Dr. Sjoerd Groeskamp

Stirring the oceans

Expertise

1. Understanding and quantifying ocean mixing from local to global scales.

2. Water mass transformation and transport of biogeochemical tracers.

3. Seal level rise: The Northern European Enclosure Dam (NEED).

4. Miscellaneous studies: Resonantly Generated Internal Waves

Keywords: Mixing, Inverse Methods, Internal Waves, Sea Level Rise, water masss transformation, tracers.

My extended webpages can be found under www.sjoerdgroeskamp.com.

No one-person can answer these important questions discussed above in perfect detail, but we can all contribute our piece of the puzzle. I study ocean processes that influence the answers to these questions, and I deliver these pieces of the puzzle to the broader science community. As a community we then try to solve the puzzle and answer these questions as a whole.

"My work is to contribute to our understanding of
the role of the ocean in climate and ecosystems."

• From the weather we experience to the climate we live in.
• ​From the oxygen we breathe to the food we eat.
• ​From the resources mined and extracted from the ocean bottom, to the first signs of life on this planet.
• ​The ocean is key to (our) life on earth.
• The ocean can both be the source and the solution for the many problem we face.

Examples

The ocean has absorbed about 30% of the CO2 emitted by humans and 90% of the extra warmth (heat) added to the atmosphere by human activity. Imagine how warm it could have been now without this effect! Small changes in these numbers can have enormous impacts on our weather and climate. So how much heat and CO2 will the ocean keep absorbing in the future? 

Another example is sea level rise predictions that vary from 1 to 3 meters in 2100 and possibly over 20 meters in the following centuries. Which of these predictions are most accurate? How fast will sea level rise occur? And how do we cope with such changes?

These are only a few of many reasons why we should care about the ocean.

Although the Amazon is often considered to be the lungs of the planet, as it produces about 20% of the oxygen we breath, it is actually ocean phytoplankton (single celled algae) that produce about 50% of the oxygen in our atmosphere. This picture shows phytoplankton near Finland. Phytoplankton growth depends strongly on ocean circulation and mixing processes. This is a NASA Earth Observatory images by Joshua Stevens and Lauren Dauphin, using Landsat data from the U.S. Geological Survey and MODIS data from LANCE/EOSDIS Rapid Response on July 18, 2018.

Understanding and quantifying ocean mixing from local to global scales.

A cartoon by Malou Zuidema Illustrations, showing a combination of external ingredients and ocean mixing, will lead to the creation of different types of water (fresher Vs Saltier, Warmer Vs Cooler, etc).

Mixing is a fundamental processes occurring in the ocean. With fundamental, I refer to both the small scales at which mixing occurs, as the fact that mixing feeds into many other important ocean features. Examples are transport of heat and carbon, ocean-atmosphere interaction and food availability for marine animals. Clearly, understanding mixing is important for understanding many other things that happen in the ocean.

​Not only should we understand ocean mixing processes, we also need to quantify them. Evidently, mixing is not the same everywhere (think of the difference between calm waters and the surf zone). However, the spatial and temporal distribution of mixing strengths are not well known. This is because mixing is difficult to measure due to do technological, logistical and financial limitation.

Therefore, I develop techniques that estimate mixing indirectly from observations that are available, such as temperature and salinity. These estimates help understand how to implement mixing in numerical simulations of our future climate and sea level.

​Water mass transformation and transport of biogeochemical tracers.

A cartoon by Malou Zuidema Illustrations, illustrating the processes that influence water mass transformation. This figure is part of the paper Groeskamp et al (2019) - The Water Mass Transformation Framework for Ocean Physics and Biogeochemistry.

Water mass transformation described how properties of a bit of water in the ocean (a water mass) can change (transform). These properties can be heat, density, carbon, oxygen, amongst many others. Studying water mass transformation improves improve our understanding of how these properties are absorbed, transported, stored in the ocean.

​In an abstract way, water mass transformation is a form of ocean circulation, but instead of using “location” as a property, we use a tracer as property. This trick provides completely new description and insights into the movement of these properties through the ocean.

Seal level rise: The Northern European Enclosure Dam (NEED).

A sketch of the Northern European Enclosure Dam, conceptualised to protect many countries and cities against Sea Level Rise. However, I emphasise that this is the very last thing we actually want to do, due to its immense consequences for nature, the maritime industry, the weather and many other things. The best approach is to avoid SLR as much as possible, as a whole, by reducing climate change to a minimum.

Society today is shaped by the climate of the past. Now that human activities rapidly change the climate, society will need to adapt. Among many other damaging effects, sea level rise (SLR) is also a consequence of climate change. Cities and agricultural land are now threatened by flooding and may become inhabitable or unusable.

The best solution to avoid problems is to mitigate (avoid) human-caused climate change. Considering the uncertainty of our ability to do so, I believe we need to simultaneously prepare for worst case scenario’s. I think about such solutions, while I also try to understand and quantify the effects on SLR due to various fundamental oceanographic processes such as mixing.

The figure above illustrates NEED: "The Northern European Enclosure Dam". It would possibly be a solution, if climate mitigation fails. However, this solution is so dramatic that it may feel unrealistic. And yet, it is merely an example of the scale of the problems we are facing. That is, the threat of SLR is so large, that we need to think in solution that are equally large. Let us hope we can limit climate change and SLR, such that solutions as NEED will not be required.

For more information on my research, my publication list and alternative research topics, please visit www.sjoerdgroeskamp.com