[1] Multiple proxy data reveal that the early to middle Holocene (ca. 8-6 kyr B.P.) was warmer than the preindustrial period in most regions of the Northern Hemisphere. This warming is presumably explained by the higher summer insolation in the Northern Hemisphere, owing to changes in the orbital parameters. Subsequent cooling in the late Holocene was accompanied by significant changes in vegetation cover and an increase in atmospheric CO 2 concentration. The essential question is whether it is possible to explain these changes in a consistent way, accounting for the orbital parameters as the main external forcing for the climate system. We investigate this problem using the computationally efficient model of climate system, CLIMBER-2, which includes models for oceanic and terrestrial biogeochemistry. We found that changes in climate and vegetation cover in the northern subtropical and circumpolar regions can be attributed to the changes in the orbital forcing. Explanation of the atmospheric CO 2 record requires an additional assumption of excessive CaCO 3 sedimentation in the ocean. The modeled decrease in the carbonate ion concentration in the deep ocean is similar to that inferred from CaCO 3 sediment data [Broecker et al., 1999]. For 8 kyr B.P., the model estimates the terrestrial carbon pool ca. 90 Pg higher than its preindustrial value. Simulated atmospheric d 13 C declines during the course of the Holocene, similar to d 13 C data from the Taylor Dome ice core [Indermühle et al., 1999]. Amplitude of simulated changes in d 13 C is smaller than in the data, while a difference between the model and the data is comparable with the range of data uncertainty.

[1] During sea ice formation in polar areas, brine rejection increases the density in the underlying water column and thereby contributes to the formation of deep and intermediate water masses in the world ocean. Here we present evidence that dissolved inorganic carbon (TCO 2 ) is rejected together with brine from growing sea ice and that low temperatures may result in a significant change in the ratio of TCO 2 and alkalinity in Arctic sea ice compared with surface waters. Model calculations show that this sea ice-driven carbon pump affects surface water partial pressure of CO 2 significantly in polar seas and potentially sequesters large amounts of CO 2 to the deep ocean.Citation: Rysgaard, S., R. N. Glud, M. K. Sejr, J. Bendtsen, and P. B. Christensen (2007), Inorganic carbon transport during sea ice growth and decay: A carbon pump in polar seas,

Recent warming of Subpolar Mode Water off Greenland has been suggested to accelerate the mass loss from tidal outlet glaciers of the Greenland Ice Sheet. We present a comprehensive analysis of water masses, dynamics, and interannual hydrographic variability in Godthåbsfjord, a sill fjord in contact with tidal outlet glaciers on the west coast of Greenland. Through seasonal observations we recognize an intermediate baroclinic circulation mode driven by tidal currents and an associated important local heat source for the fjord. During summer this results in significant warming and freshening of the intermediate layer of the main fjord, and the increase in heat content is equivalent to melting of ∼2.1 km3 of glacial ice. This is comparable to ∼8 km3 glacial ice discharge estimated from the Kangiata Nunâta Sermia calving front per year. During winter the external heat source in the West Greenland Current enters the fjord as intermittent inflows of either cold (<2°C) or warm (>2°C) dense water in pulses of 1 to 3 months duration. Four distinct circulation modes are observed in the fjord, of which all can contribute to glacial ice melt. An important aspect of the ice distribution in the fjord is that only a minor fraction is exported out of the fjord.

[1] The Greenland Ice Sheet releases large amounts of freshwater into the fjords around Greenland and many fjords are in direct contact with the ice sheet through tidewater outlet glaciers. Here we present the first seasonal hydrographic observations from the inner part of a sub-Arctic fjord, relatively close to and within 4-50 km of a fast-flowing tidewater outlet glacier. This region is characterized by a dense glacial and sea ice cover. Freshwater from runoff, subglacial freshwater (SgFW) discharge, glacial, and sea ice melt are observed above 50-90 m depth. During summer, SgFW and subsurface glacial melt mixed with ambient water are observed as a layered structure in the temperature profiles below the low-saline summer surface layer (<7 m). During winter, the upper water column is characterized by stepwise halo-and thermoclines formed by mixing between deeper layers and the surface layer influenced by ice melt. The warm (T > 1 C) intermediate water mass is a significant subsurface heat source for ice melt. We analyze the temperature and salinity profiles observed in late summer with a thermodynamic mixing model and determine the total freshwater content in the layer below the summer surface layer to be between 5% and 11%. The total freshwater contribution in this layer from melted glacial ice was estimated to be 1-2%, while the corresponding SgFW was estimated to be 3-10%. The winter measurements in the subsurface halocline layer showed a total freshwater content of about 1% and no significant contribution from SgFW.

