skip to content
Home

Conservation Research Institute

 

Feed aggregator Subscribe to Conservation Research Institute aggregator

Wed 09 Apr 15:00: Title to be confirmed

Conservation at Cambridge - Thu, 13/02/2025 - 11:48
Title to be confirmed

Abstract not available

Add to your calendar or Include in your list

Wed 19 Mar 14:00: Tipping points of the Ross and Filchner-Ronne Ice Shelves: how worried should we be?

Conservation-related talks - Thu, 13/02/2025 - 11:47
Tipping points of the Ross and Filchner-Ronne Ice Shelves: how worried should we be?

Ocean models consistently project that with sufficient climate change forcing, the Ross and Filchner-Ronne ice shelf cavities could abruptly transition from a cold state to a warm state. Crossing these tipping points would have profound consequences for basal melt rates, buttressing of ice streams, and ultimately sea level rise. Here we analyse over 14,000 years of “overshoot” simulations with the UK Earth System Model, which includes a fully coupled Antarctic Ice Sheet. As the climate warms, stabilises at different temperatures, and cools again, we simulate many examples of the cavities tipping and recovering. We find that global warming thresholds of around 3.5°C and 5°C tip the Ross and Filchner-Ronne respectively. We also find evidence of hysteresis: the climate must cool back down beyond the tipping thresholds in order for each cavity to return to its original cold state. Even if the oceanography recovers, the ice sheet does not: sea level contribution from each catchment takes centuries even to stabilise, and the ice does not begin to regrow on this timescale. Therefore, if the Ross or Filchner-Ronne Ice Shelves cross tipping points, the resulting sea level rise will be effectively irreversible.

Add to your calendar or Include in your list

Wed 19 Mar 14:00: Tipping points of the Ross and Filchner-Ronne Ice Shelves: how worried should we be?

Conservation Talks - Thu, 13/02/2025 - 11:47
Tipping points of the Ross and Filchner-Ronne Ice Shelves: how worried should we be?

Ocean models consistently project that with sufficient climate change forcing, the Ross and Filchner-Ronne ice shelf cavities could abruptly transition from a cold state to a warm state. Crossing these tipping points would have profound consequences for basal melt rates, buttressing of ice streams, and ultimately sea level rise. Here we analyse over 14,000 years of “overshoot” simulations with the UK Earth System Model, which includes a fully coupled Antarctic Ice Sheet. As the climate warms, stabilises at different temperatures, and cools again, we simulate many examples of the cavities tipping and recovering. We find that global warming thresholds of around 3.5°C and 5°C tip the Ross and Filchner-Ronne respectively. We also find evidence of hysteresis: the climate must cool back down beyond the tipping thresholds in order for each cavity to return to its original cold state. Even if the oceanography recovers, the ice sheet does not: sea level contribution from each catchment takes centuries even to stabilise, and the ice does not begin to regrow on this timescale. Therefore, if the Ross or Filchner-Ronne Ice Shelves cross tipping points, the resulting sea level rise will be effectively irreversible.

Add to your calendar or Include in your list

Wed 19 Mar 14:00: Tipping points of the Ross and Filchner-Ronne Ice Shelves: how worried should we be?

Conservation at Cambridge - Thu, 13/02/2025 - 11:47
Tipping points of the Ross and Filchner-Ronne Ice Shelves: how worried should we be?

Ocean models consistently project that with sufficient climate change forcing, the Ross and Filchner-Ronne ice shelf cavities could abruptly transition from a cold state to a warm state. Crossing these tipping points would have profound consequences for basal melt rates, buttressing of ice streams, and ultimately sea level rise. Here we analyse over 14,000 years of “overshoot” simulations with the UK Earth System Model, which includes a fully coupled Antarctic Ice Sheet. As the climate warms, stabilises at different temperatures, and cools again, we simulate many examples of the cavities tipping and recovering. We find that global warming thresholds of around 3.5°C and 5°C tip the Ross and Filchner-Ronne respectively. We also find evidence of hysteresis: the climate must cool back down beyond the tipping thresholds in order for each cavity to return to its original cold state. Even if the oceanography recovers, the ice sheet does not: sea level contribution from each catchment takes centuries even to stabilise, and the ice does not begin to regrow on this timescale. Therefore, if the Ross or Filchner-Ronne Ice Shelves cross tipping points, the resulting sea level rise will be effectively irreversible.

