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Anutaliya, A, Send U, Sprintall J, McClean JL, Lankhorst M, Koelling J.  Submitted.  Morning and PIES end-point measurements at the southern entrance of the Solomon Sea: subseasonal to interannual flow variability. Journal of Geophysical Research-Oceans.
In Press
Golaz, J-C, Caldwell PM, Van Roekel LP, Petersen MR, Tang Q, Wolfe JD, Abeshu G, Anantharaj V, Asay-Davis XS, Bader DC, Baldwin SA, Bisht G, Bogenschutz PA, Branstetter M, Brunke MA, Brus SR, Burrows SM, Cameron-Smith PJ, Donahue AS, Deakin M, Easter RC, Evans KJ, Feng Y, Flanner M, Foucar JG, Fyke JG, Griffin BM, Hannay C, Harrop BE, Hunke EC, Jacob RL, Jacobsen DW, Jeffery N, Jones PW, Keen ND, Klein SA, Larson VE, Leung LR, Li H-Y, Lin W, Lipscomb WH, Ma P-L, Mahajan S, Maltrud ME, Mametjanov A, McClean JL, McCoy RB, Neale RB, Price SF, Qian Y, Rasch PJ, Eyre JE, Riley WJ, Ringler TD, Roberts AF, Roesler EL, Salinger AG, Shaheen Z, Shi X, Singh B, Tang J, Taylor MA, Thornton PE, Turner AK, Veneziani M, Wan H, Wang H, Wang S, Williams DN, Wolfram PJ, Worley PH, Xie S, Yang Y, Yoon J-H, Zelinka MD, Zender CS, Zeng X, Zhang C, Zhang K, Zhang Y, Zhang X, Zhou T, Zhu Q.  In Press.  The DOE E3SM coupled model version 1: Overview and evaluation at standard resolution. JAMES.   10.1029/2018MS001603  
Palóczy, A, Gille ST, McClean JL.  2018.  Oceanic heat delivery to the Antarctic continental shelf: Large-scale, low-frequency variability. Journal of Geophysical Research: Oceans. 123:7678-7701.: Wiley-Blackwell   10.1029/2018JC014345   Abstract

Onshore penetration of oceanic water across the Antarctic continental slope (ACS) plays a major role in global sea level rise by delivering heat to the Antarctic marginal seas, thus contributing to the basal melting of ice shelves. Here, the time-mean (Φmean) and eddy (Φeddy) components of the heat transport (Φ) across the 1000 m isobath along the entire ACS are investigated using a 0.1° global coupled ocean/sea ice simulation based on the Los Alamos Parallel Ocean Program (POP) and sea ice (CICE) models. Comparison with in situ hydrography shows that the model successfully represents the basic water mass structure, with a warm bias in the Circumpolar Deep Water layer. Segments of on-shelf Φ, with lengths of O(100-1000 km), are found along the ACS. The circumpolar integral of the annually-averaged Φ is O(20 TW), with Φeddy always on-shelf, while Φmean fluctuates between on-shelf and off-shelf. Stirring along isoneutral surfaces is often the dominant process by which eddies transport heat across the ACS, but advection of heat by both mean flow-topography interactions and eddies can also be significant depending on the along- and across-slope location. The seasonal and interannual variability of the circumpolarly-integrated Φmean is controlled by convergence of Ekman transport within the ACS. Prominent warming features at the bottom of the continental shelf (consistent with observed temperature trends) are found both during high-SAM and high-Ni??o 3.4 periods, suggesting that climate modes can modulate the heat transfer from the Southern Ocean to the ACS across the entire Antarctic margin.

