Comparing & Contrasting Regional Sea Ice Changes · PDF fileComparing & Contrasting...

Sharon Stammerjohn

Institute of Arctic & Alpine Research

University of Colorado Boulder

(& many esteemed and cited colleagues)

Comparing & Contrasting Regional Sea

Ice Changes

Photo taken by author, Oden 2007, southern Bellingshausen Sea

Sea Ice Challenges Workshop

Hobart, Tasmania 12-13 May 2015

Outline

Photo: Maria Stenzel, Amundsen Sea (NBP0901)

1. The Mean Seasonal & Regional Picture

sea ice, winds, ice motion, ice thickness

2. Regional Atmosphere-Ocean-Ice Changes

wind/waves, ice motion, ice edge location, ice

concentration, ice thickness

3. Seasonal Atmosphere-Ocean-Ice

Feedbacks

Simpkins et al (2012), Fig 2

Seasonal Sea Ice Concentration (SIC) & Variability S

tan

da

rd D

evia

tio

n

(Contours mark 25%, 50% & 75% SIC)

Summer

(1980-2008)

Autumn

Winter

Spring

Stammerjohn et al (2012), updated

Mean Ice Season Duration & Variability

1979-2014

Mean Ice Season Duration

Autumn Ice Edge Advance (STD)

Spring Ice Edge Retreat (STD)

Holland and Kwok (2012), Fig 1

Mean Sea-Level Pressure & Ice Motion

Apr-Oct (1992-

2010)

Correlation between Winds & Ice Motion

Apr-Oct (1992-

2010)

Summer (JFM)

Autumn (AMJ)

Winter (JAS)

Spring (OND)

Mean Seasonal Sea Ice Thickness Holland et al (2014) Fig 3

2003-2008

Antarctic ice edge changes are

largely wind-driven, especially

during spring & autumn

Photo: Maria Stenzel, Amundsen Sea (NBP0901)

But what appears on the surface

is very different from what

appears below…

Photo: Langdon Quetin, Western Antarctic Peninsula (beset during NBP0107)

Seasonal pack ice thickening > ~1 m is largely

due to wind-forced rafting and ridging

Wind/Waves & Ice Drift Lead to Changes in:

• Timing of ice edge advance/retreat

• Ice concentration

• Ice thickness

Ice Season Duration Trend

Stammerjohn et al (2012), Fig 1f

Now ~3 months

shorter

Now ~2 months longer

(1979-2013) Now ~1

months

shorter

Now ~1

months

longer

Wind-Driven Trends in Sea-Ice Motion Holland & Kwok (2012), Fig 3

Ice Motion & Concentration Trends

Ice Motion (vectors)

(black, sig >90%)

Ice Concentration

Apr-Jun

(1992-2010)

Wind (vectors)

(black, sig >90%)

Sea-level pressure

Apr-Jun

(1992-2010)

Wind & Sea-Level Pressure Trends

Kohout et al (2014), Fig 4

Trends in Ice Edge Latitude & Significant Wave Heights

(1997-2009)

(Sep-Feb)

(Mar-Aug)

Ob

serv

ed Mod

eled

Holland et al. (2014), Fig 9

Modeled Ice Thickness & Ice Velocity Trends

Autumn (AMJ) Winter (JAS) (1992-2010) (1992-2010)

Massonnet et al (2013), Fig 2d

Modeled Ice Thickness Trends (1980-2008)

With assimilated

sea ice

concentration

Stammerjohn et al (2012), Fig 4

Ice-Ocean Feedbacks

See also Nihashi & Ohshima (2001) & Holland (2014)

Bellingshausen Sea

Amundsen Sea

Weddell gyre

Ross gyre

Figure: Doug Martinson (adapted from Orsi et al, 1995)

The Regional Proximity of warm Circumpolar Deep Water

(CDW) to Continental Shelves

Paolo et al (2015), Fig 1

Ice shelf

thickness &

volume changes

Volume losses increased

by 70% in last decade

Upwelled ocean

heat a factor?

Summary

Photo: Palmer LTER, Avian Island, west Antarctic Peninsula

• Regional differences in sea ice changes largely reflect regional differences in

atmospheric circulation patterns, that in turn can lead to differences in wind-

and wave-forcing

• Continental shelf regions also differ in their coastal icescapes (e.g., polynyas, ice

tongues, fast ice), which in turn contributes to regional differences in sea ice

• Continental shelf regions differ in their bathymetry and proximity to the ACC,

thus differ with respect to shelf currents and in the degree to which they may be

influenced by warm CDW

• Seasonal sea ice changes exhibit strong feedbacks between spring and the

subsequent autumn, consistent with ice-albedo/ocean feedbacks, accentuating

regions of strong sea ice changes

Extra Slides

(Holland & Kwok, 2012)

Fig 1b

Sfig 4c

Apr-Oct 1992-2010 Correlations

Vector correlation

(ice motion & winds)