Add to your calendar or Include in your list

Wed 26 Mar 15:30: Title to be confirmed

Conservation-related talks - Thu, 13/02/2025 - 11:46
Title to be confirmed

Abstract not available

Add to your calendar or Include in your list

Wed 26 Mar 15:30: Title to be confirmed

Conservation Talks - Thu, 13/02/2025 - 11:46
Title to be confirmed

Abstract not available

Add to your calendar or Include in your list

Wed 26 Mar 15:30: Title to be confirmed

Conservation at Cambridge - Thu, 13/02/2025 - 11:46
Title to be confirmed

Abstract not available

Add to your calendar or Include in your list

Wed 12 Mar 14:00: Title to be confirmed

Conservation-related talks - Thu, 13/02/2025 - 11:46
Title to be confirmed

Abstract not available

Add to your calendar or Include in your list

Wed 12 Mar 14:00: Title to be confirmed

Conservation Talks - Thu, 13/02/2025 - 11:46
Title to be confirmed

Abstract not available

Add to your calendar or Include in your list

Wed 12 Mar 14:00: Title to be confirmed

Conservation at Cambridge - Thu, 13/02/2025 - 11:46
Title to be confirmed

Abstract not available

Add to your calendar or Include in your list

Wed 26 Feb 15:30: Title to be confirmed

Conservation-related talks - Thu, 13/02/2025 - 11:43
Title to be confirmed

Abstract not available

Add to your calendar or Include in your list

Wed 26 Feb 15:30: Title to be confirmed

Conservation Talks - Thu, 13/02/2025 - 11:43
Title to be confirmed

Abstract not available

Add to your calendar or Include in your list

Wed 26 Feb 15:30: Title to be confirmed

Conservation at Cambridge - Thu, 13/02/2025 - 11:43
Title to be confirmed

Abstract not available

Add to your calendar or Include in your list

Fri 14 Feb 16:00: Synchronization in Navier-Stokes turbulence and its role in data-driven modeling

Conservation at Cambridge - Wed, 12/02/2025 - 11:12
Synchronization in Navier-Stokes turbulence and its role in data-driven modeling

In Navier-Stokes (NS) turbulence, large-scale turbulent flows determine small-scale flows; in other words, small-scale flows are synchronized to large-scale flows. In 3D turbulence, previous numerical studies suggest that the critical length separating these two scales is determined by the Kolmogorov length. In this talk, I will introduce our theoretical framework for characterizing synchronization phenomena [1]. Specifically, it provides a computational method for the exponential rate of convergence to the synchronized state, and identifies the critical length based on the NS equations via the “transverse” Lyapunov exponent. I will also discuss the synchronization property of 2D NS turbulence and how it differs from the 3D case [2]. These insights into synchronization and critical length scales are essential for developing machine-learning closure models for turbulence, in particular their stable reproducibility [3]. Finally, I will illustrate how “generalized” synchronization is crucial for predicting chaotic dynamics [4].

[1] M. Inubushi, Y. Saiki, M. U. Kobayashi, and S. Goto, Characterizing small-scale dynamics of Navier-Stokes turbulence with transverse Lyapunov exponents: A data assimilation approach, Phys. Rev. Lett. 131, 254001 (2023).

[2] M. Inubushi and C. P. Caulfield (in preparation).

[3] S. Matsumoto, M. Inubushi, and S. Goto, Stable reproducibility of turbulence dynamics by machine learning, Phys. Rev. Fluids 9, 104601 (2024).

[4] A. Ohkubo and M. Inubushi, Reservoir computing with generalized readout based on generalized synchronization, Sci. Rep. 14, 30918 (2024).

Add to your calendar or Include in your list

Mon 17 Mar 13:00: Volcanic fissure localisation and lava delta formation: Modelling of volcanic flows undergoing rheological evolution

Conservation at Cambridge - Tue, 11/02/2025 - 17:18
Volcanic fissure localisation and lava delta formation: Modelling of volcanic flows undergoing rheological evolution

In this talk, I will present two volcanologically motivated modelling problems. In the first, I will detail how thermoviscous localisation of volcanic eruptions is influenced by the irregular geometry of natural volcanic fissures. Fissure eruptions typically start with the opening of a linear fissure that erupts along its entire length, following which activity localises to one or more isolated vents within a few hours or days. Previous work has proposed that localisation can arise through a thermoviscous fingering instability driven by the strongly temperature dependent viscosity of the rising magma. I will show that, even for relatively modest variations of the fissure width, a non-planar geometry supports strongly localised steady states, in which the wider parts of the fissure host faster, hotter flow, and the narrower parts of the fissure host slower, cooler flow. This geometrically-driven localisation differs from the spontaneous thermoviscous fingering localisation observed in planar geometries, and is potentially more potent for parameter values relevant to volcanic fissures.

