Retreat characteristics and geometries for 59 glaciers in West Greenland between 2000-2009

Recent changes in the dynamics of Greenland's marine terminating outlet glaciers indicate a rapid and complex response to external forcing. Despite observed ice front retreat and recent geophysical evidence for accelerated mass loss along Greenland's northwestern margin, it is unclear whether west Greenland glaciers have undergone the synchronous speed-up and subsequent slow-down as observed in southeastern glaciers earlier in the decade. To investigate changes in west Greenland outlet glacier dynamics and the potential controls behind their behavior, we derive time series of front position, surface elevation, and surface slope for 59 marine terminating outlet glaciers and surface speeds for select glaciers in west Greenland from 2000 to 2009. Using these data, we look for relationships between retreat, thinning, acceleration, and geometric parameters to determine the first-order controls on glacier behavior. Our data indicate that changes in front positions and surface elevations were asynchronous on annual time scales, though nearly all glaciers retreated and thinned over the decade. We found no direct relationship between retreat, acceleration, and external forcing applicable to the entire region. In regard to geometry, we found that, following retreat, (1) glaciers with grounded termini experienced more pronounced changes in dynamics than those with floating termini and (2) thinning rates declined more quickly for glaciers with steeper slopes. Overall, glacier geometry should influence outlet glacier dynamics via stress redistribution following perturbations at the front, but our data indicate that the relative importance of geometry as a control of glacier behavior is highly variable throughout west Greenland.

Spatial distribution of key zooplankton species using continuous plankton recorder (CPR) data from the North Atlantic (2000-2009)

The continuous plankton recorder (CPR) survey is an upper layer plankton monitoring program that has regularly collected samples, at monthly intervals, in the North Atlantic and adjacent seas since 1946. Water from approximately 6 m depth enters the CPR through a small aperture at the front of the sampler and travels down a tunnel where it passes through a silk filtering mesh of 270 µm before exiting at the back of the CPR. The plankton filtered on the silk is analyzed in sections corresponding to 10 nautical miles (approx. 3 m**3 of seawater filtered) and the plankton microscopically identified (Richardson et al., 2006 and reference therein). In the present study we used the CPR data to investigate the current basin scale distribution of C. finmarchicus (C5-C6), C. helgolandicus (C5-C6), C. hyperboreus (C5-C6), Pseudocalanus spp. (C6), Oithona spp. (C1-C6), total Euphausiida, total Thecosomata and the presence/absence of Cnidaria and the Phytoplankton Colour Index (PCI). The PCI, which is a visual assessment of the greenness of the silk, is used as an indicator of the distribution of total phytoplankton biomass across the Atlantic basin (Batten et al., 2003). Monthly data collected between 2000 and 2009 were gridded using the inverse-distance interpolation method, in which the interpolated values were the nodes of a 2 degree by 2 degree grid. The resulting twelve monthly matrices were then averaged within the year and in the case of the zooplankton the data were log-transformed (i.e. log10 (x+1).

Spring snowmelt and midwinter thaw and refreeze north of 60°N based on Seawinds QuikScat 2000-2009

The scatterometer SeaWinds on QuikSCAT provided regular measurements at Ku-band from 1999 to 2009. Although it was designed for ocean applications, it has been frequently used for the assessment of seasonal snowmelt patterns aside from other terrestrial applications such as ice cap monitoring, phenology and urban mapping. This paper discusses general data characteristics of SeaWinds and reviews relevant change detection algorithms. Depending on the complexity of the method, parameters such as long-term noise and multiple event analyses were incorporated. Temporal averaging is a commonly accepted preprocessing step with consideration of diurnal, multi-day or seasonal averages.

(Table 1) Ice thickness at lake Nam Co, Tibet, during 2008-2009

Lake ice change is one of the sensitive indicators of regional and global climate change. Different sources of data are used in monitoring lake ice phenology nowadays. Visible and Near Infrared bands of imagery (VNIR) are well suited for the observation of freshwater ice change, for example data from AVHRR and MODIS. Active and passive microwave data are also used for the observation of lake ice, e.g., from satellite altimetry and radiometry, backscattering coefficient from QuickSCAT, brightness temperature (Tb) from SSM/I, SMMR, and AMSR-E. Most of the studies are about lake ice cover phenology, while few studies focus on lake ice thickness. For example, Hall et al. using 5 GHz (6 cm) radiometer data showed a good relationship between Tb and ice thickness. Kang et al. found the seasonal evolution of Tb at 10.65 GHz and 18.7 GHz from AMSR-E to be strongly influenced by ice thickness. Many studies on lake ice phenology have been carried out since the 1970s in cold regions, especially in Canada, the USA, Europe, the Arctic, and Antarctica. However, on the Tibetan Plateau, very little research has focused on lake ice-cover change; only a small number of published papers on Qinghai Lake ice observations. The main goal of this study is to investigate the change in lake ice phenology at Nam Co on the Tibetan Plateau using MODIS and AMSR-E data (monitoring the date of freeze onset, the formation of stable ice cover, first appearance of water, and the complete disappearance of ice) during the period 2000-2009.

