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Model-observation and reanalyses comparison at key locations for heat transport to the Arctic (D2.1)

Moat, Ben; Herbaut, Christophe; Larsen, Karin Margretha; Hansen, Bogi; Sinha, Bablu; Sanchez-Franks, Alejandra; Houpert, Loic; Liu, Yang; Hazeleger, Wilco; Attema, Jisk; Yeager, Stephen; Small, Justin; Valdimarsson, Hedinn; Berx, Barbara; Cunningham, Stuart; Houpert, Loic; Hallam, Samantha; Woodgate, Rebecca; Lee, Craig; Kwon, Young Oh; Flemming, Laura; Mercier, Herle; Jochumsen, Kerstin; Mecking, Jennifer; Holliday, Penny Holliday; Josey, Simon


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{
  "publisher": "Zenodo", 
  "DOI": "10.5281/zenodo.3631100", 
  "language": "eng", 
  "title": "Model-observation and reanalyses comparison at key locations for heat transport to the Arctic (D2.1)", 
  "issued": {
    "date-parts": [
      [
        2020, 
        1, 
        30
      ]
    ]
  }, 
  "abstract": "<p>Assessment of key lower latitude influences on the Arctic and their simulation</p>\n\n<p><strong>Summary</strong></p>\n\n<p>Blue-Action Work Package 2 (WP2) focuses on lower latitude drivers of Arctic change, with a focus on<br>\nthe influence of the Atlantic Ocean and atmosphere on the Arctic. In particular, warm water travels from<br>\nthe Atlantic, across the Greenland-Scotland ridge, through the Norwegian Sea towards the Arctic. A<br>\nlarge proportion of the heat transported northwards by the ocean is released to the atmosphere and<br>\ncarried eastward towards Europe by the prevailing westerly winds. This is an important contribution to<br>\nnorthwestern Europe&#39;s mild climate. The remaining heat travels north into the Arctic. Variations in the<br>\namount of heat transported into the Arctic will influence the long term climate of the Northern<br>\nHemisphere. Here we assess how well the state of the art coupled climate models estimate this<br>\nnorthwards transport of heat in the ocean, and how the atmospheric heat transport varies with changes<br>\nin the ocean heat transport. We seek to improve the ocean monitoring systems that are in place by<br>\nintroducing measurements from ocean gliders, Argo floats and satellites.<br>\nThese state of the art computer simulations are evaluated by comparison with key trans-Atlantic<br>\nobservations. In addition to the coupled models &lsquo;ocean-only&rsquo; evaluations are made. In general the<br>\ncoupled model simulations have too much heat going into the Arctic region and the transports have too<br>\nmuch variability. The models generally reproduce the variability of the Atlantic Meridional Ocean<br>\nCirculation (AMOC) well. All models in this study have a too strong southwards transport of freshwater<br>\nat 26&deg;N in the North Atlantic, but the divergence between 26&deg;N and Bering Straits is generally<br>\nreproduced really well in all the models.</p>\n\n<p>Altimetry from satellites have been used to reconstruct the ocean circulation 26&deg;N in the Atlantic, over<br>\nthe Greenland Scotland Ridge and alongside ship based observations along the GO-SHIP OVIDE Section.<br>\nAlthough it is still a challenge to estimate the ocean circulation at 26&deg;N without using the RAPID 26&deg;N<br>\narray, satellites can be used to reconstruct the longer term ocean signal. The OSNAP project measures<br>\nthe oceanic transport of heat across a section which stretches from Canada to the UK, via Greenland.<br>\nThe project has used ocean gliders to great success to measure the transport on the eastern side of the<br>\narray. Every 10 days up to 4000 Argo floats measure temperature and salinity in the top 2000m of the<br>\nocean, away from ocean boundaries, and report back the measurements via satellite. These data are<br>\nemployed at 26&deg;N in the Atlantic to enable the calculation of the heat and freshwater transports.