The second problem concerns lava delta formation. A lava delta arises when a volcanic lava flow enters a body of water, extending the pre-eruption shoreline via the creation of new, relatively flat land. A combination of cooling induced rheological changes and the reduction in gravitational driving forces controls the morphology and evolution of the delta. I will present shallow-layer continuum models for this process, highlighting how different modes of delta formation manifest in different late-time behaviours. In particular, I will derive a steady state shoreline extent when the delta formation is driven only by buoyancy forces, and late time similarity solutions for the evolution of the shoreline when the viscous lava fragments and forms `hyaloclastic’ debris on contact with the water.

Add to your calendar or Include in your list

Fri 21 Feb 14:00: Post-doc talks

Conservation at Cambridge - Tue, 11/02/2025 - 15:14
Post-doc talks

Dario Klingenberg: Using nonlinear optimisation to investigate shear turbulence

Much research has focused on understanding how flows transition to turbulence. However, an equally important question is how, once established, turbulence is sustained. Interestingly, the same methods used for the transition problem are also useful in the turbulent setting, despite the stark differences between the two. In this work, I will use nonlinear optimisation to find the initial perturbation that, over a given time horizon, experiences the highest energy growth in channel flow with a friction Reynolds number of 180. Although the precise form of the initial condition depends on this time horizon, and also the initial energy available to it, it turns out that over a wide range in this parameter space, optimals with very similar dynamics arise. Interestingly, many important aspects of these dynamics are consistent with observations made in real turbulence. Based on these results, it is argued that nonlinear optimals are a conceptually simple and valuable concept to investigate turbulence.

Philipp Vieweg: Large-scale flow structures and their induced mixing in horizontally extended forced stratified shear flows

Covering about 70% of Earth’s surface, the oceans represent the biggest heat sink in climate and weather models. However, our understanding of the oceans’ inherent turbulent processes is still far from complete. Here, we study an idealised or simplified configuration that is stably stratified and continuously forced. The basic configuration has been introduced by Smith et al. (Journal of Fluid Mechanics 910, A42 (2021)) for small numerical domains and may be susceptible to Kelvin-Helmholtz instabilities. We extend these results to horizontally extended domains by conducting direct numerical simulations using the GPU -accelerated open-source spectral element solver NekRS.

On the one hand, we analyse the formation and convergence of large-scale flow structures in extended domains. Due to the anisotropic nature of the flow, this involves separate treatments of the stream-wise and span-wise direction. On the other hand, we analyse the impact of these flow structures on their induced mixing of the two layers of fluid.

Based on these structural and statistical analyses of stratified turbulent flows, this research contributes to advancing our current understanding of oceanic flows and allowing for improved predictions using global simulations that involve turbulence modelling.

James Shemilt: Viscoplastic dynamics of mucus transport during coughing

Coughing is a mechanism by which excess mucus is cleared from the lungs’ airways. In obstructive lung diseases such as cystic fibrosis, the rheology of mucus changes, including its yield stress increasing, and coughing can become a central mechanism for mucus clearance. I will present thin-film modelling of a viscoplastic liquid layer driven by high-speed confined air flow, which is a model for mucus transport during a cough that accounts for the yield stress of mucus. Numerical solutions of the thin-film equations, and travelling-wave solutions, are used to quantify how the liquid’s yield stress alters the dynamics. Criteria are determined for finite-time blow-up of solutions, where the liquid layer reaches the upper wall of the channel. I will also discuss how these theoretical results compare with experiments in which viscoplastic liquid layers are exposed to high-speed air flow.

Fabio Pino: Stability and Dynamics of Evaporating/Condensing Liquid Film Flows

Pulsating heat pipes (PHPs) have emerged as an effective heat transfer device for small-scale electronics. Their enhanced thermal performance relies on the periodic evaporation and condensation of a liquid film lining the pipe walls. However, an incomplete understanding of the phase change mechanism limits its broader application.

