Lin Xiaopei

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Lin

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Xiaopei

ORCID

0000-0001-6413-4479

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A mechanism for the latitudinal dependence of peak-spectrum sea surface height variability

(John Wiley & Sons, 2014-02-25) Lin, Xiaopei ; Yin, Yuqi ; Yang, Jiayan

Previous studies have shown that the power spectrum of satellite-observed sea surface height (SSH) variability peaks at a certain frequency (or a wave number) band at a given latitude. Lin et al. (2008) attributed this latitudinal dependence to the critical frequency of the first baroclinic mode Rossby waves in the tropical and subtropical oceans. Their study was based on the linear Rossby wave theory and focused on SSH variability in the tropical and subtropical oceans since the altimetry data do not adequately resolve lengths of baroclinic Rossby waves at and near the critical frequency in high latitudes. In this study, we expand their analysis to high-latitude oceanic basins and to include nonlinear eddy effects, by using a linear wave model and a high-resolution model output from the OGCM for the Earth Simulator (OFES). It is found that the linear wave mechanism by and large remains valid in the tropical and subtropical oceans. In higher latitudes as well as in some regions in the western tropical and subtropical oceans, other mechanisms, like nonlinear eddy, play more important role in determining the SSH variability.
Characteristics of 3-dimensional structure and heat budget of mesoscale eddies in the South Atlantic Ocean

(American Geophysical Union, 2021-04-26) Wang, Xue ; Zhang, Shaoqing ; Lin, Xiaopei ; Qiu, Bo ; Yu, Lisan

Mesoscale eddies redistribute heat, salt, and nutrients in oceans. The South Atlantic Ocean (SA) is a basin that has active mesoscale eddies for which characteristics of the three-dimensional structure and its leading mechanism are complex but have yet been studied sufficiently. Here based on ocean reanalysis datasets we use a composite analysis approach to analyze the mixed layer anomalous heat budget and find distinct two types of spatial patterns: dipole and monopole – mainly present in the northern and southern regions of the SA, respectively. The dipole can be attributed to ocean horizontal advection, especially to the combined effect of eddy anomalous meridional current and meridional gradient of mean temperature. The monopole, on the other hand, is associated with complex contributions, for which zonal and meridional advections play opposite roles as cooling or heating around the eddies. At the eddy center, the vertical advection is non-negligible, especially the mean upwelling and vertical temperature gradient playing a vital role in the formation of a monopole. The analysis of eddy meridional heat transport shows that the stirring component is dominant, and poleward in most areas, especially at high latitudes. Such analysis on the leading mechanism of eddy-induced temperature anomaly could help improve our understanding on meso- and small-scale air-sea interactions and eddy-induced heat transport in the SA.
An asymmetric upwind flow, Yellow Sea Warm Current : 1. New observations in the western Yellow Sea

(American Geophysical Union, 2011-04-29) Lin, Xiaopei ; Yang, Jiayan ; Guo, Jingsong ; Zhang, Zhixin ; Yin, Yuqi ; Song, Xiangzhou ; Zhang, Xiaohui

The winter water mass along the Yellow Sea Trough (YST), especially on the western side of the trough, is considerably warmer and saltier than the ambient shelf water mass. This observed tongue-shape hydrographic feature implies the existence of a winter along-trough and onshore current, often referred to as the Yellow Sea Warm Current (YSWC). However, the YSWC has not been confirmed by direct current measurements and therefore skepticism remains regarding its existence. Some studies suggest that the presence of the warm water could be due to frontal instability, eddies, or synoptic scale wind bursts. It is noted that in situ observations used in most previous studies were from the central and eastern sides of the YST even though it is known that the warm water core is more pronounced along the western side. Data from the western side have been scarce. Here we present a set of newly available Chinese observations, including some from a coordinated effort involving three Chinese vessels in the western YST during the 2006–2007 winter. The data show unambiguously the existence of the warm current on the western side of YST. Both the current and hydrography observations indicate a dominant barotropic structure of YSWC. The westward deviation of YSWC axis is particularly obvious to the south of 35°N and is clearly associated with an onshore movement of warm water. To the north of 35°N, the YSWC flows along the bathymetry with slightly downslope movement. We conclude that the barotropic current is mainly responsible for the warm water intrusion, while the Ekman and baroclinic currents play an important but secondary role. These observations help fill an observational gap and establish a more complete view of the YSWC.
Author correction : Meridional heat transport variability induced by mesoscale processes in the subpolar North Atlantic

