antarctic sea ice highlights06
Wor k shop
May 2017
HigHligHts
Antarctic Sea Ice Variability in the Southern
Ocean-Climate System
the extent and concentration of the sea ice surrounding
Antarctica increased from the late 1970s until 2015. this
increase is not reproduced by climate models, and comes
despite the overall warming of the global climate and the
region. At a January 2016 workshop, leading scientists
gathered to discuss the potential mechanisms driving
changes in Antarctic sea ice and ways to better understand the complex relationship between Antarctic sea
ice and the broader ocean-climate system. A number of
hypotheses have been posed to explain the recent expansion of Antarctic sea ice extent; more research is needed
to make deinitive statements about the mechanisms.
improvements in sea ice observations and models would
improve scientists’ ability to tease apart the many local, regional,
and global processes that inluence sea ice extent and thickness.
the winter sea ice surrounding Antarctica extended further between
2012 and 2014 than at any time since the late 1970s, when the satellite-based
Mean winter seaice extent
observed record began. the increase in sea ice extent was modest, but it
Mean summer sea ice extent
was unexpected: climate models generally simulate a decrease in sea ice in
Presented by Dr. Sarah Das, map modiied
the oceans surrounding Antarctica as climate warms. While sea ice extent
from Abram et al., 2013.
decreased in 2015 and 2016, many questions remain about what controls
year-to-year sea ice variability in this region.
scientists have some clues about what factors control Antarctic sea ice extent. Measurements of ocean temperature show that the surface waters of the southern Ocean have warmed more slowly in response to human-caused
greenhouse gas emissions than other oceans. Many local, regional, and global processes are known to inluence sea ice
extent and thickness, including surface winds, snowfall, and rain rates above the ice surface, and water temperatures
and salinity below.
teasing apart these factors to better understand Antarctic sea ice variability is important because sea ice plays
many critical roles in the climate and Earth system. in addition to helping to control the lux of heat, gases, and momentum between the atmosphere and the ocean, sea ice is a vital part of Antarctic ecosystems and an important inluence
on the stability of Antarctica’s glacial ice sheets (see Box 1).
THE OBSERVATIONAL RECORD OF ANTARCTIC SEA ICE VARIABILITY
the longest running and most geographically extensive of sea ice records come from satellite observations, which
began in the late 1970s with the launch of satellites carrying passive microwave radiometers. these observations are
almost universally drawn upon for studies of sea ice variability and change in both hemispheres. sea ice thickness
observations also have been gathered from iCEsat, a laser
altimeter, and from ship-based observations.
Workshop participants noted that the accuracy and
precision of some sea-ice observations are affected by
data, algorithm, and environmental factors. in addition,
a better understanding of the mechanisms and processes
driving sea ice variability and trends is limited by the lack
of a homogenous record of sea ice extent and concentration that extends prior to the satellite era.
In situ ocean observations are also critical to understand the important role of the southern Ocean in many
processes that affect sea ice. Argo loats located in the
southern Ocean record data on the temperature and
salinity of the water, but coverage is geographically
sparse—much of the southern Ocean sea ice zone has
only 25 percent of target Argo loat coverage. Precipitation measurements for southern sea ice are also available,
but these measurements are challenging because most
precipitation is either blown off into the ocean or accumulates in ridges.
several participants expressed the view that more
effort should go into extending the observational record
using proxies, historical records, and data assimilation. At
this time, the data that have been captured to extend the
historical record indicate a larger sea ice extent prior to
the satellite period. However, questions were raised as to
Box 1. The Roles of Antarctic Sea Ice
Antarctic sea ice functions in many Earth and climate
processes including:
• the
sea ice-albedo feedback—in which melting
sea ice can accelerate climate warming by exposing dark ocean areas that absorb more sunlight—is
widely recognized as a factor in the ampliication
of climate warming in the Arctic. Antarctic sea ice
extent is approximately 20 percent greater than in
the Arctic, and thus changes in its sea ice extent
could result in relatively large change in albedo.
• Feedbacks between sea ice production and ocean
water temperature and salinity may play a role in
determining the stability of Antarctica’s massive
sheets of glacial ice. thus, understanding sea ice
variability may be important for anticipating the
rate of ice sheet melt and sea level rise over the
next few decades.