Wang, H, McClean JL, Talley LD, Yeager S.  2018.  Seasonal cycle and annual reversal of the Somali Current in an eddy-resolving global ocean model. Journal of Geophysical Research- Oceans. 123:6562-6580.   10.1029/2018JC013975  
Delman, AS, McClean JL, Sprintall J, Talley LD, Bryan FO.  2018.  Process-specific contributions to anomalous Java mixed layer cooling during positive IOD events. Journal of Geophysical Research- Oceans. 123:4153-4176.   10.1029/2017JC013749  
Centurioni, LR, V. Hormann V, Talley LD, Arzeno I, Beal L, Caruso M, Conroy P, Echols R, Fernando HJS, Giddings SN, Gordon A, Graber H, Harcourt R, Jayne SR, Jensen TG, Lee CM, Lermusiaux PFJ, L'Hegaret P, Lucas AJ, Mahadevan A, McClean JL, Pawlak G, Rainville L, Riser S, Seo H, Shcherbina AY, Skyllingstad E, Sprintall J, Subrahmanyan B, Terrill E, Todd RE, Trott C, Ulloa HN, Wang H.  2017.  Northern Arabian Sea Circulation - Autonomous Research (NASCar): a research initiative based on autonomous sensors. Oceanography . 30(2):74-87.   10.5670/oceanog.2017.224  
Chen, R, Gille ST, McClean JL.  2017.  Isopycnal eddy mixing across the Kuroshio Extension: Stable vs unstable states in an eddying model. Journal of Geophysical Research: Oceans. 122:4329-4345.   10.1002/2016JC012164  
Anutaliya, A, Send U, McClean JL, Sprintall J, Rainville L, Lee C, Priyantha Jinadasa SU, Wallcraft AJ, Metzger EJ.  2017.  An undercurrent off the east coast of Sri Lanka. Ocean Science. 13:1035-1044.   10.5194/os-13-1035-2017  
Hewitt, HT, Bell MJ, Chassignet EP, Czaja A, Ferreira D, Griffies SM, Hyder P, McClean JL, New AL, Roberts MJ.  2017.  Will high-resolution global ocean models benefit coupled predictions on short-range to climate timescales? Ocean Modelling . 120:120-136.   10.1016/j.ocemod.2017.11.002  
Delman, AS, Sprintall J, McClean JL, Talley LD.  2016.  Anomalous Java cooling at the initiation of positive Indian Ocean Dipole events. Journal of Geophysical Research: Oceans. 121(8):5805-5824.   10.1002/2016JC011635   AbstractWebsite

Anomalous sea surface temperature (SST) cooling south of Java, initiated during May–July, is an important precursor to positive Indian Ocean Dipole (pIOD) events. As shown previously, the Java SST anomalies are spatially and temporally coincident with seasonal upwelling induced locally by southeasterly trade winds. However, we confirm earlier findings that interannual variability of the Java cooling is primarily driven by remote wind forcing from coastal Sumatra and the equatorial Indian Ocean (EqIO); we also find an influence from winds along the Indonesian Throughflow. The wind forcing in the EqIO and along coastal Sumatra does not initiate SST cooling locally due to a deep thermocline and thick barrier layer, but can force upwelling Kelvin waves that induce substantial surface cooling once they reach the seasonally shallower thermocline near the coast of Java. Satellite altimetry is used to obtain a Kelvin wave coefficient that approximates Kelvin wave amplitude variations along the equator. All pIOD years in the satellite record have anomalous levels of upwelling Kelvin wave activity along the equator during April–June, suggesting that upwelling waves during this season are necessary for pIOD event development. However, a change to wind-forced downwelling Kelvin waves during July–August can abruptly terminate cool Java SST anomalies and weaken the pIOD event. Upwelling Kelvin wave activity along the equator and wind stress anomalies west of Sumatra are both robust predictors of the IOD index later in the calendar year, while values of the Kelvin wave coefficient are the most reliable predictor of pIOD events specifically.

Delman, AS, McClean JL, Sprintall J, Talley LD, Yulaeva E, Jayne SR.  2015.  Effects of eddy vorticity forcing on the mean state of the Kuroshio Extension. Journal of Physical Oceanography. 45:1356-1375.   10.1175/JPO-D-13-0259.1   Abstract