(Nature Publishing Group, 2018-06-14) Zhao, Jian ; Bower, Amy S. ; Yang, Jiayan ; Lin, Xiaopei
Overturning in the Subpolar North Atlantic Program : a new international ocean observing system

(American Meteorological Society, 2017-04-24) Lozier, M. Susan ; Bacon, Sheldon ; Bower, Amy S. ; Cunningham, Stuart A. ; de Jong, Marieke Femke ; de Steur, Laura ; deYoung, Brad ; Fischer, Jürgen ; Gary, Stefan F. ; Greenan, Blair J. W. ; Heimbach, Patrick ; Holliday, Naomi Penny ; Houpert, Loïc ; Inall, Mark E. ; Johns, William E. ; Johnson, Helen L. ; Karstensen, Johannes ; Li, Feili ; Lin, Xiaopei ; Mackay, Neill ; Marshall, David P. ; Mercier, Herlé ; Myers, Paul G. ; Pickart, Robert S. ; Pillar, Helen R. ; Straneo, Fiamma ; Thierry, Virginie ; Weller, Robert A. ; Williams, Richard G. ; Wilson, Christopher G. ; Yang, Jiayan ; Zhao, Jian ; Zika, Jan D.

For decades oceanographers have understood the Atlantic meridional overturning circulation (AMOC) to be primarily driven by changes in the production of deep-water formation in the subpolar and subarctic North Atlantic. Indeed, current Intergovernmental Panel on Climate Change (IPCC) projections of an AMOC slowdown in the twenty-first century based on climate models are attributed to the inhibition of deep convection in the North Atlantic. However, observational evidence for this linkage has been elusive: there has been no clear demonstration of AMOC variability in response to changes in deep-water formation. The motivation for understanding this linkage is compelling, since the overturning circulation has been shown to sequester heat and anthropogenic carbon in the deep ocean. Furthermore, AMOC variability is expected to impact this sequestration as well as have consequences for regional and global climates through its effect on the poleward transport of warm water. Motivated by the need for a mechanistic understanding of the AMOC, an international community has assembled an observing system, Overturning in the Subpolar North Atlantic Program (OSNAP), to provide a continuous record of the transbasin fluxes of heat, mass, and freshwater, and to link that record to convective activity and water mass transformation at high latitudes. OSNAP, in conjunction with the Rapid Climate Change–Meridional Overturning Circulation and Heatflux Array (RAPID–MOCHA) at 26°N and other observational elements, will provide a comprehensive measure of the three-dimensional AMOC and an understanding of what drives its variability. The OSNAP observing system was fully deployed in the summer of 2014, and the first OSNAP data products are expected in the fall of 2017.
Decadal to multidecadal variability of the mixed layer to the south of the Kuroshio Extension region

(American Meteorological Society, 2020-08-05) Wu, Baolan ; Lin, Xiaopei ; Yu, Lisan

The decadal to multidecadal mixed layer variability is investigated in a region south of the Kuroshio Extension (130°E–180°, 25°–35°N), an area where the North Pacific subtropical mode water forms, during 1948–2012. By analyzing the mixed layer heat budget with different observational and reanalysis data, here we show that the decadal to multidecadal variability of the mixed layer temperature and mixed layer depth is covaried with the Atlantic multidecadal oscillation (AMO), instead of the Pacific decadal oscillation (PDO). The mixed layer temperature has strong decadal to multidecadal variability, being warm before 1970 and after 1990 (AMO positive phase) and cold during 1970–90 (AMO negative phase), and so does the mixed layer depth. The dominant process for the mixed layer temperature decadal to multidecadal variability is the Ekman advection, which is controlled by the zonal wind changes related to the AMO. The net heat flux into the ocean surface Qnet acts as a damping term and it is mainly from the effect of latent heat flux and partially from sensible heat flux. While the wind as well as mixed layer temperature decadal changes related to the PDO are weak in the western Pacific Ocean. Our finding proposes the possible influence of the AMO on the northwestern Pacific Ocean mixed layer variability, and could be a potential predictor for the decadal to multidecadal climate variability in the western Pacific Ocean.
Explaining the global distribution of peak-spectrum variability of sea surface height

