A numerical ocean model is a computer programme representing the equations of motion (momentum, conservation of mass and thermodynamics) for the ocean. The model stores each of the physical properties of the ocean (temperatures, salinities and currents) on a three-dimensional grid, writes Ana Aguiar.
Ocean models store physical properties such as salinity, temperature and currents on a three-dimensional grid. Picture: Adobe Stock
Smaller ocean features can be resolved by using a finer grid with more points, but this requires more computational power. The model evolves these physical properties forward in time using its equations of motion. Models of sea ice and biogeochemistry work using similar principles.
Why do we need a numerical ocean model?
We need these models to predict the state of the ocean within short and long timescales for a variety of purposes, ranging from support to operations at sea (for example, search and rescue) to understanding the role of the ocean in the Earth’s climate system. As the ocean sits beneath the atmosphere, sea-surface temperature patterns have widespread impact on the weather over land. Largely because two-thirds of the Earth is covered by ocean and the heat capacity of water considerably outweighs that of the air, the ocean acts as a regulator of the atmosphere.
In polar regions temperatures become cold enough for seawater to freeze and sea ice forms on the surface of the ocean. Sea ice plays an important role in the climate system because it insulates the ocean from the colder atmosphere in winter and, being whiter than the ocean, reflects sunlight in the summer.
The NEMO modelling framework includes a sea-ice model component, known as SI³ (Sea Ice modelling Integrated Initiative). The sea-ice component is run along with the ocean component in a similar manner but using a different set of equations. To understand and prepare for climate change we need to account for the role of the ocean and sea ice.
How is the NEMO model developed?
Nucleus for European Modelling of the Ocean (NEMO) is a state-of-the-art ocean modelling framework. NEMO is developed by a European consortium with the objective of ensuring long-term reliability and sustainability of the code. In other words, the task of maintaining and developing such a complex computer programme requires a well-coordinated team effort, involves tens of developers and hundreds of users.
In the UK there are two member organisations: the Met Office and the National Oceanography Centre (NOC). Met Office Scientific Manager in Ocean Modelling, Ana Aguiar explains: “We work in partnership through the Joint Marine Modelling Programme, contributing to the development of NEMO. The code is publicly available for use in research and commercial applications. It is imperative to reach as many users as possible, to ensure the code gets tested and pushed to the limits of its usability. User requirements then prompt further advances.”
NEMO benefits from continual work to improve its performance (scientific and computational efficiency), to incorporate new scientific and process understanding, and to exploit the increase in supercomputer resources. When the developments are sufficiently mature and can provide significant scientific or technical improvements, a new NEMO version is released. Along with scientific upgrades (which tend to be increasingly computationally demanding), we must deliver code optimisation to make the best use of the available computing resources. This video presents how NEMO is used by the Copernicus Marine Environment Monitoring Service.
What’s next?
The next NEMO release (expected to be rolled out this summer) will deliver significant improvements to model performance allowing it to run considerably faster. In the long term, among other things, we are also working towards porting the NEMO code to Graphical Processing Units (GPUs) to ensure continuity of the code in future mainstream High Performance Computing architectures
During April we are exploring the topic of the ocean and climate. Follow the #GetClimateReady hashtag on X (formerly Twitter) to learn more throughout the month.
Warmer weather, flooding, and droughts are already affecting rugby, but how will the increasing effects of climate change impact rugby in the future?
A new report by World Rugby (the rugby union governing body), has identified six major climate risks which could impact the sport, either directly or indirectly, in the future if action is not taken to increase the sport’s resilience against the risks of climate change.
The Climate Change and Rugby report investigated climate hazards across ten countries (Argentina, Australia, England, Fiji, France, India, Japan, New Zealand, South Africa, and the USA), and found there would be significant impacts for each region if global average temperature were to reach levels of +2°C above a pre-industrial level.
The IPCC Sixth Assessment Report (AR6) states that since the Industrial Revolution, the average temperature of the planet has risen by around 1.1°C.
Using a methodology which includes projections alongside observations, research by the Met Office indicates the current global warming level could be as high as 1.25°C. This is a rapid change in terms of our global climate system and is already leading to changes in the extreme weather we experience on the Earth’s surface.
Extreme heat days
As global temperatures rise, so do the instances of extreme heat days (days in which the temperature exceeds 35°C). This not only puts rugby players at risk, but fans of the sport too. This has been seen in other sports in the past where matches have needed to be called off because of scorching temperatures. For example, in 2014, play had to be suspended on all uncovered courts for more than 4 hours at the Australian open due to temperatures rising to over 40°C, causing a risk of heat exhaustion or heatstroke for the athletes.
World Rugby’s report found that six out of the ten countries they investigated would face ten or more additional days each year where playing rugby would be ill advised or even impossible due to climbing temperatures.
Increased frequency and intensity of droughts
Droughts affect the availability of water, and reduced access to this resource could result in drier, harder and less grassy pitches. The report indicates that dry conditions will reduce the quality of playing surfaces, affecting ball bounce and player movement. This could also increase the risk of players getting injured when athletes tumble onto hard ground. Half of all countries in the study would likely see an increase in the frequency and intensity of droughts, leading to less days where pitches are suitable for use.
