in my Visualforce page I have created an apex:pageblock that consists of an apex:selectList for sorting and an apex:tabPanel (Leads & Accounts)

Now when I switch between these tabs the entire visualforce page reloads which includes a google map. This not what I want and at the same time can't figure out why this is happening. What 'action' tells the page to reRender when switching tabs?

I only want the pageblock to reRender. This behaviour is fine when I change the value of the 'selectList' element in order to sort the records inside the tabs.

Here is the code that handles the pageblock:
 

<apex:pageblock id="sort">
        <apex:form >
            sortieren nach:   <apex:selectList value="{!selectedField}" size="1">
                                 <apex:actionSupport event="onchange" rerender="sort" action="{!findNearbyPotentials}"></apex:actionSupport>
                                    <apex:selectOption itemValue="Distance" itemLabel="Entfernung"/>
                                    <apex:selectOption itemValue="Jobads" itemLabel="Anzahl Anzeigen"/>
                              </apex:selectList>
         </apex:form>


    <apex:tabPanel >
     <!-- TAB LEADS -->
      <apex:tab label="Leads ({!warehouses.size})" disabled="{!IF(warehouses.size = 0,true,false)}" >
       <apex:pageBlockSectionItem >
        <apex:outputPanel styleClass="container-fluid">
         <div style="height:300px; overflow:auto !important;">     
          <apex:repeat value="{!warehouses}" var="war">

             <style type="text/css">
               .col1 {width:5px; text-align:left;}
               .col2 {width:400px; text-align:left;}
             </style>

              <apex:panelGrid columns="2" columnClasses="col1, col2" onmouseover="this.style.backgroundColor='#e2ecf1'" onmouseout="this.style.backgroundColor =''">
                <apex:image url="{!IF(war.Nicht_zugewiesene_Leadevents_Counter__c > 0,URLFOR($Resource.mitle),IF(war.WirtschaftszweigWZ08__c = currentAccount.WirtschaftszweigWZ08__c && war.Mitarbeiternzahl_final__c = currentAccount.Mitarbeiternzahl_final__c,URLFOR($Resource.perfect_fit), 
                      URLFOR($Resource.ms_marker)))}" styleClass="imageStyle" id="MyImage" onmouseover="ImageOver(this)" onmouseout="ImageNormal(this)"/> 
                  <apex:panelGroup >

                                <!-- Hover for Detail -->   
                                <a id="{!war.Id}"
                                onmouseover="LookupHoverDetail.getHover('{!war.Id}', '/{!war.Id}/m?retURL={!war.Id}&isAjaxRequest=1').show();"
                                onmouseout="LookupHoverDetail.getHover('{!war.Id}').hide();"
                                onfocus="LookupHoverDetail.getHover('{!war.Id}', '/{!war.Id}/m?retURL={!war.Id}&isAjaxRequest=1').show();"
                                onblur="LookupHoverDetail.getHover('{!war.Id}').hide();"
                                href="/{!war.Id}" target="_blank"> 
                                {!war.company}
                                 </a> <br/>

                                <!-- Jump to location and highlight -->
                                <apex:form > 
                                 <apex:commandLink action="{!findNearbyPotentials}" value="{!war.Street}, {!war.PostalCode} {!war.City}" reRender="map">  
                                     <apex:param name="HoverLead" value="{!war.id}" assignTo="{!HoverLead}" /> 
                                      <apex:param name="center" value="{!war.MapCurrentAddress__c}" assignTo="{!mapCenter}" />
                                      <apex:param name="zoom" value="13" assignTo="{!zoom}"/>
                                      <apex:param name="HoverAccount" value="" assignTo="{!HoverAccount}" /> 
                                 </apex:commandLink>  
                                </apex:form>  

                                 <!-- Distanz -->
                                 <apex:variable var="url" value="GoogleDistance | https://www.google.com/maps?saddr=+{!currentAccount.Geolocation__c}&daddr=+{!war.Geolocation__c}" />
                                 <apex:outputLink rendered="{!IF(NOT(CONTAINS(selectedField,'Jobads')), true, false)}" value="{!MID(url, FIND('|', url) + 1, LEN(url))}" target="_blank">{!distances[war.id]}</apex:outputLink>  

                                 <!-- Anzahl Anzeigen -->             
                                 <apex:outputLink rendered="{!IF(CONTAINS(selectedField,'Jobads'), true, false)}" value="{!war.indexurl__c}" target="_blank">{!war.AD_MS_Rel_Anzahl_bez__c} Anzeigen</apex:outputLink>                     

