a useful stepping stone for future development of floe size modelling

Sea hazards on offshore structures: waves, currents, tides and sea ice combined

Offshore structures experience several kinds of sea hazards. Over most of the world ocean high waves or strong currents are the concern. In high latitudes sea ice poses an additional hazard. Loads on offshore structures from waves and current can be calculated using the well-known Morison equation. We have modified the equation to calculate the loads from sea ice, both static and dynamic. A global sea ice-ocean numerical model, combined with a waves-in-ice module, allows us to estimate loads on offshore structures from ocean waves, currents, tides and sea ice, both in ice-free and ice-covered conditions. Several types of structures can be considered. Here we consider monopoles for shallow areas and floating spar structures for deeper waters. Maps of ocean and sea ice loads for the whole Arctic and the North Sea area are created, as well as time series and associated statistics of expected loads for chosen locations or regions. This allows us to examine the relative importance of different hazards based on geographical location. For instance, waves are the main hazard in the North Sea area, except at the shelf slope, where the current is fast. In some coastal areas strong tidal currents are responsible for the largest loads on the structures and are the principal hazard. The approach developed here allows us to use ocean environmental information to predict the integrity of off-shore structures and help assessment of the potential risks for off-shore operations. For the study we acknowledge support from the NERC UK Innovation Grant no NE/N017099/1: ’Safer Operations at Sea - Supported by Operational Simulations (SOS-SOS)’ and the EU FP7 Project ‘Ships and waves reaching Polar Regions (SWARP), grant agreement 607476. We also acknowledge funding from the NERC Programme “The North Atlantic Climate System Integrated Study (ACSIS)” NE/N018044/1

Attenuation of ocean surface waves in pancake and frazil sea ice along the coast of the Chukchi Sea

Alaskan Arctic coastlines are protected seasonally from ocean waves by the presence of coastal and shorefast sea ice. This study presents field observations collected during the autumn 2019 freeze up near Icy Cape, a coastal headland in the Chukchi Sea of the Western Arctic. The evolution of the coupled air-ice-ocean-wave system during a four-day wave event was monitored using drifting wave buoys, a cross-shore mooring array, and ship-based measurements. The incident wave field with peak period of 2.5 s was attenuated by coastal pancake and frazil sea ice, reducing significant wave height by 40\% over less than 5 km of cross-shelf distance spanning water depths from 13 to 30 m. Spectral attenuation coefficients are evaluated with respect to wave and ice conditions and the proximity to the ice edge. Attenuation rates are found to be three times higher within 500 m of the ice edge, relative to values farther in the ice cover. Attenuation coefficients are in the range of $\langle 2.3,2.7\rangle$ \si{\meter^{-1}}, and follow a power-law dependence on frequency

Mooring results from Coastal Ocean Dynamics in the Arctic (CODA)

National Science Foundation, Office of Naval Researc

Data to accompany the article "Attenuation of ocean surface waves in pancake and frazil sea ice along the coast of the Chukchi Sea"

Data to accompany "Attenuation of ocean surface waves in pancake and frazil sea ice along the coast of the Chukchi Sea," Journal of Geophysical Research - Oceans, 2020. https://doi.org/10.1029/2020JC016746National Science Foundatio

Safer operations in changing ice-covered seas: approaches and perspectives

The last decades witnessed an increase in Arctic offshore operations,partly driven by rising energy needs and partly due to easing of sea ice conditions and improved accessibility of shipping routes. The study examines changes in sea ice and ocean conditions in the Arctic with their implications for off-shore safety. The objective of the research is to develop a basis for forecasting technologies for maritime operations.We assess loads on off-shore structures from sea ice and ocean in centennial climate future projections and implications for the accessibility and future Arctic shipping. As a test case, we calculate loads on a tubular structure of 100-m wide and 20-m tall, similar to installations in the Beaufort Sea in the 1980s. With sea ice retreating, loads are predicted to increase from ~0.1   106 N (MN) at present to ~50–200 MN in the 2090s, primarily due to wave loads. This study asserts the need for new approaches in forecasting to make marine operations in the Arctic safer