Ice-Interactions

Oceanography 109B

David Porter is an Associate Research Scientist at the Lamont-Doherty Earth Observatory in the Climate School at Columbia University. He studies how the atmosphere and ocean drive changes in the ice sheets, and how the resulting changing sea level affects coastal communities. His research involves climate processes at high-latitudes, and is particularly interested in the interactions between different Earth System components. His expertise is at this intersection of traditional disciplines.

At the ice-ocean interface, he studies how ice is melting in warming ocean waters, likely the most pressing question for the future of the Greenland and Antarctic ice sheets. Are warming ocean waters responsible for the increase in mass loss of marine-terminating glaciers worldwide? How stable are Antarctic ice shelves, especially the Ross Ice Shelf which holds back several meters of sea level rise? At the atmosphere-ice interface, he asks “what drives the newly-observed liquid water on the surface of the frigid Southern Continent?” And at the solid earth-ice interface, under the massive and ancient ice sheets themselves, he’s involved in projects to link geological controls on fast moving glaciers and ice streams.

news

Oct 22, 2022	New Website!
Feb 22, 2022	Postdoc opening! Work on our new NASA project on aerogrephysics of ice shelf basal channels

selected publications

Evolution of the Seasonal Surface Mixed Layer of the Ross Sea, Antarctica, Observed With Autonomous Profiling Floats

David F Porter, Scott R Springer, Laurie Padman, and 5 more authors

Journal Of Geophysical Research 2019

Abs

Oceanographic conditions on the continental shelf of the Ross Sea, Antarctica, affect sea ice production, Antarctic Bottom Water formation, mass loss from the Ross Ice Shelf, and ecosystems. Since ship access to the Ross Sea is restricted by sea ice in winter, most upper ocean measurements have been acquired in summer. We report the first multiyear time series of temperature and salinity throughout the water column, obtained with autonomous profiling floats. Seven Apex floats were deployed in 2013 on the midcontinental shelf, and six Air‐Launched Autonomous Micro Observer floats were deployed in late 2016, mostly near the ice shelf front. Between profiles, most floats were parked on the seabed to minimize lateral motion. Surface mixed layer temperatures, salinities, and depths, in winter were −1.8 °C, 34.34, and 250–500 m, respectively. Freshwater from sea ice melt in early December formed a shallow (20 m) surface mixed layer, which deepened to 50–80 m and usually warmed to above −0.5 °C by late January. Upper‐ocean freshening continued throughout the summer, especially in the eastern Ross Sea and along the ice shelf front. This freshening requires substantial lateral advection that is dominated by inflow from melting of sea ice and ice shelves in the Amundsen Sea and by inputs from the Ross Ice Shelf. Changes in upper‐ocean freshwater and heat content along the ice shelf front in summer affect cross‐ice front advection, ice shelf melting, and calving processes that determine the rate of mass loss from the grounded Antarctic Ice Sheet in this sector.
Local and large-scale atmospheric responses to reduced Arctic sea ice and ocean warming in the WRF model

David F Porter, John J Cassano, and Mark C Serreze

Journal Of Geophysical Research-Atmospheres 2012

Abs

The Weather Research and Forecasting (WRF) model is used to explore the sensitivity of the large-scale atmospheric energy and moisture budgets to prescribed changes in Arctic sea ice and sea surface temperatures (SSTs). Observed sea ice fractions and SSTs from 1996 and 2007, representing years of high and low sea ice extent, are used as lower boundary conditions. A pan-Arctic domain extending into the North Pacific and Atlantic Oceans is used. ERA-Interim reanalysis data from 1994 to 2008 are employed as initial and lateral forcing data for each high and low sea ice simulation. The addition of a third ensemble, with a mixed SST field between years 1996 and 2007 (using 2007 SSTs above 66 degrees N and 1996 values below), results in a total of three 15-member ensembles. Results of the simulations show both local and remote responses to reduced sea ice. The local polar cap averaged response is largest in October and November, dominated by increased turbulent heat fluxes resulting in vertically deep heating and moistening of the Arctic atmosphere. This warmer and moister atmosphere is associated with an increase in cloud cover, affecting the surface and atmospheric energy budgets. There is an enhancement of the hydrologic cycle, with increased evaporation in areas of sea ice loss paired with increased precipitation. Most of the Arctic climate response results from within-Arctic changes, although some changes in the hydrologic cycle reflect circulation responses to midlatitude SST forcing, highlighting the general sensitivity of the Arctic climate.