Royal Netherlands Institute for Sea Research

Femke de Jong

Tenure track Scientist
Phone number
+31 (0)222 369 411
Location
Texel
Department
Ocean Systems (OCS)
Function
Tenure track Scientist

Expertise

  • Physical oceanography
  • Fieldwork & in situ observations
  • Deep convection
  • Mesoscale eddies
  • Atlantic Meridional Overturning Circulation (AMOC)

Research interest

My research is mostly based in the North Atlantic Subpolar Gyre, investigating processes like dense water overflows, deep convection and boundary current – interior exchange. I am particularly interested in the relation between these processes and the Atlantic Meridional Overturning Circulation (AMOC).

I am a sea going oceanographer with a preference for hydrographic and Lagrangian observations, though I often use models and theory to better understand these observations.

NACLIM/OSNAP Irminger Current array

Oceanographic research carried out in the North Atlantic Ocean is of great importance to understand the role of the ocean in our climate and future climate change. As part of an international collaboration between the US, UK, Germany, France, the Netherlands, Canada and China the Netherlands Institute for Sea Research (NIOZ) deployed a moored array on the western flank of the Mid Atlantic Ridge. These 5 moorings (four tall and one short) sample the northward flow of warm, saline water in the Irminger Current in the upper water column as well as the dense North East Atlantic Deep Water (also called Iceland Scotland Overflow Water) in the lower water column.

The complete OSNAP array will provide a high-resolution time series of full water-column transs-baisn fluxes of volume, heat and freshwater. This will provide a measure of the strength and variability of the Atlantic Meridional Overturning Circulation in the Subpolar North Atlantic.

Schematic of the OSNAP array.

This video shows our research on the currents in the subpolar North Atlantic. More information can be found on the OSNAP webpage at www.o-snap.org. Here you can find video's of the NACLIM project.

Pathways to Denmark Strait

The water mass that overflows the shallow sill of Denmark Strait (aptly named Denmark Strait Overflow Water or DSOW) is the densest constituent of North Atlantic Deep Water, which forms the deep southward return flow in the Meridional Overturning Circulation. There are two main hypothesized sources of DSOW, the Greenland Sea via the East Greenland Current, or the Iceland Sea via the North Icelandic Jet (or possibly a both). 

RAFOS floats were deployed in the Iceland Sea to elucidate the sources of DSOW and the pathways of dense water to the Denmark sill. The first batch of 26 floats was deployed in July 2013, the second batch of 26 floats was deployed in July 2014. These floats can be tracked using the signals of six sound sources moored in the Iceland Sea.

The Iceland Sea: topography, main currents and RAFOS deployment positions.

(Funded by NSG grant# 1259210: de Jong & Bower, in collaboration with Henrik Soiland of the Institute of Marine Research, Bergen, Norway.)

Meso-scale eddies in the Labrador Sea

The Labrador Sea is one of few regions where deep convection occurs. During strong winters the surface waters are cooled to the point where they become dense enough to sink and mix with deeper waters. This process forms a cold water mass called Labrador Sea Water that extends from the surface down to 1 to 2 km deep. During spring and summer the central Labrador Sea restratifies. The warm, saline water responsible for the restratification is thought to originate from the Irminger Current along the west Greenland shelf. Due to a sudden steepening of the shelf the current becomes unstable and sheds warm-core eddies. These eddies can transport heat and salt to the interior basin.

Example of modelled and observed eddies in the Labrador Sea.

 

Using observations from a mooring we estimated the heat transport of eddies into the Labrador Sea. We found that these eddies vary strongly in size, with radii from 11 to 35 km. Seasonally varying properties add to the large range in transport estimates.

Linked news

Friday 01 June 2018
3 Vidi-beurzen voor NIOZ-onderzoekers | 3 Vidi grants for NIOZ researchers
[Scroll down for English version] De Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) heeft aan drie ervaren NIOZ-onderzoekers een Vidi-financiering van 800.000 euro toegekend. Hiermee kunnen zij de komende vijf jaar een eigen,…

NIOZ publications

  • 2018
    de Jong, M.F.; Oltmanns , M.; Karstensen, J.; de Steur, L. (2018). Deep convection in the Irminger Sea observed with a Dense Mooring Array. Oceanography 31(1): 50-59. https://dx.doi.org/10.5670/oceanog.2018.109
  • 2017
    Lozier, M.S.; Bacon, S.; Bower, A.S.; Cunningham, S.A.; de Jong, M.F.; de Steur, L.; de Young, B.; Fischer, J.; Gary, S.F.; Greenan, B.J.W.; Heimbach, P.; Holliday, N.P.; Houpert, L.; Inall, M.E.; Johns, W.E.; Johnson, H.L.; Karstensen, J.; Li, F.; Lin, X.; Mackay, N.; Marshall, D.P.; Mercier, H.; Myers, P.G.; Pickart, R.S.; Pillar, H.R.; Straneo, F.; Thierry, V.; Weller, R.A.; Williams, R.G.; Wilson, C.; Yang, J.; Zhao, J.; Zika, J.D. (2017). Overturning in the Subpolar North Atlantic Program : a new international ocean observing system. Bull. Am. Meteorol. Soc. 98(4): 737-752. https://dx.doi.org/10.1175/BAMS-D-16-0057.1
  • 2016
    de Jong, M.F.; Bower, A.S.; Furey, H.H. (2016). Seasonal and Interannual Variations of Irminger Ring Formation and Boundary–Interior Heat Exchange in FLAME. J. Phys. Oceanogr. 46: 1717-1731. dx.doi.org/10.1175/JPO-D-15-0124.1
    de Jong, M.F.; de Steur, L. (2016). Strong winter cooling over the Irminger Sea in winter 2014–2015, exceptional deep convection, and the emergence of anomalously low SST. Geophys. Res. Lett. 43: 7106–7113. dx.doi.org/10.1002/2016GL069596

Linked projects

Blue-Action_Lower latitude drivers of Arctic changes
Supervisor
Gert Jan Reichart
Funder
European Community
Project duration
1 Dec 2016 - 28 Feb 2021