Oceanography The Official Magazine of
The Oceanography Society
Volume 31 Issue 01

View Issue TOC
Volume 31, No. 1
Pages 50 - 59

Deep Convection in the Irminger Sea Observed with a Dense Mooring Array

M. Femke de Jong Marilena OltmannsJohannes KarstensenLaura de Steur
Article Abstract

Deep convection is a key process in the Atlantic Meridional Overturning Circulation, but because it acts at small scales, it remains poorly resolved by climate models. The occurrence of deep convection depends on weak initial stratification and strong surface buoyancy forcing, conditions that are satisfied in only a few ocean basins. In 2014, one of the Ocean Observatories Initiative (OOI) global arrays was installed close to the Central Irminger Sea (CIS) and the Long-term Ocean Circulation Observations (LOCO) moorings in the central Irminger Sea. These programs’ six moorings are located in the center of an area of deep convection and are distributed within a 50 km radius, thus offering detailed insight into spatial differences during the strong convection events that occurred during the winters of 2014/2015 and 2015/2016. Deep mixed layers, down to approximately 1,600 m, formed during both winters. The properties of the convectively renewed water mass at each mooring converge to a common temperature and salinity before restratification sets in at the end of winter. The largest differences in onset (or timing) of convection and restratification are seen between the northernmost and southernmost moorings. High-resolution atmospheric reanalysis data show there is higher atmospheric forcing at the northernmost mooring due to a more favorable position with respect to the Greenland tip jet. Nevertheless, earlier onset, and more continuous cooling and deepening of mixed layers, occurs at the southernmost mooring, while convection at the northern mooring is frequently interrupted by warm events. We propose that these warm events are associated with eddies and filaments originating from the Irminger Current off the coast of Greenland and that convection further south benefits from cold inflow from the southwest.


de Jong, M.F., M. Oltmanns, J. Karstensen, and L. de Steur. 2018. Deep convection in the Irminger Sea observed with a dense mooring array. Oceanography 31(1):50–59, https://doi.org/10.5670/oceanog.2018.109.


Böning, C.W., E. Behrens, A. Biastoch, K. Getzlaff, and J. Bamber. 2016. Emerging impact of Greenland meltwater on deepwater formation in the North Atlantic Ocean. Nature Geoscience 9:523–528, https://doi.org/10.1038/NGEO2740.

Bosse, A., P. Testor, L. Houpert, P. Damien, L. Prieur, D. Hayes, V. Taillandier, X. Durrieu de Madron, F. D’Ortenzio, L. Coppola, and others. 2016. Scales and dynamics of submesoscale coherent vortices formed by deep convection in the northwestern Mediterranean Sea. Journal of Geophysical Research 121:7,716–7,742, https://doi.org/​10.1002/2016JC012144.

Bromwich, D.H., A.B. Wilson, L.-S. Bai, G.W.K. Moore, and P. Bauer. 2016. A comparison of the regional Arctic System Reanalysis and the global ERA-Interim Reanalysis for the Arctic. Quarterly Journal of the Royal Meteorological Society 142:644–658, https://doi.org/10.1002/qj.2527.

Dee, D.P., S.M. Uppala, A.J. Simmons, P. Berrisford, P. Poli, S. Kobayashi, U. Andrae, M.A. Balmaseda, G. Balsamo, P. Bauer, and others. 2011. The ERA-Interim reanalysis: Configuration and performance of the data assimilation system. Quarterly Journal of the Royal Meteorological Society 137:553–597, https://doi.org/10.1002/qj.828.

de Jong, M.F., and L. de Steur. 2016. Strong winter cooling over the Irminger Sea in winter 2014–2015, exceptional deep convection, and the emergence of anomalously low SST. Geophysical Research Letters 43:7,106–7,113, https://doi.org/​10.1002/2016GL069596.

de Jong, M.F., H.M. van Aken, K. Våge, and R.S. Pickart. 2012. Convective mixing in the central Irminger Sea: 2002–2010, Deep Sea Research Part I 63:36–51, https://doi.org/10.1016/​j.dsr.​2012.​01.003.

Doyle, J.D., and M.A. Shapiro. 1999. Flow response to large-scale topography: The Greenland tip jet. Tellus A 51:728–748, https://doi.org/10.3402/tellusa.v51i5.14471.

Fan, X., U. Send, P. Testor, J. Karstensen, and P. Lherminier. 2013. Observations of Irminger Sea anticyclonic eddies. Journal of Physical Oceanography 43:805–823, https://doi.org/10.1175/JPO-D-11-0155.1.

