Meet our young researchers: Erwin Lambert
Sometimes things are so complicated that you're forced to think simple. Erwin Lambert is an expert at that. With a few, plain boxes he tries to calculate how a rainy future will influence Atlantic currents.
Meet our young researchers: Marius Årthun
What if we could predict how much sea ice there will be in the Nordic Seas in two years? Or twenty? In the gap between ordinary weather forecasts and climate projections, there is a dialog between the ocean and the atmosphere. Without understanding how they interact, we cannot predict variations in climate, says Marius Årthun.
Meet our young researchers: Ingrid Onarheim
North Pole explorers send summer photos of melt water pools and cracks that become harder and harder to cross. If they had winter expeditions, they would see that ice covers as much of the Arctic Ocean as in the past. Only the Barents Sea and the region just north of Svalbard have lost winter ice.
Meet our young researchers: Carina Bringedal
The Gulf Stream transports warm water towards Northern Europe. This flow is driven by northward flows replacing water that sink in the Norwegian Sea, but also by the wind blowing over the sea. In some regions, the wind can be the strongest driver. Carina Bringedal studies the role of the winds at the entrance of the Norwegian Sea.
The northern thermohaline circulation (THC; PI Haugan, UiB) PhD student Erwin Lambert started his NORTH thesis project at UiB October 2014. Erwin is well into the construction and analysis of a conceptual model of northern THC. Motivated by Stommel's classical “two-box” model for THC, a similar model has been formulated more in line with the observed structure of Arctic–Atlantic oceanic exchanges and buoyancy forcing. By including the model equivalent of an East Greenland Current, Erwin allows for an estuarine circulation – and thus a corresponding fraction of Atlantic salt and heat transport northward – that is sustained by freshwater input. An important finding is that the qualitative and quantitative effect of an amplified freshwater cycle on the strength of the Atlantic inflow depends on the geographical distribution of freshwater input. The inlet figure details the Atlantic inflow’s sensitivity to the strength of the freshwater cycle for five distinct cases, with “100%” being equivalent to Stommel’s original model and the most critically sensitive (percentages quantify the fraction of northern freshwater input that occurs over the dense water formation region; the remaining fraction feeds the estuarine circulation).
WP2 Laboratory experiments (PI Drange, UiB)
Profs Helge Drange (UiB) and Rune Time (UiS) at present pursue the use of laboratory experiments along two complimentary pathways. Helge, and also NORTH PhD student Ingrid Onarheim, are focusing on the outreach of NORTH-related research to students and the general public using a “mobile lab”, whereas Rune and Senior Engineer Dr Herimonja Rabenjafimanantsoa are carefully constructing the experimental set-up eventually to demonstrate models such as Erwin’s in the lab (more below). Since the fall 2014, approximately 560 high school students have been introduced to the mobile rotating table run by Helge – in addition to its use in Ingrid and Helge’s teaching at UiB. The purpose of
this outreach activity has been to bridge (mostly) counter-intuitive properties of rotating fluids with various weather and climate phenomena. Related to this, Ingrid and Helge were nominated for the UiB Faculty of Mathematics and Natural Sciences’ annual award for best teaching. In Stavanger, Rune and Benja have constructed a 4.5 m high loop of plastic pipes, a laser gun and advanced measuring equipment to assess ocean circulation experimentally. This is the first time UiS use their hi-tech Petroleum Engineering Lab to assess flows related to oceanography or climate. The construction of the experimental set-up has already attracted MSc students in engineering, and we look forward to the interactions within NORTH on actual THC experiments in the years to come. Their ongoing work was recently featured at optics.org.
Dr Anne Britt Sandø is leading the work on resolving the basic forcing of North Atlantic–Nordic Seas exchanges, including larger scale ocean-atmosphere interaction. This WP is now gaining momentum with the recent hiring of Carina Bringedal in NORTH’s postdoctoral position. She recently – and very successfully – defended her PhD thesis (Modeling of heat transfer in porous media in the context of geothermal energy extraction) at the Department of Mathematics, UiB. Carina is presently diving into the literature on basic climate dynamics and air-sea interaction of the northern seas in particular, while at the same time trial-and-erroring with the MITgcm.
Related to the forcing of the northern seas, Tor Eldevik contributed NORTH diagnostics to paleo reconstructions of the Nordic Seas overflows, inferring that reconstructed overflow variance through the last 8.000 years largely reflected a co-varying inflow and poleward ocean heat transport, whereas freshwater forcing appears a more likely explanation for the transition from a cold-to-warm climate the preceding 2000 years.
