A stylized image shows the massive icebergs that an observer sitting on a beach in southern Florida would have periodically seen drifting along the coast ~18,000 years ago – Image courtesy the researchers
story by Helen Hill
This fascinating study from long time MITgcm user Alan Condron (UMass) working with geologist Jenna Hill (CCU) uses a combination of high-resolution glacial numerical ocean circulation modeling and high-resolution multibeam bathymetry data to show that massive (up to 300m thick) icebergs and large volumes of meltwater were periodically transported along the east coast of North America to southern Florida during the last deglaciation (~21,000 to 6,000 years ago). These events would have been marked by the sudden appearance of enormous icebergs along the entire east coast of the United States, as far south as Miami, Florida.
Abrupt centennial-to-millennial shifts in Northern Hemisphere climate during the last deglaciation are thought to have been triggered by the discharge of large volumes of meltwater and icebergs to the subpolar North Atlantic. In Subtropical iceberg scours and meltwater routing in the deglacial western North Atlantic, published in Nature Geoscience in October, long time user Research Assistant Professor in the Geosciences Department at UMass Amherst Alan Condron ( Small Storms; Big Floods: Far-Reaching Impacts) uses MITgcm to help interpret the geological record
Condron uses high-resolution numerical ocean circulation models to understand the importance of the Arctic and sub-Arctic regions on the stength of the meridional overturning circulation and the stability of the climate system. In particular, he has worked extensively with the MITgcm numerical ocean sea-ice model, projected onto a cube-sphere as part of the ECCO2 project. .
Hill and Condron show that meltwater and icebergs were transported directly from the Laurentide ice margin to the subtropical North Atlantic in a narrow coastal current. High-resolution bathymetric data from south of Cape Hatteras they present shows numerous scours that they interpret as relict iceberg keel marks indicating that icebergs up to 300 m thick drifted to southern Florida (24.5° N). In Condron’s model simulations, during deglaciation, fresh water and icebergs routinely reached as far south as 32.5° N, in a period of less than four months with the authors noting that the southernmost scours formed only during periods of high meltwater discharge from the Northern Hemisphere ice sheets.
In the simulations, such extreme periods of meltwater release were observed to lead to a reversal of the typically northward surface flow in the nearshore subtropical western North Atlantic leading the authors to suggest that significant volumes of iceberg-laden meltwater may routinely have bypassed subpolar regions and spread across the subtropical North Atlantic.
To find out more about this work email Alan
When not MITgcming Condron enjoys canoeing, hiking, cross country skiing and surfing. He has been using MITgcm since 2007.
This Month’s Featured Publication
- Hill, Jenna C. and Alan Condron (2014), Subtropical iceberg scours and meltwater routing in the deglacial western North Atlantic, Nature Geoscience , published online October 12, doi: 10.1038/ngeo2267
Other New Publications this Month
Hilla Afargan and Hezi Gildor (2015), The role of the wind in the formation of coherent eddies in the Gulf of Eilat/Aqaba, Journal of Marine Systems, Volume 142, February 2015, Pages 75–95, doi: 10.1016/j.jmarsys.2014.09.006
Paturi, S., Boegman, L., Bouffard, D., and Rao, Y. (2014), Three-Dimensional Simulation of Lake Ontario North-Shore Hydrodynamics and Contaminant Transport, J. Hydraul. Eng. , doi: 10.1061/(ASCE)HY.1943-7900.0000963 , 04014082.