(American Geophysical Union, 2008-07-19) Lin, Xiaopei ; Yang, Jiayan ; Wu, Dexing ; Zhai, Ping

A 14-year satellite observation of sea surface height (SSH) reveals an interesting pattern. Along any latitude, there is a frequency at which the SSH power spectrum peaks, regardless of which hemisphere or oceanic basin. This peak-spectrum frequency is nearly identical to the critical frequency at which the zonal energy propagation of Rossby waves becomes stagnant. The interior ocean adjusts to atmospheric forcing by radiating energy away through Rossby waves. There are two distinct groups of Rossby waves, long ones carry the energy to the west while short ones send the energy to the east. At the critical frequency, these two waves merge and their zonal energy propagation becomes stagnant. Consequently, the energy from atmospheric forcing may accumulate in the ocean interior, and thus result in a spectrum peak.
An asymmetric upwind flow, Yellow Sea Warm Current : 2. Arrested topographic waves in response to the northwesterly wind

(American Geophysical Union, 2011-04-29) Lin, Xiaopei ; Yang, Jiayan

A warm and salty water mass exists along the Yellow Sea Trough (YST) in winter. This oceanic water mass is distinct from the ambient shelf water and is distributed on the western side of the YST. It has long been reasoned that a Yellow Sea Warm Current (YSWC) must exist. A recent observational study indeed supports the existence of the YSWC and shows that its position moved progressively westward as the warm water intrudes further shoreward toward the northwest. In this paper, we explain mechanisms for sustaining the YSWC and for its westward displacement. The northwesterly monsoonal wind prevails in the winter and is directed against the YSWC. The cross-trough scale is small compared with the spatial scale of monsoonal variation, so one can assume, to the first order, that the wind stress is uniform across the trough. The curl of depth-averaged wind stress has opposite signs on the two sides of the trough. Consequently, two oppositely rotating gyres develop initially and they converge along the trough giving rise to a barotropic upwind flow. But this upwind flow lasts only for a few days as the two gyres evolve and propagate as topographic waves. For a northerly wind, both gyres move westward since the positive (negative) potential vorticity flux on the western (eastern) side of the trough pushes the water toward shore (trough). If the bottom friction is negligible, the steady response becomes a large anticyclonic gyre over the trough and the upwind current is squeezed toward the shore line. In this case, no YSWC is sustained along or near the trough. This runaway warm current can be arrested by a moderate bottom friction. We therefore propose that the YSWC is actually arrested topographic waves in response to local wind stress forcing.
Recent decadal change in the North Atlantic subtropical underwater associated with the poleward expansion of the surface salinity maximum

(American Geophysical Union, 2019-06-11) Liu, Hao ; Yu, Lisan ; Lin, Xiaopei

Yu et al. (2017, https://doi.org/10.1002/2017GL075772) reported that the annual mean sea surface salinity maximum (SSS‐max) in the North Atlantic expanded northward by 0.35 ± 0.11° per decade over the 34‐year data record (1979–2012). The expansion shifted and expanded the ventilation zone northward and increased the production of the Subtropical Underwater (STUW). As a result, the STUW became deeper, thicker, and saltier. In this study, the seasonal characteristics of the poleward expansion of the North Atlantic SSS‐max and their effects on the STUW are examined. The results show that the SSS‐max expansion occurred primarily during boreal spring (April, May, and June) and expanded northward by 0.43 ± 0.21° per decade over the 34‐year period. The annual volume of the STUW increased by 0.21 ± 0.09 1014 m3 per decade over the same period, and the spring (April, May, and June) volume increased by 0.31 ± 0.02 1014 m3 per decade (a relative increase of 48 ± 1%). The characteristics of the decadal changes in STUW were attributable to the increased subduction rate associated with the northward expansion of the SSS‐max. The annual subduction rate increased by 0.29 ± 0.07 Sv per decade over the 34 years, and the greatest increase of 1.73 ± 0.61 Sv per decade occurred in April. The change in subduction associated with the expansion of the SSS‐max appeared to be consistent with the Atlantic Multidecadal Oscillation.
On the dynamics of the seasonal variation in the South China Sea throughflow transport