• Changes to sea ice-dependent communities at the
bottom of the Antarctic food chain affect ish and
other animals higher on the trophic ladder. For
example, algal communities within the ice provide
a critical food source for krill year round. these
same communities also contribute to massive phytoplankton blooms during the spring and summer
melt season.
whether there is enough conidence in the diverse set of
proxies to make such a deinitive statement. in addition,
some participants highlighted the need for more validation of the passive microwave observations of sea ice
concentrations taken from space-based platforms.
Workshop discussions emphasized the regional variability of Antarctic sea ice patterns. there are large and
strongly contrasting regional trends in sea ice extent,
some with magnitudes equivalent to those observed in
the Arctic. in particular, there have been strongly negative
trends in monthly sea ice extent in the Bellingshausen and
Amundsen seas, and strongly positive trends in the Ross
sea. the length of the sea ice season also has changed
dramatically in some areas, becoming shorter in the Bellingshausen sea area and longer in the Ross sea.
For example, the southern Ocean has warmed more
slowly than the global ocean in response to greenhouse
gas emissions since 1950. the mechanism traditionally
proposed for this slow warming is eficient heat uptake by
the southern Ocean, where there is signiicant upwelling
of cool, deep ocean waters that don’t have time to warm
at the ocean’s surface. there are also divergent lows: a
stronger northward low that transports heat away from
the continent and a smaller southward low that brings
heat up toward the continent. the Arctic has no comparable upwelling mechanism and is therefore free to warm
under climate warming.
THE DRIVERS OF SEA ICE VARIABILITY
Workshop presentations and discussions highlighted
several processes and mechanisms that could inluence
Antarctic sea ice growth and melt. these include internal variability from interactions among the atmosphere,
ocean, and sea ice; and external forcings such as those
caused by stratospheric ozone depletion and emissions
of greenhouse gases. these processes are not necessarily mutually exclusive and each region of the Antarctic is
sensitive to different climate anomaly patterns. At present,
no single mode or mechanism could explain the recent
records in total sea ice extent.
One possible driver of Antarctic sea ice variability discussed at the workshop is the feedback between
atmospheric warming, hydrology, sea ice formation, and
ocean circulation. For example, atmospheric warming
could accelerate the melting of Antarctic ice shelves, leading to increased freshwater input to the surface ocean,
which in turn that reduces ocean lux from deep ocean
to surface waters. this would result in cooler, fresher sea
surface conditions and enhanced sea ice formation.
Another atmospheric driver of Antarctic sea ice variability is the Amundsen sea low, which controls meridional
winds in the Amundsen, Bellinghausen, and Ross seas.
some studies indicate that changes in the Amundsen sea
low (Asl) and increases in ocean heat
content are driving decreases in sea
ice cover and duration in the Bellingshausen sea.
sea ice variability could also be
related to an increase in westerly winds
due to the depletion of stratospheric
ozone. this has led to colder winds
rushing over the waters surrounding
Antarctica, creating areas of open water
near the coast, known as polynyas, that
promote sea ice production.
CLIMATE MODELS
Climate models provide an important
tool for interpreting Antarctic sea ice
observations, many participants said,
as well as for exploring the potential
mechanisms inluencing the observed
variability. However, model improvement is necessary given that models
Figure 1. this graph shows how much the september southern hemisphere
sea ice extent for each year from 1979 to 2016 varied from the mean september
generally fail to exhibit the observed
extent (calculated for the 30 year period from 1980 to 2010). the anomaly data
decline in Antarctic sea ice extent over
points are plotted as circles and the trend line is plotted with a dashed grey
the past 30–50 years.
line. Overall, there is a slightly positive trend in sea ice extent compared to the
Many of the models have a poor
30-year mean. sea ice returned to near-average extent in 2015, and was below
representation of the mean state of the
average in 2016. source: http://nsidc.org/data/seaice_index/.
southern Ocean, which is important to
reproduce observed trends in Antarctic
FUTURE DIRECTIONS
sea ice. Furthermore, model biases affect how the models
respond to forcing, although there is uncertainty on how
A number of overarching themes arose from the worklarge an impact the biases have.
shop discussions related to needs for future observations
and research. Many participants said that process-based
if the models are improved to the point that they can
understanding is critical for improving understanding of
reliably reproduce past sea ice conditions, then they could
the mechanisms of Antarctic sea ice variability. Process
also be used to disentangle the roles of internal variability
studies also provide validation of global coupled models.
and human-caused drivers of changes in sea ice, as well as
However, higher-resolution atmosphere and ocean modto project how sea ice may change in the future, several
els may be necessary to more fully understand some
participants said.