Houpert, L., X. Durrieu de Madron, P. Testor, A. Bosse, F. D’Ortenzio, M.N. Bouin, D. Dausse, H. Le Goff, S. Kunesch, M. Labaste, and others. 2016. Observations of open-ocean deep convection in the northwestern Mediterranean Sea: Seasonal and interannual variability of mixing and deep water masses for the 2007–2013 period. Journal of Geophysical Research 121:8,139–8,171, https://doi.org/​10.1002/2016JC011857.

Holdsworth, A.M., and P.G. Myers. 2015. The influence of high-frequency atmospheric forcing on the circulation and convection of the Labrador Sea. Journal of Climate 28:4,980–4,996, https://doi.org/10.1175/JCLI-D-14-00564.1.

Killworth, P.D. 1979. On chimney formation in the ocean. Journal of Physical Oceanography 9:531–554, https://doi.org/10.1175/​1520-0485(1979)009<0531:OFITO>2.0.CO;2.

Lazier, J.R. 1973. The renewal of Labrador Sea Water. Deep Sea Research 20:341–353, https://doi.org/​10.1016/0011-7471(73)90058-2.

Lozier, M., S. Bacon, A. Bower, S. Cunningham, M. de Jong, L. de Steur, B. deYoung, J. Fischer, S. Gary, B. Greenan, and others. 2017. Overturning in the Subpolar North Atlantic Program: A new international ocean observing system. Bulletin of the American Meteorological Society 98(4):737–752, https://doi.org/10.1175/BAMS-D-16-0057.1.

Marshall, J., and F. Schott. 1999. Open-ocean convection: Observations, theory and models. Reviews of Geophysics 37:1–64, https://doi.org/​10.1029/98RG02739.

Moore, G.W.K. 2003. Gale force winds over the Irminger Sea to the east of Cape Farewell, Greenland. Geophysical Research Letters 30, 1894, https://doi.org/10.1029/2003GL018012.

Moore, G.W.K., D.H. Bronwich, A.B. Wilson, I. Renfrew, and L. Bai. 2016. Arctic system reanalysis improvements in topographically forced winds near Greenland. Quarterly Journal of the Royal Meteorological Society 142:2,033–2,045, https://doi.org/10.1002/qj.2798.

Moore, G.W.K., and I.A. Renfrew. 2005. Tip jets and barrier winds: A QuickSCAT climatology of high wind speed events around Greenland. Journal of Climate 18:3,713–3,725, https://doi.org/10.1175/JCLI3455.1.

Moore, G.W.K., I.A. Renfrew, B.E. Harden, and S.H. Mernild. 2015. The impact of resolution on the representation of southeast Greenland barrier winds and katabatic flows. Geophysical Research Letters 42:3,011–3,018, https://doi.org/​10.1002/2015GL063550.

Nansen, F. 1912. Das Bodenwasser und die Abkuhlung des Meeres. Internationale Revue der gesamten Hydrobiologie und Hydrographie 5:1–42, https://doi.org/10.1002/iroh.19120050102.

Palevsky, H.I., and D.P. Nicholson. 2018. The North Atlantic biological pump: Insights from the Ocean Observatories Initiative Irminger Sea Array. Oceanography 31(1):42–49, https://doi.org/10.5670/oceanog.2018.108.

Pickart, R.S., F. Straneo, and G.W.K. Moore. 2003. Is Labrador Sea Water formed in the Irminger Basin? Deep Sea Research Part I 50(1):23–52, https://doi.org/​10.1016/S0967-0637(02)00134-6.

Sverdrup, H.U., M.W. Johnson, and R.H. Fleming. 1942. The Oceans: Their Physics, Chemistry, and General Biology. Prentice-Hall Inc., Englewood Cliffs, NJ, USA, 1,060 pp.

Testor, A. Bosse, L. Houpert, F. Margirier, L. Mortier, H. Legoff, D. Dausse, M. Labaste, J. Karstensen, D. Hayes, and others. 2017. Multiscale observations of deep convection in the northwestern Mediterranean Sea during winter 2012–2013 using multiple platforms. Journal of Geophysical Research, https://doi.org/10.1002/2016JC012671.

Våge, K., R.S. Pickart, G.W.K. Moore, and M.H. Ribergaard. 2008. Winter mixed layer development in the central Irminger Sea: The effect of strong, intermittent wind events. Journal of Physical Oceanography 38:541–565, https://doi.org/​10.1175/2007JPO3678.1.

Yashayaev, I., and J.W. Loder. 2017. Further intensification of deep convection in the Labrador Sea in 2016. Geophysical Research Letters 44:1,429–1,438, https://doi.org/​10.1002/2016GL071668.