(John Wiley & Sons, 2013-12-16) Yang, Jiayan ; Lin, Xiaopei ; Wu, Dexing

The Luzon Strait transport (LST) of water mass from the Pacific Ocean to the South China Sea (SCS) varies significantly with seasons. The mechanisms for this large variability are still not well understood. The steady-state island rule, which is derived from a steady-state model, is not applicable to seasonal time scale variations in a large basin like the Pacific Ocean. In this paper, we will use a theoretical model that is based on the circulation integral around the Philippines. The model relates the LST variability to changes in the boundary currents along the east coast of the Philippines, including the North Equatorial Current (NEC) Bifurcation Latitude (NECBL), the transports of Kuroshio and Mindanao Currents (KC and MC), and to the local wind-stress forcing. Our result shows that a northward shift of the NECBL, a weakening of the KC or a strengthening of the MC would enhance the LST into the SCS. This relationship between the LST and the NEC-KC-MC is consistent with observations. The analytical result is tested by a set of idealized numerical simulations.
Dynamic millennial-scale climate changes in the northwestern Pacific over the past 40,000 years

(American Geophysical Union, 2010-12-03) Chen, Min-Te ; Lin, Xiaopei ; Chang, Yuan-Pin ; Chen, Y.-C. ; Lo, L. ; Shen, Chuan-Chou ; Yokoyama, Yusuke ; Oppo, Delia W. ; Thompson, William G. ; Zhang, Rong

Ice core records of polar temperatures and greenhouse gases document abrupt millennial-scale oscillations that suggest the reduction or shutdown of thermohaline Circulation (THC) in the North Atlantic Ocean may induce the abrupt cooling in the northern hemisphere. It remains unknown, however, whether the sea surface temperature (SST) is cooling or warming in the Kuroshio of the Northwestern Pacific during the cooling event. Here we present an AMS 14C-dated foraminiferal Mg/Ca SST record from the central Okinawa Trough and document that the SST variations exhibit two steps of warming since 21 ka — at 14.7 ka and 12.8 ka, and a cooling (∼1.5°C) during the interval of the Younger Dryas. By contrast, we observed no SST change or oceanic warming (∼1.5–2°C) during the episodes of Northern Hemisphere cooling between ∼21–40 ka. We therefore suggest that the “Antarctic-like” timing and amplitude of millennial-scale SST variations in the subtropical Northwestern Pacific between 20–40 ka may have been determined by rapid ocean adjustment processes in response to abrupt wind stress and meridional temperature gradient changes in the North Pacific.
An open-ocean forcing in the East China and Yellow seas

(American Geophysical Union, 2010-12-21) Ma, Chao ; Wu, Dexing ; Lin, Xiaopei ; Yang, Jiayan ; Ju, Xia

Recent studies have demonstrated that the annual mean barotropic currents over the East China and Yellow seas (ECYS) are forced primarily by the oceanic circulation in the open-ocean basin through the Kuroshio Current (KC), the western boundary current of the subtropical gyre in the North Pacific Ocean. The local wind stress forcing plays an important but secondary role. Those previous results were mainly qualitative and from a simple barotropic model forced by a steady wind stress field. They remain to be tested in a more complete 3-D model with both wind stress and buoyancy fluxes. In addition, the seasonal variability of major ECYS currents may involve different forcing mechanisms than their annually averaged fields do, and this can only be addressed when a seasonally varying forcing is used in the model. In this paper, we will address these issues by using a 3-D baroclinic model. Our results confirm the finding from the previous studies that the KC is the primary forcing mechanism for major annually mean currents in the ECYS, which include the Taiwan Strait Current, the Tsushima Warm Current, and the Yellow Sea Warm Current (YSWC), etc. However, the local monsoonal forcing plays a prominent role in modulating the seasonal variability of all major currents in the region. A deep northwestward intrusion of the YSWC in winter, for instance, is mainly due to a robustly developed China Coastal Current and Korea Coastal Current, which draw water along the Yellow Sea Trough to feed the southward flows along the west and east coasts of the Yellow Sea.
Poleward shift of the Kuroshio Extension front and its impact on the North Pacific Subtropical Mode Water in the recent decades

