Early detection of anthropogenic climate change signals in the ocean interior

Robust detection of anthropogenic climate change is crucial to: (i) improve our understanding of Earth system responses to external forcing, (ii) reduce uncertainty in future climate projections, and (iii) develop efficient mitigation and adaptation plans. Here, we use Earth system model projections to establish the detection timescales of anthropogenic signals in the global ocean through analyzing temperature, salinity, oxygen, and pH evolution from surface to 2000 m depths. For most variables, anthropogenic changes emerge earlier in the interior ocean than at the surface, due to the lower background variability at depth. Acidification is detectable earliest, followed by warming and oxygen changes in the subsurface tropical Atlantic. Temperature and salinity changes in the subsurface tropical and subtropical North Atlantic are shown to be early indicators for a slowdown of the Atlantic Meridional Overturning Circulation. Even under mitigated scenarios, inner ocean anthropogenic signals are projected to emerge within the next few decades. This is because they originate from existing surface changes that are now propagating into the interior. In addition to the tropical Atlantic, our study calls for establishment of long-term interior monitoring systems in the Southern Ocean and North Atlantic in order to elucidate how spatially heterogeneous anthropogenic signals propagate into the interior and impact marine ecosystems and biogeochemistry.publishedVersio

The Global Ocean Data Analysis Project version 2 (GLODAPv2) – an internally consistent data product for the world ocean

27 páginas, 11 tablas, 9 figuras.-- Are Olsen ... et al.-- This work is distributed under the Creative Commons Attribution 3.0 License.-- Proyecto CarbochangeVersion 2 of the Global Ocean Data Analysis Project (GLODAPv2) data product is composed of data from 724 scientific cruises covering the global ocean. It includes data assembled during the previous efforts GLODAPv1.1 (Global Ocean Data Analysis Project version 1.1) in 2004, CARINA (CARbon IN the Atlantic) in 2009/2010, and PACIFICA (PACIFic ocean Interior CArbon) in 2013, as well as data from an additional 168 cruises. Data for 12 core variables (salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon, total alkalinity, pH, CFC-11, CFC-12, CFC-113, and CCl4) have been subjected to extensive quality control, including systematic evaluation of bias. The data are available in two formats: (i) as submitted but updated to WOCE exchange format and (ii) as a merged and internally consistent data product. In the latter, adjustments have been applied to remove significant biases, respecting occurrences of any known or likely time trends or variations. Adjustments applied by previous efforts were re-evaluated. Hence, GLODAPv2 is not a simple merging of previous products with some new data added but a unique, internally consistent data product. This compiled and adjusted data product is believed to be consistent to better than 0.005 in salinity, 1 % in oxygen, 2 % in nitrate, 2 % in silicate, 2 % in phosphate, 4 µmol kg−1 in dissolved inorganic carbon, 6 µmol kg−1 in total alkalinity, 0.005 in pH, and 5 % for the halogenated transient tracersThe GLODAPv2 project itself received support from a number of agencies and projects. Importantly, the EU-IP CARBOCHANGE (FP7 264878) provided funding for A. Olsen, M. Hoppema, S. van Heuven, and T. Tanhua as well as travel support for R. Key and the project framework that instigated GLODAPv2. A. Olsen further acknowledges generous support from the FRAM – High North Research Centre for Climate and the Environment, the Centre for Climate Dynamics at the Bjerknes Centre for Climate Research, the EU AtlantOS (grant agreement no. 633211) project, and the Norwegian Research Council project SNACS (229752). R. Key was supported by KeyCrafts grant 2012-001, CICS grants NA08OAR4320752 and NA14OAR4320106, NASA grant NNX12AQ22G, NSF grants OCE-0825163 (with a supplement via WHOI P.O. C119245) and PLR-1425989, and Battelle contract #4000133565 to CDIAC. A. Kozyr was supported by DOE contract DE-AC05-00OR2272 to UT-Battelle, operators of CDIAC under ORNL. S. K. Lauvset and E. Jeansson appreciate support from the Norwegian Research Council (projects DECApH, 214513 and VENTILATE, 229791). The International Ocean Carbon Coordination Project (IOCCP) also supported this activity through the U.S. National Science Foundation grant (OCE- 1243377) to the Scientific Committee on Oceanic Research. A. Velo and F. F. Pérez acknowledge the support provided by BOCATS project (CTM2013-41048-P) co-funded by the Spanish Government and the Fondo Europeo de Desarrollo Regional (FEDER), and the AtlantOS project (grant agreement no. 633211) funded by EU H2020 research and innovation programme.Peer reviewe