Box 2. Poles Apart: Important Distinctions Between the Arctic and Antarctic Oceans
the increase in Antarctic sea ice extent contrasts sharply
with pronounced declines in Arctic sea ice over the same
period. the Arctic average monthly sea ice index has been
declining at a rate of 2.7 percent per decade for March (the
month in which sea ice reaches its maximum extent in the
northern hemisphere). the direction of the Arctic trend
is consistent with global climate model simulations, and
shrinking Arctic sea ice extent is frequently cited as an indicator of greenhouse gas-induced climate warming.
the Antarctic sea ice record is often presented as a conundrum for global climate change science—but workshop
participants noted that the southern and Arctic Oceans
are very different dynamic systems, and so the two regions
are not expected to respond to warming in the same way.
Antarctica has a large overlying atmospheric variability
compared to the Arctic. Furthermore, the two regions have
different geographies, heat exchange processes, and ocean
circulation patterns.
For example, the southern Ocean has warmed more
slowly than the global ocean in response to greenhouse
gas emissions since 1950. the mechanism traditionally proposed for this slow warming is eficient heat uptake by the
southern Ocean, where there is signiicant upwelling of
cool, deep ocean waters that don’t have time to warm at
the ocean’s surface. there are also divergent lows: a stronger northward low that transports heat away from the
continent and a smaller southward low that brings heat
up toward the continent. the Arctic has no comparable
upwelling mechanism and is therefore free to warm under
climate forcing.
important processes, such as mixed layer
depth, and the relationship between
polynyas and ice formation.
Another barrier to process-based
understanding is the dearth of observations in the southern Ocean (e.g., under
the sea ice), particularly those that are
necessary to make heat and freshwater
budget calculations. such calculations
require estimates of sea ice thickness, estimates of precipitation over the southern
Ocean, estimates of exchange of water
between the ocean and under-ice-shelf
cavities, and hydrographic measurements
of temperature, salinity, and isotopes.
Figure 2. this schematic depicts southern Ocean circulation, which is charModels that project climate condiacterized by deep water returning to the surface where it is reprocessed
into new water masses. source: Figure by ilissa Ocko, courtesy of Princeton
tions decades and longer into the future
University, presented by Dr. Michael Meredith.
indicate that the Antarctic sea ice will
eventually respond to global warming
and decline. Observations from late 2016 and early 2017
the mechanisms is critical to making conident statements
indeed show decreases in Antarctic sea ice extent. Neverabout the future of Antarctic sea ice.
theless, many participants said a better understanding of
DISCLAIMER: this Workshop Highlights was prepared by Alison Macalady and Katie Thomas as a factual summary
of what occurred at the workshop. the planning committee’s role was limited to planning the workshop. the statements
made are those of the rapporteurs or individual meeting participants and do not necessarily represent the views of all meeting participants, the planning committee, or the National Academies of sciences, Engineering, and Medicine.
PLAnnIng COMMIttEE On AntARCtIC SEA ICE VARIAbILIty In thE SOuthERn CLIMAtE-OCEAn SyStEM: Julienne
Stroeve (Chair), University of Colorado Boulder; David Holland, New York University, New York; Marika Holland,
National Center for Atmospheric Research, Boulder, Colorado; Ted Maksym, Woods Hole Oceanographic institution,
Woods Hole, Massachusetts; Marilyn Raphael, University of California, los Angeles; Susan Solomon, Massachusetts
institute of technology, Cambridge; Xiaojun Yuan, Columbia University, Palisades, New York; Katie Thomas (Senior
Program Oficer), Alison Macalady (Program Oficer [until August 2016]), Amanda Staudt (Director), Yasmin Romitti
(Research Associate), Rob Greenway (Program Associate), Michael Hudson (Senior Program Assistant), Shelly Freeland
(Financial Associate), National Academies of sciences, Engineering, and Medicine
SPOnSORS: this Workshop was supported by the National Aeronautics and space Administration and the National science
Foundation.
For More Information . . . contact the Polar Research Board at (202) 334-3479 or visit www.nationalacademies.org/
prb. Antarctic Sea Ice Variability in the Southern Ocean-Climate System can be purchased or downloaded free from the
National Academies Press, 500 Fifth street, NW, Washington, DC 20001; (800) 624-6242; www.nap.edu.
Division on Earth and life studies
Copyright 2017 by the National Academy of Sciences. All rights reserved.
