scholarly journals Improvement of Ocean State Estimation by Assimilating Mapped Argo Drift Data

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
Shuhei Masuda ◽  
Nozomi Sugiura ◽  
Satoshi Osafune ◽  
Toshimasa Doi
Keyword(s):  
State Estimation ◽  
Current Data ◽  
Global Ocean ◽  
Ocean Current ◽  
Oceanic Circulation ◽  
Synthesis System ◽  
Wind Stress Curl ◽  
Data Synthesis ◽  
Ocean State Estimation ◽  
The Impact

We investigated the impact of assimilating a mapped dataset of subsurface ocean currents into an ocean state estimation. We carried out two global ocean state estimations from 2000 to 2007 using the K7 four-dimensional variational data synthesis system, one of which included an additional map of climatological geostrophic currents estimated from the global set of Argo floats. We assessed the representativeness of the volume transport in the two exercises. The assimilation of Argo ocean current data at only one level, 1000 dbar depth, had subtle impacts on the estimated volume transports, which were strongest in the subtropical North Pacific. The corrections at 10°N, where the impact was most notable, arose through the nearly complete offset of wind stress curl by the data synthesis system in conjunction with the first mode baroclinic Rossby wave adjustment. Our results imply that subsurface current data can be effective for improving the estimation of global oceanic circulation by a data synthesis.

U.S. GODAE: Sustained Global Ocean State Estimation for Scientific and Practical Application

2004 ◽  
Author(s):  
Carl Wunsch ◽  
Ichiro Fukumori ◽  
Tong Lee ◽  
Dimitris Menemenlis ◽  
David W. Behringer ◽  
...  
Keyword(s):  
State Estimation ◽  
Global Ocean ◽  
Practical Application ◽  
Ocean State Estimation

scholarly journals Trends in Southern Hemisphere Circulation in IPCC AR4 Models over 1950–99: Ozone Depletion versus Greenhouse Forcing

2007 ◽  
Vol 20 (4) ◽  
pp. 681-693 ◽  
Author(s):  
Wenju Cai ◽  
Tim Cowan
Keyword(s):  
Southern Hemisphere ◽  
Wind Stress ◽  
Ozone Depletion ◽  
Southern Annular Mode ◽  
Positive Trend ◽  
Oceanic Circulation ◽  
Wind Stress Curl ◽  
Intergovernmental Panel ◽  
Environmental Prediction ◽  
The Impact

Abstract Simulations by the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) models on the Southern Hemisphere (SH) circulation are assessed over the period 1950–99, focusing on the seasonality of the trend and the level of its congruency with the southern annular mode (SAM) in terms of surface zonal wind stress. It is found that, as a group, the models realistically produce the seasonality of the trend, which is strongest in the SH summer season, December–February (DJF). The modeled DJF trend is principally congruent with the modeled SAM trend, as in observations. The majority of models produce a statistically significant positive trend, with decreasing westerlies in the midlatitudes and increasing westerlies in the high latitudes. The trend pattern from an all-experiment mean achieves highest correlation with that from the National Centers for Environmental Prediction (NCEP) data. A total of 48 out of the 71 experiments were run with ozone-depletion forcing, which offers an opportunity to assess the importance of ozone depletion in driving the late-twentieth-century trends. The AR4 model ensemble that contains an ozone-depletion forcing produces an averaged trend that is comparable to the trend from the NCEP outputs corrected by station-based observations. The trend is largely generated after the mid-1970s. Without ozone depletion the trend is less than half of that in the corrected NCEP, although the errors in the observed trend are large. The impact on oceanic circulation is inferred from wind stress curl in the group with ozone-depletion forcing. The result shows an intensification of the southern midlatitude supergyre circulation, including a strengthening East Australian Current flowing through the Tasman Sea. Thus, ozone depletion also plays an important role in the subtropical gyre circulation change over the past decades.

scholarly journals The impact of atmospheric and oceanic circulations on the Greenland Sea iceconcentration