(American Meteorological Society, 2021-01-26) Wu, Baolan ; Lin, Xiaopei ; Yu, Lisan

The meridional shift of the Kuroshio Extension (KE) front and changes in the formation of the North Pacific Subtropical Mode Water (STMW) during 1979–2018 are reported. The surface-to-subsurface structure of the KE front averaged over 142°–165°E has shifted poleward at a rate of ~0.23° ± 0.16° decade−1. The shift was caused mainly by the poleward shift of the downstream KE front (153°–165°E, ~0.41° ± 0.29° decade−1) and barely by the upstream KE front (142°–153°E). The long-term shift trend of the KE front showed two distinct behaviors before and after 2002. Before 2002, the surface KE front moved northward with a faster rate than the subsurface. After 2002, the surface KE front showed no obvious trend, but the subsurface KE front continued to move northward. The ventilation zone of the STMW, defined by the area between the 16° and 18°C isotherms or between the 25 and 25.5 kg m−3 isopycnals, contracted and displaced northward with a shoaling of the mixed layer depth hm before 2002 when the KE front moved northward. The STMW subduction rate was reduced by 0.76 Sv (63%; 1 Sv ≡ = 106 m3 s−1) during 1979–2018, most of which occurred before 2002. Of the three components affecting the total subduction rate, the temporal induction (−∂hm/∂t) was dominant accounting for 91% of the rate reduction, while the vertical pumping (−wmb) amounted to 8% and the lateral induction (−umb ⋅ ∇hm) was insignificant. The reduced temporal induction was attributed to both the contracted ventilation zone and the shallowed hm that were incurred by the poleward shift of KE front.
The annual cycle of the Japan Sea throughflow

(American Meteorological Society, 2016-01) Kida, Shinichiro ; Qiu, Bo ; Yang, Jiayan ; Lin, Xiaopei

The mechanism responsible for the annual cycle of the flow through the straits of the Japan Sea is investigated using a two-layer model. Observations show maximum throughflow from summer to fall and minimum in winter, occurring synchronously at the three major straits: Tsushima, Tsugaru, and Soya Straits. This study finds the subpolar winds located to the north of Japan as the leading forcing agent, which first affects the Soya Strait rather than the Tsushima or Tsugaru Straits. The subpolar winds generate baroclinic Kelvin waves along the coastlines of the subpolar gyre, affect the sea surface height at the Soya Strait, and modify the flow through the strait. This causes barotropic adjustment to occur inside the Japan Sea and thus affect the flow at the Tsugaru and Tsushima Straits almost synchronously. The barotropic adjustment mechanism explains well why the observations show a similar annual cycle at the three straits. The annual cycle at the Tsugaru Strait is further shown to be weaker than that in the other two straits based on frictional balance around islands, that is, frictional stresses exerted around an island integrate to zero. In the Tsugaru Strait, the flows induced by the frictional integrals around the northern (Hokkaido) and southern (Honshu) islands are in opposite directions and tend to cancel out. Frictional balance also suggests that the annual cycle at the Tsugaru Strait is likely in phase with that at the Soya Strait because the length scale of the northern island is much shorter than that of the southern island.
Unusual cross-shelf transport driven by the changes of wind pattern in a marginal sea

(American Geophysical Union, 2021-11-01) Yao, Zhigang ; Chen, Ke ; Ding, Yang ; Lin, Xiaopei ; Bao, Xianwen ; Qiao, Lulu

The traditional understanding of the regional circulation in the Northwest Pacific marginal seas is that the Korean Coastal Current flows southward, following the isobaths of 20–50 m. However, an unusual tongue-shaped structure of cold water is observed in satellite SST data in January 2017, indicating a possible offshore spread of cold coastal water into the middle Southern Yellow Sea (SYS). Additional observations, including in situ hydrographic data as well as direct current measurement, also suggest this cross-shelf transport of the Korean Coastal Water in January 2017. Our analysis shows that this flow breaks through the isobaths at ∼37°N, moves southward between 50–75 m, and eventually veers anti-cyclonically at ∼35°N to join the western slope of the SYS. This circulation pattern is further supported by heat budget analysis. Diagnosis of potential vorticity (PV) reveals that the elevated negative PV anomaly imposed by surface wind stress favors this unusual cross-shelf transport. The change of wind pattern, although under a deceasing wind speed condition, plays an important role. This work provides an alternative view of the wintertime circulation pattern and motivates future studies of the variability of the coastal currents over interannual and longer time scales in the SYS.
Ocean climate observing requirements in support of climate research and climate information