Eddy-mean flow interactions along the Kuroshio Extension (KE) jet are investigated using a vorticity budget of a high-resolution ocean model simulation, averaged over a 13-yr period. The simulation explicitly resolves mesoscale eddies in the KE and is forced with air-sea fluxes representing the years 1995-2007. A mean-eddy decomposition in a jet-following coordinate system removes the variability of the jet path from the eddy components of velocity; thus, eddy kinetic energy in the jet reference frame is substantially lower than in geographic coordinates and exhibits a cross-jet asymmetry that is consistent with the baroclinic instability criterion of the long-term mean field. The vorticity budget is computed in both geographic (i. e., Eulerian) and jet reference frames; the jet frame budget reveals several patterns of eddy forcing that are largely attributed to varicose modes of variability. Eddies tend to diffuse the relative vorticity minima/maxima that flank the jet, removing momentum from the fast-moving jet core and reinforcing the quasi-permanent meridional meanders in the mean jet. A pattern associated with the vertical stretching of relative vorticity in eddies indicates a deceleration (acceleration) of the jet coincident with northward (southward) quasi-permanent meanders. Eddy relative vorticity advection outside of the eastward jet core is balanced mostly by vertical stretching of the mean flow, which through baroclinic adjustment helps to drive the flanking recirculation gyres. The jet frame vorticity budget presents a well-defined picture of eddy activity, illustrating along-jet variations in eddy-mean flow interaction that may have implications for the jet's dynamics and cross-frontal tracer fluxes.

Schonau, MC, Rudnick DL, Cerovecki I, Gopalakrishnan G, Cornuelle BD, McClean JL, Qiu B.  2015.  The Mindanao Current: Mean structure and connectivity. Oceanography . 28(4):34-45.   10.5670/oceanog.2015.79  
Chen, R, Gille ST, McClean JL, Flierl GR, Grisesel A.  2015.  A multi-wavenumber theory for eddy diffusivities and its application to the southeast Pacific (DIMES) region. Journal of Physical Oceanography. 45:1877-1896.   10.1175/JPO-D-14-0229.1  
Qiu, B, Rudnick DL, Cerovecki I, Cornuelle BD, Chen S, Schonau MC, McClean JL, Gopalakrishnan G.  2015.  The Pacific North Equatorial Current: New insights from the Origins of the Kuroshio and Mindanao Currents (OKMC) Project. Oceanography. 28(4):24-33.   10.5670/oceanog.2015.78  
Li, L, Miller AJ, McClean JL, Eisenman I, Hendershott MC.  2014.  Processes driving sea ice variability in the Bering Sea in an eddying ocean/sea ice model: anomalies from the mean seasonal cycle. Ocean Dynamics. 64:1693-1717.: Springer Berlin Heidelberg   10.1007/s10236-014-0769-7   AbstractWebsite

A fine-resolution (1/10°) ocean/sea ice model configured in the Community Earth System Model framework is compared with observations and studied to determine the basin-scale and local balances controlling the variability of sea ice anomalies from the mean seasonal cycle in the Bering Sea for the time period 1980–1989. The model produces variations in total Bering Sea ice area anomalies that are highly correlated with observations. Surface air temperature, which is specified from reanalysis atmospheric forcing, strongly controls the ice volume variability in this simulation. The thermodynamic ice volume change is dominated by surface energy flux via atmosphere-ice sensible heat flux, except near the southern ice edge where it is largely controlled by ocean-ice heat flux. While thermodynamic processes dominate the variations in ice volume in the Bering Sea on the large scale, dynamic processes are important on the local scale near ice margins (both oceanic and land), where dynamic and thermodynamic ice volume changes have opposite signs and nearly cancel each other. Ice motion is generally consistent with winds driving the flow, except near certain straits in the north where ice motion largely follows ocean currents. Two key climate events, strong ice growth with cold air temperature and northerly wind anomalies in February 1984 and weak ice growth with warm air temperature and southerly wind anomalies in February 1989, are studied here in detail. While the processes controlling the ice changes are generally similar to those in other years, these large events help reveal the characteristic spatial patterns of ice growth/melt and transport anomalies.