2020 ◽  
Author(s):  
Sourav Chatterjee ◽  
Roshin P. Raj ◽  
Laurent Bertino ◽  
Sebastian H. Merlind ◽  
Nuncio Murukesh ◽  
...  
Keyword(s):  
Sea Ice ◽  
Large Scale ◽  
Ice Formation ◽  
Oceanic Circulation ◽  
Greenland Sea ◽  
Wind Stress Curl ◽  
Northerly Wind ◽  
Sea Ice Concentration ◽  
Ice Dynamics ◽  
The Impact

Abstract. The amount and spatial extent of Greenland Sea (GS) sea ice are primarily driven by the sea ice export across the Fram Strait (FS) and by local seasonal sea ice formation, melting and sea ice dynamics. Maximum sea ice concentration (SIC) variability is found in the marginal ice zone and ‘Odden’ region in the central GS. In this study, using satellite passive microwave sea ice observations, atmospheric and a coupled ocean-sea ice reanalysis system we show that both the atmospheric and oceanic circulation in the GS act in tandem to explain the SIC variability in the GS. Anomalous low/high sea level pressure (SLP) over the Nordic Seas is found to strengthen/weaken the Greenland Sea Gyre (GSG) circulation. The large-scale atmospheric circulation pattern associated with this GSG variability features North Atlantic Oscillation (NAO) like SLP pattern with its northern center of action shifted north-eastward from its canonical position. During anomalous low SLP periods, northerly wind anomalies reduce the sea ice export in the central GS due to westward Ekman drift of sea ice. This in turn decreases the freshwater content and weakens ocean stratification in the central GS. At the same time, the associated positive wind stress curl anomaly strengthens the GSG circulation which recirculates warm and saline Atlantic water (AW) into this region. Under a weakly stratified condition, the subsurface AW anomalies can reach the surface to inhibit new sea ice formation, further reducing the SIC in the central GS. Thus, this study highlights combined influence of atmospheric and oceanic circulation in the central GS SIC variability.

U.S. GODAE: Sustained Global Ocean State Estimation for Scientific and Practical Application

2007 ◽  
Author(s):  
Carl Wunsch ◽  
Ichiro Fukumori ◽  
Tong Lee ◽  
Dimitris Menemenlis ◽  
David W. Behringer ◽  
...  
Keyword(s):  
State Estimation ◽  
Global Ocean ◽  
Practical Application ◽  
Ocean State Estimation

scholarly journals Demographic reconstruction from ancient DNA supports rapid extinction of the great auk

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Jessica E Thomas ◽  
Gary R Carvalho ◽  
James Haile ◽  
Nicolas J Rawlence ◽  
Michael D Martin ◽  
...  
Keyword(s):  
North Atlantic ◽  
Population Viability ◽  
Current Data ◽  
Ocean Current ◽  
Widespread Species ◽  
The North ◽  
Rapid Extinction ◽  
Population Viability Analyses ◽  
The Impact ◽  
Complete Mitochondrial Genomes

The great auk was once abundant and distributed across the North Atlantic. It is now extinct, having been heavily exploited for its eggs, meat, and feathers. We investigated the impact of human hunting on its demise by integrating genetic data, GPS-based ocean current data, and analyses of population viability. We sequenced complete mitochondrial genomes of 41 individuals from across the species’ geographic range and reconstructed population structure and population dynamics throughout the Holocene. Taken together, our data do not provide any evidence that great auks were at risk of extinction prior to the onset of intensive human hunting in the early 16th century. In addition, our population viability analyses reveal that even if the great auk had not been under threat by environmental change, human hunting alone could have been sufficient to cause its extinction. Our results emphasise the vulnerability of even abundant and widespread species to intense and localised exploitation.

scholarly journals How the Deep, Cold Currents of the Labrador Sea Affect Climate

Eos ◽  
2017 ◽  
Author(s):  
Emily Underwood
Keyword(s):  
Current Data ◽  
Ocean Current ◽  
Labrador Sea ◽  
Oceanic Circulation ◽  
Data Link

Seventeen years of ocean current data link global atmospheric and oceanic circulation.

Sign in / Sign up

Export Citation Format

Share Document