With his project Groeskamp wants to provide a solution to accurately and globally quantify a fundamental physical process that can’t be measured on large scales; ocean mixing. Ocean mixing processes profoundly impact climate and ecosystems by redistributing and storing dissolved tracers such as heat, carbon, oxygen and nutrients. However, ocean mixing occurs on space and time scales that can’t be measured globally and can’t be resolved in many observational-based studies or numerical simulations of ocean and climate.

Groeskamp explains: "Mixing occurs when we stir milk into our coffee with a spoon. Now imagine that process, but in the ocean. Instead of a spoon the ocean mixes with breaking waves in the ocean interior and large whirls of hundreds of kilometres. Mixing is very important for local and global scale ocean processes that influence our society. Such processes are future sea level rise, ocean circulation, marine oxygen production, the hydrological cycle (rain and droughts), hurricane strengths and climate change. Due to our limited knowledge of ocean mixing, we also limit how accurately we can predict these important processes for our society. Unfortunately, ocean mixing is almost impossible to measure. Therefore, we develop techniques to estimate mixing indirectly, from variables affected by mixing that are easy to measure (e.g. temperature), therewith improving future climate predictions."

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).

"Instead of measuring mixing directly, we develop new technologies to estimate mixing indirectly, but from variables that are already widely measured and available on a global scale (e.g, ocean's temperature and salinity).  Together with a PhD candidate, we will test and calibrate these new methods using ship-based expedition to deploy and retrieve instruments that are designed to collect data for this purpose, such that the new techniques can be applied globally".

The results of such studies will ultimately inform the international research-based summaries of the state of the climate such as the Intergovernmental Panel on Climate Change (IPCC) upon which international climate policy is based (e.g. the Paris agreement).

Sjoerd Groeskamp on an earlier expedition on RV Southern Surveyor, near Brisbane Australia, measuring the Eastern Ausralian Current.

'Mapping of ocean mixing' ontvangt Open Competitie ENW-M beurs

NIOZ oceanograaf Sjoerd Groeskamp heeft de beurs gekregen voor zijn project 'Measuring the immeasurable: mapping of ocean mixing' . Het bestuur van het NWO-domein Exacte en Natuurwetenschappen heeft in totaal 16 aanvragen in de Open Competitie ENW-M gehonoreerd. M-subsidies zijn bedoeld voor vernieuwend, fundamenteel onderzoek van hoge kwaliteit en/of wetenschappelijke urgentie.

Groeskamp licht toe wat hij met dit onderzoek wil bereiken: "Melk meng je door je koffie met een lepel. Menging in de oceaan gaat niet met een lepel, maar door brekende (onderwater)golven en wervels van 100 km doorsnee. Deze menging beïnvloedt het klimaat, omdat het de opname en opslag faciliteert van warmte en CO2 uit de atmosfeer in de oceaan. We moeten weten hoe sterk deze menging is, en waar deze plaatsvindt, om ons toekomstige klimaat te begrijpen en te voorspellen. Helaas is menging bijna onmeetbaar. Daarom ontwikkelen wij technieken om menging in de oceaan te schatten gebruikmakende van waarden die we wel kunnen meten, zoals temperatuur en zoutgehalte."