Pteropod sedimentation at AWI HAUSGARTEN central station HGIV from 2000 to 2012

Pteropods are an important component of the zooplankton community and hence of the food web in the Fram Strait. They have a calcareous (aragonite) shell and are thus sensitive in particular to the effects of the increasing CO2 concentration in the atmosphere and the associated changes of pH and temperature in the ocean. In the eastern Fram Strait, two species of thecosome pteropods occur, the cold water-adapted Limacina helicina and the subarctic boreal species Limacina retroversa. Both species were regularly observed in year-round moored sediment traps at ~ 200-300 m depth in the deep-sea long-term observatory HAUSGARTEN (79°N, 4°E). The flux of all pteropods found in the trap samples varied from < 20 to ~ 870 specimen/m**2/d in the years 2000-2009, being lower during the period 2000-2006. At the beginning of the time series, pteropods were dominated by the cold-water-adapted L. helicina, whereas the subarctic boreal L. retroversa was only occasionally found in large quantities (> 50/m**2/d). This picture completely changed after 2005/6 when L. retroversa became dominant and total pteropod numbers in the trap samples increased significantly. Concomitant to this shift in species composition, a warming event occurred in 2005/6 and persisted until the end of the study in 2009, despite a slight cooling in the upper water layer after 2007/8. Sedimentation of pteropods showed a strong seasonality, with elevated fluxes of L. helicina from August to November. Numbers of L. retroversa usually increased later, during September/October, with a maximum at the end of the season during December/January. In terms of carbonate export, aragonite shells of pteropods contributed with 11-77% to the annual total CaCO3 flux in Fram Strait. The highest share was found in the period 2007 to 2009, predominantly during sedimentation events at the end of the year. Results obtained by sediment traps occasionally installed on a benthic lander revealed that pteropods also arrive at the seafloor (~ 2550 m) almost simultaneous with their occurrence in the shallower traps. This indicates a rapid downward transport of calcareous shells, which provides food particles for the deep-sea benthos during winter when other production in the upper water column is shut down. The results of our study highlight the great importance of pteropods for the biological carbon pump as well as for the carbonate system in Fram Strait at present, and indicate modifications within the zooplankton community. The results further emphasize the importance of long-term investigation to disclose such changes.

Paleoclimate reconstructions from sediment core MD01-2378

On the basis of the radiocarbon (14C) plateau-tuning method a new age model for Timor Sea Core MD01-2378 was established. It revealed a precise centennial-scale phasing of climate events in the ocean, cryo-, and atmosphere during the last deglacial and provides important new insights into causal linkages controlling events of global climate change. At Site MD01-2378 reservoir ages of surface waters dropped from 1600 yr prior to 20 cal ka to 250-500 yr after 18.8 cal ka. This evidence was crucial for generating a high-resolution age model for deglacial events in the Indo-Pacific Warm Pool. Sea-surface temperatures (SST) started to change near 18.8 cal ka, that is ~500 yr after the start of, presumably northern hemispheric, deglacial melt and sea level rise as shown by the benthic foraminiferal oxygen isotope ratio (d18O). However, the SST rise occurred 500-1000 yr prior to the onset of deglacial Antarctic warming and the first major rise in atmospheric carbon dioxide at about 18 ka. The increase in SST may partly reflect reduced seasonal upwelling of cold subsurface waters along the eastern margin of the Indian Ocean, which is reflected by a doubling of the thermal gradient between the sea surface and the thermocline, a halving of chlorin productivity from 19 to 18.5 cal ka, and in particular, by the strong decrease in surface water reservoir ages. Two significant increases in deglacial Timor Sea surface salinities from 19-18.5 and 15.5-14.5 cal ka, may partly reflect the deglacial increase in the distance of local river mouths, partly an inter-hemispheric millennial-scale see-saw in tropical monsoon intensity, possibly linked to a deglacial increase in the dominance of Pacific El Niño regimes over Heinrich stadial 1.

Data collection of depth and time integrated Calanus finmarchicus abundances, averaged temperatures, and integrated Chlorophyll concentration in the North Atlantic Ocean

Here we present a new, pan-North-Atlantic compilation of data on key mesozooplankton species, including the most important copepod, Calanus finmarchicus. Distributional data of eight representative zooplankton taxa, from recent (2000-2009) Continuous Plankton Recorder data, are presented, along with basin-scale data of the phytoplankton colour index. Then we present a compilation of data on C. finmarchicus, including observations of abundance, demography, egg production and female size, with accompanying data on temperature and chlorophyll. . This is a contribution by Canadian, European and US scientists and their institutions.

Downscaled land surface temperatures obtained by a particle smoothing approach, with links to NetCDF files

This dataset contains continuous time series of land surface temperature (LST) at spatial resolution of 300m around the 12 experimental sites of the PAGE21 project (grant agreement number 282700, funded by the EC seventh Framework Program theme FP7-ENV-2011). This dataset was produced from hourly LST time series at 25km scale, retrieved from SSM/I data (André et al., 2015, doi:10.1016/j.rse.2015.01.028) and downscaled to 300m using a dynamic model and a particle smoothing approach. This methodology is based on two main assumptions. First, LST spatial variability is mostly explained by land cover and soil hydric state. Second, LST is unique for a land cover class within the low resolution pixel. Given these hypotheses, this variable can be estimated using a land cover map and a physically based land surface model constrained with observations using a data assimilation process. This methodology described in Mechri et al. (2014, doi:10.1002/2013JD020354) was applied to the ORCHIDEE land surface model (Krinner et al., 2005, doi:10.1029/2003GB002199) to estimate prior values of each land cover class provided by the ESA CCI-Land Cover product (Bontemps et al., 2013) at 300m resolution . The assimilation process (particle smoother) consists in simulating ensemble of LST time series for each land cover class and for a large number of parameter sets. For each parameter set, the resulting temperatures are aggregated considering the grid fraction of each land cover and compared to the coarse observations. Miniminizing the distance between the aggregated model solutions and the observations allow us to select the simulated LST and the corresponding parameter sets which fit the observations most closely. The retained parameter sets are then duplicated and randomly perturbed before simulating the next time window. At the end, the most likely LST of each land cover class are estimated and used to reconstruct LST maps at 300m resolution using ESA CCI-Land Cover. The resulting temperature maps on which ice pixels were masked, are provided at daily time step during the nine-year analysis period (2000-2009).