Transient tracer distributions in the Fram Strait in 2012 and inferred anthropogenic carbon content and transport

Abstract

Abstract. The storage of anthropogenic carbon in the ocean's interior is an important process which modulates the increasing carbon dioxide concentrations in the atmosphere. The polar regions are expected to be net sinks for anthropogenic carbon. Transport estimates of dissolved inorganic carbon and the anthropogenic offset can thus provide information about the magnitude of the corresponding storage processes.Here we present a transient tracer, dissolved inorganic carbon (DIC) and total alkalinity (TA) data set along 78• 50 N sampled in the Fram Strait in 2012. A theory on tracer relationships is introduced, which allows for an application of the inverse-Gaussian-transit-time distribution (IG-TTD) at high latitudes and the estimation of anthropogenic carbon concentrations. Mean current velocity measurements along the same section from 2002-2010 were used to estimate the net flux of DIC and anthropogenic carbon by the boundary currents above 840 m through the Fram Strait.The new theory explains the differences between the theoretical (IG-TTD-based) tracer age relationship and the specific tracer age relationship of the field data, by saturation effects during water mass formation and/or the deliberate release experiment of SF 6 in the Greenland Sea in 1996, rather than by different mixing or ventilation processes. Based on this assumption, a maximum SF 6 excess of 0.5-0.8 fmol kg

Ocean circulation and freshwater pathways in the Arctic Mediterranean based on a combined Nd isotope, REE and oxygen isotope section across Fram Strait

“…Relatively long residence times (10-20 years) of NEGSBW on the shelf are evident from transient tracer data obtained during the same cruise (Stöven et al, 2016) and are in agreement with previous studies (Budéus et al, 1997;Top et al, 1997) thus promoting seawater-particle interactions and remineralization processes.…”

“…7). This is also in agreement with the relatively low ventilation ages of dAAW (~30 years) based on transient tracer data (Stöven et al, 2016), which suggests that these waters took the short loop within the AO (cf. Tanhua …”

Shelf–Basin interaction along the East Siberian Sea

“…The precision is given in concentration since it is related to the absolute value per kg seawater. Age modelling based on these transient tracers is complicated and erroneous at high latitudes due to ambiguous reasons (Stöven et al, 2015(Stöven et al, , 2016. Hence, we do not provide any statements about the ventilation timescale but rather the ventilation states of the water masses in the Arctic Ocean based on the concentration distribution.…”

“…The partial pressure of carbon dioxide (pCO 2 ) was calculated from the combination of pH and TA, and pH and DIC, using CO2SYS version 1.1 (van Heuven et al, 2011) with the stoichiometric dissociation constants of carbonic acid (K * 1 and K * 2 ) and bisulfate (K * ) given by Millero (2010) and Dickson (1990), respectively. Input data included salinity, temperature, PO 4 , and SiO 2 .…”

“…In 1979 the silicate maximum was observed during the LOREX study over the Lomonosov Ridge and into the fringe of the Amundsen Basin (Moore et al, 1983). In 1994 no silicate maximum was observed in the Makarov Basin along a section from the Chukchi Sea to the North Pole (Swift et al, 1997). It is clear that the distribution of the upper halocline with its prominent silicate signature has varied much in the past and with changing sea-ice coverage it might vary even more in the future.…”