A US CLIVAR-sponsored international workshop was convened in June 2013 to discuss the problem of “Understanding the Response of Greenland’s MarineTerminating Glaciers to Oceanic and Atmospheric Forcing” and the challenges to improving observations, process understanding, and modeling. The rationale for holding the workshop derives from observations over the last decade of increased mass loss from the margins of the Greenland ice sheet (GrIS). The widespread, regionally synchronous acceleration, and thinning of some of its major marineterminating outlet glaciers point to a common climatic driver, consistent with the observed warming of the North Atlantic subpolar gyre and nearsurface atmospheric warming. Detailed process understanding, however, is currently lacking. This hampers assessment of the impact of increased freshwater flux from the GrIS, not only on regional and global sea level, but also on the North Atlantic circulation and its effect on climate over the Atlantic sector.
The workshop brought together oceanographers, glaciologists, atmospheric, paleo, and climate scientists, including observationalists, modelers, and theoreticians. The 90 attendees included 47 US scientists funded by many research funding US agencies and 40 non-US experts from 10 countries. Specific meeting goals were:
- Advancing the science, through improved communication, coordination, and collaboration between the diverse communities;
- Establishment of the foundation for multidisciplinary efforts that will lead to deeper understanding of physical processes, better representation of these processes in climate models, and, consequently, more reliable projections of the Greenland Ice Sheet contribution to sea level;
- Training and network building across disciplines for scientists at all career levels, with specific focus on advanced graduate students and early career scientists.
- Identification of synergies of national and international projects;
- A document describing a prioritized set of recommendations to advance this urgent and complex interdisciplinary problem.
The workshop was structured into sessions covering the following themes: Evidence from Glacier Variability; What are the proposed Mechanisms? Evidence from the Paleo Record; The IceOcean Boundary; The Role of (Sub)glacial Hydrology; Oceanic Forcing; Continental Shelf and LargeScale Ocean Circulation; Glacier Calving and Ice Mélange; Modeling Glaciers, Ice Sheets, and Climate; Role of Bottom Topography.
In discussing a research strategy to move the science forward, workshop attendees identified six basic components:
- Improved Bottom Topography – Subglacial bedrock, sediment, and seafloor bathymetry are of fundamental importance for both glacier and ocean modeling efforts. It is the leading source of uncertainty in simulations that attempt to conduct centennial ice sheet projections. A dedicated effort targeted at obtaining highaccuracy bottom topography of key outlet glaciers, connected fjords, and adjacent continental shelves is crucial.
- Data Compilation and Sharing – The challenges involved in advancing the science and the crossdisciplinary nature of the subject require special emphasis to ensure ease of access of crucial data sets. Efforts should focus on collating and providing all existing data in consistent, easily accessible formats, in particular those data required to conduct model simulation and validation.
- Process Studies – A set of targeted studies are required to provide an understanding of the dynamics of specific processes (e.g., submarine melting, calving, fjord circulation, ice mélange, proglacial sedimentation, etc.), especially coupled processes between two systems. The rationale is that their dynamics may be easier to study in isolation. Special attention should be paid to processes that lead to improved dating of paleo proxy records.
- Megasites – In depth studies of all components (glaciological, oceanographic, and atmospheric) of a few key glacierfjordshelf systems is needed to provide an understanding of the interconnectedness of the system and a platform for interdisciplinary studies. Field experiments at these sites should include: a glacier node, a fjord/cavity node, a continental shelf node, and an atmosphere node. A list of ideal characteristics for megasites is proposed.
- Greenland Ice Ocean Observing System (GrIOOS) – Long-term in-situ time series of critical glaciological, oceanographic, and atmospheric variables at a number of key locations are needed to provide information on the timeevolving relationships between the different climate forcings and the glacier flow. A further goal is the ability to capture potential events in locations that, at present, exhibit little glacier activity, but may do so in the future. Roughly 10 sites will be chosen and measurements sustained for at least a decade. A list of ideal characteristics for megasites is proposed.
- Linkages to other programs – Planning of megasites, process studies, and a Greenlandwide observing network should take into account the availability of existing data from complementary networks. It should also assess existing satellite and airborne remote sensing capabilities and required new technologies.