Marine submersion and flooding risks
The report shows that rising sea levels pose a threat to stadiums near the coast, while flash floods caused by the increased frequency and intensity of rain pose a threat to both coastal pitches and those further inland. Floods could make stadiums inaccessible for extended periods of time, as even after the water subsides, turf and building structures can be left with substantial damage. Repairing stadiums after flooding can be costly and take a long time. World Rugby says that 11% of the 111 stadiums in the report can expect to see an increased annual submersion risk, while eight out of ten countries studied will face an increase in the frequency and intensity of heavy precipitation and flash floods.
Increased humidity
Increased humidity can cause additional heat-related suffering for athletes, officials, and spectators. Higher levels of humidity can make heat feel more intense and reduce the body’s ability to perform certain functions, such as sweating. Additionally, high levels of humidity can cause issues with the health and growth of certain grass varieties that may be used on pitches. The report found that most climate regions will experience periods of higher humidity, impacting the ability to play rugby.
Adaptation
To reduce the impacts of climate change on rugby, some adaptations will need to be made in the future. World Rugby has suggested in their report the development and implementation of individual sustainability plans, to help reduce rugby’s environmental impact. As well as this, climate projections will need to be considered when implementing new policies to prepare the game for a changing climate.
In a recent blog, we shared details of a piece of work by the Met Office which explores expected future climatic conditions for a range of range of cultural, sporting and social events across the UK. The study compares observations and climate projections for temperature and rainfall may change in the future for the start of the Six Nations (February) at the Twickenham (London), Murrayfield (Edinburgh) and Principality (Cardiff) stadiums.
Climate change already has, and will likely continue to affect rugby, but with research and the implementation of new strategies and adaptation, risks can be minimised to allow fans and athletes to continue to enjoy the sport.
The Met Office has just published its latest briefing on Arctic and Antarctic sea ice.
The update doesn’t reveal any record-breaking figures, but it does reveal that sea ice loss remains a serious issue.
Alex West who co-ordinates the sea ice briefings said: “After last year’s record-breaking minimum extent of sea ice in the Antarctic, the latest update shows greater sea ice extent than last year, but it is still the second lowest on record for the time of year.
Following a warm June, Arctic sea ice extent is below average for the time of year but some way above record low levels, with conditions fairly typical of recent years.
“Extent is particularly low in the Laptev Sea and in the Atlantic sector, but nearer average in other parts of the Arctic.
“This year’s September Arctic sea ice extent is likely to be well below average, but there are not yet heightened indications of a new record low.”
The Advancing Arctic Capabilities programme – a new project led by the Met Office -brings international partners to develop an improved understanding of what is happening to the region’s ice, ocean and atmosphere to support global climate resilience.
The project will deliver cutting-edge insights into Arctic weather patterns and ocean currents.
Hurricane Beryl, which has been tearing through the Caribbean, has been hitting the headlines for several reasons.
Firstly, there is the undeniable fact that during her existence as a Category 4 and 5 hurricane Beryl caused much damage and loss of life across several nations and territories, including Grenada, St Vincent and the Grenadines, Jamaica and the British Overseas Territory of the Cayman Islands.
Satellite image of Hurricane Beryl crossing Jamaica in early July 2024
Secondly, Beryl has become infamous for being the earliest Category 5 hurricane in the historical record in the Atlantic Basin. Category 5 is the highest ranking for hurricanes requiring sustained wind speeds of at least 157 mph. Hurricane Beryl’s wind actually peaked at 165 mph on 2 July. The earliest date in the year any previous Atlantic hurricane had achieved winds of this strength was a full month later on 5 August.
Active hurricane season
Julian Heming is a Met Office tropical cyclone expert who has been studying these systems for many years. He said: “In the second half of May several prediction centres, including the Met Office, forecast an active Atlantic hurricane season with between 150% and 200% of usual activity.
“These Atlantic seasonal forecasts have been influenced by the development of cooler waters in the equatorial eastern Pacific in recent months – in line with the anticipated La Niña or cooler phase of the naturally-variable El Niño Southern Oscillation (ENSO) cycle.
“Developing La Niña conditions have a known association with a more active Atlantic hurricane season. So, we know that natural variation in the climate system has a huge observable effect on hurricane activity.
“But this trend towards La Niña favouring hurricane development would not solely explain Hurricane Beryl and the prediction of an active hurricane season.
“Sea temperatures across the tropical Atlantic and Caribbean Sea have been well above average since the Spring of 2023 which provides fuel for intense hurricanes like Beryl. There is much meteorologists do not yet understand about how these high sea-surface temperatures have developed and why they have persisted for so long. This is an active area of research.”
“Furthermore, higher sea-surface temperatures in line with a warming climate are expected to favour the development of a greater proportion of intense tropical cyclones in the long term.”
International effort
Will Lang is the Met Office’s head of Situational Awareness. He said: “Met Office forecasts are a crucial part of the international effort to predict Atlantic hurricanes, and our experts work at the heart of UK Government’s international response to damaging hurricanes such as Beryl.”
You can watch an interview about Hurricane Beryl here.