                                 <!-- Branche -->     
                                 <br/>          
                                 <apex:outputText value="{!war.WirtschaftszweigWZ08__c}"></apex:outputText>                         

                     </apex:panelGroup>                                                  
                    </apex:panelGrid> 
                   </apex:repeat> 
                  </div>                 
                 </apex:outputpanel> 
                </apex:pageBlockSectionItem>    
               </apex:tab>


    <!-- TAB ACCOUNTS -->
       <apex:tab label="Accounts ({!pot.size})" disabled="{!IF(pot.size = 0,true,false)}" >  
        <apex:pageBlockSectionItem >
         <apex:outputPanel styleClass="container-fluid">
          <div style="height:300px; overflow:auto !important;">     
           <apex:repeat value="{!pot}" var="pote">

                <style type="text/css">
                     .col1 {width:5px; text-align:left;}
                     .col2 {width:400px; text-align:left;}
                </style>

                    <apex:panelGrid columns="2" columnClasses="col1, col2" onmouseover="this.style.backgroundColor='#e2ecf1'" onmouseout="this.style.backgroundColor =''">
                      <apex:image url="{!IF(pote.Nicht_zugewiesene_Leadevents_Counter__c > 0,URLFOR($Resource.mitle),IF(pote.WirtschaftszweigWZ08__c = currentAccount.WirtschaftszweigWZ08__c && pote.Mitarbeiternzahl_final__c = currentAccount.Mitarbeiternzahl_final__c,URLFOR($Resource.perfect_fit), 
                      URLFOR($Resource.ms_marker)))}" styleClass="imageStyle" id="MyImage" onmouseover="ImageOver(this)" onmouseout="ImageNormal(this)"/> 
                        <apex:panelGroup >

                               <!-- Hover for Detail -->   
                                <a id="{!pote.Id}"
                                onmouseover="LookupHoverDetail.getHover('{!pote.Id}', '/{!pote.Id}/m?retURL={!pote.Id}&isAjaxRequest=1').show();"
                                onmouseout="LookupHoverDetail.getHover('{!pote.Id}').hide();"
                                onfocus="LookupHoverDetail.getHover('{!pote.Id}', '/{!pote.Id}/m?retURL={!pote.Id}&isAjaxRequest=1').show();"
                                onblur="LookupHoverDetail.getHover('{!pote.Id}').hide();"
                                href="/{!pote.Id}" target="_blank"> 
                                {!pote.Name}
                                </a> 
                                <br/>

                                <!-- Jump to location and highlight -->
                                 <apex:form >  
                                    <apex:commandLink action="{!findNearbyPotentials}" value="{!pote.ShippingStreet}, {!pote.ShippingPostalCode} {!pote.ShippingCity}" reRender="map">  
                                    <apex:param name="HoverAccount" value="{!pote.id}" assignTo="{!HoverAccount}" />
                                    <apex:param name="center" value="{!pote.MapCurrentAddress__c}" assignTo="{!mapCenter}" />
                                    <apex:param name="zoom" value="13" assignTo="{!zoom}"/>
                                    <apex:param name="HoverLead" value="" assignTo="{!HoverLead}" /> 
                                  </apex:commandLink>  
                                 </apex:form>   

                                <!-- Distanz -->
                                <apex:variable var="url" value="GoogleDistance | https://www.google.com/maps?saddr=+{!currentAccount.Geolocation__c}&daddr=+{!pote.Geolocation__c}" />
                                <apex:outputLink rendered="{!IF(NOT(CONTAINS(selectedField,'Jobads')), true, false)}" value="{!MID(url, FIND('|', url) + 1, LEN(url))}" target="_blank">{!distances[pote.id]}</apex:outputLink>  

                                <!-- Anzahl Anzeigen -->             
                                <apex:outputLink rendered="{!IF(CONTAINS(selectedField,'Jobads'), true, false)}" value="{!pote.indexurl__c}" target="_blank">{!pote.AD_MS_Rel_Anzahl_bez__c} Anzeigen</apex:outputLink> 

                                 <!-- Branche -->   
                                 <br/>           
                                 <apex:outputText value="{!pote.WirtschaftszweigWZ08__c}"></apex:outputText>                     

                        </apex:panelGroup>                                               
                       </apex:panelGrid> 
                      </apex:repeat> 
                     </div> 
                    </apex:outputpanel>                             
                   </apex:pageBlockSectionItem>  
                  </apex:tab>     
                 </apex:tabPanel>      

     </apex:pageblock>