Antarctic sea ice thickness from airborne laser altimetry Tony Worby, - PowerPoint PPT Presentation

Antarctic sea ice thickness from airborne laser altimetry Tony Worby, Jan Lieser, Adam Steer

Antarctic Sea Ice Overturning circulation

Sea ice extent (in millions of sq km) ARCTIC Max: 16 Min: 6 - 7 Record min in 2007: 4 ANTARCTIC Max: 19 Min: 3 - 4 Source: NSIDC

Sea ice extent: Percent change per decade1979 - 2007 Arctic Antarctic Turner et al., 2009

SH sea ice concentration: trend for Autumn 1979 – 2007 Turner et al., 2009

From Stroeve et al, submitted Stroeve et al., Eos, 2008 Arctic circulation changed in late 1980s

Decline in Arctic sea ice thickness: 1958-76 to 1993-97 Rothrock et al., 1999

Much less is known about Antarctic sea ice thickness Worby et al., 2008

Courtesy: Jay Zwally ICESat Data over Antarctic Sea ice Sea Ice Thickness Snow-sea ice Freeboard Snow Depth (AMSR-E) Oct 4 - Nov 18, 2003 m cm m

AMSR ‐ E snow thickness compared with Antarctic field data ICESat and AMSR ‐ E data over Antarctic sea ice zone Field observations Factor of 2-3 Satellite data Worby et al. 2008b

Airborne sea ice research GPS Antennae Inertial Nav System (Location & Aerial Photo (Surface charact.) Orientation) Hasselblad H3D II 50 / Nikon D1x OXTS RT ‐ 4003 Scanning LiDAR (Surface elevation) Riegl LMS Q240i ‐ 60 Pyrometer (Skin surface temp.) Heitronics KT 19

LiDAR freeboard validation SIPEX Station 6: mean LiDAR : 0.24 m mean in ‐ situ : 0.25 m Worby et al., 2011

In situ measurements on Antarctic sea ice 100.0 50.0 0.0 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 -50.0 -100.0 -150.0 snow top ice top -200.0 bottom -250.0 Photo: Tony Worby

Ice thickness estimation Archimedes' buoyancy principle: mean LiDAR : 1.49 m ± 0.53 mean in ‐ situ : 1.15 m ± 0.67 Worby et al., 2011

Surface elevation questions In situ data Satellite radar data Giles et al., 2008 Worby et al., 2011

Conclusions • Accurate sea ice thickness is critical for climate model development (particularly ice thickness distribution) • Sea ice thickness retrievals from satellite altimetry require accurate snow thickness measurements • Surface topography also plays an important role in determining relative ice:snow thickness (different coefficients in buoyancy equation) • Combination of laser and radar altimetry are important to address key questions