[1] The uptake rates of atmospheric CO 2 in the Nordic Seas are among the highest in the world's oceans. This has been ascribed mainly to a strong biological drawdown, but chemical processes within the sea ice itself have also been suggested to play a role. The importance of sea ice for the carbon uptake in the Nordic Seas is currently unknown. We present evidence from 50 localities in the Arctic Ocean that dissolved inorganic carbon is rejected together with brine from growing sea ice and that sea ice melting during summer is rich in carbonates. Model calculations show that melting of sea ice exported from the Arctic Ocean into the East Greenland current and the Nordic Seas plays an important and overlooked role in regulating the surface water partial pressure of CO 2 and increases the seasonal CO 2 uptake in the area by approximately 50%.Citation: Rysgaard, S., J. Bendtsen, L. T. Pedersen, H. Ramløv, and R. N. Glud (2009), Increased CO 2 uptake due to sea ice growth and decay in the Nordic Seas,

Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO 2 and the subsequent effect on air-sea CO 2 exchange have received little attention. We review the mechanisms by which sea ice directly and indirectly controls the air-sea CO 2 exchange and use recent measurements of inorganic carbon compounds in bulk sea ice to estimate that oceanic CO 2 uptake during the seasonal cycle of sea-ice growth and decay in ice-covered oceanic regions equals almost half of the net atmospheric CO 2 uptake in ice-free polar seas. This sea-ice driven CO 2 uptake has not been considered so far in estimates of global oceanic CO 2 uptake. Net CO 2 uptake in sea-ice-covered oceans can be driven by; (1) rejection during sea-ice formation and sinking of CO 2-rich brine into intermediate and abyssal oceanic water masses, (2) blocking of air-sea CO 2 exchange during winter, and (3) release of CO 2-depleted melt water with excess total alkalinity during sea-ice decay and (4) biological CO 2 drawdown during primary production in sea ice and surface oceanic waters.

Many tidewater outlet glacier fjords surround the coast of Greenland, and their dynamics and circulation are of great importance for understanding the heat transport toward glaciers from the ice sheet. Thus, fjord circulation is a critical aspect for assessing the threat of global sea level rise due to melting of the ice sheet. However, very few observational studies describe the seasonal dynamics of fjord circulation. Here we present the first continuous current measurements (April-November) from a deep mooring deployed in a west Greenland tidewater outlet glacier fjord. Four distinct circulation phases are identified during the period, and they are related to exchange processes with coastal waters, tidal mixing, and melt processes on the Greenland Ice Sheet. During early summer, warm intermediate water is transported toward the glacier at an average velocity of about 7 cm s À1. In late summer, the average velocity decreases to 3 cm s À1 during a period with significant subglacial freshwater discharges. During this period, a large variability in current velocities is also observed. The associated average heat transport in an intermediate-depth range corresponds to 568 GW in early summer and is reduced to 287 GW in late summer. These heat fluxes are at the higher end of previously reported fluxes. Our measurements show that the intermediate heat transport varies over time and during summer provides a major contribution to the heat budget and, thereby, potentially to glacial melt. We suggest that intermediate heat transport may play a similar important role in other fjords around Greenland.

The pure rotational and rotation-vibrational Raman spectra of 14Ne, l4NI5N and 15Nz have been photographed using a previously described instrument. The analyses of the bands yield for each molecule V O , Bo, BI-Bo and D. From the values of BO and Bo-BI the internuclear distances re are calculated independently for each species. Within the experimental accuracy the distances are identical as required by the Born-Oppenheimer approximation. The mean value for re is 1.097701 & iO.000004 A.