Nicolas Cassar, Cynthia D. Nevison, and Manfredi Manizza (2014*), Correcting oceanic O2/Ar-net community production estimates for vertical mixing using N2O observation, Geophysical Research Letters, Accepted Article, doi: 10.1002/2014GL062040
F. Falcini and E. Salusti (2014), Friction and mixing effects on potential vorticity for bottom current crossing a marine strait: an application to the Sicily Channel (central Mediterranean Sea), Ocean Sci. Discuss., 11, 2495–2532, 2014 www.ocean-sci-discuss.net/11/2495/2014/ doi:10.5194/osd-11-2495-2014
David Ferreira, John Marshall, Cecilia M. Bitz, Susan Solomon and Alan Plum (2014), Antarctic ocean and sea ice response to ozone depletion: a two timescale problem, Journal of Climate 2014 ; e-View, doi: 10.1175/JCLI-D-14-00313.1
Ryo Furuea, Yanli Jia, Julian P. McCreary, Niklas Schneider, Kelvin J. Richards, Peter Müller, Bruce D. Cornuelle, Nidia Martínez Avellaneda, Detlef Stammer, Chuanyu Liu, and Armin Köhl (2014*), Ocean Modelling, *In Press, doi: 10.1016/j.ocemod.2014.10.002
Shan Gao, Tangdong Qu, and Xunwei Nie (2014), Mixed layer salinity budget in the tropical Pacific Ocean estimated by a global GCM, Journal of Geophysical Research Oceans, *Accepted Article, doi: 10.1002/2014JC010336
Carl V. Gladish, David M. Holland, Aqqalu Rosing-Asvid, Jane W. Behrens, and Jesper Boje (2014*), Oceanic Boundary Conditions for Jakobshavn Glacier: Part I. Variability and Renewal of Ilulissat Icefjord Waters, 2001-2014, Journal of Physical Oceanography 2014 ; *e-View, doi: 10.1175/JPO-D-14-0044.1
M. C. Gregg and Jody M. Klymak (2014*), Mode-2 hydraulic control of flow over a small ridge on a continental shelf, Journal of Geophysical Research Oceans, *Accepted Article, doi: 10.1002/2014JC010043
Stephen G. Hamilton, Laura Castro de la Guardia, Andrew E. Derocher, Vicki Sahanatien, Bruno Tremblay, David Huard (2014), Projected Polar Bear Sea Ice Habitat in the Canadian Arctic Archipelago, PLOS.
Kalmikov, A, G. and P. Heimbach (2014), A Hessian-based Method for Uncertainty Quantification in Global Ocean State Estimation, SIAM J. Sci Computing, Vol. 36, No. 5, pp. S267-S295, doi: 10.1137/130925311
Xin Liu, Bangqin Huang, Qiu Huang, Lei Wang, Xiaobo Ni, Qisheng Tang, Song Sun, Hao Wei, Sumei Liu, Chaolun Li, and Jun Sun (2014), Seasonal phytoplankton response to physical processes in the southern Yellow Sea, Journal of Sea Research, Volume 95, January 2015, Pages 45–55, doi: doi:10.1016/j.seares.2014.10.017
M.G. Magaldi, and T.W.N. Haine (2014*), Hydrostatic and non-hydrostatic simulations of dense waters cascading off a shelf: the East Greenland case, Deep Sea Research Part I: Oceanographic Research Papers, *In Press, doi: 10.1002/2014JC010020
Matthew R. Mazloff, Sarah T. Gille andBruce Cornuelle (2014*), Improving the geoid: Combining altimetry and mean dynamic topography in the California coastal ocean, Geophysical Research Letters, * Accepted Article, doi: 10.1002/2014GL062402
Lars Nerger, Svetlana Losa, Thorger Brüning, and Frank Janssen (2014), The HBM-PDAF assimilation system for operational forecasts in the North and Baltic Seas, EuroGOOS 2014, Lisbon, Portugal, October 28 – 30, 2014
T. Tanaka, I. Yasuda, H. Onishi, H. Ueno, M. Masujima (2014), Observations of current and mixing around the shelf break in Pribilof Canyon in the Bering Sea, Journal of Oceanography, November 2014, doi: 10.1007/s10872-014-0256-2
Daniel L. Rudnick, Ganesh Gopalakrishnan, and Bruce D. Cornuelle (2014*), Cyclonic eddies in the Gulf of Mexico: Observations by underwater gliders and simulations by numerical model, Journal of Physical Oceanography 2014 ; *e-View, doi: 10.1175/JPO-D-14-0138.1
Showman, Adam P., Zhang, Xi; Tan, Xianyu, Lewis, Nikole K (2014), Atmospheric Dynamics of Brown Dwarfs and Directly Imaged Giant Planets: Emergence of Zonal Jets and Eddies from Small-Scale Convective Perturbations, American Astronomical Society, DPS meeting #46, #210.09
Showman, Adam P., Lewis, Nikole K (2014*), Jonathen J. Fortney (2014), Three-Dimensional Atmospheric Circulation of Warm and Hot Jupiters : Effects of Orbital Distance , Rotation Perion, and Non-synchronous Rotation, *submitted to ApJ, <a href=”http://arxiv.org/pdf/1411.4731.pdf”>arXiv</a>
Philip L. Woodworth, Miguel Á. Morales Maqued, Vassil M. Roussenov, Richard G. Williams and Chris W. Hughes (2014*), Mean sea level variability along the northeast American Atlantic coast, and the roles of the wind and the overturning circulation, Journal of Geophysical Research: Oceans, *Accepted Article, doi: 10.1002/2014JC010520
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