(Frontiers Media, 2019-07-31) Stammer, Detlef ; Bracco, Annalisa ; AchutaRao, Krishna ; Beal, Lisa M. ; Bindoff, Nathaniel L. ; Braconnot, Pascale ; Cai, Wenju ; Chen, Dake ; Collins, Matthew ; Danabasoglu, Gokhan ; Dewitte, Boris ; Farneti, Riccardo ; Fox-Kemper, Baylor ; Fyfe, John ; Griffies, Stephen M. ; Jayne, Steven R. ; Lazar, Alban ; Lengaigne, Matthieu ; Lin, Xiaopei ; Marsland, Simon ; Minobe, Shoshiro ; Monteiro, Pedro M. S. ; Robinson, Walter ; Roxy, Mathew Koll ; Rykaczewski, Ryan R. ; Speich, Sabrina ; Smith, Inga J. ; Solomon, Amy ; Storto, Andrea ; Takahashi, Ken ; Toniazzo, Thomas ; Vialard, Jérôme

Natural variability and change of the Earth’s climate have significant global societal impacts. With its large heat and carbon capacity and relatively slow dynamics, the ocean plays an integral role in climate, and provides an important source of predictability at seasonal and longer timescales. In addition, the ocean provides the slowly evolving lower boundary to the atmosphere, driving, and modifying atmospheric weather. Understanding and monitoring ocean climate variability and change, to constrain and initialize models as well as identify model biases for improved climate hindcasting and prediction, requires a scale-sensitive, and long-term observing system. A climate observing system has requirements that significantly differ from, and sometimes are orthogonal to, those of other applications. In general terms, they can be summarized by the simultaneous need for both large spatial and long temporal coverage, and by the accuracy and stability required for detecting the local climate signals. This paper reviews the requirements of a climate observing system in terms of space and time scales, and revisits the question of which parameters such a system should encompass to meet future strategic goals of the World Climate Research Program (WCRP), with emphasis on ocean and sea-ice covered areas. It considers global as well as regional aspects that should be accounted for in designing observing systems in individual basins. Furthermore, the paper discusses which data-driven products are required to meet WCRP research and modeling needs, and ways to obtain them through data synthesis and assimilation approaches. Finally, it addresses the need for scientific capacity building and international collaboration in support of the collection of high-quality measurements over the large spatial scales and long time-scales required for climate research, bridging the scientific rational to the required resources for implementation.
On the mechanism of the cyclonic circulation in the Gulf of Tonkin in the summer

(American Geophysical Union, 2008-09-18) Wu, Dexing ; Wang, Yue ; Lin, Xiaopei ; Yang, Jiayan

The circulation in the Gulf of Tonkin had been traditionally considered to be anticyclonic in the summer. This view was challenged recently by results from reanalyzing observational data, which clearly revealed that the circulation is cyclonic in all seasons. The surface wind stress is monsoonal, southwesterly in the summer and reversed in the winter. It remains unexplained why the circulation is always cyclonic, while the surface forcing reverses seasonally. In this study, we hypothesize that the inflow through Qiongzhou Strait, a shallow and narrow channel between Hainan Island and the Chinese mainland, is responsible for maintaining the cyclonic circulation in the summer. Besides the requirements of mass conservation and bathymetry constraint, this flow, even with a rather small transport, carries a considerable amount of potential vorticity (PV) into the gulf, and the integral constraint of PV requires the presence of a frictional torque to be associated with a cyclonic circulation. Several numerical experiments with a three-dimensional model have been conducted to test this hypothesis. When the westward flow through Qiongzhou Strait is blocked, the model simulates an anticyclonic circulation in the summer. When the westward flow through Qiongzhou Strait is allowed, the circulation changes to a cyclonic one, consistent with our hypothesis.
Tropical pacific observing system