% explained

Smoothed fraction of autumn ice diff

trend explained by flux divergence

Key Findings

• Wind and ice motion strongly coupled

in Pacific and Atlantic sectors

• Weakly coupled around East

Antarctica, where coastal current

dominates

• Flux divergence (advection + divergence)

explains large fraction of concentration

difference around West Antarctica

• Wind-driven thermodynamic changes

dominate elsewhere

Stammerjohn et al (2012), GRL, Fig 1

2.9 months

shorter ice

season

3.3 months

shorter

2.6 months

longer

Mean Timing in Spring Sea Ice Retreat & Autumn Advance

Stammerjohn et al (2008), Fig 2

(1979-2006)

Holland (2014), Fig 2

Trends in Ice Concentration, 1979-2012

Wind (vectors)

(black, sig >90%)

Sea-level pressure

(Apr-Jun)

Trends in Sea-Level Pressure & Winds, 1992-2010 (Holland & Kwok, 2012, Nature Geoscience, Fig 3b)

(e.g., Stammerjohn et al, 2008; Turner et al, 2009)

The trends in winds are

consistent with the

trends in sea ice Warm northerlies: less sea ice

Cold southerlies: more sea ice

(Meredith et al, 2010, Prog Oc, Fig 3)

High latitude response

to SAM & ENSO

Variability

SLP vs

SAM

Atmospheric Low deepens

…during +SAM

SLP vs

ENSO

…and during La Nina

(e.g., Stammerjohn et al, 2008; Turner et al, 2009)

SAM/ENSO

partially explains

regional trends

(Meredith et al., 2010, Prog. Oceanog, Fig 3)

But there are other tropical

linkages & feedbacks too SLP vs

SAM

For example, Atmospheric Low

deepens during…

+SAM (summer-autumn trend) (e.g., Turner et al, 2009)

SLP

vs ENSO

La Nina (spring) (e.g., Fogt & Bromwich, 2006)

Central Tropical Pacific warming

(spring trend) (e.g., Schneider et al, 2012;

Ding et al, 2011)

Ice feedback (autumn trend) (e.g., Raphael et al, 2011)

Tropical & North Atlantic warming

(winter trend) (Li et al, 2014)

Annual Hydrographic Survey

(CTD-Rosette, Net Tows)

4 Thermistor Moorings

Palmer Long-Term Ecological Research (LTER) Study Region

(1993 - ongoing)

Rothera Base (UK)

Avian Island

Adélie Penguin Colonies

Charcot Island

Palmer Station (US)

Satellite remote sensing

ocean color (chlorophyll)

surface temperature

sea ice, 1978-present Process Studies

SLOCUM Glider Base

Canyons & Deeps

LTER local Time series

Semi-weekly, Oct -April

BAS RaTS Local Time Series

Weekly, year-round

Anvers Island

Antarctic Peninsula

Sediment Trap

Ice Season 90 days shorter;

Ice Advance 60 days later

(Martinson et al, 2008, DSRII, Fig 10)

Heat content of sub-

pycnocline waters has

increased

Wind & Ice Motion

Correlation (Apr-Oct)

MODIS Terra, 2 Jan 2011

Amundsen

Sea Polynya

Pine Island

Polynya

Amundsen Sea Polynya International Research Expedition

Stammerjohn et al (submitted), Elementa

Randall-Goodwin et al (submitted), Elementa

(ASPIRE, Dec 2010 to Jan 2011)

Intensive ocean obs…

…indicate high

meteoric content

Wind & Ice Motion

Correlation (Apr-Oct)

Polynyas, Ice Production & seasonal

Evolution in the Ross Sea (PIPERS)

(Jacobs & Giulivi, 2010, J Clim, Fig 3)

Sub-Surface Ross

Sea Freshening

Ice Season 80

days longer

Wind & Ice Motion

Correlation (Apr-Oct)

Inbound Stations

Outbound Stations

Buoy Array Deployments

Polynya Stations

Terra Nova Bay

Polynya

Ross Sea Polynya

PIPERS Field Campaign:

April-May 2017

(Maksym et al, 2012, Oceanography, Fig 5)

Challenges of Obtaining Sea Ice Thickness Measurements

IceSAT data courtesy of Ron Kwok

Oct-Nov 2003 Mean Sea Ice Thickness

ICESat Satellite Altimetry Ship-based Visual Observations

ASPeCt ICESat

Nihashi & Ohshima (2015), Fig 5:

Frequency of fast ice & polynya

occurrence during the freezing period

(March October) for the period 2003-

2011

Measurements from Ice Mass Balance (IMB)

buoys

Dep

th (

cm)

Dep

th (

cm)

Sea ice thickness: the balance between snow

accumulation and ocean heat

Amundsen Sea

•Warm ice regime

•Rapid snow accumulation

•Flooding, minimal freezing

•Ice rots within, overwhelming

‘conveyor belt’ growth

mechanism (snow-ice formation

top, melt bottom)

Weddell Sea

•Cold ice regime

•Thin snow cover

•Minimal surface melt in

summer

(Maksym et al, 2012, Oceanography, Fig 4)