Li, L, McClean JL, Miller AJ, Eisenman I, Hendershott MC, Papadopoulos CA.  2014.  Processes driving sea ice variability in the Bering Sea in an eddying ocean/sea ice model: Mean seasonal cycle. Ocean Modelling. 84:51-66.   10.1016/j.ocemod.2014.09.006   AbstractWebsite

The seasonal cycle of sea ice variability in the Bering Sea, together with the thermodynamic and dynamic processes that control it, are examined in a fine resolution (1/10°) global coupled ocean/sea-ice model configured in the Community Earth System Model (CESM) framework. The ocean/sea-ice model consists of the Los Alamos National Laboratory Parallel Ocean Program (POP) and the Los Alamos Sea Ice Model (CICE). The model was forced with time-varying reanalysis atmospheric forcing for the time period 1970–1989. This study focuses on the time period 1980–1989. The simulated seasonal-mean fields of sea ice concentration strongly resemble satellite-derived observations, as quantified by root-mean-square errors and pattern correlation coefficients. The sea ice energy budget reveals that the seasonal thermodynamic ice volume changes are dominated by the surface energy flux between the atmosphere and the ice in the northern region and by heat flux from the ocean to the ice along the southern ice edge, especially on the western side. The sea ice force balance analysis shows that sea ice motion is largely associated with wind stress. The force due to divergence of the internal ice stress tensor is large near the land boundaries in the north, and it is small in the central and southern ice-covered region. During winter, which dominates the annual mean, it is found that the simulated sea ice was mainly formed in the northern Bering Sea, with the maximum ice growth rate occurring along the coast due to cold air from northerly winds and ice motion away from the coast. South of St Lawrence Island, winds drive the model sea ice southwestward from the north to the southwestern part of the ice-covered region. Along the ice edge in the western Bering Sea, model sea ice is melted by warm ocean water, which is carried by the simulated Bering Slope Current flowing to the northwest, resulting in the S-shaped asymmetric ice edge. In spring and fall, similar thermodynamic and dynamic patterns occur in the model, but with typically smaller magnitudes and with season-specific geographical and directional differences.

Evans, KJ, Mahajan S, Branstetter M, McClean JL, Caron J, Maltrud ME, Hack JJ, Bader DC, Neale R, Leifeld JK.  2014.  A spectral transform dynamical core option within the Community Atmosphere Model (CAM4). Journal of Advances in Modeling Earth Systems. 6:902-922.   10.1002/2014MS000329   AbstractWebsite

An ensemble of simulations covering the present day observational period using forced sea surface temperatures and prescribed sea-ice extent is configured with an 85 truncation resolution spectral transform dynamical core (T85) within the Community Atmosphere Model (CAM), version 4 and is evaluated relative to observed and model derived data sets and the one degree finite volume (FV) dynamical core. The spectral option provides a well-known base within the climate model community to assess climate behavior and statistics, and its relative computational efficiency for smaller computing platforms allows it to be extended to perform high-resolution climate length simulations. Overall, the quality of the T85 ensemble is similar to FV. Analyzing specific features of the T85 simulations show notable improvements to the representation of wintertime Arctic sea level pressure and summer precipitation over the Western Indian subcontinent. The mean and spatial patterns of the land surface temperature trends over the AMIP period are generally well simulated with the T85 ensemble relative to observations, however the model is not able to capture the extent nor magnitude of changes in temperature extremes over the boreal summer, where the changes are most dramatic. Biases in the wintertime Arctic surface temperature and annual mean surface stress fields persist with T85 as with the CAM3 version of T85, as compared to FV. An experiment to identify the source of differences between dycores has revealed that the longwave cloud forcing is sensitive to the choice of dycore, which has implications for tuning strategies of the physics parameter settings.

Xu, LX, Xie SP, McClean JL, Liu QY, Sasaki H.  2014.  Mesoscale eddy effects on the subduction of North Pacific mode waters. Journal of Geophysical Research-Oceans. 119:4867-4886.   10.1002/2014jc009861   AbstractWebsite

Mesoscale eddy effects on the subduction of North Pacific mode waters are investigated by comparing observations and ocean general circulation models where eddies are either parameterized or resolved. The eddy-resolving models produce results closer to observations than the noneddy-resolving model. There are large discrepancies in subduction patterns between eddy-resolving and noneddy-resolving models. In the noneddy-resolving model, subduction on a given isopycnal is limited to the cross point between the mixed layer depth (MLD) front and the outcrop line whereas in eddy-resolving models and observations, subduction takes place in a broader, zonally elongated band within the deep mixed layer region. Mesoscale eddies significantly enhance the total subduction rate, helping create remarkable peaks in the volume histogram that correspond to North Pacific subtropical mode water (STMW) and central mode water (CMW). Eddy-enhanced subduction preferentially occurs south of the winter mean outcrop. With an anticyclonic eddy to the west and a cyclonic eddy to the east, the outcrop line meanders south, and the thermocline/MLD shoals eastward. As eddies propagate westward, the MLD shoals, shielding the water of low potential vorticity from the atmosphere. The southward eddy flow then carries the subducted water mass into the thermocline. The eddy subduction processes revealed here have important implications for designing field observations and improving models.