This research addresses this gap by investigating the linear and nonlinear stability of a 3D evaporating/condensing liquid film over an inclined plate. To reduce the complexity of the governing equations, we will develop a liquid film integral boundary layer model. This model will capture key liquid film dynamics, including phase change, inertia, and thermo-capillarity. The integral model’s validation will involve comparing the linear stability properties with the solution to the linearised full governing equations and assessing nonlinear dynamics against COMSOL simulations of the governing equations.

Based on the integral model, the continuation and bifurcation analysis of steady-state solutions will reveal how the liquid film’s behaviour develops as the evaporation rate or the Reynolds number varies. This analysis will identify key transitions and stability shifts affecting system performance. In addition, we will investigate the transient behaviour of disturbances via a nonlinear, nonmodal stability analysis. This approach will uncover nonlinear mechanisms that drive instabilities, such as the impact of temperature variations on the solid substrate during the evaporation or condensation phase.

The findings of this research will provide deeper insight into liquid film dynamics and develop a predictive reduced-order model for PHP systems. Additionally, these will be critical for designing optimal control laws based on liquid film stability properties, enhancing the evaporation/condensation mechanism, and guiding the design of more stable and efficient PHP configurations.

Gergely Buza: Rigorization of model reduction in fluid dynamics

The emergence of data-driven methods has fueled a newfound interest in the utilization of nonlinear tools from dynamical systems theory. In fluid dynamics, prominent examples are Koopman eigenfunctions (through dynamic mode decomposition) and spectral submanifolds. Due to their immense popularity, both of these techniques have been studied extensively, to the point that most aspects regarding their implementation are now fully fleshed out. However, there is one issue that has remained mostly untouched, and it is perhaps the most pressing one — the mathematical foundation of these tools. While the theory is well understood in the case of finite-dimensional systems, fluid dynamics is inherently infinite-dimensional, which calls for a more careful assessment. The talk will provide existence and uniqueness results for spectral submanifolds, smooth invariant foliations and Koopman eigenfunctions in the full, infinite-dimensional phase space of the Navier-Stokes system, alongside avenues to make the approximation procedure rigorous.

Add to your calendar or Include in your list

Fri 14 Feb 16:00: Synchronization in Navier-Stokes turbulence and it's role in data-driven modeling

Conservation at Cambridge - Tue, 11/02/2025 - 11:20
Synchronization in Navier-Stokes turbulence and it's role in data-driven modeling

In Navier-Stokes (NS) turbulence, large-scale turbulent flows determine small-scale flows; in other words, small-scale flows are synchronized to large-scale flows. In 3D turbulence, previous numerical studies suggest that the critical length separating these two scales is determined by the Kolmogorov length. In this talk, I will introduce our theoretical framework for characterizing synchronization phenomena [1]. Specifically, it provides a computational method for the exponential rate of convergence to the synchronized state, and identifies the critical length based on the NS equations via the “transverse” Lyapunov exponent. I will also discuss the synchronization property of 2D NS turbulence and how it differs from the 3D case [2]. These insights into synchronization and critical length scales are essential for developing machine-learning closure models for turbulence, in particular their stable reproducibility [3]. Finally, I will illustrate how “generalized” synchronization is crucial for predicting chaotic dynamics [4].

[1] M. Inubushi, Y. Saiki, M. U. Kobayashi, and S. Goto, Characterizing small-scale dynamics of Navier-Stokes turbulence with transverse Lyapunov exponents: A data assimilation approach, Phys. Rev. Lett. 131, 254001 (2023).

[2] M. Inubushi and C. P. Caulfield (in preparation).

[3] S. Matsumoto, M. Inubushi, and S. Goto, Stable reproducibility of turbulence dynamics by machine learning, Phys. Rev. Fluids 9, 104601 (2024).

[4] A. Ohkubo and M. Inubushi, Reservoir computing with generalized readout based on generalized synchronization, Sci. Rep. 14, 30918 (2024).

