S U M M A R YThe release 06 (RL06) of the Gravity Recovery and Climate Experiment (GRACE) Atmosphere and Ocean De-Aliasing Level-1B (AOD1B) product has been prepared for use as a timevariable background model in global gravity research. Available since the year 1976 with a temporal resolution of 3 hr, the product is provided in Stokes coefficients up to degree and order 180. RL06 separates tidal and non-tidal signals, and has an improved long-term consistency due to the introduction of a time-invariant reference orography in continental regions. Variance reduction tests performed with globally distributed in situ ocean bottom pressure recordings and sea-surface height anomalies from Jason-2 over a range of different frequency bands indicate a generally improved performance of RL06 compared to its predecessor. Orbit tests for two altimetry satellites remain inconclusive, but GRACE K-band residuals are reduced by 0.031 nm s −2 in a global average, and by more than 0.5 nm s −2 at numerous places along the Siberian shelf when applying the latest AOD1B release. We therefore recommend AOD1B RL06 for any upcoming satellite gravimetry reprocessing effort.

GF is high and melt water is present under ice cover [11][12] Greenland to explain the origin of the observed melting beneath the ice cover (Figure 1). This are controlled by a combination of GF and non-GF influences, we build our calibration 137 strategy on estimating GF required to reproduce the observed thawed basal ice conditions, 138 discounting basal ice melt rates as a proxy for GF. This has the effect that GF estimates will 139 likely be biased downwards where basal melt is rapid; nevertheless, our strategy is 140 sufficiently effective to separate out the signal of a strong and spatially extensive geothermal 141 anomaly beneath the GIS and provides a hard lower bound for GF values at the observed 142 basal melt locations. 143The anomalous GF zone lies in the area with the highest density of direct measurements. 150One potential cause of elevated GF is illustrated by seismic data that link our west-to-east GF 151anomaly with a zone of low-seismic-velocity mantle, a "negative anomaly", beneath Iceland 6- Greenland may be the expression of Iceland hotspot history. The geothermal anomaly 237 provides evidence for a more northerly hotspot track than previously proposed and will offer 238 a useful test for existing paleoreconstructions of absolute plate motion. This study advocates 239 a previously undocumented strong coupling between Greenland's present-day ice dynamics, 240 subglacial hydrology, and the remote tectonothermal history of the North Atlantic region.

[1] Effective angular momentum functions from atmosphere, oceans, and terrestrial water storage are obtained from European Centre for Medium-Range Weather Forecasts atmospheric data and corresponding simulations with the Ocean Model for Circulation and Tides and the Land Surface and Discharge Model (LSDM). Mass exchanges among the subsystems are realized by means of freshwater fluxes, causing the total ocean mass to vary predominantly annually. Variations in total ocean mass affect the oceanic excitations of the annual wobble by almost 1 milliarc second (mas) for both prograde and retrograde components, whereas the motion term contributions of terrestrial water flow derived from LSDM are found to be 3 orders of magnitude smaller. Since differences to geodetic excitations are not substantially reduced and regional decompositions demonstrate the large spatial variability of contributions to seasonal polar motion excitation that compensate each other when integrated globally, it is concluded that the closure of the seasonal excitation budget is still inhibited by remaining model errors in all subsystems.Citation: Dobslaw, H., R. Dill, A. Grötzsch, A. Brzeziński, and M. Thomas (2010), Seasonal polar motion excitation from numerical models of atmosphere, ocean, and continental hydrosphere,

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[1] An improved version of the OMCT ocean model with 1 spatial resolution provides bottom pressure anomalies for the new release 05 of the GRACE Atmosphere and Ocean Dealiasing Level 1B (AOD1B) product. For high-frequency signals with periods below 30 days, this model explains up to 10 cm 2 of the residual sea level variance seen by ENVISAT in large parts of the Southern Ocean, corresponding to about 40% of the observed sea level residuals in many open ocean regions away from the tropics. Comparable amounts of variance are also explained by AOD1B RL05 for colocated in situ ocean bottom pressure recorders. Although secular trends contained in AOD1B RL05 cause GRACE KBRR residuals to increase in shallow water regions, we find a reduction of those residuals over all open ocean areas, indicating that AOD1B RL05 is much better suited to remove nontidal high-frequency mass variability from satellite gravity observations than previous versions of AOD1B.Citation: Dobslaw, H., F. Flechtner, I. Bergmann-Wolf, C. Dahle, R. Dill, S. Esselborn, I. Sasgen, and M. Thomas (2013), Simulating high-frequency atmosphere-ocean mass variability for dealiasing of satellite gravity observations: AOD1B RL05,