Ocean warming is subtly changing the tides

Few aspects of the natural world are as dependable as ocean tides. These significant phenomena, shaped by the gravitational pull of the Moon and Sun, are easily observable through various oceanographic tools and satellite data. Ocean tides influence the daily lives of millions and the health of countless ecosystems.

Recently, however, scientists have observed subtle shifts in tidal patterns that cannot be explained by the usual lunar and solar influences. Emerging data suggests that these changes might be linked to the rising temperatures of ocean surfaces.

Significance of ocean tides

Ocean tides affect the distribution and behavior of marine organisms. Many species rely on tidal cycles for feeding, breeding, and migration. Changes in tidal patterns can disrupt these processes and impact marine biodiversity.

Coastal erosion

Tidal patterns also influence coastal erosion and the risk of flooding. Shifts in tides can exacerbate these issues, leading to increased damage to coastal infrastructure and habitats. Understanding tidal changes helps in planning and protecting coastal areas.

Fishing practices

Accurate predictions of tidal patterns are essential for safe navigation and effective fishing practices. Changes in tides can affect the availability of certain fish species and alter traditional fishing grounds.

Climate change

Tidal patterns serve as indicators of broader climate changes. By studying shifts in tides, scientists can gain insights into how climate change is impacting ocean dynamics and weather patterns. This information is vital for developing strategies to mitigate and adapt to climate change.

Renewable energy and coastal economies

Tidal energy is a renewable resource that relies on predictable tidal patterns. Changes in tides can affect the efficiency and viability of tidal energy projects.

Additionally, tourism, shipping, and coastal economies can be impacted by shifts in tidal behavior. Understanding these changes helps in managing economic activities linked to the ocean.

Climate change and ocean tides

Dr. Michael Schindelegger, employing state-of-the-art supercomputing facilities at the Jülich Supercomputing Centre, has dedicated his research to understanding the effects of climate change on ocean tides.

By analyzing data from 1993 to 2020, he aims to enhance the precision of three-dimensional ocean circulation models.

“Tides often mask other potentially interesting and less predictable signals related to, for example, the general circulation of the ocean or effects of climate change,” explains Dr. Schindelegger.

Accurately modeling tides, especially their changes over time, is crucial for extracting climate signals from oceanographic data.

Complexity beneath the surface

The upper 700 meters of the ocean absorbs about 90% of the excess heat from the atmosphere. This ocean layer is becoming hotter and less dense – thus increasing the density contrast with the colder, denser deep waters. Such stratification affects how tides operate.

Dr. Schindelegger and his team focus on the interaction between warming climates, ocean stratification, and tidal currents. Specifically, they study barotropic tides – those driven by gravitational forces – and baroclinic tides, which occur when ocean currents encounter underwater features, forcing denser deep water upwards.

“Warming in the upper ocean enhances the energy transfer from barotropic to baroclinic tides, resulting in open-ocean tides losing a few percent more energy to internal waves than three decades ago,” notes Dr. Schindelegger.

Understanding these dynamics is essential for predicting future impacts on coastal regions.

Duo of data and models

Modeling and observing ocean tides is an ongoing process, bolstered by continuous data acquisition. However, coastal data can suffer from noise and inaccuracies, and computational models often simplify real-world complexities. This requires a balanced approach that incorporates both observational data and detailed modeling.

“Established 2D ocean models need expansion to include depth and higher resolution to achieve meaningful accuracy,” says Dr. Schindelegger.

Computing power for complex models

The journey to model these intricate processes began with simple, single-layer ocean models that could run on a single CPU.

Over five years, Dr. Schindelegger gradually incorporated more complexity into the models, but soon realized that significant computing power was needed.

The JSC’s supercomputer, JUWELS, with its capacity to handle about 300 million grid points and execute a million core hours, became essential in advancing the research.

Projecting climate impact on ocean tides

Although the observed changes in surface tides are subtle – such as a one-centimeter drop in coastal tide levels over several decades – the implications for areas like the Gulf of Maine or northern Australia could be profound.

These regions, characterized by complex underwater topography and pronounced tidal activity, might experience significant impacts from even minor tidal changes.

As Dr. Schindelegger continues to refine the 3D models with ongoing supercomputing support, the goal remains clear. He strives to predict how ongoing changes in ocean stratification will affect coastal areas in the future.

By combining powerful computational resources with detailed observational data, researchers like Dr. Schindelegger are at the forefront of understanding how a warming climate alters the very pulse of our oceans.

This dual approach not only provides a deeper insight into the complexities of ocean tides but also underscores the broader implications of climate change on marine and coastal ecosystems.

The study is published in the journal Communications Earth & Environment.

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