Add to your calendar or Include in your list

Mon 03 Mar 13:00: Intensified shelf break exchange through submarine canyons: upwelling, internal tides, and turbidity currents

Conservation at Cambridge - Mon, 10/02/2025 - 16:46
Intensified shelf break exchange through submarine canyons: upwelling, internal tides, and turbidity currents

Submarine canyons are a ubiquitous feature of continental margins worldwide and their complex geomorphology controls several physical processes that intensify the exchange of water masses, nutrients and carbon across the shelf break – from shallow shelf seas to the deep open ocean, and vice versa. In this seminar, I will illustrate three important shelf break exchange processes that are strongly controlled by submarine canyon geomorphology and discuss their interdisciplinary impacts. I will then highlight some previous and current research into these processes, applied to an exemplar submarine canyon close to the UK, and introduce two exciting upcoming projects that will further elucidate our understanding.

Add to your calendar or Include in your list

Wed 12 Feb 13:00: Short-term, high-resolution sea ice forecasting with diffusion model ensembles

Conservation-related talks - Mon, 10/02/2025 - 15:27
Short-term, high-resolution sea ice forecasting with diffusion model ensembles

Sea ice plays a key role in Earth’s climate system and exhibits significant seasonal variability as it advances and retreats across the Arctic and Antarctic every year. The production of sea ice forecasts provides great scientific and practical value to stakeholders across the polar regions, informing shipping, conservation, logistics, and the daily lives of inhabitants of local communities. Machine learning offers a promising means by which to develop such forecasts, capturing the nonlinear dynamics and subtle spatiotemporal patterns at play as effectively—if not more effectively—than conventional physics-based models. In particular, the ability of deep generative models to produce probabilistic forecasts which acknowledge the inherent stochasticity of sea ice processes and represent uncertainty by design make them a sensible choice for the task of sea ice forecasting. Diffusion models, a class of deep generative models, present a strong option given their state-of-the-art performance on computer vision tasks and their strong track record when adapted to spatiotemporal modelling tasks in weather and climate domains. In this talk, I will present preliminary results from a IceNet-like [1] diffusion model trained to autoregressively forecast daily, 6.25 km resolution sea ice concentration in the Bellingshausen Sea along the Antarctic Peninsula. I will also touch on the downstream applications for these forecasts, from conservation to marine route planning, which are under development at the British Antarctic Survey (BAS). I welcome ideas and suggestions for improvement and look forward to discussing opportunities for collaboration within and beyond BAS .

[1] Andersson, Tom R., et al. “Seasonal Arctic sea ice forecasting with probabilistic deep learning.” Nature communications 12.1 (2021): 5124. https://www.nature.com/articles/s41467-021-25257-4

Add to your calendar or Include in your list

Wed 12 Feb 13:00: Short-term, high-resolution sea ice forecasting with diffusion model ensembles

Conservation Talks - Mon, 10/02/2025 - 15:27
Short-term, high-resolution sea ice forecasting with diffusion model ensembles

Sea ice plays a key role in Earth’s climate system and exhibits significant seasonal variability as it advances and retreats across the Arctic and Antarctic every year. The production of sea ice forecasts provides great scientific and practical value to stakeholders across the polar regions, informing shipping, conservation, logistics, and the daily lives of inhabitants of local communities. Machine learning offers a promising means by which to develop such forecasts, capturing the nonlinear dynamics and subtle spatiotemporal patterns at play as effectively—if not more effectively—than conventional physics-based models. In particular, the ability of deep generative models to produce probabilistic forecasts which acknowledge the inherent stochasticity of sea ice processes and represent uncertainty by design make them a sensible choice for the task of sea ice forecasting. Diffusion models, a class of deep generative models, present a strong option given their state-of-the-art performance on computer vision tasks and their strong track record when adapted to spatiotemporal modelling tasks in weather and climate domains. In this talk, I will present preliminary results from a IceNet-like [1] diffusion model trained to autoregressively forecast daily, 6.25 km resolution sea ice concentration in the Bellingshausen Sea along the Antarctic Peninsula. I will also touch on the downstream applications for these forecasts, from conservation to marine route planning, which are under development at the British Antarctic Survey (BAS). I welcome ideas and suggestions for improvement and look forward to discussing opportunities for collaboration within and beyond BAS .

[1] Andersson, Tom R., et al. “Seasonal Arctic sea ice forecasting with probabilistic deep learning.” Nature communications 12.1 (2021): 5124. https://www.nature.com/articles/s41467-021-25257-4

Add to your calendar or Include in your list

Contact us

The David Attenborough Building
Pembroke Street
Cambridge
CB2 3QZ

Contact: admin@conservation.cam.ac.uk

Site Privacy & Cookie Policies

Study at Cambridge

About the University

Research at Cambridge