WP4 Variance explained in ocean and climate models (PI Langehaug, NERSC)
There has been a breadth of activity on northern climate variance explained – both in models and observations, including assessing predictability and doing actual predictions. The PI, Dr Helene R. Langehaug, has been scrutinizing and inter-comparing several CMIP5 prediction models for consistency with the observational record of the northern seas, and for predictive skill in particular. Helene has also extended her evaluation of climate model variance to paleo reconstructions, specifically to assess the representativeness of the so-called “Gardar Drift” proxy locality for making inference on change in Nordic Seas overflow.
PhD student Ingrid Onarheim has faced the challenge of predicting Barents Sea ice cover from first principles and observations, and corroborating the approach using an ice-ocean GCM. Ingrid particularly – and correctly – predicted more sea ice last winter, and has predicted a slight decrease this coming winter (2016; cf. inlet panel) from the observed vigor of the Atlantic inflow to the Barents Sea. Directly related to this, NORTH postdoc Marius Årthun shows how a decrease in Arctic-Atlantic sea ice extent, and also increased Norwegian Sea heat loss to the atmosphere and consequent warmer surface air temperatures, all appear as a lagged response to more Atlantic inflow to the Norwegian Sea in a multi-century control climate model simulation. Marius further finds that both the model and observations share a common decadal time scale of variability that also includes the subpolar North Atlantic.
WP5 Outreach and capacity building (PI Sylte, Uni)
Ms Gudrun Sylte has been promoting much of our NORTH outreach, as she is very capably promoting Bjerknes Centre research in general. With respect to capacity building, former MSc student Ms Samah Satti was visiting UiB from Sudan during the autumn of 2015. Samah is now preparing a manuscript, together with Marius and Tor, on the exchanges through the strait of Bab-el-Mandab that separates the Red Sea from the Gulf of Aden and the Indian Ocean. The aim of the study is to assess the structure of exchange and its relation to regional atmospheric forcing, predominantly evaporation and wind including longer-term climate change. Data sources are idealized MITgcm simulations (Marius) and SODA reanalysis (Samah; see inlet panel for an example), partly analyzed using NORTH methodology following up on Samah’s master thesis.
KICK OFF - meeting in Bergen 22. - 23. September
The kick off for the North project will be in the Geophysical Institute at the University of Bergen. (Map )
Please find the programme here
Bert Rudel (Finnish Meteorological Institute) is visiting from Finland, and is giving a talk both in the kick-off meeting and as the weekly insitute seminar in the GFI auditorium.
Here is an abtract from his talk "Atlantic inflows, the Arctic Ocean volume and freshwater balances, and the Fram Strait branch contribution to the Arctic heat budget":
The inflows of Atlantic water from the Nordic Seas to the Arctic Ocean through Fram Strait and over the Barents Sea are examined based primarily on hydrographic observations from two cruises with RV Polarstern in 2007 and 2011.
The contrast between the high salinity Atlantic water core in the Nansen Basin and the lower Atlantic water salinity combined with an underlying salinity minimum in the Amundsen Basin suggests that the Fram Strait branch mainly remains in the Nansen
Basin, while the Barents Sea branch continues along the continental slope, enters the Amundsen Basin and provides most of the Atlantic water in the Makarov and Canada basins.
Recently published estimates of the in- and outflows of volume and liquid freshwater through the Barents Sea, Bering Strait and the Canadian Arctic Archipelago as well as river runoff, net precipitation and ice export are reviewed and added together. To achieve volume and freshwater balances net outflows through Fram Strait of 2.3 Sv and 100 mSv respectively are required, which is reasonably close to the observed Fram Strait exchanges.
The net outflows are separated into two parts, upper layer transports, less dense than the entering Atlantic water, and lower layer transports, as dense or denser than the Atlantic water. The largest net volume outflow occurs in the lower layer, 1.65 Sv, while the liquid freshwater is almost exclusively exported in the 0.64 Sv net outflow in upper layer, leading to unrealistically low salinities in the upper layer.
Atlantic water, transformed into less saline surface water through melting of sea ice north of Svalbard, can supply the necessary higher salinity (halocline) water to the upper layer. 1.23 Sv of halocline water of salinity 34.2 must be added to obtain a more realistic salinity of 33.1, leading to a total export of 1.84 Sv upper layer water in the East Greenland Current. Existing observations of the net transports into and out of the Arctic Ocean through Fram Strait in different temperature classes are then used to estimate the heat loss of the Atlantic water entering through Fram Strait. About 10 TW are supplied to the atmosphere in addition to the loss of 24 TW occurring in connection with the formation of the halocline water.
If the hypothesis that the Fram Strait branch remains in the Nansen Basin is true, it implies a heat loss between 5 and 15 Wm2 in the Nansen Basin, depending upon how much heat is temporarily stored in the water column. This is high compared to the 2 Wm2 commonly cited as the ocean heat flux to the atmosphere in the Arctic Ocean.