Surface Carbon EOV Report

Surface carbon syntheses and impact of AtlantOS observation

SOOP Data System Upgrades

Report on data and connectivity upgrading, documenting system improvements to integrate observing systems, improve network infrastructure, near-real-time delivery of data and best practice for integrated observations to provide data useful for Marine Services and other user

Trends and drivers in global surface ocean pH over the past 3 decades

We report global long-term trends in surface ocean pH using a new pH data set computed by combining fCO2 observations from the Surface Ocean CO2 Atlas (SOCAT) version 2 with surface alkalinity estimates based on temperature and salinity. Trends were determined over the periods 1981–2011 and 1991–2011 for a set of 17 biomes using a weighted linear least squares method. We observe significant decreases in surface ocean pH in ~70% of all biomes and a mean rate of decrease of 0.0018 ± 0.0004 yr−1 for 1991–2011. We are not able to calculate a global trend for 1981–2011 because too few biomes have enough data for this. In half the biomes, the rate of change is commensurate with the trends expected based on the assumption that the surface ocean pH change is only driven by the surface ocean CO2 chemistry remaining in a transient equilibrium with the increase in atmospheric CO2. In the remaining biomes, deviations from such equilibrium may reflect that the trend of surface ocean fCO2 is not equal to that of the atmosphere, most notably in the equatorial Pacific Ocean, or may reflect changes in the oceanic buffer (Revelle) factor. We conclude that well-planned and long-term sustained observational networks are key to reliably document the ongoing and future changes in ocean carbon chemistry due to anthropogenic forcing.publishedVersio

Fingerprint of Climate Change on Southern Ocean Carbon Storage

The Southern Ocean plays a critical role in the uptake, transport, and storage of carbon by the global oceans. It is the ocean's largest sink of CO2, yet it is also among the regions with the lowest storage of anthropogenic carbon. This behavior results from a unique combination of high winds driving the upwelling of deep waters and the subduction and northward transport of surface carbon. Here we isolate the direct effect of increasing anthropogenic CO2 in the atmosphere from the indirect effect of climate variability and climate change on the reorganization of carbon in the Southern Ocean interior using a combination of modeling and observations. We show that the effect of climate variability and climate change on the storage of carbon in the Southern Ocean is nearly as large as the effect of anthropogenic CO2 during the period 1998–2018 compared with the climatology around the year 1995. We identify a distinct climate fingerprint in dissolved inorganic carbon (DIC), with elevated DIC concentration in the ocean at 300–600 m that reinforces the anthropogenic CO2 signal, and reduced DIC concentration in the ocean around 2,000 m that offsets the anthropogenic CO2 signal. The fingerprint is strongest at lower latitudes (30°–55°S). This fingerprint could serve to monitor the highly uncertain evolution of carbon within this critical ocean basin, and better identify its drivers.publishedVersio

Capelin investigations in the Barents Sea in November-December 1973

Rapporten er også publisert som artikkel i Fiskets Gang,60(13),1974:257-261A joint investigation on the distribution of adult capelin was carried out in November-December 1973 by the Norwegian research vessel «G. O. Sars» and the Soviet Union research vessels «Poisk» and "Akademik Knipovich". Adult capelin was found mainly distributed between 71ºN and 76ºN and between 38ºE and 48ºE and occurred predominantly as scattered registrations with the larger part close to the bottom. This made the conditions for an acoustic abundance estimate unfavourable, and probably only part of the adult capelin present in the area was recorded. The bottom registrations of adult capelin occurred in water with temperatures between -l and 0ºC while the pelagic concentrations of adult capelin were found mainly in temperatures between 0.5 and 2.0ºC. Most of the adult capelin were in the prespawning stage and consisted mainly of the 1970 year-class with some admixture of the 1969 year-class. The majority of the adult fish had a length between 15.0 and 17.5 c

