The Thickness of Winter Water

Pine Island Glacier – Landsat image: NASA

Story by Helen Hill

This month we turn our attention to scientists working at NASA JPL who have been using MITgcm to examine what sets the thickness of so-called “Winter Water” in a region of the Antarctic off shore from the Pine Island Glacier.

The ice shelves and glaciers of the West Antarctic Ice Sheet are melting and thinning rapidly in the Amundsen Sea and Bellingshausen Sea, with consequences for global sea level rise and ocean circulation. Recent studies suggest that the thickness of Winter Water, that is, water with potential temperature below ∼-1°C located below Antarctic Surface Water and above Circumpolar Deep Water is critical in determining the ice shelf melt rate, especially for the Pine Island Glacier. Existing model studies, however, misrepresent the thickness of this layer as well as other water properties in the Amundsen Sea.

By adjusting a small number of model parameters in a regional Amundsen and Bellinghausen Seas configuration of MITgcm, Nayayama et al (2017), publishing in the Journal of Geophysical Research Oceans, report being able to much more closely reproduce the properties and thickness of Winter Water and Circumpolar Deep Water seen in observations

Although a previous modeling study suggested that the local surface heat loss upstream from the Pine Island Polynya (a polynya is an ice-free area within an otherwise extensive field of unbroken sea ice) could be the reason for an observed decline in melting of the Pine Island Glacier and thickening of the Winter Water layer in 2012, that study did not reproduce Winter Water freshening, which was observed at the same time.

The JPL team concludes that since their model sensitivity experiments for surface heat loss, Pine Island Glacier melt rate, and precipitation fail to replicate Winter Water freshening concurrent with Pine Island Glacier melt decline, these processes can not fully explain the observed decrease is melting of the glacier.

To find out more about this work contact Yoshihiro

About the Researchers:

Yoshihiro Nakayama

Yoshihiro Nakayama is a Postdoctoral Fellow in the Sea Level and Ice Group in JPL’s Earth Science division where he works with co-authors Research Scientist Dimitris Menemenlis, Postdoctoral Scholar Michael Schodlok and Eric Rignot a joint faculty appointee with the University of California, Irvine. When Nakayama is not busy trying to model how the Antarctic works he says he enjoys scuba diving, traveling, eating, drinking, and sleeping.

This Month’s Featured Publications:

Other New Publications this Month:

Yassir A. Eddebbar, Matthew C. Long, Laure Resplandy, Christian Rödenbeck, Keith B. Rodgers, Manfredi Manizza, Ralph F. Keeling (2017), Impacts of ENSO on air-sea oxygen exchange: Observations and mechanisms, Global Biogeochemical Cycles, doi: 10.1002/2017GB005630

Kesari Pradhan, Himansu; Nerger, Lars; Voelker, Christoph (2017), Assimilation of OC-CCI data into the coupled ocean-biogeochemical model MITgcm-REcoM, 19th EGU General Assembly, EGU2017, proceedings from the conference held 23-28 April, 2017 in Vienna, Austria, p.3710,

http://adsabs.harvard.edu/abs/2017EGUGA..19.3710K

Thomas Kaminski and Pierre-Philippe Mathieu (2017), Reviews and syntheses: Flying the satellite into your model: on the role of observation operators in constraining models of the Earth system and the carbon cycle, Biogeosciences, 14, 2343–2357, doi: 10.5194/bg-14-2343-2017

Chengyan Liu, Zhaomin Wang, Chen Cheng, Ruibin Xia, Bingrui Li, Zelin Xie (2017), Modeling modified Circumpolar Deep Water intrusions onto the Prydz Bay continental shelf, East Antarctica, Journal of Geophysical Research – Oceans, doi: 10.1002/2016JC012336

D.R. Munday, X. Zhai (2017), The impact of atmospheric storminess on the sensitivity of Southern Ocean circulation to wind stress changes, Ocean Modelling, Volume 115, Pages 14–26, doi: 10.1016/j.ocemod.2017.05.005

A. Romanou, J. Marshall, M. Kelley, J. Scott (2017), Role of the ocean’s AMOC in setting the uptake efficiency of transient tracers, Geophysical Research Letters, doi: 10.1002/2017GL072972

Habib Toye, Peng Zhan, Ganesh Gopalakrishnan, Aditya R. Kartadikaria, Huang Huang, Omar Knio, Ibrahim Hoteit (2017), Ensemble data assimilation in the Red Sea: sensitivity to ensemble selection and atmospheric forcing, Ocean Dynamics, July 2017, Volume 67, Issue 7, pp 915–933, doi: 10.1007/s10236-017-1064-1

Hannah R. Wakeford, David K. Sing, Tiffany Kataria, Drake Deming, Nikolay Nikolov, Eric D. Lopez, Pascal Tremblin, David S. Amundsen, Nikole K. Lewis, Avi M. Mandell, Jonathan J. Fortney, Heather Knutson, Björn Benneke, Thomas M. Evans (2017), HAT-P-26b: A Neptune-mass exoplanet with a well-constrained heavy element abundance, Science, 12 May 2017, Vol. 356, Issue 6338, pp. 628-631, doi: 10.1126/science.aah4668

Do you have news about research using MITgcm? We are looking for contributions to these pages. If you have an interesting MITgcm project (ocean, atmosphere, sea-ice, physics, biology or otherwise) that you want to tell people about, get in touch. To make a post, contact Helen