<br>\nAs explained above, both ocean and atmosphere carry vast amounts of heat poleward in the Atlantic. In<br>\nthe long term average the Atlantic ocean releases large amounts of heat to the atmosphere between<br>\nthe subtropical and subpolar regions, heat which is then carried by the atmosphere to western Europe<br>\nand the Arctic. On shorter timescales, interannual to decadal, the amounts of heat carried by ocean and<br>\natmosphere vary considerably. An important question is whether the total amount of heat transported,<br>\natmosphere plus ocean, remains roughly constant, whether significant amounts of heat are gained or<br>\nlost from space and how the relative amount transported by the atmosphere and ocean change with<br>\ntime. This is an important distinction because the same amount of anomalous heat transport will have</p>\n\n<p>very different effects depending on whether it is transported by ocean or the atmosphere. For example<br>\nthe effects on Arctic sea ice will depend very much on whether the surface of the ice experiences<br>\nanomalous warming by the atmosphere versus the base of the ice experiencing anomalous warming<br>\nfrom the ocean. In Blue-Action we investigated the relationship between atmospheric and oceanic heat<br>\ntransports at key locations corresponding to the positions of observational arrays (RAPID at 26&deg;N,<br>\nOSNAP at ~55N, and the Denmark Strait, Iceland-Scotland Ridge and Davis Strait at ~67N) in a number of<br>\ncutting edge high resolution coupled ocean-atmosphere simulations. We split the analysis into two<br>\ndifferent timescales, interannual to decadal (1-10 years) and multidecadal (greater than 10 years). In the<br>\n1-10 year case, the relationship between ocean and atmosphere transports is complex, but a robust<br>\nresult is that although there is little local correlation between oceanic and atmospheric heat transports,<br>\nCorrelations do occur at different latitudes. Thus increased oceanic heat transport at 26&deg;N is<br>\naccompanied by reduced heat transport at ~50N and a longitudinal shift in the location of atmospheric<br>\nflow of heat into the Arctic. Conversely, on longer timescales, there appears to be a much stronger local<br>\ncompensation between oceanic and atmospheric heat transport i.e. Bjerknes compensation.</p>", 
  "author": [
    {
      "family": "Moat, Ben"
    }, 
    {
      "family": "Herbaut, Christophe"
    }, 
    {
      "family": "Larsen, Karin Margretha"
    }, 
    {
      "family": "Hansen, Bogi"
    }, 
    {
      "family": "Sinha, Bablu"
    }, 
    {
      "family": "Sanchez-Franks, Alejandra"
    }, 
    {
      "family": "Houpert, Loic"
    }, 
    {
      "family": "Liu, Yang"
    }, 
    {
      "family": "Hazeleger, Wilco"
    }, 
    {
      "family": "Attema, Jisk"
    }, 
    {
      "family": "Yeager, Stephen"
    }, 
    {
      "family": "Small, Justin"
    }, 
    {
      "family": "Valdimarsson, Hedinn"
    }, 
    {
      "family": "Berx, Barbara"
    }, 
    {
      "family": "Cunningham, Stuart"
    }, 
    {
      "family": "Houpert, Loic"
    }, 
    {
      "family": "Hallam, Samantha"
    }, 
    {
      "family": "Woodgate, Rebecca"
    }, 
    {
      "family": "Lee, Craig"
    }, 
    {
      "family": "Kwon, Young Oh"
    }, 
    {
      "family": "Flemming, Laura"
    }, 
    {
      "family": "Mercier, Herle"
    }, 
    {
      "family": "Jochumsen, Kerstin"
    }, 
    {
      "family": "Mecking, Jennifer"
    }, 
    {
      "family": "Holliday, Penny Holliday"
    }, 
    {
      "family": "Josey, Simon"
    }
  ], 
  "note": "The Blue-Action project has received funding from the European Union's Horizon 2020\nResearch and Innovation Programme under Grant Agreement No 727852.", 
  "type": "report", 
  "id": "3631100"
}
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