Griesel, A, McClean JL, Gille ST, Sprintall J, Eden C.  2014.  Eulerian and Lagrangian isopycnal eddy diffusivities in the Southern Ocean of an eddying model. Journal of Physical Oceanography. 44:644-661.   10.1175/JPO-D-13-039.1  
Chen, R, McClean JL, Gille ST, Griesel A.  2014.  Isopycnal eddy diffusivities in the Kuroshio Extension from an eddying ocean circulation model. Journal of Physical Oceanography. 44:2191-2211.   10.1175/JPO-D-13-0258.1  
Wang, JB, Flierl GR, LaCasce JH, McClean JL, Mahadevan A.  2013.  Reconstructing the ocean's interior from surface data. Journal of Physical Oceanography. 43:1611-1626.   10.1175/jpo-d-12-0204.1   AbstractWebsite

A new method is proposed for extrapolating subsurface velocity and density fields from sea surface density and sea surface height (SSH). In this, the surface density is linked to the subsurface fields via the surface quasigeostrophic (SQG) formalism, as proposed in several recent papers. The subsurface field is augmented by the addition of the barotropic and first baroclinic modes, whose amplitudes are determined by matching to the sea surface height (pressure), after subtracting the SQG contribution. An additional constraint is that the bottom pressure anomaly vanishes. The method is tested for three regions in the North Atlantic using data from a high-resolution numerical simulation. The decomposition yields strikingly realistic subsurface fields. It is particularly successful in energetic regions like the Gulf Stream extension and at high latitudes where the mixed layer is deep, but it also works in less energetic eastern subtropics. The demonstration highlights the possibility of reconstructing three-dimensional oceanic flows using a combination of satellite fields, for example, sea surface temperature (SST) and SSH, and sparse (or climatological) estimates of the regional depth-resolved density. The method could be further elaborated to integrate additional subsurface information, such as mooring measurements.

Gopalakrishnan, G, Cornuelle BD, Gawarkiewicz G, McClean JL.  2013.  Structure and evolution of the cold dome off northeastern Taiwan: A numerical study. Oceanography. 26(1):66-79.   10.5670/oceanog.2013.06   AbstractWebsite

Numerous observational and modeling studies of ocean circulation surrounding Taiwan have reported occurrences of cold water and doming of isotherms (called the cold dome) that result in the formation of coastal upwelling on the northeastern Taiwan shelf. We use a high-resolution (1/24°) ocean model based on the Massachusetts Institute of Technology general circulation model to study the evolution of this distinct shelf-slope circulation phenomenon. We performed a number of model simulations spanning a five-year period (2004–2008) using realistic atmospheric forcing and initial and open boundary conditions. The model solutions were compared with satellite measurements of sea surface height (SSH), sea surface temperature (SST), and historical temperature and salinity observations. The model showed a realistically shaped cold dome with a diameter of ~ 100 km and temperature of ~ 3°C below the ambient shelf waters at 50 m depth. The occurrences of simulated cold dome events appeared to be connected with the seasonal variability of the Kuroshio Current. The model simulations showed more upwelling events during spring and summer when the core of the Kuroshio tends to migrate away from the east coast of Taiwan, compared to fall and winter when the core of the Kuroshio is generally found closer to the east coast of Taiwan. The model also reproduced weak cyclonic circulation associated with the upwelling off northeastern Taiwan. We analyzed the spatio-temporal variability of the cold dome using the model solution as a proxy and designed a "cold dome index" based on the temperature at 50 m depth averaged over a 0.5° × 0.5° box centered at 25.5°N, 122°E. The cold dome index correlates with temperature at 50 m depth in a larger region, suggesting the spatial extent of the cold dome phenomenon. The index had correlation maxima of 0.78 and 0.40 for simulated SSH and SST, respectively, in and around the cold dome box region, and we hypothesize that it is a useful indicator of upwelling off northeastern Taiwan. In addition, both correlation and composite analysis between the temperature at 50 m depth and the East Taiwan Channel transport showed no cold dome events during low-transport events (often in winter) and more frequent cold dome events during high-transport events (often in summer). The simulated cold dome events had time scales of about two weeks, and their centers aligned roughly along a northeastward line starting from the northeastern tip of Taiwan.