May 2017
HigHligHts
Antarctic Sea Ice Variability in the Southern
Ocean-Climate System
the extent and concentration of the sea ice surrounding
Antarctica increased from the late 1970s until 2015. this
increase is not reproduced by climate models, and comes
despite the overall warming of the global climate and the
region. At a January 2016 workshop, leading scientists
gathered to discuss the potential mechanisms driving
changes in Antarctic sea ice and ways to better understand the complex relationship between Antarctic sea
ice and the broader ocean-climate system. A number of
hypotheses have been posed to explain the recent expansion of Antarctic sea ice extent; more research is needed
to make deinitive statements about the mechanisms.
improvements in sea ice observations and models would
improve scientists’ ability to tease apart the many local, regional,
and global processes that inluence sea ice extent and thickness.
the winter sea ice surrounding Antarctica extended further between
2012 and 2014 than at any time since the late 1970s, when the satellite-based
Mean winter seaice extent
observed record began. the increase in sea ice extent was modest, but it
Mean summer sea ice extent
was unexpected: climate models generally simulate a decrease in sea ice in
Presented by Dr. Sarah Das, map modiied
the oceans surrounding Antarctica as climate warms. While sea ice extent
from Abram et al., 2013.
decreased in 2015 and 2016, many questions remain about what controls
year-to-year sea ice variability in this region.
scientists have some clues about what factors control Antarctic sea ice extent. Measurements of ocean temperature show that the surface waters of the southern Ocean have warmed more slowly in response to human-caused
greenhouse gas emissions than other oceans. Many local, regional, and global processes are known to inluence sea ice
extent and thickness, including surface winds, snowfall, and rain rates above the ice surface, and water temperatures
and salinity below.
teasing apart these factors to better understand Antarctic sea ice variability is important because sea ice plays
many critical roles in the climate and Earth system. in addition to helping to control the lux of heat, gases, and momentum between the atmosphere and the ocean, sea ice is a vital part of Antarctic ecosystems and an important inluence
on the stability of Antarctica’s glacial ice sheets (see Box 1).
THE OBSERVATIONAL RECORD OF ANTARCTIC SEA ICE VARIABILITY
the longest running and most geographically extensive of sea ice records come from satellite observations, which
began in the late 1970s with the launch of satellites carrying passive microwave radiometers. these observations are
almost universally drawn upon for studies of sea ice variability and change in both hemispheres. sea ice thickness
observations also have been gathered from iCEsat, a laser
altimeter, and from ship-based observations.
Workshop participants noted that the accuracy and
precision of some sea-ice observations are affected by
data, algorithm, and environmental factors. in addition,
a better understanding of the mechanisms and processes
driving sea ice variability and trends is limited by the lack
of a homogenous record of sea ice extent and concentration that extends prior to the satellite era.
In situ ocean observations are also critical to understand the important role of the southern Ocean in many
processes that affect sea ice. Argo loats located in the
southern Ocean record data on the temperature and
salinity of the water, but coverage is geographically
sparse—much of the southern Ocean sea ice zone has
only 25 percent of target Argo loat coverage. Precipitation measurements for southern sea ice are also available,
but these measurements are challenging because most
precipitation is either blown off into the ocean or accumulates in ridges.
several participants expressed the view that more
effort should go into extending the observational record
using proxies, historical records, and data assimilation. At
this time, the data that have been captured to extend the
historical record indicate a larger sea ice extent prior to
the satellite period. However, questions were raised as to
Box 1. The Roles of Antarctic Sea Ice
Antarctic sea ice functions in many Earth and climate
processes including:
• the
sea ice-albedo feedback—in which melting
sea ice can accelerate climate warming by exposing dark ocean areas that absorb more sunlight—is
widely recognized as a factor in the ampliication
of climate warming in the Arctic. Antarctic sea ice
extent is approximately 20 percent greater than in
the Arctic, and thus changes in its sea ice extent
could result in relatively large change in albedo.
• Feedbacks between sea ice production and ocean
water temperature and salinity may play a role in
determining the stability of Antarctica’s massive
sheets of glacial ice. thus, understanding sea ice
variability may be important for anticipating the
rate of ice sheet melt and sea level rise over the
next few decades.