Sparse observations induce large biases in estimates of the global ocean CO2 sink: an ocean model subsampling experiment

Estimates of ocean CO2 uptake from global ocean biogeochemistry models and pCO2-based data products differ substantially, especially in high latitudes and in the trend of the CO2 uptake since 2000. Here, we assess the effect of data sparsity on two pCO2-based estimates by subsampling output from a global ocean biogeochemistry model. The estimates of the ocean CO2 uptake are improved from a sampling scheme that mimics present-day sampling to an ideal sampling scheme with 1000 evenly distributed sites. In particular, insufficient sampling has given rise to strong biases in the trend of the ocean carbon sink in the pCO2 products. The overestimation of the CO2 flux trend by 20-35% globally and 50-130% in the Southern Ocean with the present-day sampling is reduced to less than 15% with the ideal sampling scheme. A substantial overestimation of the decadal variability of the Southern Ocean carbon sink occurs in one product and appears related to a skewed data distribution in pCO2 space. With the ideal sampling, the bias in the mean CO2 flux is reduced from 9-12% to 2-9% globally and from 14-26% to 5-17% in the Southern Ocean. On top of that, discrepancies of about 0.4 PgC yr-1 (15%) persist due to uncertainties in the gas-exchange calculation. This article is part of a discussion meeting issue 'Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities'

In the Wake of Deeper Convection: Nonsteady State Anthropogenic Carbon in the Greenland Sea

We evaluate changes in dissolved inorganic carbon (DIC) in the Greenland Sea between 2002 and 2016, a period characterized by increasing convection depths. We find a mid-depth maximum in anthropogenic carbon (Cant) accumulation that occurred as waters at these depths were rejuvenated by deeper reaching convection; broadly, these waters have caught up with the atmospheric CO2 rise that had happened between the last time they were ventilated and 2002 and also tracked the atmospheric CO2 rise 2002–2016. The overlying waters only tracked the atmospheric CO2 rise 2002–2016. The mid-depth maximum in Cant accumulation was not evident in estimates generated with commonly used multiple linear regression (MLR) methods. We analyze the reasons why and show that the eMLR(C*) method may not fully capture nonsteady state changes in Cant when applied along a single hydrographic section as done here. This nonsteady component equates to redistribution of C*, whose spatial gradients in the Greenland Sea are dominated by Cant. We also show that the regular extended multiple linear regression method is sensitive to loss of spatial DIC gradients, which now happens as more and more Cant enters the ocean. Our findings demonstrate that MLR-based estimates of the Cant accumulation rate should not be taken at face value in highly dynamical ocean regions, such as the Greenland Sea, and the need for also considering the total change in DIC and how this is affected by natural processes. Further investigations into the ability of MLR methods to reproduce nonsteady state changes in Cant are encouraged.publishedVersio

The Nordic Seas carbon budget: Sources, sinks, and uncertainties

A carbon budget for the Nordic Seas is derived by combining recent inorganic carbon data from the CARINA database with relevant volume transports. Values of organic carbon in the Nordic Seas' water masses, the amount of carbon input from river runoff, and the removal through sediment burial are taken from the literature. The largest source of carbon to the Nordic Seas is the Atlantic Water that enters the area across the Greenland-Scotland Ridge; this is in particular true for the anthropogenic CO2. The dense overflows into the deep North Atlantic are the main sinks of carbon from the Nordic Seas. The budget show that presently 12.3 ± 1.4 Gt C yr−1 is transported into the Nordic Seas and that 12.5 ± 0.9 Gt C yr−1 is transported out, resulting in a net advective carbon transport out of the Nordic Seas of 0.17 ± 0.06 Gt C yr−1. Taking storage into account, this implies a net air-to-sea CO2 transfer of 0.19 ± 0.06 Gt C yr−1 into the Nordic Seas. The horizontal transport of carbon through the Nordic Seas is thus approximately two orders of magnitude larger than the CO2 uptake from the atmosphere. No difference in CO2 uptake was found between 2002 and the preindustrial period, but the net advective export of carbon from the Nordic Seas is smaller at present due to the accumulation of anthropogenic CO2