WG4- GIA model optimisation and ice mass balance computations: this group will focus on Task 4 relating to theoretical and data assimilation advances in GIA modelling. Representatives from each of the other WGs will participate in WG4 to ensure an adequate appreciation of the strengths and limitations of the products of the other WGs. Further effort will involve investigating optimal methods of combining this new dataset with geologic data to best isolate and model the GIA signal. The limitation and regions of remaining weakness in the models will be discussed in the context of GIA model users in the WG who will produce the final Action results: estimates of ice mass balance for the major ice sheets, notably Antarctica, with realistic GIA model corrections and related uncertainties. Of particular interest will be:

• Agreement between geodetic estimates and current GIA models

• Ability of models to satisfy both geodetic and geologic constraints

• Isolation of the GIA signal in the dataset

• Improved constraints on rapid ice melting events (e.g. Meltwater Pulse-1A) during the most recent deglaciation through estimates of ice volumes in each of the previously-glaciated regions

• Through joint modelling with GRACE and geologic datasets, tighter constraints on ongoing GIA in regions of current ice mass change: Greenland, Antarctica, Svalbard, Alaska

• Model advances required to provide optimal fit to the GNSS observations

• Model ability to assimilate data with site-specific uncertainty estimates Interaction between WGs, especially WG4 and the WGs1-3, will be ensured through several all-WG workshops and through participation of WG1-3 members in WG4.

WG4 Membership List:

Adalgeirsdottir Gudfinna

Legrand Juliette

Sorensen Louise

 Amadottir Thora

Lidberg Martin 

Spada Giorgio

 Bamber Jonathan

 Makinen Jaakko

Steffen Holger

Barletta Valentina

Martinec Zdenec

Stocchi Paolo 

 Bentley Mike 

Moore John 

van de Wal Roderik

 Bordoni Andrea

Mueller Juergen 

van der Wal Wouter

 Dietrich Reinhard

Nielsen Karina 

Vassilopoulos Andreas

 Evelpidou Niki

 Omang Ove

Vermeer Martin

 Fleitout Luce

 Pausini Sabrina

Vermeersen Bert

 Fleming Kevin

Poutanen Markku

Whitehouse Pippa

 Forsberg Rene

Riva Riccardo 

 Wolf Detlef 

King Matt 

 Sabadini Roberto

Pirazzoli Paolo

 Klemann Volker

 Scherneck Hans-Georg

Gabriella Ruggieri 

Karkani Eleana