• Changes to sea ice-dependent communities at the
bottom of the Antarctic food chain affect ish and
other animals higher on the trophic ladder. For
example, algal communities within the ice provide
a critical food source for krill year round. these
same communities also contribute to massive phytoplankton blooms during the spring and summer
melt season.
whether there is enough conidence in the diverse set of
proxies to make such a deinitive statement. in addition,
some participants highlighted the need for more validation of the passive microwave observations of sea ice
concentrations taken from space-based platforms.
Workshop discussions emphasized the regional variability of Antarctic sea ice patterns. there are large and
strongly contrasting regional trends in sea ice extent,
some with magnitudes equivalent to those observed in
the Arctic. in particular, there have been strongly negative
trends in monthly sea ice extent in the Bellingshausen and
Amundsen seas, and strongly positive trends in the Ross
sea. the length of the sea ice season also has changed
dramatically in some areas, becoming shorter in the Bellingshausen sea area and longer in the Ross sea.
For example, the southern Ocean has warmed more
slowly than the global ocean in response to greenhouse
gas emissions since 1950. the mechanism traditionally
proposed for this slow warming is eficient heat uptake by
the southern Ocean, where there is signiicant upwelling
of cool, deep ocean waters that don’t have time to warm
at the ocean’s surface. there are also divergent lows: a
stronger northward low that transports heat away from
the continent and a smaller southward low that brings
heat up toward the continent. the Arctic has no comparable upwelling mechanism and is therefore free to warm
under climate warming.
THE DRIVERS OF SEA ICE VARIABILITY
Workshop presentations and discussions highlighted
several processes and mechanisms that could inluence
Antarctic sea ice growth and melt. these include internal variability from interactions among the atmosphere,
ocean, and sea ice; and external forcings such as those
caused by stratospheric ozone depletion and emissions
of greenhouse gases. these processes are not necessarily mutually exclusive and each region of the Antarctic is
sensitive to different climate anomaly patterns. At present,
no single mode or mechanism could explain the recent
records in total sea ice extent.
One possible driver of Antarctic sea ice variability discussed at the workshop is the feedback between
atmospheric warming, hydrology, sea ice formation, and
ocean circulation. For example, atmospheric warming
could accelerate the melting of Antarctic ice shelves, leading to increased freshwater input to the surface ocean,
which in turn that reduces ocean lux from deep ocean
to surface waters. this would result in cooler, fresher sea
surface conditions and enhanced sea ice formation.
Another atmospheric driver of Antarctic sea ice variability is the Amundsen sea low, which controls meridional
winds in the Amundsen, Bellinghausen, and Ross seas.
some studies indicate that changes in the Amundsen sea
low (Asl) and increases in ocean heat
content are driving decreases in sea
ice cover and duration in the Bellingshausen sea.
sea ice variability could also be
related to an increase in westerly winds
due to the depletion of stratospheric
ozone. this has led to colder winds
rushing over the waters surrounding
Antarctica, creating areas of open water
near the coast, known as polynyas, that
promote sea ice production.
CLIMATE MODELS
Climate models provide an important
tool for interpreting Antarctic sea ice
observations, many participants said,
as well as for exploring the potential
mechanisms inluencing the observed
variability. However, model improvement is necessary given that models
Figure 1. this graph shows how much the september southern hemisphere
sea ice extent for each year from 1979 to 2016 varied from the mean september
generally fail to exhibit the observed
extent (calculated for the 30 year period from 1980 to 2010). the anomaly data
decline in Antarctic sea ice extent over
points are plotted as circles and the trend line is plotted with a dashed grey
the past 30–50 years.
line. Overall, there is a slightly positive trend in sea ice extent compared to the
Many of the models have a poor
30-year mean. sea ice returned to near-average extent in 2015, and was below
representation of the mean state of the
average in 2016. source: http://nsidc.org/data/seaice_index/.
southern Ocean, which is important to
reproduce observed trends in Antarctic
FUTURE DIRECTIONS
sea ice. Furthermore, model biases affect how the models
respond to forcing, although there is uncertainty on how
A number of overarching themes arose from the worklarge an impact the biases have.
shop discussions related to needs for future observations
and research. Many participants said that process-based
if the models are improved to the point that they can
understanding is critical for improving understanding of
reliably reproduce past sea ice conditions, then they could
the mechanisms of Antarctic sea ice variability. Process
also be used to disentangle the roles of internal variability
studies also provide validation of global coupled models.
and human-caused drivers of changes in sea ice, as well as
However, higher-resolution atmosphere and ocean modto project how sea ice may change in the future, several
els may be necessary to more fully understand some
participants said.