Ivanova, DP, McClean JL, Hunke EC.  2012.  Interaction of ocean temperature advection, surface heat fluxes and sea ice in the marginal ice zone during the North Atlantic Oscillation in the 1990s: A modeling study. Journal of Geophysical Research-Oceans. 117(C02031):1-22.   10.1029/2011jc007532   AbstractWebsite

A moderately fine-resolution (0.4 degrees, 40 vertical levels), global, coupled ice-ocean model was configured and run for 24 years (1979-2002), forced with high-frequency National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) atmospheric fluxes. The model consists of the Los Alamos National Laboratory Parallel Ocean Program (POP) and sea ice model (CICE). The fidelity of the simulated mean climatological state and variability of key variables such as ice concentration, total ice area, ice thickness and drift were compared to observational data sets from satellite and ice drift buoy measurements. Basin-scale changes in the lower atmosphere/surface ocean/sea-ice in the simulated Arctic and Nordic Seas before and after the North Atlantic Oscillation (NAO) phase switch in 1995 were examined using winter composite analyses over the period 1990-1999. Ice cover changes between the two NAO phases were consistent with observations in that reduced concentrations were found in the Nordic and Barents Seas and increased values occurred in the Labrador Sea. Next we regionally evaluated the relative importance of winter anomalies of upper-ocean mixed layer net heat fluxes and of ocean temperature advection on marginal ice zone variability in the Irminger, Greenland, and Barents Seas for this ten-year period. We found that the net heat flux winter anomaly was at least four times more important than the winter anomaly of ocean temperature advection in the Greenland and Barents Seas, while it was twice as important in the Irminger Sea. The Ekman ocean temperature advection component generally dominated the geostrophic component in all three regions.

Lenn, YD, Chereskin TK, Sprintall J, McClean JL.  2011.  Near-surface eddy heat and momentum fluxes in the Antarctic Circumpolar Current in Drake Passage. Journal of Physical Oceanography. 41:1385-1407.   10.1175/jpo-d-10-05017.1   AbstractWebsite

The authors present new estimates of the eddy momentum and heat fluxes from repeated high-resolution upper-ocean velocity and temperature observations in Drake Passage and interpret their role in the regional Antarctic Circumpolar Current (ACC) momentum balance. The observations span 7 yr and are compared to eddy fluxes estimated from a 3-yr set of output archived from an eddy-resolving global Parallel Ocean Program (POP) numerical simulation. In both POP and the observations, the stream-averaged cross-stream eddy momentum fluxes ((u'v') over bar) correspond to forcing consistent with both a potential vorticity flux into the axis of the Subantarctic Front (SAF) and a sharpening of all three main ACC fronts through Drake Passage. Further, the POP analysis indicates that the mean momentum advection terms reflect the steering of the mean ACC fronts and are not fully balanced by the eddy momentum forcing, which instead impacts the strength and number of ACC fronts. The comparison between POP and observed eddy heat fluxes was less favorable partly because of model bias in the water mass stratification. Observed cross-stream eddy heat fluxes ((v'T') over bar) are generally surface intensified and poleward in the ACC fronts, with values up to approximately -290 +/- 80 kW m(-2) in the Polar and Southern ACC Fronts. Interfacial form stresses F(T), derived from observed eddy heat fluxes in the SAF, show little depth dependence below the Ekman layer. Although F(T) appears to balance the surface wind stress directly, the estimated interfacial form stress divergence is only an order of magnitude greater than the eddy momentum forcing in the SAF. Thus, although the eddy momentum forcing is of secondary importance in the momentum balance, its effect is not entirely negligible.