(Frontiers Media, 2019-02-18) Smith, Neville ; Kessler, William S. ; Cravatte, Sophie ; Sprintall, Janet ; Wijffels, Susan E. ; Cronin, Meghan F. ; Sutton, Adrienne J. ; Serra, Yolande L. ; Dewitte, Boris ; Strutton, Peter G. ; Hill, Katherine Louise ; Sen Gupta, Alexander ; Lin, Xiaopei ; Takahashi, Ken ; Chen, Dake ; Brunner, Shelby

This paper reviews the design of the Tropical Pacific Observing System (TPOS) and its governance and takes a forward look at prospective change. The initial findings of the TPOS 2020 Project embrace new strategic approaches and technologies in a user-driven design and the variable focus of the Framework for Ocean Observing. User requirements arise from climate prediction and research, climate change and the climate record, and coupled modeling and data assimilation more generally. Requirements include focus on the upper ocean and air-sea interactions, sampling of diurnal variations, finer spatial scales and emerging demands related to biogeochemistry and ecosystems. One aim is to sample a diversity of climatic regimes in addition to the equatorial zone. The status and outlook for meeting the requirements of the design are discussed. This is accomplished through integrated and complementary capabilities of networks, including satellites, moorings, profiling floats and autonomous vehicles. Emerging technologies and methods are also discussed. The outlook highlights a few new foci of the design: biogeochemistry and ecosystems, low-latitude western boundary currents and the eastern Pacific. Low latitude western boundary currents are conduits of tropical-subtropical interactions, supplying waters of mid to high latitude origin to the western equatorial Pacific and into the Indonesian Throughflow. They are an essential part of the recharge/discharge of equatorial warm water volume at interannual timescales and play crucial roles in climate variability on regional and global scales. The tropical eastern Pacific, where extreme El Niño events develop, requires tailored approaches owing to the complex of processes at work there involving coastal upwelling, and equatorial cold tongue dynamics, the oxygen minimum zone and the seasonal double Intertropical Convergence Zone. A pilot program building on existing networks is envisaged, complemented by a process study of the East Pacific ITCZ/warm pool/cold tongue/stratus coupled system. The sustainability of TPOS depends on effective and strong collaborative partnerships and governance arrangements. Revisiting regional mechanisms and engaging new partners in the context of a planned and systematic design will ensure a multi-purpose, multi-faceted integrated approach that is sustainable and responsive to changing needs.
Global Ocean Summit : a forum for institutional coordination of global ocean observations

( 2014-11) Cai, Wenju ; Avery, Susan K. ; Leinen, Margaret S. ; Lee, Kenneth ; Lin, Xiaopei ; Visbeck, Martin

A sustainable global ocean observation system requires timely implementation of a global ocean observation framework. The recent Qingdao Global Ocean Summit offers an effective mechanism for a coherent institutional response to emerging scientific and societal drivers, and for promoting the capacity building in developing economies that is essential for increasing the value and broadening the funding base of the observation system.
Dynamics of an idealized Beaufort Gyre : 1. The effect of a small beta and lack of western boundaries

(John Wiley & Sons, 2016-02-12) Yang, Jiayan ; Proshutinsky, Andrey ; Lin, Xiaopei

The Beaufort Gyre in the Arctic Ocean differs from a typical moderate-latitude gyre in some major aspects of its dynamics. First, it is located in a basin without a western boundary, which is essential for closing midlatitude circulations. Second, the gradient in Coriolis parameter, β, is small and so the validity of the Sverdrup balance is uncertain. In this paper, we use an idealized two-layer model to examine several processes that are related to these two issues. In a circular basin with closed geostrophic contours in interior, the variability of vorticity in the upper layer is dominated by eddies. But in the time-mean circulation, the main dynamical balance in the basin's interior is between the curl of wind stress and the eddy vorticity fluxes. The torque of friction becomes important along the boundary where the rim current is strong. It is found that the smallness of β has only a relatively small impact in a circular basin without a meridional boundary. The gyre is considerably more sensitive to the existence of a meridional boundary. The time-mean circulation weakens considerably when a peninsula is inserted between the model's center and the rim. (One side of the peninsula is dynamically equivalent to a midlatitude western boundary.) The gyre's sensitivity to β has also increased significantly when a meridional boundary is present. Subsurface ridges have similar effects on the gyre as a boundary, indicating that such topographic features may substitute, to some extents, the dynamical role of a western boundary.

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