Box 2. Poles Apart: Important Distinctions Between the Arctic and Antarctic Oceans
the increase in Antarctic sea ice extent contrasts sharply
with pronounced declines in Arctic sea ice over the same
period. the Arctic average monthly sea ice index has been
declining at a rate of 2.7 percent per decade for March (the
month in which sea ice reaches its maximum extent in the
northern hemisphere). the direction of the Arctic trend
is consistent with global climate model simulations, and
shrinking Arctic sea ice extent is frequently cited as an indicator of greenhouse gas-induced climate warming.
the Antarctic sea ice record is often presented as a conundrum for global climate change science—but workshop
participants noted that the southern and Arctic Oceans
are very different dynamic systems, and so the two regions
are not expected to respond to warming in the same way.
Antarctica has a large overlying atmospheric variability
compared to the Arctic. Furthermore, the two regions have
different geographies, heat exchange processes, and ocean
circulation patterns.
For example, the southern Ocean has warmed more
slowly than the global ocean in response to greenhouse
gas emissions since 1950. the mechanism traditionally proposed for this slow warming is eficient heat uptake by the
southern Ocean, where there is signiicant upwelling of
cool, deep ocean waters that don’t have time to warm at
the ocean’s surface. there are also divergent lows: a stronger northward low that transports heat away from the
continent and a smaller southward low that brings heat
up toward the continent. the Arctic has no comparable
upwelling mechanism and is therefore free to warm under
climate forcing.
important processes, such as mixed layer
depth, and the relationship between
polynyas and ice formation.
Another barrier to process-based
understanding is the dearth of observations in the southern Ocean (e.g., under
the sea ice), particularly those that are
necessary to make heat and freshwater
budget calculations. such calculations
require estimates of sea ice thickness, estimates of precipitation over the southern
Ocean, estimates of exchange of water
between the ocean and under-ice-shelf
cavities, and hydrographic measurements
of temperature, salinity, and isotopes.
Figure 2. this schematic depicts southern Ocean circulation, which is charModels that project climate condiacterized by deep water returning to the surface where it is reprocessed
into new water masses. source: Figure by ilissa Ocko, courtesy of Princeton
tions decades and longer into the future
University, presented by Dr. Michael Meredith.
indicate that the Antarctic sea ice will
eventually respond to global warming
and decline. Observations from late 2016 and early 2017
the mechanisms is critical to making conident statements
indeed show decreases in Antarctic sea ice extent. Neverabout the future of Antarctic sea ice.
theless, many participants said a better understanding of
DISCLAIMER: this Workshop Highlights was prepared by Alison Macalady and Katie Thomas as a factual summary
of what occurred at the workshop. the planning committee’s role was limited to planning the workshop. the statements
made are those of the rapporteurs or individual meeting participants and do not necessarily represent the views of all meeting participants, the planning committee, or the National Academies of sciences, Engineering, and Medicine.
PLAnnIng COMMIttEE On AntARCtIC SEA ICE VARIAbILIty In thE SOuthERn CLIMAtE-OCEAn SyStEM: Julienne
Stroeve (Chair), University of Colorado Boulder; David Holland, New York University, New York; Marika Holland,
National Center for Atmospheric Research, Boulder, Colorado; Ted Maksym, Woods Hole Oceanographic institution,
Woods Hole, Massachusetts; Marilyn Raphael, University of California, los Angeles; Susan Solomon, Massachusetts
institute of technology, Cambridge; Xiaojun Yuan, Columbia University, Palisades, New York; Katie Thomas (Senior
Program Oficer), Alison Macalady (Program Oficer [until August 2016]), Amanda Staudt (Director), Yasmin Romitti
(Research Associate), Rob Greenway (Program Associate), Michael Hudson (Senior Program Assistant), Shelly Freeland
(Financial Associate), National Academies of sciences, Engineering, and Medicine
SPOnSORS: this Workshop was supported by the National Aeronautics and space Administration and the National science
Foundation.
For More Information . . . contact the Polar Research Board at (202) 334-3479 or visit www.nationalacademies.org/
prb. Antarctic Sea Ice Variability in the Southern Ocean-Climate System can be purchased or downloaded free from the
National Academies Press, 500 Fifth street, NW, Washington, DC 20001; (800) 624-6242; www.nap.edu.
Division on Earth and life studies
Copyright 2017 by the National Academy of Sciences. All rights reserved.