Data Analysis and Modeling of the Amundsen Sea Embayment - Towards an Interdisciplinary Approach in Earth System Science - page 121

Pritchard et al. 2012 ). This relatively warm water flows onto the continental shelf

through submarine glacial troughs (Jacobs et al. 2011 ). When this warm water
reaches the grounding line, it melts basal ice and forms a buoyant plume of CDW
mixed with meltwater. This plume

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flows out from the ice shelf cavity and drives the
continuous intrusion of CDW into the PIIS cavity. Recent results show that the
averaged melt rates for PIIS in 2009 and 2010 are estimated to be about 30 m year − 1
(Jacobs et al. 2011 ; Nakayama et al. 2013 ).
The melting of PIIS and other ice shelves of the WAIS can have large impacts on
the global ocean. First, 10 % of the observed sea level rise has been attributed to the
thinning of the WAIS (Rignot et al. 2008 )

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the WAIS has the potential to raise
global sea level by about 3.3 m (Bamber et al. 2009 ). Second, it may cause the
freshening of the shelf water locally in the Amundsen Sea as well as remotely in the
Ross Sea (Jacobs et al. 2002 ). This may lead to a change in the characteristics of the
Antarctic Bottom Water (AABW) formed in the Ross Sea (Jacobs et al. 2002 ;
Rintoul 2007 ) and thus may in

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uence the global thermohaline circulation. There-
fore, investigations related to the PIIS melting and its impact on the ocean is crucial
for understanding climate change in the Southern Ocean.
In this study, we show hydrographic data obtained during Polarstern cruise
ANTXXVI/3 in 2010 with focus on the CDW intrusion. Then, we discuss the
dif

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culties of modeling the CDW intrusions into the Amundsen Sea embayment
and the sensitivity of CDW intrusion to the different model forcings.

2 Hydrographic Data Analysis

Sampling was carried out during ANTXXVI/3 from the research ice breaker RV
Polarstern (Gohl 2010 ). In total 62 conductivity-temperature-depth (CTD) pro les

were collected on this cruise including one Heli-CTD measurement Fig. 1 a. The
details of the measurements are summarized in Nakayama et al. ( 2013 ).
The vertical distribution of potential temperature for Sects. 1 , 2 (Fig. 1 ) mainly
show Winter Water (WW) with the potential temperature minimum at 100

300 m

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and warm CDW from 300 400 m to the bottom. The potential temperature section

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for the north south Sect. 2 (Fig. 1 c), which connects the deepest stations of each

east-west section, shows that CDW clearly dominates the lower part of the water
column, and that CDW is present all along the bottom towards the PIIS cavity. A
similar result is presented in Jacobs et al. ( 2011 ) from their observations in 2009.
Along the surface-referenced isopycnal of 27.7, CDW with the potential tempera-
ture of 1

-

C, salinity of 34.5, and dissolved oxygen of 4.2 ml kg − 1 ows onto the

continental shelf and into the PIIS cavity (Jacobs et al. 2011 ; Nakayama et al.
2013 ). The maximum isopycnal that reaches PIIS is

° fl

27.79 (not shown), while the
27.8-isopycnal only advances to the center of Pine Island Trough (PIT). When
compared with the previous observations, the bottom CDW properties do not
change largely within the last two decades [e.g. the temporal variability of potential
temperature in PIT is small (

*

0.2 ° C) (Nakayama et al. 2013 )].

*